Mid Sweden University

Introduction: To date, no study has compared anaerobic capacity (AnC) estimates computed with the maximal accumulated oxygen deficit (MAOD) method and the gross energy cost (GEC) method applied to treadmill running exercise.

Purpose: Four different models for estimating anaerobic energy supply during treadmill running exercise were compared.

Methods: Fifteen endurance-trained recreational athletes performed, after a 10-min warm-up, five 4-min stages at ∼55–80% of peak oxygen uptake, and a 4-min time trial (TT). Two linear speed-metabolic rate (MR) regression models were used to estimate the instantaneous required MR during the TT (MRTT_req), either including (5+YLIN) or excluding (5-YLIN) a measured Y-intercept. Also, the average GEC (GECAVG) based on all five submaximal stages, or the GEC based on the last submaximal stage (GECLAST), were used as models to estimate the instantaneous MRTT_req. The AnC was computed as the difference between the MRTT_req and the aerobic MR integrated over time.

Results: The GEC remained constant at ∼4.39 ± 0.29 J⋅kg–1⋅m–1 across the five submaximal stages and the TT was performed at a speed of 4.7 ± 0.4 m⋅s–1. Compared with the 5-YLIN, GECAVG, and GECLAST models, the 5+YLIN model generated a MRTT_req that was ∼3.9% lower, with corresponding anaerobic capacities from the four models of 0.72 ± 0.20, 0.74 ± 0.16, 0.74 ± 0.15, and 0.54 ± 0.14 kJ⋅kg–1, respectively (F1.07,42 = 13.9, P = 0.002). The GEC values associated with the TT were 4.22 ± 0.27 and 4.37 ± 0.30 J⋅kg–1⋅m–1 for 5+YLIN and 5-YLIN, respectively (calculated from the regression equation), and 4.39 ± 0.28 and 4.38 ± 0.27 J⋅kg–1⋅m–1 for GECAVG and GECLAST, respectively (F1.08,42 = 14.6, P < 0.001). The absolute typical errors in AnC ranged between 0.03 and 0.16 kJ⋅kg–1 for the six pair-wise comparisons and the overall standard error of measurement (SEM) was 0.16 kJ⋅kg–1.

Conclusion: These findings demonstrate a generally high disagreement in estimated anaerobic capacities between models and show that the inclusion of a measured Y-intercept in the linear regression (i.e., 5+YLIN) is likely to underestimate the MRTT_req and the GEC associated with the TT, and hence the AnC during maximal 4-min treadmill running.

Purpose: This study aimed to compare performance and pacing strategies between elite male and female cross-country skiers during a sprint competition on snow using the skating technique.

Methods: Twenty male and 14 female skiers completed an individual time-trial prolog (TT) and three head-to-head races (quarter, semi, and final) on the same 1,572-m course, which was divided into flat, uphill and downhill sections. Section-specific speeds, choice of sub-technique (i.e., gear), cycle characteristics, heart rate and post-race blood lactate concentration were monitored. Power output was estimated for the different sections during the TT, while metabolic demand was estimated for two uphill camera sections and the final 50-m flat camera section.

Results: Average speed during the four races was ∼12.5% faster for males than females (P < 0.001), while speeds on the flat, uphill and downhill sections were ∼11, 18, and 9% faster for the males than females (all P< 0.001 for terrain, sex, and interaction). Differences in uphill TT speed between the sexes were associated with different sub-technique preferences, with males using a higher gear more frequently than females (P < 0.05). The estimated metabolic demand relative to maximal oxygen uptake (V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V˙V˙O2max) was similar for both sexes during the two uphill camera sections (∼129% of V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V˙V˙O2max) and for the final 50-m flat section (∼153% of V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V˙V˙O2max). Relative power output during the TT was 18% higher for males compared to females (P < 0.001) and was highly variable along the course for both sexes (coefficient of variation [CV] between sections 4–9 was 53%), while the same variation in heart rate was low (CV was ∼3%). The head-to-head races were ∼2.4% faster than the TT for both sexes and most race winners (61%) were positioned first already after 30 m of the race. No sex differences were observed during any of the races for heart rate or blood lactate concentration.

Conclusion: The average sex difference in sprint skiing performance was ∼12.5%, with varying differences for terrain-specific speeds. Moreover, females skied relatively slower uphill (at a lower gear) and thereby elicited more variation in their speed profiles compared to the males.

Purpose: The present study aimed to compare four methods of estimating anaerobic energy production during supramaximal exercise.

Methods: Twenty-one junior cross-country skiers competing at a national and/or international level were tested on a treadmill during uphill (7°) diagonal-stride (DS) roller-skiing. After a 4-minute warm-up, a 4 × 4-min continuous submaximal protocol was performed followed by a 600-m time trial (TT). For the maximal accumulated O2 deficit (MAOD) method the V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2-speed regression relationship was used to estimate the V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand during the TT, either including (4+Y, method 1) or excluding (4-Y, method 2) a fixed Y-intercept for baseline V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2. The gross efficiency (GE) method (method 3) involved calculating metabolic rate during the TT by dividing power output by submaximal GE, which was then converted to a V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand. An alternative method based on submaximal energy cost (EC, method 4) was also used to estimate V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand during the TT.

Results: The GE/EC remained constant across the submaximal stages and the supramaximal TT was performed in 185 ± 24 s. The GE and EC methods produced identical V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demands and O2 deficits. The V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand was ~3% lower for the 4+Y method compared with the 4-Y and GE/EC methods, with corresponding O2 deficits of 56 ± 10, 62 ± 10, and 63 ± 10 mL·kg−1, respectively (P < 0.05 for 4+Y vs. 4-Y and GE/EC). The mean differences between the estimated O2 deficits were −6 ± 5 mL·kg−1 (4+Y vs. 4-Y, P < 0.05), −7 ± 1 mL·kg−1 (4+Y vs. GE/EC, P < 0.05) and −1 ± 5 mL·kg−1 (4-Y vs. GE/EC), with respective typical errors of 5.3, 1.9, and 6.0%. The mean difference between the O2 deficit estimated with GE/EC based on the average of four submaximal stages compared with the last stage was 1 ± 2 mL·kg−1, with a typical error of 3.2%.

Conclusions: These findings demonstrate a disagreement in the O2 deficits estimated using current methods. In addition, the findings suggest that a valid estimate of the O2 deficit may be possible using data from only one submaximal stage in combination with the GE/EC method.

Introduction

Two frequently used approaches for estimating anaerobic energy production during supramaximal exercise are the maximal accumulated oxygen (O2) deficit (MAOD) method and the gross efficiency (GE) method (Noordhof et al., 2011). Despite clear computational differences between the two methods, only one direct comparison has been performed (Noordhof et al., 2011). In cross-country roller-skiing, both the MAOD and the GE methods have been employed (Andersson et al., 2016). Therefore, this study aimed to compare the O2 deficits attained with these methods.

Methods

Eleven male and ten female cross-country skiers were tested on a treadmill employing uphill (7°) diagonal-stride roller-skiing. After collecting a 1-min baseline VO2, participants performed a 4 × 4-min continuous submaximal protocol (~ 60-90% of VO2max) followed by, a self-paced 600-m time-trial (TT). Speed and VO2 were measured continuously during the TT. For the MAOD method, the linear relationship between treadmill velocity and VO2 during the final 30 seconds of each 4 × 4-min submaximal stage was derived with the baseline VO2 as a Y-intercept included (4+Y) in or excluded (4-Y) from the model. The two regression equations were then used to estimate the VO2 demand during the TT. For the GE method, the metabolic rate during the TT was calculated by taking the average power output divided by the GE (an average of the four submaximal stages) and converted to a VO2 demand. 

Results

The VO2 demand was significantly higher for the GE (68.9 ± 8.5 mL/kg/min) and 4-Y (68.4 ± 8.7 mL/kg/min) procedures compared with the 4+Y (64.3 ± 7.6 mL/kg/min) procedure (P < 0.05). The corresponding O2 deficits for the GE, 4-Y and, 4+Y procedures were 63.7 ± 9.7, 62.3 ± 10.4 and, 50.2 ± 9.6 mL/kg, respectively (P < 0.05 for GE and 4-Y vs. 4+Y). The mean difference between the O2 deficits estimated from the 4-Y and GE procedure -1.4 ± 3.9 mL/kg, and between the 4+Y and GE procedures was -13.5 ± 2.5 mL/kg.  Corresponding typical errors for the two comparisons were 2.74% and 1.74% while the intra-class correlation coefficients together with linear equations were r = 0.93 (0.99x – 0.8) for [4-Y vs. GE] and r = 0.97 (0.95x - 10.5) for [4+Y vs. GE].

