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Short-term Changes In Dietary Pattern Following Glycogen Depletion And Post-exercise Supplementation: 3248 Board #9 May 30, 8
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This study examined the effect of the type, amount, and the frequency of feeding of carbohydrates on muscle glycogen resynthesis after running. Trained male runners performed a 16.1 km run at 80% VO2 max to decrease gastrocnemius glycogen levels. A complex or simple carbohydrate diet (approximately 3000 kcal) resulted in similar muscle glycogen levels 24 h after exercise. Forty-eight hours after exercise the complex carbohydrate diet resulted in significantly higher (p less than 0.05) muscle glycogen levels. Consuming increasing amounts of carbohydrate, between 88 to 648 g carbohydrate/day, resulted in increasingly larger amounts of muscle glycogen resynthesis (24 h) after exercise. Frequent feedings of a high carbohydrate diet did not enhance muscle glycogen synthesis when compared to equal amounts of carbohydrates in two meals. It appears that muscle glycogen can be normalized between daily strenuous running activity.
To examine the effects of a high dose (two high-intensity exercise sessions) of exercise on energy intake (EI) and subjective states (hunger and mood).
Using a within subjects design, there were two treatment conditions, each of two consecutive days.
The Human Appetite Research Unit at Leeds University Psychology Department.
Eight lean males who were regular exercisers were recruited from the student/staff population of Leeds University.
The effects of the high dose of exercise Ex1 were compared with the effects on the day immediately after exercise (Ex2) and two consecutive days of no exercise (R1 and R2). EI was monitored using self-record food diaries and subjective states were tracked using a new Electronic Appetite Rating System (EARS). Heart rate and physical activity were also measured.
Feelings of hunger were not elevated by the high dose of exercise on Ex1 or on the day after exercise (Ex2). In fact, average daily feeling of hunger on Ex1 was significantly lower compared with the average daily feeling of hunger on Ex2 (t = 3.15, d.f. = 7, P < 0.05), but not when compared with R1 or R2. EI and macronutrient intakes were not different on Ex1, Ex2, R1 or R2. Therefore, there were no increase in EI on Ex1 or Ex2 to account for the measured increase in exercise-induced energy expenditure (1200 kcal). Continuously monitored heart rate and activity profiles indicated that there was no difference in activity during the non-exercise periods between the four days.
This study indicates that a high dose of exercise in one day failed to have any effect on EI within the same day or on the day immediately after exercise, compared with days of no exercise. These results demonstrate that an acute but substantial increase in energy expenditure (EE) due to intense exercise does not automatically increase hunger or EI within 48 h. This indicates the absence of any strong coupling between EE and EI in the short-term, probably as a result of food intake being held in place by environmental contingencies and short-term pre-absorptive physiological responses arising from eating itself.
The present study tested the hypothesis that habitual exercisers demonstrate an increased accuracy of regulation of food intake in compensation for previous dietary energy intake. Twenty-three lean healthy male subjects were divided into two groups on the basis of their habitual exercise levels: non-exercisers (no exercise sessions/week, n 9), and exercisers (>two exercise sessions of 40 min or more/week, n 14). The appetite response to covert liquid preloads of high (2513 kJ) energy (HE) and low (1008 kJ) energy (LE) was investigated Sixty minutes after the preload subjects were offered an ab libitum buffet-style meal and energy intake (EI) was calculated. Subjective hunger and satiety were assessed throughout using self-rated visual-analogue scales. Buffet EI in non-exercisers was not significantly different following the LE or HE preloads (mean compensation 7 %), but the exercise group significantly reduced their energy intake following the HE, compared with the LE, preload (mean compensation 90 %; P=0.0035). A broadly similar pattern of response was observed for both moderate (two to three sessions/week, n 7) and high exercisers (>four sessions/week, n 7). There were no significant differences between hunger or satiety ratings following HE or LE preloads for either group. However non-exercisers scored significantly higher on their self-ratings of hunger at the start of the study, before preload consumption, compared with the exercisers (P<0.01). These findings demonstrate that habitual exercisers have an increased accuracy of short-term regulation of food intake in compensation for preload manipulation, and provide additional support for advocating regular exercise in the prevention of overweight and obesity.
Nine male, endurance-trained cyclists performed an interval workout followed by 4 h of recovery, and a subsequent endurance trial to exhaustion at 70% VO2max, on three separate days. Immediately following the first exercise bout and 2 h of recovery, subjects drank isovolumic amounts of chocolate milk, fluid replacement drink (FR), or carbohydrate replacement drink (CR), in a single-blind, randomized design. Carbohydrate content was equivalent for chocolate milk and CR. Time to exhaustion (TTE), average heart rate (HR), rating of perceived exertion (RPE), and total work (WT) for the endurance exercise were compared between trials. TTE and WT were significantly greater for chocolate milk and FR trials compared to CR trial. The results of this study suggest that chocolate milk is an effective recovery aid between two exhausting exercise bouts.