Cardiorespiratory kinetics during exercises of different muscle
groups and mass in old and young.
Chilibeck, P. D., D. H. Paterson, W. D. F. Smith, and D. A.
Cunningham.
The Centre for Activity and Ageing, Faculty of Kinesiology, The
University of Western Ontario, London, Ontario, Canada, N6A 3K7
APStracts 3:0232A, 1996.
The purpose was to compare cardiorespiratory kinetics during exercises
of different muscle groups (double leg cycling versus treadmill
walking and single leg ankle plantar flexion) in old and young
subjects. Oxygen uptake (VO2) during exercise transitions was
measured breath-by-breath and the phase 2 portion of the response fit
by a monoexponential for determination of the time constant ([tau])
of VO2. Two separate studies were performed: In study 1, 12 old (aged
66.7y) and 16 young (aged 26.3y) subjects were compared during
cycling and ankle plantar flexion exercise, and in study 2, five old
(aged 69.6y) and five young (aged 24.4y) subjects were compared
during cycling and treadmill walking. VO2 transients during square
-wave cycling exercise were significantly slower in the old compared
with the young groups. In contrast, VO2 kinetics did not differ
between old and young during plantar flexion exercise. Heart rate
kinetics followed the same pattern, with [tau]HR being significantly
slower in the old versus young groups during transitions to cycling,
but not plantar flexion. In study 2, [tau]VO2 and [tau]HR during on
-transients to treadmill square-wave exercise were significantly
slower in the old group compared to the young, but [tau]VO2 was
significantly faster during treadmill than cycling in the old. The
differences with ageing between the modes of exercise may be related
to the muscle mass involved, and the circulatory demands. On the
other hand, slowed VO2 kinetics with age appear to occur in a mode
(cycling) in which the muscles are not accustomed to the activity,
while in a mode of normal activity (walking) and with the muscle
groups (plantar flexors) accustomed to the activity, VO2 kinetics are
not slowed to the same degree with age.
Received 11 January 1996; accepted in final form 22 April 1996.
APS Manuscript Number A28-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96