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Björklund, G., Swarén, M., Born, D.-P. & Stöggl, T. (2019). Biomechanical Adaptations and Performance Indicators in Short Trail Running. Frontiers in Physiology, 10, Article ID 506.
Open this publication in new window or tab >>Biomechanical Adaptations and Performance Indicators in Short Trail Running
2019 (English)In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 10, article id 506Article in journal (Refereed) Published
Abstract [en]

Our aims were to measure anthropometric and oxygen uptake (V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; 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; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2) variables in the laboratory, to measure kinetic and stride characteristics during a trail running time trial, and then analyse the data for correlations with trail running performance. Runners (13 men, 4 women: mean age: 29 ± 5 years; stature: 179.5 ± 0.8 cm; body mass: 69.1 ± 7.4 kg) performed laboratory tests to determine V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; 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; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max, running economy (RE), and anthropometric characteristics. On a separate day they performed an outdoor trail running time trial (two 3.5 km laps, total climb: 486 m) while we collected kinetic and time data. Comparing lap 2 with lap 1 (19:40 ± 1:57 min vs. 21:08 ± 2:09 min, P < 0.001), runners lost most time on the uphill sections and least on technical downhills (-2.5 ± 9.1 s). Inter-individual performance varied most for the downhills (CV > 25%) and least on flat terrain (CV < 10%). Overall stride cycle and ground contact time (GCT) were shorter in downhill than uphill sections (0.64 ± 0.03 vs. 0.84 ± 0.09 s; 0.26 ± 0.03 vs. 0.46 ± 0.90 s, both P < 0.001). Force impulse was greatest on uphill (248 ± 46 vs. 175 ± 24 Ns, P < 0.001) and related to GCT (r = 0.904, P< 0.001). Peak force was greater during downhill than during uphill running (1106 ± 135 vs. 959 ± 104 N, P< 0.01). Performance was related to absolute and relative V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; 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; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max (P < 0.01), vertical uphill treadmill speed (P < 0.001) and fat percent (P < 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; 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; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max, vertical running speed and fat percent are important predictors for trail running performance. Performance between runners varied the most on downhills throughout the course, while pacing resembled a reversed J pattern. Future studies should focus on longer competition distances to verify these findings and with application of measures of 3D kinematics.

Keywords
downhill running, foot forces, ground contact time, pacing, stride frequency
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-36060 (URN)10.3389/fphys.2019.00506 (DOI)000466549100002 ()2-s2.0-85068357933 (Scopus ID)
Available from: 2019-04-30 Created: 2019-04-30 Last updated: 2019-08-12Bibliographically approved
Sjöström, R., Söderström, L., Klockmo, C., Patrician, A., Sandström, T., Björklund, G., . . . Stenfors, N. (2019). Qualitative identification and characterisation of self-reported symptoms arising in humans during experimental exposure to cold air. International Journal of Circumpolar Health, 78(1), Article ID 1583528.
Open this publication in new window or tab >>Qualitative identification and characterisation of self-reported symptoms arising in humans during experimental exposure to cold air
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2019 (English)In: International Journal of Circumpolar Health, ISSN 2242-3982, E-ISSN 2242-3982, Vol. 78, no 1, article id 1583528Article in journal (Refereed) Published
Abstract [en]

Background: Exposure to cold air is associated with increased morbidity and mortality in the general population. It is difficult to study the effects of whole-body exposure to cold air under controlled conditions in real life. Objectives: The aim of this study was to (1) explore and describe the experience of symptoms in humans during experimental and controlled exposures to cold air, by using controlled environmental chamber exposures and qualitative methodology, and to (2) categorise the symptoms. Method: The study used a randomised, double blind design, in which 34 subjects undertook rest and moderate-intensity exercise in an environmental chamber set to two or three different temperatures (0, −10, and −17°C) on separate occasions. During the chamber exposures, subjects were interviewed. Qualitative content analysis was selected as the method of analysis. Findings: Subjects reported 50 distinct symptoms during the exposures. The symptoms were grouped into ten sub-categories and two major categories; airway versus whole-body symptoms. Conclusion: We have identified a broad range of symptoms in humans undertaking rest and moderate-intensity exercise at sub-zero temperatures. The symptoms and their categories may well be used to more extensively and quantitatively map cold-induced morbidity.

