INTRODUCTION: Fatigue compensation strategies have been proposed by Kroel, et al. to help skiers cope with the stress of multiple days of training; however, no one has published a systematic study of metabolic requirements and muscle fatigue characteristics of alpine skiing over a period as long as a week or more. METHOD: Subjects (N=14) were divided into two groups of matched pairs. A sub-group of 6 subjects also skied with a portable metabolic System (Oxycon Mobile) to better determine energy demands of various training sessions. All subjects completed several components of testing: 1.) A 60%MVC knee extension task (fixed at 120 degrees) to fatigue repeated every 3rd day, 2.) Daily dietary records, 3.) Daily water intake based on body mass using a Camelbak 4.) Training impulse (Trimp) perceived effort multiplied by the training runs taken each day, and 5.) The experimental group (n=7) received 5-6 Accel Gels/day during training. RESULTS: Metabolic demands of four different training sessions revealed varied oxygen demands while skiing. Slow free skiing was quite low in its demands for energy as reflected by the mean VO2 (11.2+1.6 ml/kg/min) and mean HR (114+4 bpm). This was followed by similar demands for short bouts (~30s) of either fast free skiing (21.0+.3.1 ml/kg/min) and mean HR (139+15 bpm) or GS training (19.7+3.3 ml/kg/min) and mean HR (120+17 bpm). The highest demands were seen in SL training (~45s) (27.2+2.9 ml/kg/min) with a range all the way to 45.1 ml/kg/min. For calorie intake, independent t-tests revealed no differences between the two groups; however, the difference in Delta Calories [(Dietary intake+Gel Calories)/RDA] just reached significance (t,2= 1.78, P<.05). Without the gels, almost everyone was in a negative calorie balance. Only one subject in the control group took in an adequate number of calories to match estimated energy expenditure. Values for RPE, laps and Trimp scores were not different between groups or over time (repeated ANOVA, P>.05). There was a statistical difference in Delta fatigue between groups (repeated ANOVA, F(2,10)=3.73, P<.05). Post hoc t-tests revealed there were differences both at Day 6 and Day 13. No differences in muscle soreness were observed. DISCUSSION: All the VO2 values are lower than previously reported and would merit further investigation. It would appear that shaped skis have shifted the metabolic requirements toward anaerobic Systems; albeit, one cannot dismiss the importance of aerobic capacity to sustain repeated bouts of activities less dependent on oxygen uptake. Ad lib calorie intake without supplementing appears to be inadequate for ski training. The deficit seen here is also similar to several previous studies by Meyer, et al. CONCLUSION: Metabolic demands for ski training exceed the normal dietary intake of young athletes in spite of encouragement from coaches to eat. Supplementing a skier's diet with 500-600 Calories while race training, appears to provide enough energy to match the metabolic demand of a 3-4 hour Session on a glacier. These additional calories may help reduce muscle fatigue as measured by a sustained 60%MVC leg extension task to exhaustion.
© Copyright 2008 Science and Skiing IV. Veröffentlicht von Meyer & Meyer. Alle Rechte vorbehalten.