Discussion

The main finding of the current study was the high agreement between the 4-Y and GE procedures which is in contrast to previous findings of Noordhof et al. (2011). Moreover, the inclusion of a Y-intercept for baseline VO2 resulted in a 20% lower O2 deficit compared to the 4-Y and GE procedures.  

References

Andersson E, Björklund G, Holmberg HC, Ørtenblad N. (2016). Scand J Med Sci Sports. Noordhof DA, Vink AM, de Koning JJ. Foster C. (2011). Int J Sports Med, 32, 422-8

INTRODUCTION: The aim of this study was to compare the pacing strategies, choice of sub-technique (i.e., gear) and overall performance between elite male and female cross-country (XC) skiers during a ski-skating sprint time-trial (TT) on snow.

METHODS: Thirty-four elite XC skiers (20 males and 14 females: age, 23 ± 4 and 21 ± 3 yr; body mass, 76 ± 8 and 64 ± 5 kg; height, 183 ± 7 and 171 ± 5 cm; sprint FIS points, 86 ± 42 and 90 ± 54) performed a 1.6 km TT, which was 56% flat (or undulating), 21% uphill and 22% downhill. The sprint course was measured with a differential global navigation satellite system and divided into four flat, three uphill and two downhill sections. Race time was measured with the EMIT timing system (Emit AS, Oslo, Norway) and one 25-m uphill (4°) section was filmed continuously with a fixed camcorder (50 Hz). All skiers used a similar stone-grind and all skis were glide-waxed similarly. The air temperature was +1°C (fresh snow at ±0°C), relative humidity was 90% and the friction coefficient between ski and snow was estimated to 0.045 (i.e., very slow).

RESULTS: Average speed during the TT was 25 ± 1 and 22 ± 1 km/h (TT time: 227 ± 11 and 254 ± 10 s) for males and females, respectively (P < 0.001, Cohen’s d effect size [ES] = 2.6). Average relative power output (PO) was estimated to 3.9 ± 0.3 and 3.3 ± 0.2 W/kg for males and females, respectively (P < 0.001, ES = 2.5). Average heart rate was 95 ± 2% and 96 ± 1% of maximum for males and females (P = 0.51), with a 2-min post-race blood lactate concentration of 10 ± 2 mmol/L for both sexes (P = 0.64). Within-athlete coefficient of variation in speed between sections was 20 ± 2% for males and 24 ± 1% for females (P < 0.001, ES = 2.6). Speeds on the flat, uphill and downhill sections were 26 ± 1, 19 ± 1 and 32 ± 1 km/h for males and 23 ± 1, 16 ± 1 and 30 ± 1 km/h for females (main effects for terrain, sex and interaction, all P < 0.01) corresponding to 9%, 16% and 8% slower speeds on flat, uphill and downhill terrain for females. Speeds relative to the average TT speed were 103 ± 1%, 77 ± 2% and 129 ± 4% for males and 105 ± 1%, 72 ± 2% and 133 ± 2% for females (main effects for terrain, sex and interaction, all P < 0.001). Relative PO on the flat, uphill and downhill sections were estimated to 4.0 ± 0.3, 4.9 ± 0.4 and 1.9 ± 0.2 W/kg for males and 3.5 ± 0.2, 4.0 ± 0.3 and 1.5 ± 0.2 W/kg for females (main effects for terrain, sex and interaction, all P < 0.001). The males were 20% faster than the females on the uphill video section (16 ± 1 versus 13 ± 1 km/h, P < 0.001, ES = 2.6), with 95% of the male skiers and 21% of the female skiers using gear 3 exclusively, and the remaining skiers using gear 2 exclusively or a combination of gears 2 and 3.

CONCLUSION: The present results indicate an overall sex difference in sprint skiing performance of ~12% and reveal differences in terrain-specific pacing as well as gear choice between sexes with females showing a higher overall variation in speed and considerably slower uphill skiing.

Purpose: This study aimed to compare physiological factors and cycle characteristics during cross-country (XC) roller-skiing at matched inclines and speeds using the double-poling (DP) and diagonal-stride (DS) sub-techniques in junior female and male XC skiers. Methods: Twenty-three well-trained junior XC skiers (11 women, 12 men; age 18.2 ± 1.2 yr.) completed two treadmill roller-skiing tests in a randomized order using either DP or DS. The exercise protocols were identical and included a 5 min warm-up, 4 × 5 min submaximal stages, and an incremental test to exhaustion, all performed at a 5° incline. Results: No significant three-way interactions were observed between sex, submaximal exercise intensity, and sub-technique. For the pooled sample, higher values were observed for DP versus DS during submaximal exercise for the mean oxygen uptake kinetics response time (33%), energy cost (18%), heart rate (HR) (9%), blood lactate concentration (5.1 versus 2.1 mmol·L−1), rating of perceived exertion (12%), and cycle rate (25%), while cycle length was lower (19%) (all P &lt; 0.001). During the time-to-exhaustion (TTE) test, peak oxygen uptake (V˙ O2peak), peak HR, and peak oxygen pulse were 8%, 2%, and 6% lower, respectively, for DP than DS, with a 29% shorter TTE during DP (pooled data, all P &lt; 0.001). Conclusion: In well-trained junior XC skiers, DP was found to exert a greater physiological load than DS during uphill XC roller-skiing at submaximal intensities. During the TTE test, both female and male athletes were able to ski for longer and reached markedly higher V˙ O2peak values when using DS compared to DP. 

Background: In the last decade, a growing body of research has focused on the many aspects and challenges of combining parenthood with elite sport. Although the number of father-athletes is significantly higher than the number of mother-athletes, few studies to date have focused on male athletes’ experiences in a parenting context. Aim: The aims of the present study were to explore how father-athlete challenges manifest among elite Nordic skiers in Norway, and to better understand how male athletes balance their priorities as they initiate, maintain, and/or discontinue their athletic career as a father-athlete. Methods: Qualitative data were collected through semi-structured interviews with 10 world-class male Nordic skiers in Norway (3 athletes without a child, 4 current father-athletes and 3 former father-athletes) and the content was analyzed using thematic analysis. Results: Four main stages were identified in the father-athlete transition: (a) Expecting incompatibility (b) Taking the step, (c), The first blow, and (d) Finding the optimal balance. Through these stages the informants expected/had experienced challenges such as performance decline, disturbed sleeping patterns, fear of sickness and role conflicts. To manage these challenges, the father-athletes had developed various strategies to balance their dual roles (e.g., adapting training and competition seasons). Among the benefits, the father-athletes mentioned that they had become more structured, time efficient and ruthless with their priorities, enhanced motivation to train and a better work-life balance. Conclusion: This study offers valuable insights into father-athlete challenges that can be used to support career longevity and work-life balance among male athletes. 

Challenges facing mother-athletes (MAs) have aroused research and media attention in recent years, with an increasing number of sportswomen attempting to successfully combine pregnancy and motherhood with an elite athletic career. The aims of this study were to explore how MA-specific challenges manifest in elite cross-country skiing in Scandinavia and to better understand how female athletes balance their priorities as they initiate, maintain, and/or discontinue their role as a MA. Qualitative data were collected through semistructured interviews with 13 female cross-country skiers from Norway and Sweden. Thematic analyses revealed four MA-specific challenges facing the athletes: (a) Biological clock versus peak performance, (b) Maintaining fitness versus training safely, (c) Receiving support versus facing deselection, and (d) Balancing competing MA demands. Many of the athletes felt pressured into prioritizing either motherhood or athletic excellence, particularly in their early to mid-30s when the window of opportunity for building a family was considered limited. Further, maintaining fitness and training safely during pregnancy were perceived as a challenge, as was balancing the MA role after childbirth. In many cases, athletes felt uncertain about whether they would receive support from their team or federation. Moreover, there were expectations of incompatibility surrounding the MA role. More research and educational efforts to promote MA-specific knowledge, as well as developing structured processes and providing policies to support female athletes, are identified as vital future steps. These measures may prolong athletic careers and enhance well-being for elite female athletes.

The mother-athlete (MA) dilemma is a social phenomenon that has emerged due to challenges associated with pregnancy and motherhood during a woman’s athletic career. The aims of this study were to explore how MA dilemmas manifest in elite cross-country skiing in Scandinavia and to better understand how female athletes balance their priorities as they initiate, maintain and/or discontinue their role as a MA. Qualitative data was collected through semi-structured interviews with 13 Swedish and Norwegian female cross-country skiers. Thematic analyses revealed four MA-specific dilemmas facing the athletes:

1. Biological clock vs. peak performance

2. Maintaining fitness vs. training safely

3. Receiving support vs. facing deselection

4. Balancing competing MA demands.

Many of the athletes felt pressured into prioritising either athletic excellence or motherhood, particularly in their early to mid-thirties when the window of opportunity for building a family was considered limited. Further, maintaining fitness and training safely during pregnancy (without risking the unborn baby’s health) was perceived as a challenge, as was balancing the MA role after childbirth (i.e., achieving a successful athletic career and being a good mother). In many cases athletes felt uncertain about the support they may or may not receive from their team or federation and there were expectations of incompatibility surrounding the MA role. More research and educational efforts to promote MA-specific knowledge, as well as developing structured processes and providing policies to support female athletes, are identified as vital steps. These interventions may prolong athletic careers and enhance wellbeing for elite female athletes.

