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Jensen, Kurt
Publications (8 of 8) Show all publications
Jensen, K., Höök, M., Willis, S. & Holmberg, H.-C. (2014). Changes in physical performance parameters during and after moderate altitude training in elite cross-country skiers. In: Erich Muller, Josef Kroll, Stefan Lindinger (Ed.), Science & Skiing VI: (pp. 414-420). Meyer & Meyer Sport
Open this publication in new window or tab >>Changes in physical performance parameters during and after moderate altitude training in elite cross-country skiers
2014 (English)In: Science & Skiing VI / [ed] Erich Muller, Josef Kroll, Stefan Lindinger, Meyer & Meyer Sport, 2014, p. 414-420Chapter in book (Refereed)
Place, publisher, year, edition, pages
Meyer & Meyer Sport, 2014
National Category
Health Sciences Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-24012 (URN)9781782550662 (ISBN)
Available from: 2014-12-23 Created: 2014-12-23 Last updated: 2015-01-09Bibliographically approved
Hébert-Losier, K., Jensen, K. & Holmberg, H.-C. (2014). Jumping and hopping in elite and amateur orienteering athletes and correlations to sprinting and running. International Journal of Sports Physiology and Performance, 9(6), 993-999
Open this publication in new window or tab >>Jumping and hopping in elite and amateur orienteering athletes and correlations to sprinting and running
2014 (English)In: International Journal of Sports Physiology and Performance, ISSN 1555-0265, E-ISSN 1555-0273, Vol. 9, no 6, p. 993-999Article in journal (Refereed) Published
Abstract [en]

PURPOSE:

Jumping and hopping are used to measure lower-body muscle power, stiffness, and stretch-shortening-cycle utilization in sports, with several studies reporting correlations between such measures and sprinting and/or running abilities in athletes. Neither jumping and hopping nor correlations with sprinting and/or running have been examined in orienteering athletes.

METHODS:

The authors investigated squat jump (SJ), countermovement jump (CMJ), standing long jump (SLJ), and hopping performed by 8 elite and 8 amateur male foot-orienteering athletes (29 ± 7 y, 183 ± 5 cm, 73 ± 7 kg) and possible correlations to road, path, and forest running and sprinting performance, as well as running economy, velocity at anaerobic threshold, and peak oxygen uptake (VO(2peak)) from treadmill assessments.

RESULTS:

During SJs and CMJs, elites demonstrated superior relative peak forces, times to peak force, and prestretch augmentation, albeit lower SJ heights and peak powers. Between-groups differences were unclear for CMJ heights, hopping stiffness, and most SLJ parameters. Large pairwise correlations were observed between relative peak and time to peak forces and sprinting velocities; time to peak forces and running velocities; and prestretch augmentation and forest-running velocities. Prestretch augmentation and time to peak forces were moderately correlated to VO(2peak). Correlations between running economy and jumping or hopping were small or trivial.

CONCLUSIONS:

Overall, the elites exhibited superior stretch-shortening-cycle utilization and rapid generation of high relative maximal forces, especially vertically. These functional measures were more closely related to sprinting and/or running abilities, indicating benefits of lower-body training in orienteering.

Keywords
athletic performance, foot orienteering, jump tests, off-road running, stiffness
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-23798 (URN)10.1123/ijspp.2013-0486 (DOI)000344834500016 ()24664965 (PubMedID)2-s2.0-84911925147 (Scopus ID)
Available from: 2014-12-16 Created: 2014-12-16 Last updated: 2017-12-05Bibliographically approved
Gejl, K. D., Hvid, L. G., Frandsen, U., Jensen, K., Sahlin, K. & Ørtenblad, N. (2014). Muscle glycogen content modifies SR Ca2+ release rate in elite endurance athletes. Medicine & Science in Sports & Exercise, 46(3), 496-505
Open this publication in new window or tab >>Muscle glycogen content modifies SR Ca2+ release rate in elite endurance athletes
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2014 (English)In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 46, no 3, p. 496-505Article in journal (Refereed) Published
Abstract [en]

Purpose: The aim of the present study was to investigate the influence of muscle glycogen content on sarcoplasmic reticulum (SR) function and peak power output (Wpeak) in elite endurance athletes. Methods: Fourteen highly trained male triathletes (V̇O2max = 66.5 ± 1.3 mL O2·kg·min), performed 4 h of glycogen-depleting cycling exercise (HRmean = 73% ± 1% of maximum). During the first 4 h of recovery, athletes received either water (H2O) or carbohydrate (CHO), separating alterations in muscle glycogen content from acute changes affecting SR function and performance. Thereafter, all subjects received CHO-enriched food for the remaining 20-h recovery period. Results: Immediately after exercise, muscle glycogen content and SR Ca release rate was reduced to 32% ± 4% (225 ± 28 mmol·kg dw) and 86% ± 2% of initial levels, respectively (P < 0.01). Glycogen markedly recovered after 4 h of recovery with CHO (61% ± 2% of preexercise) and SR Ca release rate returned to preexercise level. However, in the absence of CHO during the first 4 h of recovery, glycogen and SR Ca release rate remained depressed, with the normalization of both parameters at the end of the 24 h of recovery after receiving a CHO-enriched diet. Linear regression demonstrated a significant correlation between SR Ca release rate and muscle glycogen content (P < 0.01, r = 0.30). The 4 h of cycling exercise reduced Wpeak by 5.5%-8.9% at different cadences (P < 0.05), and Wpeak was normalized after 4 h of recovery with CHO, whereas Wpeak remained depressed (P < 0.05) after water provision. Wpeak was fully recovered after 24 h in both the H2O and the CHO group. Conclusion: In conclusion, the present results suggest that low muscle glycogen depresses muscle SR Ca release rate, which may contribute to fatigue and delayed recovery of Wpeak 4 h postexercise. © 2014 by the American College of Sports Medicine.

