Gender differences in carbohydrate loading are related to energy intake
MARK A. TARNOPOLSKY,1,2 CAROL ZAWADA,2 LINDSAY B. RICHMOND,2 SHERRY CARTER,1 JANE SHEARER,3 TERRY GRAHAM,3 AND STUART M. PHILLIPS2 1 Departments of Medicine (Neurology and Rehabilitation) and 2Kinesiology, McMaster University, Hamilton, Ontario L8N 3Z5; and 3Human Biology and Nutrition, University of Guelph, Guelph, Ontario, Canada N1G ZW1
Received 5 July 2000; accepted in ﬁnal form 6 April 2001
Tarnopolsky, Mark A., Carol Zawada, Lindsay B. Richmond, Sherry Carter, Jane Shearer, Terry Graham, and Stuart M. Phillips. Gender differences in carbohydrate loading are related to energy intake. J Appl Physiol 91: 225–230, 2001.—We demonstrated that female endurance athletes did not increase their muscle glycogen concentration after an increase in the dietary carbohydrate intake (58 3 74%), whereas men did (Tarnopolsky MA, SA Atkinson, SM Phillips, and JD McDougall, J Appl Physiol 78: 1360–1368, 1995). This may have been related to a lower energy or carbohydrate intake by the women or due to an inherent gender difference in glycogen storage capacity. We examined whether well-trained men (n 6) and women (n 6) increased muscle glycogen concentration after an increase in both the relative (58 3 75%) and absolute energy and carbohydrate intake and whether potential gender differences were related to muscle hexokinase enzyme activity. Subjects were randomly allocated to three diets [Hab, habitual; CHO, high carbohydrate (75%); and CHO E, extra energy CHO (1 34%)] for a 4-day period before a muscle biopsy for analysis of total and pro- and macroglycogen and hexokinase activity. Total glycogen concentration was higher for the men on the CHO and CHO E trials compared with Hab (P 0.05), whereas women increased only on the CHO E trial compared with Hab (P 0.05). There were no gender differences in the proportion of pro- and macroglycogen or hexokinase activity. A low
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