Physiological variables at lactate threshold under-represent cycling time-trial intensity.

BACKGROUND: The importance of lactate threshold (LT) as a determinant of performance in endurance sports has been established. In addition, it has been shown that during running and selected other endurance competitions, athletes perform at a velocity and VO2 slightly above LT for the duration of the event. Prior work indicates however, that this may not be true during a cycling time-trial (TT). This investigation sought to compare physiological variables during a 20-k TT with those corresponding to the athlete's LT. METHODS: Thirteen male cyclists (22.7+/-0.8 yrs; 180.6+/-8.0 cm; 77.1+/-10.0 kg; 8.3+/-2.5% fat; 4.9+/-2.2 l x min(-1), VO2max) participated in the study. Subjects performed a graded protocol starting at 150 Watts (W) to determine LT (2 mmol x L(-1) above baseline) which consisted of 20 W increases every 4-min. Following an 8 min-recovery, subjects cycled at the wattage corresponding to LT-20 W for 1 min and then workload increased 20 W every minute until volitional exhaustion to determine VO2max x On a separate occasion a self-paced, 20-k TT was completed. RESULTS: Mean values of blood lactate, HR and % HRmax, VO2 and % VO2max, and power output throughout the 20-k TT were greater (p<0.01) than those at LT. During the TT these cyclists performed at an intensity well above LT (blood lactate=252.0+/-0.1%, HR=9.4+/-0.03%, %HRmax=9.2+/-0.15%, VO2=26.5+/-0.7%, %VO2max=17.2+/-0.08% and power out-put=14.8+/-0.14% above LT) for over 30 min. CONCLUSIONS: Therefore, while LT may be highly correlated to performance, it may not be representative of race pace for a cycling TT, and may be questionable as a benchmark used to prescribe training intensity for competitive TT-cycling.

Physiological determinants of cross-country ski racing performance.

PURPOSE: Previous laboratory testing has identified the importance of upper-body aerobic and anaerobic power to cross-country skiing performance. The purpose of this investigation was to extend laboratory research into a field setting to identify predictors of performance through ski-specific testing. METHODS: Thirteen male collegiate skiers performed three field-testing sessions on roller skis to establish lactate threshold (LT) and ski economy (ECON) and maximal oxygen uptake (SK VO(2max)) and a 1-km double-pole time trial (UBTT) to determine peak upper-body oxygen uptake (UB VO(2)). As a measure of skiing performance, the subjects performed a 10-km skating time trial (TT) and were ranked according to competitive season performance (RANK). RESULTS: Significant correlations (P < 0.05) were found between SK VO(2max), LT VO(2), UB VO(2), and RANK (r = -0.66 to -0.84) and TT time (r = -0.74 to -0.79), as well as ECON to RANK (r = 0.57) and TT time (r = 0.68). Time to complete the UBTT (UB time) exhibited the strongest correlation to both RANK (r = 0.95) and TT time (r = 0.92). Multiple regression analyses revealed that UB time was the best predictor of RANK and TT time, as demonstrated by the significant beta values (0.77, P < 0.001, and 0.79, P < 0.001, respectively). The importance of the UB component was further seen in that UB time was still the best predictor of performance when the subjects were divided into two distinct groups of greater and lesser competitive ability. CONCLUSIONS: These findings identify the importance of the upper body component to cross-country skiing performance, suggesting a need to focus on upper-body conditioning within a well-rounded endurance training program. Additionally, the UBTT exhibits potential as a simple field test to predict cross-country skiing performance over more sophisticated and costly laboratory and field testing.