Keywords
CALCIUM REGULATION, ELITE ATHLETES, FATIGUE, MUSCLE FUNCTION, RECOVERY
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-22045 (URN)10.1249/MSS.0000000000000132 (DOI)000335840900009 ()2-s2.0-84894454628 (Scopus ID)
Note

Language of Original Document: English

Available from: 2014-05-30 Created: 2014-05-30 Last updated: 2017-12-05Bibliographically approved
Hébert-Losier, K., Jensen, K., Mourot, L. & Holmberg, H.-C. (2014). The influence of surface on the running velocities of elite and amateur orienteer athletes. Scandinavian Journal of Medicine and Science in Sports, 24(6), 448--455
Open this publication in new window or tab >>The influence of surface on the running velocities of elite and amateur orienteer athletes
2014 (English)In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 24, no 6, p. 448--455Article in journal (Refereed) Published
Abstract [en]

We compared the reduction in running velocities from road to off-road terrain in eight elite and eight amateur male orienteer athletes to investigate whether this factor differentiates elite from amateur athletes. On two separate days, each subject ran three 2-km time trials and three 20-m sprints "all-out" on a road, on a path, and in a forest. On a third day, the running economy and maximal aerobic power of individuals were assessed on a treadmill. The elite orienteer ran faster than the amateur on all three surfaces and at both distances, in line with their better running economy and aerobic power. In the forest, the elites ran at a slightly higher percentage of their 2-km (∼3%) and 20-m (∼4%) road velocities. Although these differences did not exhibit traditional statistical significance, magnitude-based inferences suggested likely meaningful differences, particularly during 20-m sprinting. Of course, cognitive, mental, and physical attributes other than the ability to run on different surfaces are required for excellence in orienteering (e.g., a high aerobic power). However, we suggest that athlete-specific assessment of running performance on various surfaces and distances might assist in tailoring training and identifying individual strengths and/or weaknesses in an orienteer.

Keywords
Athletic performance, Field testing, Foot orienteering, Off-road, Sport surface, Sprint, Time trial
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-23796 (URN)10.1111/sms.12224 (DOI)000345703300004 ()2-s2.0-84912045348 (Scopus ID)
Available from: 2014-12-16 Created: 2014-12-16 Last updated: 2017-12-05Bibliographically approved
Höök, M., Jensen, K., Willis, S. J. & Holmberg, H.-C. (2013). Changes in maximal double poling performance during and after mderate altitude training in elite cross-country skiers. In: Erich Mueller, Josef Kröll, Stefan Josef Lindinger, Jurgen Pfusterschmied, Thomas Stöggl (Ed.), Proceedings for the 6th International Congress on Science and Skiing: . Paper presented at 6th International Congress on Science and Skiing (pp. 95).
Open this publication in new window or tab >>Changes in maximal double poling performance during and after mderate altitude training in elite cross-country skiers
2013 (English)In: Proceedings for the 6th International Congress on Science and Skiing / [ed] Erich Mueller, Josef Kröll, Stefan Josef Lindinger, Jurgen Pfusterschmied, Thomas Stöggl, 2013, p. 95-Conference paper, Oral presentation with published abstract (Refereed)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:miun:diva-20940 (URN)978-3-200-03417-4 (ISBN)
Conference
6th International Congress on Science and Skiing
Available from: 2014-01-02 Created: 2014-01-02 Last updated: 2014-01-02Bibliographically approved
Jensen, K., Höök, M., Willis, S. J. & Holmberg, H.-C. (2013). Changes in physical performance parameters during and after moderate altitude training in elite cross country skiers. In: Erich Mueller, Josef Kröll, Stefan Josef Lindinger, Jurgen Pfusterschmied, Thomas Stöggl (Ed.), Proceedings for the 6th International Congress on Science and Skiing: . Paper presented at 6th International Congress on Science and Skiing (pp. 115).
Open this publication in new window or tab >>Changes in physical performance parameters during and after moderate altitude training in elite cross country skiers
2013 (English)In: Proceedings for the 6th International Congress on Science and Skiing / [ed] Erich Mueller, Josef Kröll, Stefan Josef Lindinger, Jurgen Pfusterschmied, Thomas Stöggl, 2013, p. 115-Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

INTRODUCTION: The Olympic cross country skiing competitions in 2014 will be held in Sochi, Russia at an altitude of approximately 1500m. Although moderate, this altitude is known to reduce performance in highly trained endurance athletes. It is also known that individuals react differently during altitude exposure. The purpose of this study was to evaluate performance changes during and after three weeks of training in moderate altitude in elite skiers.