Background: Beetroot juice (BJ) and caffeine (CAF) are considered as ergogenic aids among athletes to enhance performance, however, the ergogenic effects of BJ and CAF co-ingestion are unclear during team-sport-specific performance. This study aimed to investigate the acute effects of BJ and CAF co-ingestion on team-sport-specific performance, compared with placebo (PL), BJ, and CAF alone. Method: Sixteen semi-professional male soccer players (age: 19.8 ± 2.2 years, body mass: 69.2 ± 6.1 kg, height: 177.3 ± 6.0 cm) completed four experimental trials using a randomized, double-blind study design: BJ + CAF, CAF + PL, BJ + PL, and PL + PL. Countermovement jump with arm swing (CMJAS) performance and cognitive function by Stroop Word-Color test were evaluated before and after the Yo–Yo Intermittent Recovery Test level 1 (YYIR1). Also, rate of perceived exertion (RPE), heart rate, and gastrointestinal (GI) discomfort were measured during each session. Results: No significant differences were shown between test conditions for total distance covered in YYIR1 (BJ + CAF: 1858 ± 455 m, CAF + PL: 1798 ± 422 m, BJ + PL: 1845 ± 408 m, PL + PL 1740 ± 362 m; p = 0.55). Moreover, CMJAS performance, cognitive function, and RPE during the YYIR1 were not significantly different among conditions (p > 0.05). However, the average heart rate during the YYIR1 was higher in CAF + PL compared to PL + PL (by 6 ± 9 beats/min; p < 0.05), and GI distress was greater in BJ + CAF compared to PL + PL (by 2.4 ± 3.6 a.u.; p < 0.05). Conclusion: These results suggest, neither acute co-ingestion of BJ + CAF nor BJ or CAF supplementation alone significantly affected team-sport-specific performance compared to the PL treatment. 

This study investigated the energy, macronutrient and fluid intakes, as well as hydration status (urine specific gravity; USG), in elite cross-country skiers during a typical day of training (day one) and a sprint skiing competition the following day (day two). Thirty-one (18 male and 13 female) national team skiers recorded their food and fluid intakes and USG was measured on days one and two. In addition, the females completed the Low Energy Availability in Females-Questionnaire (LEAF-Q) to assess their risk of long-term energy deficiency. Energy intake for males was 65+/-9 kcal/kg on day one versus 58+/-9 kcal/kg on day two (P=0.002), and for females was 57+/-10 on day one versus 55+/-5 kcal/kg on day two (P=0.445). Carbohydrate intake recommendations of 10-12 g/kg/day were not met by 89% of males and 92% of females. All males and females had a protein intake above the recommended 1.2-2.0 g/kg on both days, and a post-exercise protein intake above the recommended 0.3 g/kg. Of the females, 31% were classified as being at risk of long-term energy deficiency. In the morning of day one, 50% of males and 46% of females were dehydrated; on day two this was the case for 56% of males and 38% of females. In conclusion, these data suggest that elite cross-country skiers ingested more protein and less carbohydrate than recommended, and one third of the females were considered at risk for long-term energy deficiency. Furthermore, many of the athletes were dehydrated prior to training and competition.

Introduction: Habitual nutritional intakes in cross-country skiers have previously been reported (Fogelholm et al., 1992), however in elite cross-country skiers there is limited knowledge about race-specific nutritional practices, or the prevalence of dehydration and persistent low energy availability (EA). This study aimed to investigate, in the context of a simulated sprint race, energy intake, macronutrient intake, hydration status and the risk of persistent low EA in elite cross-country skiers. Methods: Thirty-two male (n = 18) and female (n = 14) elite Swedish cross-country skiers completed weighed food records the day prior to (day 1) and the day of a simulated sprint race (day 2); the food records were analysed for energy (kcal/kg), macronutrient (g/kg) and fluid intake (L). Urine specific gravity (USG) was also measured on day 1 and day 2. The risk for persistent low EA was assessed in the female skiers using the Low Energy Availability in Females Questionnaire (LEAF-Q; Melin et al., 2014). Results were analysed using a three-way mixed ANOVA. Statistical significance was set to a level of p ≤ 0.05. Results: Males had a higher energy intake (65±9 kcal/kg) on day 1, (pre-race) compared with day 2 (simulated sprint race; 58±9kcal/kg; p = 0.002). Females consumed 57±10 kcal/kg on day 1, which was similar to their day 2 energy intake (54±6 kcal on day 2; p > 0.05). Males consumed less carbohydrate (8.2±2.3g/kg) on day 1 compared with day 2 (8.9±2.3g/kg) (p = 0.026), as did females, consuming 7.0±1.5g/kg on day 1, and 8.4±1.7g/kg on day 2 (p = 0.003). There were similar fluid intakes across the two days for males (p > 0.05) and females (p > 0.05). Nine of the 18 males and 6 of the 14 females were dehydrated (USG > 1.020) on day 1, and 9 males and 5 females were dehydrated on day 2. Five of the 14 females were classified as being at risk of persistent low EA. Discussion: This study provides an initial insight into nutritional competition habits in elite cross-country skiers. The findings indicate that elite skiers’ nutritional intakes are consistent with guidelines, particularly those for endurance athletes’ carbohydrate intake for competitive events (Burke et al., 2001). There was however some evidence of persistent low EA and dehydration, suggesting additional considerations that may be relevant to cross-country skiers’ nutritional intakes for sprint races.

Purpose: The aim of this study was to examine the relationships between health problems, defined as injury or illness, on performance during a competitive season among elite XC skiers (9 females; 9 males).

Methods: Data was collected for 17 weeks using the Oslo Sports Trauma Research Center questionnaire on health problems, resulting in a total of 296 athlete weeks’ worth of data. Prevalence and severity measures were calculated for all health problems and substantial health problems (defined as problems leading to moderate or severe reductions in training volume or sports performance, or complete inability to participate). Acssociations between health problems and performance were analyzed using regressions with change in FIS points from the 2018/19 season to the 2019/20 season, representing performance.

Results: The average weekly prevalence of all health problems was 19% (95% CI: 3.5% to 34%). Prevalence of substantial health problems was 12% (95% CI: -0.4% to 25%). Illness was the most common health problem, representing 74 days (71%) of total time loss compared to overuse injuries (12 days, 12%) and acute injuries (18 days, 17%). There was no significant association between the cumulative severity score of health problems (-0.03; 95% CI: -0.08 to 0.02; p = 0.25).

Conclusions: No relationship was identified between the cumulative severity of health problems and performance.

Practical applications: The findings from this study suggest that ongoing surveillance programs could be useful in mapping athlete injury and illness trends.

The purpose of this study was to establish whether critical power, as traditionally determined from the performance of three constant-load tests to exhaustion, is attained at the end of a 90-s all-out test in children. Sixteen healthy children (eight males and eight females; mean age 12.3 years, s_x  = 0.1; body mass 39.6 kg, s_x  = 1.8; peak VO₂ 2.0 litres · min⁻¹, s_x  = 0.1) completed an incremental test to exhaustion to determine peak oxygen uptake (peak VO₂), three separate constant-load tests to exhaustion to calculate critical power, and an isokinetic 90-s all-out test. The end power of the 90-s test averaged over the last 10 s (140 W, s_x  = 8) was significantly higher than critical power (105 W, s_x  = 6; t = 6.8; P < 0.01), yet the two parameters were strongly correlated (r = 0.74; P < 0.01). After 60 s, there were no further reductions in power output during the 90-s test (P < 0.0001). In conclusion, at the end of a 90-s all-out test, children are able to produce power outputs well above critical power. This suggests that 90 s is not long enough to completely exhaust the anaerobic work capacity in children.

