The effect of treadmill incline and speed on metabolic rate during
exercise in thoroughbred horses.
Eaton, Michael D., David L. Evans, David R. Hodgson, and Reuben J.
Rose.
Department of Veterinary Clinical Sciences, Animal Science and
Animal Health, The University of Sydney NSW 2006, Australia
APStracts 2:0202A, 1995.
Due to the wide range of exercise intensities achieved by different
treadmill inclinations and speeds used in equine physiology studies,
we compared the interaction of treadmill slope and speed on some
physiological responses to exercise. We examined the effect of
treadmill speed and incline on oxygen uptake (V.O2), carbon dioxide
production (V.CO2), heart rate (HR), plasma lactate concentration,
economy of locomotion, stride frequency (SF) and stride length (SL).
A further aim was to examine the relationships between HR and V.O2,
and lactate and V.O2 and whether these relationships vary with
alterations in treadmill incline. The experiment was a latin square
design, using 5 horses and 5 treadmill inclines (0, 2.5, 5.0, 7.5 and
10.0%). Fit Thoroughbred horses exercised for 4 min at 3 m.s-1 at 0%
slope as a warm-up, then the treadmill was set to the allocated
incline. Speeds tested ranged from 1 to 13 m.s-1, with the speed
being increased every 2 min at 1 m.s-1 increments. At each speed,
measurements were taken for V.O2, V.CO2, HR, plasma lactate
concentration, SF and SL. The relationships of V.O2 and V.CO2 with
speed were curvilinear at 0% and 2.5% inclines and linear at 5%, 7.5%
and 10%. The was a linear relationship of HR and speed with a
significant effect of incline. The plasma [lactate] increased
exponentially with speed and there was a significant effect of
incline. The SL increased linearly and SF increased in a curvilinear
manner with speed but there was no effect of incline. There were
linear relationships of HR with V.O2 and HR with V.O2, when expressed
as percentages of maximum V.O2 (%V.O2max) and maximum HR (%HRmax),
that were not affected by incline. The oxygen cost of exercise on a
10% incline was approximately 2.5 times that for exercise on the
flat. The strong relationship between %HRmax and %V.O2max indicates
that over a wide range of exercise intensities the relative V.O2 can
be accurately predicted from measurements of HR.
Received 8 December 1994; accepted in final form 8 May 195.
APS Manuscript Number A1256-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.