Keywords
Cold temperature, environmental chamber, healthy, physical activity, qualitative analysis, respiratory disease
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-35730 (URN)10.1080/22423982.2019.1583528 (DOI)000459975500001 ()30821652 (PubMedID)2-s2.0-85062417054 (Scopus ID)
Available from: 2019-03-03 Created: 2019-03-03 Last updated: 2019-03-25Bibliographically approved
Björklund, G., Danvind, J. & Sundström, D. (2019). The effect of speed and gradient on running economy and oxygen uptake during downhill running. In: : . Paper presented at The 24th Annual Congress of the European College of Sport Science, 2019, 3-6 July, Prague, Czech Republic..
Open this publication in new window or tab >>The effect of speed and gradient on running economy and oxygen uptake during downhill running
2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Downhill running poses challenges were the gradient is of importance for energy cost and oxygen uptake. While demonstrated that downhill running at a slight gradient is most efficient, the energy cost increases with a steeper gradient (1). However, the additional effect of running speed has not been studied for downhill running. Therefore, the aim of the study was to analyse the combined effect of gradient and speed in downhill running on oxygen cost and running economy. METHODS:Runners (n=6) were recruited for the study and performed 1) VO2max and running economy (J·kg-1·m-1) tests and 2) an experimental running protocol at two speeds,12 km·h-1 and 80% of the speed at VO2max (V80) and three gradients (0, -5° and -10°). V80 was higher than 12 km·h-1 for all participants. All testing was performed on a large treadmill 3x5 m (Rodby, Sweden) that were controlled for speed and gradient. The experimental protocol was performed continuously with 5 min at each workload in a randomized order, 30 min in total. VO2 was measured throughout the experimental protocol using a mixing chamber (Moxus Metabolic Cart, USA). RESULTS:VO2 expressed as ml·kg-1·min-1 increased because of speed (F1,5=27.8, p=0.003) and decreased with gradient (F1,5=87.6, p<0.001). Between -5° and -10°, VO2 decreased less during V80 compared to 12 km·h-1 shown by an interaction (F2,10=7.9, p=0.009). However, speed did not influence running economy (F1,5=0.9, p=0.38) while gradient increased running economy (F1,5=90.1, p<0.001). A non-significant interaction effect suggests a shift in running economy between -5° and -10° depending on speed (F2,10=3.5, p=0.07). The running economy at V80 was higher compared to 12 km·h-1 at -5° but reversed at -10°. While a relation between running economy at V80 -10°, V80 -5° and 12 km·h-1 -10° (rs>0.88, p<0.019) was found, no relations between running economy on level terrain and steep downhill running (-10°) were recognised. CONCLUSION:While we found no effect on running economy from speed alone, we did see a shift in the running economy for different speeds at an increased downhill gradient. This indicates that a high speed (V80) is more efficient at moderate downhill gradients, while a lower speed (12 km·h-1) is more efficient in steeper downhill gradients. While previous research demonstrate that gradient is of great influence to running economy, the findings of this study suggest that speed also affects the running economy in downhill running.

National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-36647 (URN)
Conference
The 24th Annual Congress of the European College of Sport Science, 2019, 3-6 July, Prague, Czech Republic.
Available from: 2019-07-07 Created: 2019-07-07 Last updated: 2019-08-13Bibliographically approved
Ekström, A., Hafsteinsson Östenberg, A., Björklund, G. & Alricsson, M. (2019). The effects of introducing Tabata interval training and stability exercises to school children as a school-based intervention program. International Journal of Adolescent Medicine and Health, 31(4), Article ID 20170043.
Open this publication in new window or tab >>The effects of introducing Tabata interval training and stability exercises to school children as a school-based intervention program
2019 (English)In: International Journal of Adolescent Medicine and Health, ISSN 0334-0139, E-ISSN 2191-0278, Vol. 31, no 4, article id 20170043Article in journal (Refereed) Published
Abstract [en]

Background

Physical activities during leisure time as well as school hours have changed over the past few years, with adolescents being less physically active and adopting a sedentary lifestyle.

Objective

The overall objective of this mixed-methods study was to evaluate the feasibility of introducing a 4-min Tabata interval training into a lower secondary school context. A further aim was to evaluate the possible effects on: coordination, balance, and strength.

Methods

The study was conducted as an intervention study with a mixed-method approach. Forty-three children, aged 7–9 years, participated in the intervention group. Additionally, 13 children were recruited as a control group. The intervention itself was delivered by the teachers and was performed for 4-min every day in a classroom setting. All participants performed physical tests before and after the intervention period to evaluate the Tabata training. After the completion of the 6-week Tabata interval training, the four teachers were interviewed.

Results

The push-ups (p = 0.004), kneeling push-ups (p = 0.03), and standing long jump (p = 0.01) improved in the intervention group after 6 weeks. No differences were observed between the genders. The teachers experienced that it worked well to integrate the Tabata interval training in the classroom setting.

Conclusion

After 6 weeks, a school-based Tabata intervention program improved physical performance. The teachers saw no obstacles in including the Tabata intervention program in a classroom setting and pointed out several positive aspects such as an increased energy level and development in the children’s movement patterns.