This study investigated whether commercially available compression garments (COMP) exerting a moderate level of pressureand/or neuromuscular electrical stimulation (NMES) accelerate recovery following a cross-country sprint skiing competitioncompared with a control group (CON) consisting of active recovery only. Twenty-one senior (12 males, 9 females) and 11junior (6 males, 5 females) Swedish national team skiers performed an outdoor sprint skiing competition involving foursprints lasting ∼3–4 min. Before the competition, skiers were matched by sex and skiing level (senior versus junior) andrandomly assigned to COMP (n = 11), NMES (n = 11) or CON (n = 10). Creatine kinase (CK), urea, countermovementjump (CMJ) height, and perceived muscle pain were measured before and 8, 20, 44 and 68 h after competition. NeitherCOMP nor NMES promoted the recovery of blood biomarkers, CMJ or perceived pain post-competition compared withCON (all P > .05). When grouping all 32 participants, urea and perceived muscle pain increased from baseline, peaking at8 h (standardised mean difference (SMD), [95% confidence intervals (CIs)]): 2.8 [2.3, 3.2]) and 44 h (odds ratio [95%CI]: 3.3 [2.1, 5.1]) post-competition, respectively. Additionally, CMJ was lower than baseline 44 and 68 h postcompetitionin both males and females (P < .05). CK increased from baseline in males, peaking at 44 h (SMD: 1.4 [−0.4,0.9]), but was decreased in females at 20 h post-competition (SMD: −0.8 [−1.4, −0.2]). In conclusion, cross-countrysprint skiing induced symptoms of exercise-induced muscle damage peaking 8–44 h post-competition. However, neitherCOMP nor NMES promoted physiological or perceptual recovery compared with CON.

Purpose: To investigate whether compression garments (CG) and neuromuscular electrical stimulation (NMES) augment post-race recovery compared with a passive control group (CON) following a cross-country sprint skiing competition. Methods: Twenty-one senior (12 males, 9 females) and 11 junior (6 males, 5 females) Swedish national team skiers performed a sprint skiing competition involving four, ~3-4 min sprints. After the race, skiers were matched by sex and skiing level (senior versus junior) and randomly assigned to a CON (n = 10), CG (n = 11) or NMES group (n = 11). Creatine kinase (CK) and urea, countermovement jump height (CMJ) and perceived sleep duration, sleep quality and muscle pain were measured before and 8, 20, 44 and 68 h after the race to assess the efficacy of each recovery intervention. Results: Neither CG nor NMES promoted the recovery of blood biomarkers, perceived wellness nor CMJ post-race compared with the passive control group (all P < 0.05). When grouping all 32 participants, CK, urea and muscle pain increased from pre-race values, peaking 20-44 h post-race (P < 0.05). CMJ was lower than pre-race values 44 and 60 h post-race in males and females (both P < 0.05). Sleep duration increased from pre-race to post-race (P < 0.05), whereas sleep quality was unchanged (P > 0.05). Conclusion: A cross-country sprint skiing competition induced symptoms of exercise-induced muscle damage peaking 20-44 h post-race. However, CG and NMES did not augment the recovery of physiological, perceptual or performance parameters compared with a passive control group after the sprint skiing competition.

Splenic contraction, which leads to ejection of stored erythrocytes, is greater in athletes involved in regular freediving or high-altitude activities. As this response facilitates oxygen-carrying capacity, similar characteristics may be expected of elite endurance athletes. Therefore, our aims were to compare resting and apnea-induced splenic volume in endurance athletes and untrained individuals, and to assess the athletes' exercise-induced splenic volume. Twelve elite biathletes (7 women) and 12 controls (6 women) performed a maximal effort apnea in a seated position. In addition, the biathletes completed a maximal roller-skiing time trial. Splenic dimensions were measured by ultrasonic imaging for subsequent volume calculations, whereas Hb was analyzed from capillary blood samples and cardiorespiratory variables were monitored continuously. Baseline splenic volume was larger in the biathletes (214 +/- 56 mL) compared with controls (157 +/- 39 mL, P = 0.008) and apnea-induced splenic contraction was also greater in the biathletes (46 +/- 20 mL vs. 30 +/- 16 mL, P = 0.035). Hb increased immediately after apnea in the biathletes (4.5 +/- 4.8%, P = 0.029) but not in the controls (-0.7 +/- 3.1%, P = 0.999). Increases in exercise-induced splenic contraction (P = 0.008) and Hb (P = 0.001) were greater compared with the apnea-induced responses among the athletes. Baseline splenic volume tended to be correlated with <(V)over dot>o(2max) (r= 0.584, P = 0.059). We conclude that elite biathletes have greater splenic volume with a greater ability to contract and elevate Hb compared with untrained individuals. These characteristics may transiently enhance O-2-carrying capacity and possibly increase O-2 uptake, thereby helping biathletes to cope with high intermittent O-2 demands and severe O-2 deficits that occur during biathlon training and competition. NEW & NOTEWORTHY This study demonstrates that elite biathletes have larger splenic volume, apnea-induced splenic contraction, and Hb elevation compared with untrained individuals, which is likely functional to cope with high O-2 demands and substantial O-2 deficits. We believe that enhanced splenic contraction may be of importance during competitions involving crosscountry skiing, to regulate circulating Hb and enhance O-2-carrying capacity, which may protect Ca-O2, and increase O-2 uptake.

DesignProspective, observational.SettingBaseline monitoring at <500 m for 2 weeks and altitude monitoring at 1800 m for 17-22 days.

ParticipantsThirty-three senior national-team endurance athletes (mean age 25.8 ± S.D. 2.8 years, 16 women).

MeasurementsDaily measurements of sleep (using a microwave Doppler radar at baseline and altitude), oxygen saturation (SpO2), training load and subjective recovery (at altitude).

ResultsAt altitude vs. baseline, sleep duration (P = .036) and light sleep (P < .001) decreased, while deep sleep (P < .001) and respiration rate (P = .020) increased. During the first altitude week vs. baseline, deep sleep increased (P = .001). During the first vs. the second and third altitude weeks, time in bed (P = .005), sleep duration (P = .001), and light sleep (P < .001) decreased. Generally, increased SpO2 was associated with increased deep sleep while increased training load was associated with increased respiration rate.

ConclusionThis is the first study to document changes in sleep from near-sea-level baseline and during a training camp at 1800 m in elite endurance athletes. Ascending to altitude reduced total sleep time and light sleep, while deep sleep and respiration rate increased. SpO2 and training load at altitude were associated with these responses. This research informs our understanding of the changes in sleep occurring in elite endurance athletes attending training camps at competition altitudes.

Purpose: This study aimed to compare physiological factors and cycle characteristics during cross-country (XC) roller-skiing at matched inclines and speeds using the double-poling (DP) and diagonal-stride (DS) sub-techniques in male and female XC skiers.

Methods: Following familiarization to treadmill roller-skiing, 23 well-trained junior XC skiers (12 males, 11 females; age 18.2 ± 1.2 y) completed two roller-ski tests in a randomized order using either DP or DS. The exercise protocols were identical and included a 5-min warm-up, 4 x 5-min submaximal stages and an incremental test to exhaustion all performed at a 5° incline.

Results: Submaximal energy cost, mean O2 kinetics response time, blood lactate concentration, heart rate (HR), rating of perceived exertion and cycle rate were all significantly lower during DS compared to DP, while cycle length was significantly higher (all P<0.001). In addition, O2peak and peak HR were higher and time to exhaustion was longer during DS compared to DP (all P<0.001).

Conclusion: In well-trained junior XC skiers, DP was found to exert a greater physiological load than DS during uphill XC roller-skiing at submaximal intensities. Moreover, athletes were able to ski for longer and reached markedly higher O2peak and HR values during incremental exercise to exhaustion when using DS compared to DP.

Practical application: It is important to consider the specific demands of DS and DP when planning and implementing training programs and sessions, as these two sub-techniques elicit distinct responses among junior XC skiers.

Competitive female athletes perceive their hormonal cycles to affect their training, com-petition performance and overall well-being. Despite this, athletes rarely discuss hormonal-cycle-related issues with others. The aim of this study was to gain an in-depth understanding of the perceptions and experiences of endurance athletes and their coaches in relation to barriers to athlete– coach communication about female hormonal cycles. Thirteen Swedish national-/international-level female cross-country skiers (age 25.8 ± 3.6 y) and eight of their coaches (two women and six men; age 47.8 ± 7.5 y) completed an online survey relating to their educational background, prior knowledge about female hormonal cycles and a coach–athlete relationship questionnaire (CART-Q). They then participated in an online education session about female hormonal cycles and athletic performance before participating in semi-structured focus-group interviews. Thematic analyses revealed three main barriers to communication: knowledge, interpersonal, and structural. In addition, the results suggested that a good coach–athlete relationship may facilitate open communication about female hormonal cycles, while low levels of knowledge may hinder communication. To over-come the perceived barriers to communication, a model is proposed to improve knowledge, de-velop interpersonal relationships and strengthen structural systems through educational exchanges and forums for open discussion. 

