Journal of Applied Physiology, Vol 67, Issue 2 570-577, Copyright © 1989 by American Physiological Society
Effects of a draft-loaded interval-training program on skeletal muscle in the horse
M. Gottlieb, B. Essen-Gustavsson, A. Lindholm and S. G. Persson
Department of Medicine and Surgery, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Five Standardbred trotters were trained on a treadmill 3 times/wk for 12 wk
by intervals of draft-loaded exercise. The draft load was 34 kp and the
velocity approximately 7 m/s. Muscle biopsies were taken from the gluteus
medius and longissimus muscles before training and after 2, 4, 8, and 12 wk
of training and from the brachiocephalicus muscle before and after
training. Both the percentage and the area of type IIa fibers increased and
the percentage of type IIb fibers decreased in the gluteus medius muscle
during the first 2 wk of training, and then no further significant
difference was noted. The percentage of type I fibers increased in the
brachiocephalicus muscle, and the area of type IIb fibers increased in the
longissimus muscle. The citrate synthase activity increased in the gluteus
muscle only, and the increase was seen during the first 2 wk. No
significant differences were seen in 3-hydroxy-acyl-CoA dehydrogenase and
lactate dehydrogenase activities in the muscles during the entire training
period. Less glycogen was utilized in the gluteus muscle and less blood
lactate accumulated when the horses performed an unloaded submaximal
exercise test after compared with before training. It can be concluded that
rapid changes are induced in the gluteus medius muscle when horses are
trained pulling a light-draft resistance at a submaximal trotting speed.