Keywords
classroom exercise, exertion, physical activity, school exercise program
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-32469 (URN)10.1515/ijamh-2017-0043 (DOI)2-s2.0-85072281883 (Scopus ID)
Available from: 2017-12-15 Created: 2017-12-15 Last updated: 2019-09-30Bibliographically approved
Björklund, G., Elgh, T. & Styfberg, P. (2018). Fysiologi och träningslära. In: Specialidrott: Tränings- och tävlingslära (pp. 27-72). SISU Idrottsböcker
Open this publication in new window or tab >>Fysiologi och träningslära
2018 (Swedish)In: Specialidrott: Tränings- och tävlingslära, SISU Idrottsböcker , 2018, p. 27-72Chapter in book (Other academic)
Place, publisher, year, edition, pages
SISU Idrottsböcker, 2018
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-34288 (URN)978-91-7727-026-3 (ISBN)
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2018-08-28Bibliographically approved
Swarén, M., Fredrik, H., Larsson, A. & Björklund, G. (2018). Key performance indicators of ice hockey sprint performance. In: Journal of Sports Sciences: BASES Conference 2018 – Programme and Abstracts. Paper presented at BASES Conference, Harrogate, UK, 27-28 November, 2018 (pp. 1-94). Routledge, 36 (S1)
Open this publication in new window or tab >>Key performance indicators of ice hockey sprint performance
2018 (English)In: Journal of Sports Sciences: BASES Conference 2018 – Programme and Abstracts, Routledge, 2018, Vol. 36 (S1), p. 1-94Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Ice hockey is a physical demanding sport with high intensity and repetitive start and stop movements. Hence, players need to have excellent physical condition and ice skating skills with good acceleration and sprint capacities. However, little biomechanical research has been conducted on elite ice hockey players to analyse applicable key performance indicators of skating acceleration and short sprint performance. The aim of the study was to collect plantar forces data of elite ice hockey players during short sprints in order to analyse and identify plausible performance indicators. With institutional ethics approval, twelve professional male ice hockey players, (Age 22.8 ± 5.2 years, height 185.6 ± 5.0 cm, weight 86.9 ± 6.2 kg) from the Swedish Hockey League participated in the study. Following an individual warm up, each player performed three maximal sprints (18.4 m) from a stationary position, with three minutes of rest between each sprint. Sprint time was collected with timing gates (Brower Timing system, USA). The best trial for each player was chosen for further analysis. Plantar forces were collected at 100 Hz with pressure insoles (Novel GmbH, Germany), placed in both skates (Buckeridge et al., 2015, PLOS ONE, 10, 5). Analyses were made for stride rate, symmetry left-right, contact time, force production and impulse. Only the step frequency, 3.35 ± 0.38 strides/s was correlated to skating performance (r = -0.6, P < 0.05). For the second to seventh step, the mean contact time was 0.26 ± 0.04 s, the mean force was 844 ± 152 N and the mean peak force was 1335 ± 224 N. The mean impulse was 230 ± 52 Ns and the group showed greater force production for the left leg compared to the right leg −2.07 ± 9.08 %. The present study is the first study to analyse plantar forces on professional ice hockey players. The significance of stride rate is in line with previous research (Renaud et al., 2017, Sports Engineering, 20, 255–266) whereas the plantar force production is higher, compared to findings by Buckeridge et al. (2015). This is likely explained by the use of higher skilled players in the present study. Still, plantar force production is not significant for performance which points to the importance of skating kinematics and/or shear forces. Hence, the combination of kinetics and 3D kinematics on ice is important to enhance the knowledge about skating performance of elite ice hockey players as well as developing a kinetic measurement system to measure shear forces in combination with plantar forces.

Place, publisher, year, edition, pages
Routledge, 2018
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-34993 (URN)10.1080/02640414.2018.1521633 (DOI)
Conference
BASES Conference, Harrogate, UK, 27-28 November, 2018
Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2018-12-06Bibliographically approved
Björklund, G. (2018). Shooting efficiency for winners of World Cup and World Championship races in men’s and women’s biathlon: where is the cut-off?. International Journal of Performance Analysis in Sport, 18(4), 545-553
Open this publication in new window or tab >>Shooting efficiency for winners of World Cup and World Championship races in men’s and women’s biathlon: where is the cut-off?
2018 (English)In: International Journal of Performance Analysis in Sport, ISSN 1474-8185, E-ISSN 1474-8185, Vol. 18, no 4, p. 545-553Article in journal (Refereed) Published
Abstract [en]