INTRODUCTION: Athletes may suffer from mental illnesses, eating disorders, low energy availability and/or hormonal symptoms (1-3), all of which negatively affect health and performance. Knowledge about these issues is limited among coaches and athletes, which makes attempts to solve problems difficult. Education is recommended to increase the willingness of athletes and coaches to communicate about sensitive or “taboo” topics (4), but information about how best to educate these individuals is limited. The overall aim of this project was to develop, implement and evaluate a programme of education using an action research approach (5). This paper critically discusses the application of action research when seeking to develop such education programmes.

METHODS: Action research is the process of using collaborative work to create change to address meaningful substantive issues. It involves the use of systematic enquiry to introduce and evaluate change, whilst also generating new knowledge in relation to that change. Initial insights into the education needs of the participants (32 female and male junior cross-country skiers and their 2 female and 2 male coaches) were gained by the lead author through observations, informal conversations, and a survey. Further data was then collected using a reflective journal, informal conversations, feedback, focus groups and mind-mapping. A series of educational presentations were developed and shared with the participants throughout the data collection process.

RESULTS: Initial results from this study demonstrate that action research is beneficial for supporting the development of an education programme where athletes, coaches and researchers work closely together to co-create and evaluate specific content. In this sports performance setting, the education programme was effective at increasing knowledge and communication between athletes and coaches regarding a range of sensitive topics, which have typically been considered “taboo”.

DISCUSSION: Action research is useful for developing education programmes pertaining to sensitive or “taboo” issues, thereby facilitating increased knowledge, communication and problem-solving opportunities among athletes and coaches.

 REFERENCES: 

1.    Gouttebarge, V. et al. 2019 Br. J. Sports Med

2.    Logue, D. et al. 2018 Sports Med

3.    Solli, G.S. et al. 2020 Int. J. Sports Phys. Perf.

4.    Höök, M. et al. 2021 Int. J. Environ. Res. Public Health

5.    Macisaac, D. & Bodner, G.M., 1999 Moscow University Chemistry Bulletin

Purpose: To determine body composition, energy availability, training load, and menstrual status in young elite endurance running athletes (ATH) over 1 year, and in a secondary analysis, to investigate how these factors differ between nonrunning controls (CON), amenorrheic (AME), and eumenorrheic (EUM) ATH. Correlations to injury, illness, and performance were also examined. Methods: 13 ATH and 8 CON completed the Low Energy Availability in Females Questionnaire. Anthropometric, energy intake, and peak oxygen uptake assessments were made at 4 time points throughout the year: at baseline post competition season, post general preparation, post-specific preparation, and post competition season the following year. Logs of physical activity, menstrual cycle, illness, and injury were kept by all participants. Performance was defined using the highest International Association of Athletics Federations points prior to and after the study. Results: ATH had significantly lower body mass (P=.008), fat percentage (P<.001), and body mass index (P=.027) compared with CON, while energy availability did not differ between ATH and CON. The Low Energy Availability in Females Questionnaire score was higher in ATH than in CON (P=.028), and 8 ATH (vs zero CON) were AME. The AME had significantly more injury days (P=.041) and ran less (P=.046) than EUM, while total annual running distance was positively related to changes in performance in ATH (r=.62, P=.043, n=11). Conclusions: More than half of this group of runners was AME, and they were injured more and ran less than their EUM counterparts. Furthermore, only the EUM runners increased their performance over the course of the year.

The purpose of the present study was to analyze micro-pacing strategies in cross-country skiing, and their relation to section and total race times. Eleven competitive female cross-country skiers were tracked during a classic sprint time-trial race using a global navigation satellite system (GNSS) unit. A coordinate mapping procedure was applied to the GNSS unit measurements to analyze the instantaneous velocities and split times. The track was divided into nine sections and individual section times were calculated. Statistical parametric mapping (SPM) was used to analyze the relationships between instantaneous velocity and section or total race time. SPM analyses revealed two uphill sections and one flat section where greater instantaneous velocities were related to faster total race times. The first major uphill section on the track demonstrated a more conservative micro-pacing strategy (SPM supra-threshold clusters along the entire uphill, p < 0.05–0.001) compared to the more aggressive strategy used in the last uphill section (clusters on the first half of the uphill, p < 0.05–0.001). Faster flat section times were associated with greater instantaneous velocities throughout the section (p < 0.001), while faster downhill section times were related to greater instantaneous velocities at the top of the downhill (p < 0.001), and in the downhill turns (p < 0.001). In conclusion, micro-pacing strategies were related to overall skiing performance and distinct track sections were identified where instantaneous velocities were related to section or total race times. In order to improve skiing performance, athletes could focus on more aggressive pacing early on in the “end spurt”, during the transitions from uphill to flat sections, and during the transitions from flat or uphill to downhill sections.

Purpose: To provide a descriptive account of the warm up strategies (WU) employed by cross country skiers prior to distance and sprint competitions at a national championship; analyze the skiers’ planned WU; compare skiers’ planned and actual WUs carried out prior to the respective  competitions.

Methods: Twenty-one national- and international-level skiers (11 females and 10 males) participated. Skiers submitted WU plans prior to the competitions and reported any deviations from the plans after the respective competitions. Participants used personal hear rate (HR) monitors to record HR and were instructed to start the recording upon starting the WU and end the data collection following their cool down after the competition.

Results: Skiers’ planned WU for the distance and sprint competitions were of similar content and planned time in HR derived intensity zones. Skiers spent similar durations within the lowest zone (A1, 60–74% peak HR) as planned for distance and sprint competitions. Prior to the sprint competition skiers spent significantly (p < 0.05) less time than planned in the highest intensity domain (A3+, >95% peak HR). Forty five % of female and 20% of male skiers reported their WU was not carried out as planned.

Conclusions: Planned WU were not sufficiently tailored for the differing demands of distance and sprint competition. Prior to the sprint competition skiers failed to accumulate the planned volume of high intensity work (time in A3+).

Practical applications: Skiers examined here would benefit from more bespoke WU, tailored to the specific demands of distance and sprint competition.

Purpose: To provide a descriptive analysis of the warm-up (WU) strategies employed by cross-country skiers prior to distance and sprint competitions at a national championship and to compare the skiers' planned and executed WUs prior to the respective competitions.

Methods: Twenty-one national- and international-level skiers (11 women and 10 men) submitted WU plans prior to the distance and sprint competitions, and after the competitions, reported any deviations from the plans. Skiers used personal monitors to record heart rate (HR) during WU, races, and cooldown. Quantitative statistical analyses were conducted on WU durations, durations in HR-derived intensity zones, and WU loads. Qualitative analyses were conducted on skiers' WU plans and their reasons for deviating from the plans.

Results: Skiers' planned WUs were similar in content and planned time in HR-derived intensity zones for both the distance and sprint competitions. However, 45% of the women and 20% of the men reported that their WU was not carried out as planned, with reasons detailed as being due to incorrect intensities and running out of time. WU activities including skiing across variable terrain, muscle-potentiating exercises, and heat-maintenance strategies were missing from the skiers' planned routines.

Conclusions: Skiers favored a long, traditional WU approach for both the sprint and distance events, performing less high-intensity and more moderate-intensity exercise during their WUs than planned. In addition, elements likely relevant to successful performance in cross-country skiing were missing from WU plans.

Purpose This study aimed to describe changes in laboratory-assessed anthropometric and physiological characteristics, training volumes, and competitive performance in national development-team cross-country skiers over a 25-month period, and to analyze whether changes in competitive performance could be predicted by changes in laboratory-assessed qualities and training volumes.

Methods Data collected over 25 months from 30 national development-team cross-country skiers (14 women, 16 men; age, 18–23 yr) were analyzed retrospectively using multivariate statistics. Anthropometric and physiological characteristics were assessed via dual-energy x-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Total training volumes and distributions of low- and high-intensity training were analyzed from online training diaries, and competitive performance was determined by International Ski Federation (FIS) distance and sprint points.

Results Whole- and upper-body lean mass increased in the full cohort of skiers (n = 30; both P < 0.05), whereas lower-body lean mass, whole-body fat mass, speed and oxygen uptake (V˙O2) at a blood lactate concentration (BLa) of 2 and 4 mmol·L−1, as well as time-trial completion time, power output, and peak V˙O2, improved in the women only (all P < 0.05). Valid predictive models were identified for female skiers’ best FIS distance points (R2 = 0.81/Q2 = 0.51) and changes in FIS distance points (R2 = 0.83/Q2 = 0.54), with body mass, fat mass, lean mass, V˙O2peak, and speed at a BLa of 4 mmol·L−1 identified as consistently important variables for projection.

Conclusions The valid prediction of competitive performance was achieved for women only in distance events. This study suggests that improvements in body composition and aerobic capacity may be more beneficial for elite female development-level skiers than for their male counterparts. These results have implications for athlete selection and performance development.

