The effect of forced exercise on development of heart, lung and diaphragm muscle in weanling horses

Eleven weanling Quarter Horses were separated into two treatment groups, EX = exercise (n=5) and NEX = non-exercise (n=5). At 150 days-of-age, EX horses were started on a 120-day exercise conditioning program. Horses were exercised over a sandy track using a mechanical walker at 3 m/second for from 3.4 to 34.0 minutes/day, 5 days per week; they travelled in opposite directions on alternate days. Horses were weighed and measured for height at the withers at the beginning and end of the study. Homes were euthanized at approximately 270 days-of-age. Rump fat thickness was measured, and heart, lung and diaphragm muscles were removed, dried to constant weight and expressed as percent of body weight or in ratio to height at the withers.