Predicting Maximal Oxygen Uptake in Nordic Skiers

Abstract

Maximal oxygen uptake (VO2MAX) is a common lab-based measure of cardiovascular fitness and strong correlate of endurance performance in young Nordic skiers. The measurement of VO2MAX, however, requires expensive metabolic testing equipment that is not available to all testing facilities. PURPOSE: This study sought to derive a VO2MAX prediction equation specific to young Nordic skiers that could be used in place of metabolic testing equipment. METHODS: 13 female (Mean±SD [Range]: 19±4 [16-26] yrs; 168±5 [161-176] cm height; 59.3±5 [46.8-66.0] kg body mass) and 16 male (20±4 [16-29] yrs; 178±7 [169-190] cm height; 71.0±8 [61.8-86.4] kg body mass) competitive Nordic skiers performed a treadmill test to volitional exhaustion to measure VO2MAX. The test protocol started at 99.2 m/min and 6% grade and increased by 8 m/min and 2% grade each stage thereafter with subjects using rubber-tipped ski poles and a ski striding technique that simulates diagonal stride. Measures of VO2 were recorded using standard indirect calorimetry procedures and a 20-sec sampling interval. Using standard stepwise multiple linear regression procedures, relative VO2MAX (ml/kg/ min) for the validation (V) group was predicted using a pool of potential dependent variables: Test completion time (T, mins), age (A, yrs), body mass (M, kg), gender (G; 0 = females, 1 = males), and final treadmill speed and grade at test completion. Data for a separate group of 4 female and 4 male Nordic skiers (20±2 yrs, 172±9 cm, 69.5±8.8 kg), all of whom completed the same testing as the V group, were used to cross-validate (CV) the final equation using a paired t-test. RESULTS: Females averaged 61.1±4.1 [55.4-68.8) ml/kg/min and 6.9±0.8 [5.7-8.1] mins for VO2MAX and T, respectively, while males averaged 70.5±4.3 [61.9-78.3] ml/kg/min and 7.9±0.9 [6.3-9.3] mins. The best predicted equation was as follows: VO2MAX (ml/kg/min) = 33.98 + 3.95xT + 5.34xG (R2= 0.84, SEE = ±2.6 ml/kg/min). Predicted and measured VO2MAX for both V (Mean±SE: 66.3±1.1 vs 66.3±1.1 ml/kg/min) and CV groups (65.5±3.1 vs 66.6±3.2 ml/kg/min) did not differ significantly (P=0.98 and 0.14, respectively). CONCLUSIONS: Accurate prediction of relative VO2MAX in young Nordic skiers is possible with gender and time to exhaustion as predictor variables from a ski striding treadmill protocol.