Metabolic parameters in two different cross-country skiing techniques during simulated competitions

Introduction

The aim of this study was to investigate some physiological responses of athletes of both genders of cross-country skiing during two simulated short competitions in both the techniques, Skating (S) and Classic (C).

Methods

Eight athletes (4 males, 4 females) of the Italian B national team {average values (+/-sd) in males and females respectively, ys 22.3 (1.7) and 23.5 (4.1); % fat: 7.9 (0.7) and 15.8 (2.6); V’O2max (carried out at 1000m asl): 65.5 (2.8) and 56 (3.1) ml/kg/min}performed twice a simulated competition (6 km for females and 9 km for males) on a 3 km ring at 1350m asl, with two days recovery in between. The two skiing technique (S and C) were applied in a cross-over design. During each test heart rate (HR) and oxygen consumption (V’O2) on breath-by-breath basis were measured, by telemetric metabolimeter (K4b2, Cosmed, Italy) [1]. Average V’O2 (V’O2av) and V’O2peak (V’O2pk), expressed as % of V’O2max, as well as the rate of V’O2 increase at the beginning of the race (Mean Response Time - MRT) were calculated. Blood lactate concentration (BL) was measured (Lactate Pro, Arkray, Japan): a) just before the start; b) at each passage on the top of the main slope (1.8 km after the start); c) at the end of each lap ; d) at the end of the test and during recovery (2°, 4°, 6°, 12° min). Maximal (BLmax) and Average (BLav) BL were expressed as net values by subtracting the basal value.

Results

Males were always faster than females, but more in C than in S. Females were slower than males mainly climbing the slope. S was faster than C, both in males and females; but females showed the largest difference climbing the slope, while males showed an opposite trend.Females showed higher BLmax than males (11.3 mM vs 8.6 mM). Most of the BL increase was detected just after the first slope (7.2 mM in females and 5.7 mM in males). Males showed higher BLmax (about 1.7mM) in C than in S, while almost no BLmax difference was found in females.With an opposite behaviour to BL, females showed higher V’O2av and V’O2pk in C than in S, while males showed higher V’O2av in S than in C.MRT was faster in S than in C both in males (-7s) and females (-5s). It was also faster (-5s) in males than in females.Neither the differences and the correlations were found to be statistically significant. However, not taking into account the skiing technique, the highest correlation indexes were found in the following relationships: MRT vs Total race time (R2=0.58 in males and 0.35 in females); MRT vs BLmax in males (R2=0.34); MRT vs BLav (R2=0.32 in females and 0.35 in males).

Discussion/Conclusions

Females are slower than males mainly in climbing the slope and in C technique, even if they showed V’O2av higher than in S. This could suggest that (besides to have more body fat than males) females are weaker than males; this has also been shown to increase energy cost of skiing [2]. A technical analysis could probably help to understand why the main difference between S and C was found in the flat part and in climbing the slope, for males and females respectively. Technical differences with a different muscles recruitment, as well as a different aerobic and anaerobic involvement during the performance, could also explain the opposite behaviour of V’O2 and BL in males and females. The good, even if not significant, relationship between MRT and total time confirms that aerobic metabolism is a limiting factor of performance in cross-country skiing [2, 3, 4], but above all it suggests that the capability to quickly activate it can help in the whole race, saving anaerobic metabolism at every sudden change of intensity.

References

[1]. Doyon KH (2001) Can J Appl Physiol, 26, 1-1.
[2]. Hoff J (1999) Med Sci Sports Exerc, 31, 870-77.
[3]. Mahood NV (2001) Med Sci Sports Exerc, 33, 1379-84.
[4]. Millet GY (1998) Med Sci Sports Exerc, 30, 755-62.