Yoshiharu Nabekura

Effects of post-absorptive and postprandial exercise on 24 h fat oxidation

OBJECTIVE Fat oxidation during exercise depends on nutritional state, and exercise performed in the post-absorptive state oxidizes more fat than that performed in the postprandial state. However, the effects of exercise on energy metabolism continue during the post-exercise period, and the difference in fat oxidation during exercise may be compensated for during the post-exercise period. The present study compared the effects of an acute exercise bout in the post-absorptive or postprandial state on 24 h fat oxidation. METHODS Twelve young male athletes stayed twice in a room-size metabolic chamber for 24 h indirect calorimetry in a randomized repeated-measure design. Before or after breakfast, i.e. in the post-absorptive or postprandial state, subjects exercised at 50% VO(2)max for 60 min. RESULTS During the 60 min of exercise, energy expenditure in the two exercise trials were equivalent, but exercise in the post-absorptive state was performed with lower RQ compared with that in the postprandial state (P<0.01). The time of exercise relative to breakfast did not affect 24 h energy expenditure (P>0.5). However, accumulated 24 h fat oxidation was higher (P<0.05) and that of carbohydrate oxidation was lower (P<0.05) when exercise was performed in the post-absorptive state. CONCLUSIONS Compared with exercise performed in the postprandial state, exercise performed in the post-absorptive state oxidized more fat and saved more carbohydrate in the body, without affecting 24 h energy expenditure.

Exercise Increases 24-h Fat Oxidation Only When It Is Performed Before Breakfast.

Background As part of the growing lifestyle diversity in modern society, there is wide variation in the time of day individuals choose to exercise. Recent surveys in the US and Japan have reported that on weekdays, more people exercise in the evening, with fewer individuals exercising in the morning or afternoon. Exercise performed in the post-prandial state has little effect on accumulated fat oxidation over 24 h (24-h fat oxidation) when energy intake is matched to energy expenditure (energy-balanced condition). The present study explored the possibility that exercise increases 24-h fat oxidation only when performed in a post-absorptive state, i.e. before breakfast. Methods Indirect calorimetry using a metabolic chamber was performed in 10 young, non-obese men over 24 h. Subjects remained sedentary (control) or performed 60-min exercise before breakfast (morning), after lunch (afternoon), or after dinner (evening) at 50% of VO2max. All trials were designed to be energy balanced over 24 h. Time course of energy and substrate balance relative to the start of calorimetry were estimated from the differences between input (meal consumption) and output (oxidation). Findings Fat oxidation over 24 h was increased only when exercise was performed before breakfast (control, 456 ± 61; morning, 717 ± 64; afternoon, 446 ± 57; and evening, 432 ± 44 kcal/day). Fat oxidation over 24 h was negatively correlated with the magnitude of the transient deficit in energy and carbohydrate. Interpretation Under energy-balanced conditions, 24-h fat oxidation was increased by exercise only when performed before breakfast. Transient carbohydrate deficits, i.e., glycogen depletion, observed after morning exercise may have contributed to increased 24-h fat oxidation.

Transient energy deficit induced by exercise increases 24-h fat oxidation in young trained men

Whole body fat oxidation increases during exercise. However, 24-h fat oxidation on a day with exercise often remains similar to that of sedentary day, when energy intake is increased to achieve an energy-balanced condition. The present study aimed to examine a possibility that time of the day when exercise is performed makes differences in 24-h fat oxidation. As a potential mechanism of exercise affecting 24-h fat oxidation, its relation to exercise-induced transient energy deficit was examined. Nine young male endurance athletes underwent three trials of indirect calorimetry using a metabolic chamber, in which they performed a session of 100 min of exercise before breakfast (AM), after lunch (PM), or two sessions of 50 min of exercise before breakfast and after lunch (AM/PM) at 65% of maximal oxygen uptake. Experimental meals were designed to achieve individual energy balance. Twenty-four-hour energy expenditure was similar among the trials, but 24-h fat oxidation was 1,142 ± 97, 809 ± 88, and 608 ± 46 kcal/24 h in descending order of its magnitude for AM, AM/PM, and PM, respectively (P < 0.05). Twenty-four-hour carbohydrate oxidation was 2,558 ± 110, 2,374 ± 114, and 2,062 ± 96 kcal/24 h for PM, AM/PM, and AM, respectively. In spite of energy-balanced condition over 24 h, exercise induced a transient energy deficit, the magnitude of which was negatively correlated with 24-h fat oxidation (r = -0.72, P < 0.01). Similarly, transient carbohydrate deficit after exercise was negatively correlated with 24-h fat oxidation (r = -0.40, P < 0.05). The time of the day when exercise is performed affects 24-h fat oxidation, and the transient energy/carbohydrate deficit after exercise is implied as a factor affecting 24-h fat oxidation.

Continuous Glucose Monitoring During a 100-km Race: A Case Study in an Elite Ultramarathon Runner

The current case study intended to measure blood glucose fluctuation in 2 marathon runners during a 100-km race using a continuous glucose-monitoring system (CGMS) and investigate the relationship between glucose profile and change in running speed. Two experienced ultramarathon runners participated in this study. A CGMS glucose sensor was inserted into the subcutaneous abdominal tissue at 35 h before the 100-km race, and the glucose profile was monitored continuously until the end of the race. Race pace and energy intake during the race were recorded. Participants finished the race in 6h:51min:17s (runner A) and 8h:56min:04s (runner B), and the race-pace decrement ratios were 17.6% for runner A and 27.2% for runner B. The average relative intensity throughout the 100-km race was 89.9% ± 5.8% lactate threshold (LT) in runner A and 78.4% ± 8.6% LT in runner B. The total amount of carbohydrate intake during the race was 249 g and 366 g in runners A and B, respectively. Despite lower carbohydrate intake, runner A maintained a normal glucose level throughout the race, while runner B rapidly decreased blood glucose and became hypoglycemic after the 80-km point. These results suggest that elite ultramarathon runners may have the ability to prevent a large decrement in blood glucose level regardless of the amount of energy intake during the race to maintain higher relative running intensity.

