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The importance of body-mass exponent optimization for evaluation of performance capability in cross-country skiing
Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Sports medicine. School of Education, Health and Social Studies, Dalarna University, Falun, Sweden..
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Introduction Performance in cross-country skiing is influenced by the skier’s ability to continuously produce propelling forces and force magnitude in relation to the net external forces. A surrogate indicator of the “power supply” in cross-country skiing would be a physiological variable that reflects an important performance-related capability, whereas the body mass itself is an indicator of the “power demand” experienced by the skier. To adequately evaluate an elite skier’s performance capability, it is essential to establish the optimal ratio between the physiological variable and body mass. The overall aim of this doctoral thesis was to investigate the importance of body-mass exponent optimization for the evaluation of performance capability in cross-country skiing.

Methods In total, 83 elite cross-country skiers (56 men and 27 women) volunteered to participate in the four studies. The physiological variables of maximal oxygen uptake (V̇O2max) and oxygen uptake corresponding to a blood-lactate concentration of 4 mmol∙l-1 (V̇O2obla) were determined while treadmill roller skiing using the diagonal-stride technique; mean oxygen uptake (V̇O2dp) and upper-body power output () were determined during double-poling tests using a ski-ergometer. Competitive performance data for elite male skiers were collected from two 15-km classical-technique skiing competitions and a 1.25-km sprint prologue; additionally, a 2-km double-poling roller-skiing time trial using the double-poling technique was used as an indicator of upper-body performance capability among elite male and female junior skiers. Power-function modelling was used to explain the race and time-trial speeds based on the physiological variables and body mass.

Results The optimal V̇O2max-to-mass ratios to explain 15-km race speed were V̇O2max divided by body mass raised to the 0.48 and 0.53 power, and these models explained 68% and 69% of the variance in mean skiing speed, respectively; moreover, the 95% confidence intervals (CI) for the body-mass exponents did not include either 0 or 1. For the modelling of race speed in the sprint prologue, body mass failed to contribute to the models based on V̇O2max, V̇O2obla, and V̇O2dp. The upper-body power output-to-body mass ratio that optimally explained time-trial speed was m-0.57 and the model explained 63% of the variance in speed.

Conclusions The results in this thesis suggest that V̇O2max divided by the square root of body mass should be used as an indicator of performance in 15-km classical-technique races among elite male skiers rather than the absolute or simple ratio-standard scaled expression. To optimally explain an elite male skier’s performance capability in sprint prologues, power-function models based on oxygen-uptake variables expressed absolutely are recommended. Moreover, to evaluate elite junior skiers’ performance capabilities in 2-km double-poling roller-skiing time trials, it is recommended that divided by the square root of body mass should be used rather than absolute or simple ratio-standard scaled expression of power output.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2015. , 58 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1712
Keyword [en]
allometric scaling, power-function modelling, maximal oxygen uptake, body mass, elite skiers, distance skiing, lactate threshold, double poling, sprint skiing, competition, power output, time trial
National Category
Sport and Fitness Sciences
Identifiers
URN: urn:nbn:se:umu:diva-102872ISBN: 978-91-7601-270-3 (print)OAI: oai:DiVA.org:umu-102872DiVA: diva2:810894
Public defence
2015-06-05, Föreläsningssal 6, Högskolegatan 2, 791 88, Falun, 14:00 (Swedish)
Opponent
Supervisors
Note

Incorrect ISBN in printed thesis: 973-91-7601-270-3

Available from: 2015-05-13 Created: 2015-05-08 Last updated: 2015-06-30Bibliographically approved
List of papers
1. Scaling maximal oxygen uptake to predict performance in elite-standard men cross-country skiers
Open this publication in new window or tab >>Scaling maximal oxygen uptake to predict performance in elite-standard men cross-country skiers
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2013 (English)In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 31, no 16, 1753-1760 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of this study was to: 1) establish the optimal body-mass exponent for maximal oxygen uptake (VO2max) to indicate performance in elite-standard men cross-country skiers; and 2) evaluate the influence of course inclination on the body-mass exponent. Twelve elite-standard men skiers completed an incremental treadmill roller-skiing test to determine VO2max and performance data came from the 2008 Swedish National Championship 15-km classic-technique race. Log-transformation of power-function models was used to predict skiing speeds. The optimal models were found to be: Race speed = 7.86 · VO2max · m (-0.48) and Section speed = 5.96 · VO2max · m (-(0.38 + 0.03 · α)) · e(-0.003 · Δ) (where m is body mass, α is the section's inclination and Δ is the altitude difference of the previous section), that explained 68% and 84% of the variance in skiing speed, respectively. A body-mass exponent of 0.48 (95% confidence interval: 0.19 to 0.77) best described VO2max as an indicator of performance in elite-standard men skiers. The confidence interval did not support the use of either "1" (simple ratio-standard scaled) or "0" (absolute expression) as body-mass exponents for expressing VO2max as an indicator of performance. Moreover, results suggest that course inclination increases the body-mass exponent for VO2max.