Purpose: To determine whether competitive performance, as defined by International Biathlon Union (IBU) and International Ski Federation (FIS) points in biathlon and cross-country (XC) skiing, respectively, can be projected using a combination of anthropometric and physiological metrics. Shooting accuracy was also included in the biathlon models. Methods: Data were analyzed using multivariate methods from 45 (23 female and 22 male) biathletes and 202 (86 female and 116 male) XC skiers who were all members of senior national teams, national development teams, or ski-university or high school invite-only programs (age range: 16-36 y). Anthropometric and physiological characteristics were assessed via dual-energy X-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Shooting accuracy was assessed via an outdoor standardized testing protocol. Results: Valid projective models were identified for female biathletes' IBU points (R2 = .80/ Q2 = .65) and female XC skiers' FIS distance (R2 = .81/Q2 = .74) and sprint (R2 = .81/Q2 = .70) points. No valid models were identified for the men. The most important variables for the projection of IBU points were shooting accuracy, speeds at blood lactate concentrations of 4 and 2 mmol center dot L-1, peak aerobic power, and lean mass. The most important variables for the projection of FIS distance and sprint points were speeds at blood lactate concentrations of 4 and 2 mmol center dot L-1 and peak aerobic power. Conclusions: This study highlights the relative importance of specific anthropometric, physiological, and shooting-accuracy metrics in female biathletes and XC skiers. The data can help to identify the specific metrics that should be targeted when monitoring athletes' progression and designing training plans.

Previous research has indicated that pacing strategies within biathlon are influenced by terrain. However, it is not known if biathletes shooting performance within competition influences any pacing strategies employed. As such, the purpose of this study was to assess the impact of shooting performance on skiing speed and pacing strategies within sprint and individual competitionin elite female biathletes. Global navigation satellite system (GNSS) and heart data were collected during the female sprint and individual competitions of the 2019 IBU World Championships. Eight female biathletes (age 27 ± 2 years, IBU points 45 ± 18) competing in the sprint and individual events of the 2019 IBU World Championships volunteered and gave their written informed consent to participate in the study. Statistical analyses were conducted on shooting bout accuracy and speed and GNSS data to determine whether the accuracy and speed of the shooting bout influenced skiing speed in the subsequent lap of the race. No significant differences in skiing speed nor pacing strategies were observed subsequent to accurate or inaccurate shooting bouts, furthermore no significant differences in skiing speed were observed subsequent to fast or slow shooting bouts. As such, it appears in the biathletes assessed here, skiing speed and pacing was independent of shooting performance, although this was observed in a small sample of female biathletes.

Purpose

The purpose was to investigate whether an increased amount of training while carrying the rifle affects skiing in well-trained biathletes at submaximal and maximal workloads during a pre-season period lasting a minimum of 12 weeks.

Methods

Seventeen well-trained biathletes (9 females, 8 males) were assigned to an intervention (IG, n = 10) or control (CG, n = 7) group. Before (T1) and after (T2) the training intervention all participants performed, using treadmill roller-skiing, a submaximal test without the rifle on one day and two submaximal workloads and a maximal time trial (TT) with the rifle on a subsequent day. Between T1 and T2 all participants performed a minimum of 12 weeks of normal training, the only difference between groups being that IG performed more of their training sessions carrying the rifle.

Results

IG performed more training compared to CG (15.4 ± 1.1 vs. 11.2 ± 2.6 h/week, P < 0.05), including a higher amount of training with the rifle (3.1 ± 0.6 vs. 1.1 ± 0.3 h/week, P < 0.001). Speed at 4 mmol/L of blood lactate increased significantly for CG from T1 to T2 (P = 0.028), while only tended to increase for IG (P = 0.058). Performance during the TT, VO2max and the aerobic metabolic rate increased significantly from T1 to T2, although the differences disappeared when including the speed at baseline as a covariate.

Conclusion

According to the present results, increasing training while carrying the rifle by 2 h/week does not appear to improve skiing performance in well-trained biathletes. In addition, physiological markers at submaximal and maximal intensities while carrying the rifle were not affected after the training intervention.

Purpose: This study aimed to investigate the physiological factors affected by rifle carriage during biathlon skiing performance, as well as the sex differences associated with rifle carriage.

Methods: Seventeen national- and international-level biathletes (nine females and eight males; age 23.0 ± 3.3 years, V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2max 59.4 ± 7.6 mL.kg–1.min–1) performed a submaximal incremental test and a maximal time-trial (TT) using treadmill roller-skiing (gear 3, skating technique) on two occasions separated by at least 48 h. One condition involved carrying the rifle on the back (WR) and the other condition no rifle (NR) and the tests were randomized. Submaximal V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2, skiing speed at 4 mmol.L–1 of blood lactate (speed@4mmol), gross efficiency (GE), aerobic (MRae), and anaerobic (MRan) metabolic rates, and V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2max were determined.

Results: Submaximal V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 (at all intensities) and GE (16.7 ± 0.9 vs. 16.5 ± 1.1%) were higher for WR compared to NR (p < 0.05), while speed@4mmol was lower (3.1 ± 0.4 vs. 3.3 ± 0.5 m.s–1, p = 0.040). TT performance was improved (4.6 ± 0.4 vs. 4.3 ± 0.4 m.s–1, p < 0.001) and MRan was higher (31.3 ± 8.0 vs. 27.5 ± 6.5 kJ.min–1, p < 0.01) for NR compared to WR, with no difference in V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2max or MRae. For skiing WR, TT performance was correlated to speed@4mmol (r = 0.81, p < 0.001), MRan (r = 0.65, p < 0.01), V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2max (r = 0.51, p < 0.05), and relative muscle (r = 0.67, p < 0.01) and fat (r = −0.67, p < 0.01) masses. Speed@4mmol together with MRan explained more than 80% of the variation in TT performance (WR 84%, NR 81%). Despite a higher relative mass of the rifle in females compared with males (5.6 ± 0.4 vs. 5.0 ± 0.4% of body mass, p = 0.012), there were no sex differences associated with rifle carriage measured as absolute or relative differences.

Conclusion: Rifle carriage in biathlon skiing led to significantly higher physiological demands during submaximal exercise and reduced performance during maximal treadmill roller-skiing compared to NR for both sexes. The most important variables for performance in biathlon treadmill skiing seem to be speed@4mmol combined with MRan, both of which were lower for WR compared to NR. To improve skiing performance in biathlon, improving speed at 4 mmol.L–1 of blood lactate and anaerobic energy delivery while carrying the rifle are recommended.

The aim was to investigate whether rifle carriage affects gear distribution during on-snow skiing in highly-trained biathletes, and whether there were any associated sex differences. Twenty-eight biathletes (11 women, 17 men) skied a 2230-m lap at competition speed twice, one lap with the rifle (WR) and the other lap without the rifle (NR). The biathletes wore a portable 3D-motion analysis system while skiing, which enabled characterisation of distance and time in different gears. Skiing WR increased lap time compared to NR (412 (90) vs. 395 (91) s, p < 0.001). The biathletes used gear 2 to a greater extent WR compared to NR (distance: 413 ± 139 vs. 365 ± 142 m; time: 133 (95) vs. 113 (86) s; both p < 0.001) and gear 3 less (distance: 713 ± 166 vs. 769 ± 182 m, p < 0.001; time: 141 ± 33 vs. 149 ± 37 s, p = 0.008), with similar patterns for women and men. Differences between WR and NR in the use of gears 3 and 2 were more extensive for moderate compared to steeper uphill terrain. Rifle carriage increased the use of gear 2, which was negatively associated with performance. Therefore, preparing biathletes to be able to cover more distance in gear 3 WR, especially in moderate uphill terrain, may improve biathlon skiing performance.

INTRODUCTION: A greater usage of gear 3 is associated with improved performance in cross-country skiing. However, it remains unclear whether rifle carriage in biathlon affects sub-technique choice, and therefore biathlon skiing performance. Therefore,this study aimed to investigate whether rifle carriage affects gear distribution during on-snow skiing in biathletes, and whether there are any associated sex differences.

METHODS: Twenty-eight tier 3 biathletes (17 men, 11 women) skied a 2230-m lap at competition speed twice, once with the rifle (WR) and once without the rifle (NR) in a counter-balanced and randomized order. The course was divided into seven uphill sections, three flat sections and seven downhill sections. The biathletes wore aportable 3D-motion analysis system while skiing, which together with GNSS data enabled the characterization of distance covered and time spent in gears 2–4 and skiing without poles (NP). A two-way mixed model ANOVA was used to investigate whether rifle carriage and/or sex influenced gear distribution or performance.

