To examine the effects of a 3-day high carbohydrate (H-CHO) and low carbohydrate (L-CHO) diet on 45 min of cycling exercise, 12 endurance-trained cyclists performed a 45-min cycling exercise at 82 ± 2% VO2peak following an overnight fast, after a 6-day diet and exercise control. The 7-day protocol was repeated under 2 randomly assigned dietary trials H-CHO and L-CHO. On days 1–3, subjects consumed a mixed diet for both trials and for days 4–6 consumed isocaloric diets that contained either 600 g or 100 g of carbohydrates, for the HCHO and the L-CHO trials, respectively. Muscle biopsy samples, taken from the vastus lateralis prior to the beginning of the 45-min cycling test, indicated that muscle glycogen levels were significantly higher (p < .05) for the H-CHO trial (104.5 ± 9.4 mmol/kg wet wt) when compared to the L-CHO trial (72.2 ± 5.6 mmol/kg wet wt). Heart rate, ratings of perceived exertion, oxygen uptake, and respiratory quotient during exercise were not significantly different between the 2 trials. Serum glucose during exercise for the H-CHO trial significantly increased (p < .05) from 4.5 ± 0.1 mmol · L−1 (pre) to 6.7 ± 0.6 mmol · L−1 (post), while no changes were found for the L-CHO trial. In addition, post-exercise serum glucose was significantly greater (p < .05) for the H-CHO trial when compared to the L-CHO trial (H-CHO, 6.7 ± 0.6 mmol · L−1; L-CHO, 5.2 ± 0.2 mmol · L−1). No significant changes were observed in serum free fatty acid, triglycerides, or insulin concentration in either trial. The findings suggest that L-CHO had no major effect on 45-min cycling exercise that was not observed with H-CHO when the total energy intake was adequate.
Stavros A. Kavouras, John P. Troup and Jacqueline R. Berning
Suzanne Nelson Steen
The dietary strategies of a 25-year-old bodybuilder were studied as he prepared for a contest. Food records were kept over a 6-month period that included the off-season, weight reduction phase, and week of a contest. Mean caloric intake during the off-season was 4,193 kcal (49 kcal/kg), Average intake per kg body weight was 8.7 g/kg carbohydrate and 2.8 g/kg protein. During the weight reduction phase of training, mean caloric intake was 3,020 kcal (37 kcal/kg). Carbohydrate intake averaged 6.1 g/kg and protein averaged 2.7 g/kg. The RDA was met for all micronutrients without any need for supplementation. Beginning at 3 weeks before the contest, dietary intake changed dramatically and haddock, rice, or potato were eaten every 2 hours. Protein intake averaged 4 g/kg. Carbo-loading was practiced the week precontest to enhance muscularity. During all phases the subject used anabolic steroids and consumed various supplements. During the off-season he took a high potency multivitamin/multimineral daily and 60-100 grams of amino acids when “needed.” As the competition drew closer, numerous additional supplements were taken. In light of these many unhealthy practices, alternative strategies should be negotiated with the athlete that are realistic, and changes should be implemented slowly.