METHOD: Four male and three female skiers were tested on a roller skiing treadmill using the classic technique  at sea level (NORM1), after 3 and 20 days at 1500m altitude (ALT1 and ALT2), and 10 days after altitude at sea level (NORM2). The test protocol was a standardized progressive submaximal session of 4 min exercise with 1 min rest between each stage, followed by a 6-10 min progressive “all out” exercise with an increase in first speed and then grade every minute. Oxygen uptake (VO2) was measured continuously during submaximal and maximal exercise. Blood lactate concentrations were measured during the 1 min rest between submax stages and 2 min after the max test. Power at each submax and max stage were calculated from roller ski friction and body weight against gravity [1]. Each stage power was further used for calculations of power at VO2max, (WVO2max), work efficiency at submaximal loads (GE) and for the estimation of O2 cost at maximal work load (used to calculate accumulated O2 deficit (MOD)) [2].

RESULTS: At NORM1, the skiers’ body mass was 71.9±10.7kg and VO2max 214±12ml/min/kg0.73. The GE varied between 17.9-19.5% during the 3-5 submaximal loads, with no difference between conditions (P>0.05). Also, blood lactate accumulation after submaximal exercise loads showed no difference between conditions (P<0.05). At ALT1, the VO2max and the WVO2max decreased 8.9% and 9.1%, respectively (P<0.05), however there were no differences between ALT1 and ALT2 or from NORM1 and NORM2 (P>0.05). In contrast, the average power output (322±87W) during the “all out” test increased 3.4±2.7% 10 days after the altitude training (P<0.05). Average MOD varied between 57-79 mlO2·kg-1 over the training period, but with no change between conditions (P>0.05). The coefficient of variation (CV%) for the changes in MOD between NORM1 and 2 was 40%.

DISCUSSION: This study demonstrated that performance (VO2max, WVO2max) deteriorates by 8-9% in a group of elite skiers training at a moderate altitude corresponding to 1500m. No increase in any of the physiological parameters related to performance included in the study was seen after moderate altitude training, except for the maximal power which increased 3.4%. The response after moderate altitude training seems to be related more to anaerobic than aerobic factors. However, this was not confirmed by the MOD in this group of highly trained skiers. The large CV for change in MOD reflects the individual responses to this training.

CONCLUSION: Small changes of 2-3% in performance in highly trained in elite skiers after moderate altitude training seems not to be related to any single parameter. One should not ignore individual differences in adaptation.

 

REFERENCES

1.         Ainegren, M. et al Engineering of Sport 7, Vol 2, 2008: p. 393-400.

2.         Medbo, J.I.et al J.Appl.Physiol., 1988. 64: p. 50-60.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:miun:diva-20942 (URN)978-3-200-03417-4 (ISBN)
Conference
6th International Congress on Science and Skiing
Available from: 2014-01-02 Created: 2014-01-02 Last updated: 2014-01-03Bibliographically approved
Jensen, K., Höök, M., Wedholm, L., Björklund, G. & Holmberg, H.-C. (2012). How work economy changes during a summer season with roller skiing training and its influence on performance. In: Erich Mueller, Stefan Lindinger, Thomas Stöggl (Ed.), Science and Skiing V (pp. 523-529). Meyer & Meyer Sport
Open this publication in new window or tab >>How work economy changes during a summer season with roller skiing training and its influence on performance
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2012 (English)In: Science and Skiing V / [ed] Erich Mueller, Stefan Lindinger, Thomas Stöggl, Meyer & Meyer Sport, 2012, p. 523-529Chapter in book (Refereed)
Place, publisher, year, edition, pages
Meyer & Meyer Sport, 2012
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:miun:diva-18216 (URN)1841263532 (ISBN)
Available from: 2013-01-09 Created: 2013-01-09 Last updated: 2013-01-11Bibliographically approved
Jensen, K., Höök, M., Wedholm, L., Björklund, G. & Holmberg, H.-C. (2010). How work efficiency changes during a summer season with roller skiing training and its influence on performace. In: Erich Mueller (Ed.), Proceedings for the fifth international conference on Science and Skiing: . Paper presented at 5th International Conference Science and Skiing, St Cristoph am Aarlberg (pp. 75). Salzburg: Meyer & Meyer Sport
Open this publication in new window or tab >>How work efficiency changes during a summer season with roller skiing training and its influence on performace
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2010 (English)In: Proceedings for the fifth international conference on Science and Skiing / [ed] Erich Mueller, Salzburg: Meyer & Meyer Sport, 2010, p. 75-Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Salzburg: Meyer & Meyer Sport, 2010
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-12656 (URN)978-3-200-02097-9 (ISBN)
Conference
5th International Conference Science and Skiing, St Cristoph am Aarlberg
Projects
Integrative Physiologi & Biomechanics
Available from: 2010-12-13 Created: 2010-12-13 Last updated: 2013-09-17Bibliographically approved
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