Effect of food deprivation on treadmill running in dogs

Abstract

Effect of food deprivation on endurance capacity was studied in dogs under the following conditions: a) 3 and 5 days of fasting with daily high levels of energy expenditure and b) 15 days of fasting with low daily levels of energy expenditure. Relative maximum performance, i.e. endurance capacity under conditions wherein work dehydration is a limiting factor, is unaffected by 10–15% body-weight loss and hypoglycemia induced by acute food deprivation. Even with weight loss up to 22%, capacity for daily moderate levels of work is well maintained. Absolute maximum performance (water provided exhaustive treadmill running) improves with 5 days of fasting. Associated with 74% increase in endurance capacity, there is an increased mobilization of body tissue for fuel for the working muscles and a large increase in the post-exercise blood glucose concentration. The dog is resistant to starvation ketosis. In animals tested for absolute performance capacity, the average cumulative calorie deficit, including the exhaustive running trial, was 7500 Calories; yet there was no significant change in the level of blood acetone. It is concluded that absolute performance in the dog increases with 5 days of food deprivation; this response is mediated by a unique permissive effect of such treatment particularly on ability to mobilize body energy reserves. Submitted on April 17, 1959

Effect of mild restriction of food intake on the speed of racing Greyhounds

“…A decrease in blood glucose concentrations detected in well-fed Beagles during endurance exercise was not evident in food-deprived Beagles, which suggested that delivery of glucose to muscle matched the demand in food-deprived but not well-fed dogs. 4 However, in the Greyhounds evaluated in the present study, serum glucose concentrations increased after a 30-second race, compared with the values before the race, and serum glucose concentrations after racing were unaffected by restricted access to food. Increasing body temperature has also been observed to limit performance in exercising dogs, 4,21 but the increase in rectal temperatures during a race was unaffected by food deprivation in these Greyhounds.…”

“…Beagles running on a treadmill at 6 km/h consumed less energy as they lost weight during 15 days of food deprivation, even when work load was adjusted for weight. 4 If this relationship applies to Greyhounds during a sprint, then less energy would be required by lightweight dogs than heavier dogs to complete a race. Furthermore, Greyhounds mostly rely on anaerobic and aerobic metabolism of carbohydrates during a 30-second race.…”

Effects of exercise, thyroxine, and age on corticosterone production in the male rat

“…They confirmed these reports when they demonstrated that short-term exercise caused an increase in glucocorticoids, while prolonged exercise caused a decrease. Many other workers have obtained similar results (Masson, 1941;Haldi and Wynn, 1946;Young, 1959;Stolyarova, 1968;and Chin and Evonuk, 1971). It has been suggested that adrenal steroid levels remain constant in aging (Grad et al, 1967eund Friedmsm et al, 1969.…”

Effects of age, exercise, graded thyroxine levels and adrenocorticotrophic hormone upon the in vitro secretion of corticosterone in the male rat

“…Ingbar and Freinkel (1955) have reported that long term exercise decreased indices of cortical activity, namely plasma corticoid levels. Similar results have been obtained by Young (1959), Viru and Akke (1969) and Chin and Evonuk (1971).…”

“…This latter finding is not consistent with the reports of others that prolonged exercise decreases corticosteroidogenesis (Chin and Evonuk, 1971;Craig, 1972;Young, 1959). It is of interest to note that previous interpretation of the level of cortical function was based for the most part upon plasma levels of corticosteroids and not upon the actual output of the gland.…”