RESULTS: Skiing WR increased the lap time compared to NR (412 (90) vs.395 (91) s, p < 0.001). The biathletes used gear 2 to a greater extent during WR compared to NR (distance: 413 ± 139 vs. 365 ± 142 m; time: 133 (95) vs. 113 (86) s;both p < 0.001) and gear 3 to a lesser extent (distance: 713 ± 166 vs. 769 ± 182 m,p < 0.001; time: 141 ± 33 vs. 149 ± 37 s, p < 0.01) without differences in gear 4 or NP.The women demonstrated a greater proportional use of gear 2 compared to the men (p < 0.05). For the two longest uphill sections, the uphill with a more moderate incline (4.5°) revealed more differences between WR and NR in the use of gears 2 and 3 compared to the uphill with a steeper incline (6.7°). Increased usage of gear 2 (distance and time) was also negatively related to performance during WR and NR (r = 0.516–0.901, p < 0.01).

DISCUSSION/CONCLUSION: Rifle carriage decreases the distance covered and time spent in gear 3 and increases these metrics in gear 2, and the use of gear 2 was negatively related to performance. Rifle carriage had a greater impact on gear distribution when skiing in moderate uphill terrain, where changes between gears 2 and 3 were more common, compared to in steeper terrain. This information can be useful for athletes and coaches when developing and optimizing sport-specific biathlon training to improve performance.

Purpose: This study aimed to investigate how rifle carriage and skiing speed during biathlon roller skiing affect range of motion (ROM) in joint angles and equipment (skis and poles), the vertical distance between shoulders and treadmill (vertdist), as well as possible sex differences associated with rifle carriage. Methods: Fourteen biathletes (6 women, 8 men) roller-skied on a treadmill at submaximal and simulated race speeds, with (WR) and without (NR) a rifle, using gears 3 and 2. Kinematical data for the whole body, poles, roller-skis, rifle, and treadmill were monitored using a 3D motion capture system. Movements determined as flexion/extension (x), abduction/adduction (y), and/or internal/external rotation (z) were analyzed for the hip, shoulder, thorax, knee, ankle, elbow, poles, and roller skis. ROM (the difference between maximal and minimal angles) in joints and equipment, and vertdist were analyzed over six skiing cycles during each condition (WR and NR) and speed. Results: The maximal vertdist was lower for WR compared with NR (gear 3: 1.53 ± 0.06 vs 1.54 ± 0.06 m; gear 2: 1.49 ± 0.06 vs 1.51 ± 0.06 m; both p &lt; 0.001). ROM in the upper body was altered when roller skiing WR (movements decreased in thorax and shoulder (x) and increased in elbow (only gear 3) (x), thorax (only gear 2), and shoulder (y) and (z); all p &lt; 0.05) and increased with speed, without differences between sexes (p &gt; 0.05). Conclusion: Since rifle carriage and speed appear to affect the kinematics of roller skiing, coaches, and biathletes are advised to perform skiing technique training under competition-like conditions (i.e., at race speeds while carrying the rifle). 

Purpose 

This study aimed to investigate how rifle carriage and skiing speed during biathlon roller-skiing affect range of motion (ROM) in joint angles and equipment (skis and poles), the vertical distance between shoulders and treadmill (vertdist), as well as possible sex differences associated with rifle carriage. 

Methods 

Fourteen biathletes (6 women, 8 men) roller-skied on a treadmill at submaximal and simulated race speeds, with (WR) and without (NR) a rifle, using gears 3 and 2. Kinematical data for the whole body, poles, roller-skis, rifle and treadmill were monitored using a 3D motion capture system. Movements determined as flexion/extension (x), abduction/adduction (y) and/or internal/external rotation (z) were analyzed for the hip, shoulder, thorax, knee, ankle, elbow, poles and roller-skis. ROM (the difference between maximal and minimal angles) in joints and equipment, and vertdist were analyzed over six skiing cycles during each condition (WR and NR) and speed. 

Results 

The maximal vertdist was lower for WR compared to NR (gear 3: 1.53±0.06 vs 1.54±0.06 m; gear 2: 1.49±0.06 vs 1.51±0.06 m; both p<0.001). ROM in the upper body was altered when roller-skiing WR (movements decreased in thorax and shoulder (x) and increased in elbow (only gear 3) (x), thorax (only gear 2) and shoulder (y) and (z); all p><0.05) and increased with speed, without differences between sexes (p>0.05). 

Conclusion 

Since rifle carriage and speed appear to affect the kinematics of rollerskiing, coaches and biathletes are advised to perform skiing technique training under competition-like conditions (i.e., at race speeds while carrying the rifle).

Biathlon is an endurance sport combining rifle shooting and intermittent cross-country skiing while carrying a rifle (minimum weight 3.5 kg). Previous studies have shown that the skiing component explains 60% of overall biathlon performance (1) and that rifle carriage affects different physiological responses such as blood lactate, oxygen uptake (VO2) and heart rate during skiing (2, 3). However, the effects of rifle carriage on skiing performance and variables such as maximal VO2 (VO2max), lactate threshold, efficiency of movement and anaerobic energy contribution have not yet been investigated.METHODS:Seventeen biathletes (9 females, 8 males; age 23.0 (3.3) years, VO2max 59.8 (7.3) mL/kg/min), competing at a national and/or international level, and completing approximately three biathlon training sessions/week with the rifle on the back, performed a submaximal incremental test and a 900–1000-m maximal time-trial (TT) using treadmill roller-skiing (gear 3 skating technique) on two occasions separated by at least 48 hours. One condition involved carrying the rifle on the back (WR) and the other no rifle (NR), with the order randomized. The VO2 and skiing speed at 4 mmol/L of blood lactate (VO2@4mmol and speed@4mmol, respectively), gross efficiency (GE), metabolic aerobic (MRae) and anaerobic (MRan) rates, and VO2max were determined. RESULTS:Submaximal VO2 at all levels and GE (16.7 (0.9) vs 16.5 (1.1) %, p<0.05) were higher for WR compared to NR, while speed@4mmol (11.3 (1.5) vs 11.7 (1.5) km/h, p<0.05) and MRan (27.3 (6.7) vs 30.5 (7.6) kJ/min, p<0.01) was lower. There were no differences in VO2@4mmol or MRae between the two conditions. The mean speed during the TT was higher for NR compared to WR (16.5 (1.5) vs 15.5 (1.4) km/h, p<0.001), but there was no difference in VO2max. Mean speed during the TT was correlated to speed@4mmol (WR: r=0.810, p<0.001; NR: r=0.659, p<0.01), GE (WR: r=0.691; NR r=0.529, both p<0.05) and VO2max (WR: r=0.514; NR: r=0.526, both p<0.05). Speed@4mmol together with MRan explained more than 80% of performance in the TT (WR 83.7%, NR 81.5%). There was no difference between male and female biathletes in response to rifle carriage, although the relative mass of the rifle was higher for the females (5.6 (0.4) vs 5.0 (0.4) % of body mass, p<0.01).CONCLUSION:According to this study, the most important variables for skiing speed in biathlon seem to be the speed at lactate threshold combined with the metabolic anaerobic rate, both of which were lower for skiing with the rifle compared to without. In addition, GE was related to biathlon performance and was also affected by rifle carriage. Thus, to improve skiing performance in biathlon, improving speed at the lactate threshold, anaerobic energy delivery and GE while carrying the rifle are recommended.

Background A limited number of long-term prospective studies have investigated health problems in competitive cross-country skiers. Moreover, limited information exists regarding differences in the prevalence and severity of health problems between senior and development female and male cross-country skiers.

Objective To compare the prevalence and severity of health problems between senior and development female and male national team cross-country skiers.

Design Comparative, prospective, observational cohort study.

Setting Senior and development national cross-country ski teams.

Participants Eighteen (9 women, 9 men) senior and 22 (9 women, 13 men) development national team skiers.

Intervention Skiers self-reported their health problems weekly for 17 weeks throughout the 2019/2020 competitive cross-country ski season using the Oslo Sports Trauma Research Center Questionnaire on Health Problems (OSTRC-H2).

Main Outcome Measurements We calculated weekly prevalence and severity measures for illnesses, acute and overuse injuries, substantial health problems (i.e., health problems leading to moderate or severe reductions in training volume or sports performance, or a complete inability to participate) and all health problems combined.

Results Weekly response rate to the OSTRC-H2 was 90% (SD 7%). Average weekly prevalence of substantial (~12%) and all (~25%) health problems were similar between senior and development team skiers. However, illness prevalence was lower in senior vs. development skiers (8%, 95% CI [3%, 13%] vs. 13%, 95% CI [9%, 17%], respectively; p = .026) and injuries were higher (12%, 95% CI [9%, 15%] vs. 5%, 95% CI [3%, 7%]; p < .001). There were no differences in severity measures (all p > .05).

Conclusions Health problems were relatively common among the skiers, with one quarter affected by at least one problem at any given time. While the prevalence of all health problems was similar, illnesses were less prevalent in the senior compared to the development team skiers and injuries were more prevalent.

