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Indexed/Abstracted in: Chemical Abstracts, CINAHL, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
Impact Factor 1,111
Online ISSN 1827-1928
EXERCISE PHYSIOLOGY AND BIOMECHANICS
Kenefick R. W., Mattern C. O., Mahood N. V., Quinn T. J.
University of New Hampshire Department of Kinesiology Exercise Physiology Laboratory Durham, New Hampshire, USA
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·min-1, VO2max) participated in the study. Subjects performed a graded protocol starting at 150 Watts (W) to determine LT (2 mmol·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. 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.