Resumen de Metabolic responses and pacing strategies during successive sprint skiing time trials
Erik Andersson, Hans-Christer Holmberg, Niels Ortenblad
AB Purpose: This study aimed to examine the metabolic responses and pacing strategies during the performance of successive sprint time trials (STTs) in cross-country skiing. Methods: Ten well-trained male cross-country skiers performed four self-paced 1300-m STTs on a treadmill, each separated by 45 min of recovery. The simulated sprint time trial (STT) course was divided into three flat (1[degrees]) sections (S1, S3, and S5) involving the double poling subtechnique interspersed with two uphill (7[degrees]) sections (S2 and S4) involving the diagonal stride subtechnique. Treadmill velocity and V[spacing dot above]O2 were monitored continuously, and gross efficiency was used to estimate the anaerobic energy supply. Results: The individual trial-to-trial variability in STTs performance time was 1.3%, where variations in O2 deficit and V[spacing dot above]O2 explained 69% (P < 0.05) and 11% (P > 0.05) of the variation in performance. The first and the last STTs were equally fast (228 +/- 10 s) and ~1.3% faster than the second and the third STTs (P < 0.05). These two fastest STTs were associated with a 14% greater O2 deficit (P < 0.05), whereas the average V[spacing dot above]O2 was similar during all four STTs (86% +/- 3% of V[spacing dot above]O2max). Positive pacing was used throughout all STTs, with significantly less time spent on the first than second course half. In addition, metabolic rates were substantially higher (~30%) for uphill than for flat skiing, indicating that pacing was regulated to the terrain. Conclusions: The fastest STTs were characterized primarily by a greater anaerobic energy production, which also explained 69% of the individual variation in performance. Moreover, the skiers used positive pacing and a variable exercise intensity according to the course profile, yielding an irregular distribution of anaerobic energy production. (C) 2016 American College of Sports Medicine