Objective Few long-term prospective studies have investigated health problems in elite competitive cross-country (XC) skiers. Hence, our objective was to compare the prevalence of health problems in national team XC skiers over a competitive season.

Methods Forty national team XC skiers participated in this prospective, observational study. Two groups were characterized according to performance level: senior (n=18, ~26 years old, 9 women) and development (n=22, ~21 years old, 9 women). The skiers reported all and substantial injuries and illnesses weekly for 17 consecutive weeks throughout the 2019/2020 competitive season using the Oslo Sports Trauma Research Center Questionnaire on Health Problems.

Results The average weekly prevalence of all and substantial health problems was 19% (95% CI: 16% to 22%) and 12% (95% CI: 9% to 15%), respectively, and was similar between senior and development level skiers (p>0.05). The injury prevalence was higher in senior versus development level skiers (12%, 95% CI: 9% to 15% vs 5%, 95% CI: 3% to 7%; p<0.001), while illnesses were less common (8%, 95% CI: 3% to 13% vs 13%, 95% CI: 9% to 17%, respectively; p=0.031). Illnesses accounted for 72% of all problems. The prevalence of all health problems was higher in female than in male skiers (23%, 95% CI: 19% to 27% vs 15%, 95% CI: 11% to 19%; p<0.003).

Conclusions Health problems, especially illnesses, were relatively common, with approximately one in five skiers (19%) reporting at least one problem in any given week. Both performance level and sex influenced the prevalence of different types of health problems.

Objective: To monitor the daily variations and time course of changes in selected variables during a 17–21-day altitude training camp at 1,800 m in a group of elite cross-country skiers (9 women, 12 men) and biathletes (7 women, 4 men).

Methods: Among other variables, resting peripheral oxygen saturation (SpO2rest), resting heart rate (HRrest) and urine specific gravity (USG) were monitored daily at altitude, while illness symptoms were monitored weekly. Before and after the camp, body composition (i.e., lean and fat mass) and body mass were assessed in all athletes, while roller-skiing speed at a blood lactate concentration of 4 mmol·L−1 (Speed@4mmol) was assessed in the biathletes only.

Results: Neither SpO2rest, HRrest nor USG changed systematically during the camp (p > 0.05), although some daily time points differed from day one for the latter two variables (p < 0.05). In addition, body composition and body mass were unchanged from before to after the camp (p > 0.05). Eleven out of 15 illness episodes were reported within 4 days of the outbound or homebound flight. The five biathletes who remained free of illness increased their Speed@4mmol by ~ 4% from before to after the camp (p = 0.031).

Conclusions: The present results show that measures typically recommended to monitor acclimatization and responses to altitude in athletes (e.g., SpO2rest and HRrest) did not change systematically over time. Further research is needed to explore the utility of these and other measures in elite endurance athletes at altitudes typical of competition environments.

INTRODUCTION: Reaching an international level in any endurance sport requires a large volume of systematic training performed over time. While the annual training characteristics of senior, elite-level cross-country (XC) skiers are well documented (1), limited data exist regarding the long-term training of developing XC skiers. The current study aimed to describe the training undertaken by a group of highly-trained XC skiers throughout their transition from junior- to senior-level athletes. METHODS: In this retrospective cohort study, self-reported training data were obtained from 32 highly-trained female (n = 13) and male (n = 19) XC skiers for the season they turned 16 years old (y) until the season they turned 23 y. At the time of inclusion, 26 skiers (11 females and 15 males) had represented at least one of the Swedish national teams (senior, development or junior), and eight of these skiers (6 females and 2 males) had won at least one individual U23 or Junior World Championship medal. The remaining six skiers were part of a specialist ski university in Sweden, where selection is based on the potential to perform at a world-class level. Training data were organized by training form (endurance, strength, and speed), mode (e.g. on-snow skiing, roller skiing, running, and cycling), and intensity (using a 4-zone model), which were then divided into five annual training phases (transition, general preparation [GP], specific preparation [SP], competition [CP], regeneration). RESULTS: Data from 155 seasons, including 59 026 individual training sessions and 94 964 h of training, were analysed. From age 16 to 22 y the total volume of endurance training increased from 472 ± 70 to 721 ± 86 h/yr (p < 0.001). Low-intensity training (LIT, below the first lactate threshold, <85% HRmax) and high-intensity training (HIT, above the first lactate threshold, >85% HRmax) increased from 414 ± 61 to 656 ± 72 h/yr (p < 0.001) and 58 ± 33 to 65 ± 16 h/yr (p = 0.018), respectively. The training-volume distribution developed progressively from a more even distribution across training phases at age 16 y (GP: 10.6 ± 1.8 h/wk; SP: 10.4 ± 1.5 h/wk; CP: 8.6 ± 1.5 h/wk) to a more traditional periodised model at age 22 y (GP: 17.5 ± 1.7 h/wk; SP: 12.7 ± 1.9 h/wk; CP: 11.1 ± 2.1 h/wk), whereby a higher proportion of the total training volume was performed in GP, and a lower proportion in SP and CP, as athletes developed. CONCLUSION: In conclusion, this group of highly-trained XC skiers progressively increased their endurance training volume from age 16 to 22 y, to a level that is required of elite XC skiers. This increase in training volume was primarily due to an increase in LIT in the general preparation phase. In addition, training-volume distribution became more periodised as athletes developed from junior to senior level. REFERENCES 1. Ø. Sandbakk & HC. Holmberg, International Journal of Sports Physiology and Performance 9, 117-121 (2014).

Objective This study aimed to describe the endurance training and incidence of illnesses reported by a group of well-trained cross-country (XC) skiers throughout their transition from junior to senior level. Methods Changes in self-reported training and performance, from 31 well-trained XC skiers, were analyzed from the start of the season they turned 16 y until the end of the season they turned 22 y, using linear mixed-effects models. Differences in the incidence of self-reported illness episodes were analyzed using incidence rate ratios, and the relationships between selfreported illness and training volumes were analyzed using linear mixed-effects models in a sub-group of 23 of the skiers. Results In total, 145 seasons of training data (including 85,846 h of endurance training) and 109 person- years of illness data (including 380 self-reported illness episodes) were analyzed. The athletes progressively increased their annual endurance training volume from age 16 to 22 y in a linear fashion, from ~ 470 to 730 h. Low- and high-intensity training volumes increased by 51.4 ± 2.4 h·y-1 (p < .001) and 4.9 ± 0.6 h·y-1 (p < .001), respectively. Sport-specific and non-specific training increased by 50.0 ± 2.2 h·y-1 (p < .001) and 4.6 ± 2.0 h·y-1 (p < .001), respectively. The athletes reported a median (range) of 3 (0-8) illness episodes and 17 (0- 80) days of illness per year, and there was an inverse relationship between self-reported illness days and annual training volume (-0.046 ± 0.013 d?h-1; p < .001). Conclusions This group of well-trained XC skiers increased their endurance training volume in a linear fashion by ~ 55 h annually. This was primarily achieved through an increase in low-intensity and sport-specific training. Furthermore, higher training volumes were associated with a lower number of self-reported illness days.

Skiing in biathlon is a high-intensity, intermittent endurance discipline. This study aimed to evaluate the relationships between laboratory-derived physiological variables and skiing performance during a field-based biathlon competition (BC) for female and male biathletes. Fourteen female (23 ± 3 year, VO_2max 56 ± 4 mL·kg⁻¹·min⁻¹) and 14 male (24 ± 4 year, VO_2max 66 ± 3 mL·kg⁻¹·min⁻¹) biathletes performed a submaximal incremental test and a maximal time-trial (TT) using treadmill roller-skiing for the assessment of oxygen uptake at a lactate threshold of 4 mmol·L⁻¹ (VO_2@4mmol), gross efficiency (GE), aerobic (MR_ae) and anaerobic (MR_an) metabolic rates, peak oxygen consumption (VO_2peak), anaerobic capacity and TT performance. Field-based skiing performance was assessed during a BC. The TT and BC skiing performances were significantly correlated in both sexes (r = 0.68–0.69, p < 0.01). VO_2peak (31/21%), anaerobic capacity (1/0%), and GE (35/32%) explained 67 and 52% of the variance in BC skiing performance for the females (p < 0.01) and males (p = 0.051), respectively. A second model showed that VO_2@4mmol (30/35%), anaerobic capacity (0/0%) and GE (37/13%) explained 67 and 48% of the variance in BC skiing performance for the females (p < 0.01) and males (p = 0.077), respectively. Results of this study suggest that a high VO_2@4mmol and GE, but not anaerobic capacity, are important for BC skiing performance, especially for females. In addition, a laboratory-based TT could be useful for regular laboratory testing of biathletes due to its relationship with field-based skiing performance in biathlon.