Progressive effect of endurance training on o2 kinetics at the
onset of submaximal exercise.
Phillips, S. M., H. J. Green, M. J. Macdonald, and R. L. Hughson.
Department of Kinesiology, University of Waterloo, Waterloo, ON,
Canada, N2L 3G1
APStracts 2:0310A, 1995.
The rates of increase in oxygen uptake (O2) following step changes in
work rate from 25W to 60% of pre-training O2 peak, were measured at
various time points during an endurance training program (2h/day at
60% pre-training O2 peak). Seven untrained males (23+/-1 yr, X+/-SE)
performed a series of repeated step changes in work rate pre-training
(PRE), following 4 days (4D), 9 days (9D), and 30 days (30D) of
training. O2 kinetic responses were determined from breath-by-breath
data averaged across 4 repetitions and analyzed using a two component
exponential model. Mean response time (the time taken to reach 63% of
the steady-state O2) was faster (P<0.01) than PRE (38.1+/-2.6 s) at
both 4D (34.9+/-2.4) and 9D (32.5+/-1.8), and was faster (P<0.01) at
30D versus all other time points (28.3+/-1.0). Blood lactate
concentrations (after 6 min of cycling) were also lower at 4D and 9D
versus PRE (P<0.01), and lower at 30D versus all other time points
(P<0.01). O2 peak was unchanged from PRE (3.52+/-0.20 l/min) at 8D
(3.55+/-0.20 l/min), but was increased (P<0.01) at 30D (3.89+/-0.18
l/min). Muscle oxidative capacity (maximal citrate synthase activity)
was not significantly increased until 30D of training (P<0.01). It is
concluded that at least part of the acceleration of whole-body O2
kinetics with endurance training, is a rapid phenomenon, occurring
prior to changes in O2 peak and/or muscle oxidative potential.
Received 28 December 1994; accepted in final form 5 July 1995.
APS Manuscript Number A1352-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.