european college of sport science

Friday, June 26th, 2009
THE EFFECT OF STRETCHING ON MUSCLE FORCE PRODUCTION IN HAMSTRING MUSCLES
MOE, V., AUNE, T.K.
NORD TRONDELAG UNIVERSITY COLLEGE
The purpose of this study was to explore the acute effect of proprioceptive neuromuscular facilitation stretching (PNF) on maximal voluntary
contraction (MVC), rate of force development (RFD) and power in both isometric and dynamic contractions of hamstring (knee flexion).
10 volunteer male kickboxers participated in the experiment. The subjects underwent two days of testing, and randomly the subjects were
tested with or without stretching the first or the second day of testing. The day without PNF was used as a control condition for the day
with PNF.
Each experimental condition conducted of a 10min warm up on at treadmill at 60% of the subjects HFmax. Immediately after warm up
the day without stretching the dependent variables in both the isometric and dynamic contractions of the hamstrings were tested. After
warm up the other day the subjects underwent a controlled PNF sequence of the hamstring that was immediately followed by a test of
the dependent variables. The subjects hamstring flexibility was controlled by the “sit and reach test” after warm up both days of testing,
and after PNF. Only the dominant leg was tested.
The results indicate that PNF increases hamstring flexibility, but has an acute negative effect on MVC, RFD and power in both isometric
and dynamic contractions of hamstring muscles.
Therefore it is concluded that PNF has an acute negative effect on muscle force production measured as MVC, RFD and power in both
isometric and dynamic tasks, and is not a type of stretching that should be recommended in before performing activities that require high
force production.
14:15 - 15:15
Poster presentations
PP-PH08 Physiology 8
SCALING OXYGEN CONSUMPTION TO BODY MASS IN REAL ELITE CROSS-COUNTRY SKIING PERFORMANCES
CARLSSON, T., CARLSSON, M., HAMMARSTRÖM, D., TONKONOGI, M.
LIVI
Introduction: Maximal oxygen consumption (VO2max) is a frequently evaluated test parameter in cross-country skiing. Most often the
units L min(-1) and mL min(-1) kg(-1) are used as performance ability markers, but earlier research have suggested that VO2max divided
by body mass raised to 2/3 power would theoretically better reflect the physiological demands in cross-country skiing (Bergh and Forsberg,
1992). Changes in cross-country skiing in the last decades might place different physiological demands regarding VO2max. The
purpose was therefore to find the optimal body mass exponent for test parameter VO2max for real elite cross-country skiing performances
and ranking points.
Methods: Four to seven days prior to the first ski race twelve highly motivated male Swedish national elite cross-country skiers (age
23.9+/-4.2 years; weight 76.2+/-5.8 kg; VO2max 5.34+/-0.34 L min(-1)) completed an incremental treadmill roller skiing test in diagonal
technique determining VO2max.
Performance data were collected from the Swedish National Championship (SNC) in cross-country skiing (13-17 March 2008): 15-km with
individual start in classical technique (SNC15); 30-km double pursuit with mass-start (SNC30) also divided in the two halves in classical
technique (SNC30:15c) and free-style technique (SNC30:15f); sprint prolog in free-style technique (SNCsprint). In addition to ski races,
overall seasonal ski ranking points were collected from International Ski Federation’s (FIS) 3rd Cross-Country Points List 2007/2008 published
before SNC for distance (FISdist) and sprint (FISsprint) races.
Body mass scaling of VO2max for each of the skiing performances was determined using Pearson´s correlation analysis. Optimal mass
exponent was set to the scaling value between zero (L min(-1)) and one (mL min(-1) kg(-1)) where Pearson’s product-moment correlation
coefficient showed highest correlation for the relationship between VO2max and the ski performance parameter.
Results: Optimal body mass exponents for VO2max regarding ski performances SNC15, SNC30, SNC30:15c SNC30:15f and SNCsprint
were 0.49, 0.57, 0.55, 0.58 and 0.31, respectively. Optimal scaling factor for FISdist was 0.63 and corresponding value for FISsprint was
0.25.
Discussion: This study indicates that optimal body mass exponents for maximal aerobic power depends mainly on work intensity of the
actual skiing performance. Sprint skiing performance places higher metabolic demands than distance races which are reflected by a
lower scaling factor. The fact that SNC15 had a lower optimal body mass exponent than SNC30:15c despite both were performed in the
same course and technique supports the work intensity theory because in double pursuit the physiological resources should be sufficient
to go 15-km more resulting in lower work intensity. Summarizing the reasoning above heavier skiers are favored in shorter race distances
with higher metabolic demands.
References
Bergh U, Forsberg A. (1992). Med Sci Sports Exerc., 24, 1033-9.
PHYSIOLOGICAL DEMANDS OF REAL ELITE CROSS-COUNTRY SKIING PERFORMANCES
CARLSSON, M., CARLSSON, T., HAMMARSTRÖM, D., TONKONOGI, M.
LIVI
Introduction: Which are the main physiological differences between a successful and less successful cross-country skier? To our knowledge
no previous studies have examined a real elite cross-country ski competition. Main purpose of this study was therefore to validate
commonly used test parameters to skiing time and to International Ski Federation (FIS) overall seasonal ranking points and to create
multiple regression models to predict skiing performances.
OSLO/NORWAY, JUNE 24-27, 2009 351