Place, publisher, year, edition, pages
Taylor & Francis, 2013
Keyword
scaling, cross-country skiing, course profile, body mass
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:umu:diva-79209 (URN)10.1080/02640414.2013.803586 (DOI)000326919900002 ()23829681 (PubMedID)
Available from: 2013-08-13 Created: 2013-08-13 Last updated: 2017-12-06Bibliographically approved
2. Optimal V̇O2max-to-mass ratio for predicting 15-km performance among elite male cross-country skiers
Open this publication in new window or tab >>Optimal V̇O2max-to-mass ratio for predicting 15-km performance among elite male cross-country skiers
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(English)Manuscript (preprint) (Other academic)
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:umu:diva-102886 (URN)
Available from: 2015-05-08 Created: 2015-05-08 Last updated: 2015-05-11
3. Oxygen uptake at different intensities and sub-techniques predicts sprint performance in elite male cross-country skiers
Open this publication in new window or tab >>Oxygen uptake at different intensities and sub-techniques predicts sprint performance in elite male cross-country skiers
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2014 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 12, 2587-2595 p.Article in journal (Refereed) Published
Abstract [en]

PURPOSE: To investigate the relationship between sprint-prologue performance (using the classical technique) and the oxygen uptake at the lactate threshold (V̇O2obla), maximal oxygen uptake (V̇O2max), and mean oxygen uptake during double poling (V̇O2dp).

METHODS: Eight elite male cross-country skiers [age 24.8 ± 4.8 years, (mean ± SD)] completed two treadmill roller-skiing tests using the diagonal-stride technique and a 60 s double-poling test on a ski-ergometer to determine their V̇O2obla, V̇O2max, and V̇O2dp. Performance data were generated from a 1.25 km sprint prologue. Power-function modelling was used to predict the skiers' race speeds based on the oxygen-uptake variables and body mass.

RESULTS: There were correlations between the race speed and the absolute expression of the V̇O2obla (r = 0.79, P = 0.021), V̇O2max (r = 0.86, P = 0.0069), and V̇O2dp (r = 0.94, P = 0.00062). The following power-function models were established for race-speed prediction: 1.09 · V̇O2obla(0.21), 1.05 · V̇O2max(0.21), and 1.19 · V̇O2dp(0.20); these models explained 60 % (P = 0.024), 73 % (P = 0.0073), and 87 % (P = 0.00073), respectively, of the variance in the race speed. However, body mass did not contribute to any of the models (P = 0.97, 0.88, and 0.21, respectively).

CONCLUSIONS: Oxygen uptake at different intensities and sub-techniques is an indicator of elite male sprint-prologue performance. The absolute expression of the investigated oxygen-uptake variables should be used when evaluating elite male sprint-prologue performances; if skiers oxygen uptake differs by 1 %, their performances will likely differ by 0.2 % in favour of the skier with higher oxygen uptake.

Place, publisher, year, edition, pages
Springer, 2014
Keyword
double poling, sprint skiing, scaling, V̇O2max, lactate threshold
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:umu:diva-95074 (URN)10.1007/s00421-014-2980-0 (DOI)000344740500014 ()25138966 (PubMedID)
Available from: 2014-10-21 Created: 2014-10-21 Last updated: 2017-12-05Bibliographically approved
4. Scaling of upper-body power output to predict time-trial roller skiing performance
Open this publication in new window or tab >>Scaling of upper-body power output to predict time-trial roller skiing performance
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2013 (English)In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 31, no 6, 582-588 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of the present study was to establish the most appropriate allometric model to predict mean skiing speed during a double-poling roller skiing time-trial using scaling of upper-body power output. Forty-five Swedish junior cross-country skiers (27 men and 18 women) of national and international standard were examined. The skiers, who had a body mass (m) of 69.3 +/- 8.0 kg (mean +/- s), completed a 120-s double-poling test on a ski ergometer to determine their mean upper-body power output (W). Performance data were subsequently obtained from a 2-km time-trial, using the double-poling technique, to establish mean roller skiing speed. A proportional allometric model was used to predict skiing speed. The optimal model was found to be: Skiing speed = 1.057 · W0.556 · m-0.315, which explained 58.8% of the variance in mean skiing speed (< 0.001). The 95% confidence intervals for the scaling factors ranged from 0.391 to 0.721 for W and from 0.626 to 0.004 for m. The results in this study suggest that allometric scaling of upper-body power output is preferable for the prediction of performance of junior cross-country skiers rather than absolute expression or simple ratio-standard scaling of upper-body power output.

Keyword
cross-country skiing, double-poling, body mass, testing
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:umu:diva-68265 (URN)10.1080/02640414.2012.744079 (DOI)000316216800002 ()
Available from: 2013-04-18 Created: 2013-04-15 Last updated: 2017-12-06Bibliographically approved

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