Exercise before breakfast increases 24-h fat oxidation in female subjects

Background Exercise performed in a postprandial state does not increase 24-h fat oxidation of male and female subjects. Conversely, it has been shown in male subjects that exercise performed in a postabsorptive state increases 24-h fat oxidation compared with that in sedentary control and that with exercise trials performed after breakfast, lunch, or dinner. There is a paucity of study evaluating the effect of exercise performed in a postabsorptive state in female subjects. Method Nine young female subjects participated in indirect calorimetry measurement over 24-h using a room-size metabolic chamber in which subjects remained sedentary or performed 60 min exercise before breakfast at 50% of V˙O2max. Exercise was accompanied by an increase in energy intake to ensure that subjects were in a similar state of energy balance over 24 h for the two trials. Findings Compared with the sedentary condition, exercise performed before breakfast increased 24-h fat oxidation (519 ± 37 vs. 400 ± 41 kcal/day). Time courses of relative energy balance differed between trials with transient negative energy balance observed before breakfast. The lowest values of relative energy balance observed during the 24-h calorimetry, i.e., transient energy deficit, were greater in exercise trials than in sedentary trials. The transient deficit in carbohydrate balance was also observed before breakfast, and magnitude of the deficit was greater in exercise trial compared to that of sedentary trial. Interpretation Under energy-balanced conditions, exercise performed in a post-absorptive state increases 24-h fat oxidation in female subjects. The effect of exercise performed before breakfast can be attributed to nutritional state: a transient deficit in energy and carbohydrate at the end of exercise.

Glucose Response after a Ten-Week Training in Swimming

The present study investigated the difference in blood glucose concentration (Glu) response during an incremental swimming test before and after a ten-week training period and verified whether blood glucose threshold (GT) could be determined in competitive swimmers. 7 elite male university swimmers participated in this study. 2 incremental swimming tests were conducted in a swimming flume before and after a ten-week training period. Blood lactate concentration (Bla) and Glu were measured after each swimming step, and the velocities of the lactate threshold (VLT) and glucose threshold (VGT) were analyzed. VLT increased significantly after training (1.21±0.06 m x s(-1) pre-training, 1.31±0.10 m x s(-1) post-training, p<0.05), while Glu did not increase at the higher swimming intensity steps. GT was not determined at each trial. Our results show that lactate threshold (LT) improved significantly after the ten-week training period, while the Glu response during incremental swimming tests did not change. Therefore, GT could not be determined in elite competitive swimmers before and after training.

Effects of Marathon Running on Aerobic Fitness and Performance in Recreational Runners One Week after a Race

It is not clear whether or not recreational runners can recover aerobic fitness and performance within one week after marathon running. This study aimed to investigate the effects of running a marathon race on aerobic fitness and performance one week later. Eleven recreational runners (six men, five women) completed the race in 3 h 36 min 20 s ± 41 min 34 s (mean ± standard deviation). Before and 7 days after the race, they performed a treadmill running test. Perceived muscle soreness was assessed before the race and for the following 7 days. The magnitude of changes in the treadmill running test was considered possibly trivial for maximal oxygen uptake (V˙O2max) (mean difference −1.2 ml/kg/min; ±90% confidence limits 2 ml/kg/min), unclear for %V˙O2max at anaerobic threshold (AT) (−0.5; ±4.1%) and RE (0.2; ±3.5 ml/kg/km), and likely trivial for both velocity at AT and peak (−0.2; ±0.49 km/h and −0.3; ±0.28 km/h). Perceived muscle soreness increased until 3 days after the race, but there were no clear differences between the values before the race and 4–7 days after it. These results show that physiological capacity associated with marathon running performance is recovered within 7 days after a marathon run.

Pacing strategy in a 24-hour ultramarathon race

The purpose of this study is to examine pacing among the runners in a 24-hour ultramarathon. The performances of 48 male runners who ran more than 161 km in a 24-hour ultramarathon race were analyzed. The runners were divided into five groups according to their finish in the race (Group A: 1st-10th, Group B: 11th-20th, Group C: 21th-30th, Group D: 31th-40th, and Group E: 40th-48th). Total distance run, absolute and normalized running speed for each one-hour interval, and a coefficient of variation (CV) for hourly speeds were calculated. The average 24 -hour distance within the various groups ranged from 236.38 km (SD = 11.41 km) for Group A to 164.14 km (SD = 2.49 km) for Group E. Average group CV ranged from 14.3% (SD = 4.3%) for group A to 45.0% (SD = 16.6%) for Group E. Group A runners ran at a relatively constant speed (> 8km/hour) during the second half of the race, whereas the corresponding pace was slower (< 6 km/hour) for groups C through E. CV moderately correlated with total distance run (r = -0.682, p < 0.001). In conclusion, in a 24-hour ultramarathon race, successful performance by the faster runners is achieved with less variation in speed.