CARBOHYDRATE LOADING AND METABOLISM DURING EXERCISE IN MEN AND WOMEN

During endurance exercise at similar to 65% maximal O-2 consumption, w omen oxidize more lipids, and therefore decrease carbohydrate and prot ein oxidation, compared with men (L. J. Tarnopolsky, M. A. Tarnopolsky , S. A. Atkinson, and J. D. MacDougall. J. Appl. Physiol. 68: 302-308, 1990; S. M. Phillips, S. A. Atkinson, M. A. Tarnopolsky, and J. D. Ma cDougall. J. Appl. Physiol. 75: 2134-2141, 1993). The main purpose of this study was to examine the ability of similarly trained male (n = 7 ) and female (n = 8) endurance athletes to increase muscle glycogen co ncentrations in response to an increase in dietary carbohydrate from 5 5-60 to 75% of energy intake for a period of 4 days (carbohydrate load ing). In addition, we sought to examine whether gender differences exi sted in metabolism during submaximal endurance cycling at 75% peak O-2 consumption (VO2 peak) for 60 min. The men increased muscle glycogen concentration by 41% in response to the dietary manipulation and had a corresponding increase in performance time during an 85% VO2 peak tri al (45%), whereas the women did not increase glycogen concentration (0 %) or performance time (5%). The women oxidized significantly more lip id and less carbohydrate and protein compared with the men during exer cise at 75% VO2 peak. We conclude that women did not increase muscle g lycogen in response to the 4-day regimen of carbohydrate loading descr ibed. In addition, these data support previous observations of greater lipid and lower carbohydrate and protein oxidation by women vs. men d uring submaximal endurance exercise.