The shooting profile of the biathlete is presented as the mean shooting percentage, which lacks valuable information for performance profiling. Hence, the aim of the study was to present a way of profiling biathlete shooting efficiency and profiling the men’s and women’s winners in the IBU World Cup and World Championships to clarify the fewest hits necessary to win races. Data from 106 competitions from two seasons were analysed and dichotomised. The proportions (p) (miss/hit) and 90% confidence interval were estimated, and binominal distributions for overall, standing and prone shooting. The women’s winners showed higher overall shooting efficiency than the men’s winners (−5.4 to −0.4 90%CI) season 2015/2016, due to lower prone shooting efficiency for the men. The men increased their overall shooting efficiency for the 2016/2017 season, compared to 2015/2016, due to increased prone shooting accuracy (−6.9 to −0.2 90%CI). The likelihood of winners missing three targets went from 14.7% to 3.7% and 3.5% to 4.3% for the 2015/2016 to 2016/2017 season for men and women, respectively. Overall, the men varied more than women between seasons due to reduced prone shooting efficiency, while the third miss appeared most critical for performance.

Keywords
Competition, performance analysis, prone shooting, standing shooting
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-34188 (URN)10.1080/24748668.2018.1497920 (DOI)000443883100005 ()2-s2.0-85052893980 (Scopus ID)
Available from: 2018-07-17 Created: 2018-07-17 Last updated: 2018-10-03Bibliographically approved
Björklund, G. & Lindberg, T. (2018). Tester och mätmetoder. In: Specialidrott: Tränings- och tävlingslära (pp. 73-80). SISU Idrottsböcker
Open this publication in new window or tab >>Tester och mätmetoder
2018 (Swedish)In: Specialidrott: Tränings- och tävlingslära, SISU Idrottsböcker , 2018, p. 73-80Chapter in book (Other academic)
Place, publisher, year, edition, pages
SISU Idrottsböcker, 2018
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-34289 (URN)978-91-7727-026-3 (ISBN)
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2018-08-28Bibliographically approved
Björklund, G. (2018). Tävlingslära. In: Specialidrott: Tränings- och tävlingslära (pp. 81-88). SISU Idrottsböcker
Open this publication in new window or tab >>Tävlingslära
2018 (Swedish)In: Specialidrott: Tränings- och tävlingslära, SISU Idrottsböcker , 2018, p. 81-88Chapter in book (Other academic)
Place, publisher, year, edition, pages
SISU Idrottsböcker, 2018
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-34290 (URN)978-91-7727-026-3 (ISBN)
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2018-08-28Bibliographically approved
Andersson, E., Björklund, G., Holmberg, H.-C. & Ørtenblad, N. (2017). Energy system contributions and determinants of performance in sprint cross-country skiing. Scandinavian Journal of Medicine and Science in Sports, 27(4), 385-398
Open this publication in new window or tab >>Energy system contributions and determinants of performance in sprint cross-country skiing
2017 (English)In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 27, no 4, p. 385-398Article in journal (Refereed) Published
Abstract [en]

To improve current understanding of energy contributions and determinants of sprint-skiing performance, 11 well-trained male cross-country skiers were tested in the laboratory for VO2max , submaximal gross efficiency (GE), maximal roller skiing velocity, and sprint time-trial (STT) performance. The STT was repeated four times on a 1300-m simulated sprint course including three flat (1°) double poling (DP) sections interspersed with two uphill (7°) diagonal stride (DS) sections. Treadmill velocity and VO2 were monitored continuously during the four STTs and data were averaged. Supramaximal GE during the STT was predicted from the submaximal relationships for GE against velocity and incline, allowing computation of metabolic rate and O2 deficit. The skiers completed the STT in 232 ± 10 s (distributed as 55 ± 3% DP and 45 ± 3% DS) with a mean power output of 324 ± 26 W. The anaerobic energy contribution was 18 ± 5%, with an accumulated O2 deficit of 45 ± 13 mL/kg. Block-wise multiple regression revealed that VO2 , O2 deficit, and GE explained 30%, 15%, and 53% of the variance in STT time, respectively (all P < 0.05). This novel GE-based method of estimating the O2 deficit in simulated sprint-skiing has demonstrated an anaerobic energy contribution of 18%, with GE being the strongest predictor of performance.

Keywords
Energetic cost, incline, oxygen demand, oxygen uptake, oxygen deficit, technique transitions.
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:miun:diva-27227 (URN)10.1111/sms.12666 (DOI)000395709400002 ()26923666 (PubMedID)2-s2.0-84959270767 (Scopus ID)
Funder
Swedish National Centre for Research in Sports
Note

Article first published online: 29 FEB 2016

Available from: 2016-03-14 Created: 2016-03-14 Last updated: 2017-07-07Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7781-8164

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