Failure of prior low-intensity exercise to potentiate the thermic effect of glucose

Effects of Exercise Mode on Postprandial Metabolism in Humans with Chronic Paraplegia

PURPOSE

The purpose of this study was to assess the acute effects of exercise mode and intensity on postprandial macronutrient metabolism.

METHODS

Ten healthy men age 39 ± 10 yr with chronic paraplegia (13.2 ± 8.8 yr, ASIA A-C) completed three isocaloric bouts of upper-body exercise and a resting control. After an overnight fast, participants completed circuit resistance exercise (CRE) first and the following conditions in a randomized order, separated by >48 h: i) control (CON), ~45-min seated rest; ii) moderate-intensity continuous exercise (MICE), ~40-min arm cranking at a resistance equivalent to ~30% peak power output (PPO); and iii) high-intensity interval exercise (HIIE), ~30 min arm cranking with resistance alternating every 2 min between 10% PPO and 70% PPO. After each condition, participants completed a mixed-meal tolerance test consisting of a 2510-kJ liquid meal (35% fat, 50% carbohydrate, 15% protein). Blood and expired gas samples were collected at baseline and regular intervals for 150 min after a meal.

RESULTS

An interaction (P < 0.001) was observed, with rates of lipid oxidation elevated above CON in HIIE until 60 min after a meal and in CRE at all postprandial time points up to 150 min after a meal. Postprandial blood glycerol was greater in MICE (P = 0.020) and CRE (P = 0.001) compared with CON. Furthermore, nonesterified fatty acid area under the curve had a moderate-to-strong effect in CRE versus MICE and HIIE (Cohen's d = -0.76 and -0.50, respectively).

CONCLUSIONS

In persons with paraplegia, high-intensity exercise increased postprandial energy expenditure independent of the energy cost of exercise. Furthermore, exercise combining resistance and endurance modes (CRE) showed the greater effect on postprandial lipid oxidation.

Effects of short-lasting supramaximal-intensity exercise on diet-induced increase in oxygen uptake

This study was undertaken to quantify the additional increase in diet-induced oxygen uptake after exhaustive high-intensity intermittent exercise (HIIE), consisting of 6-7 bouts of 20-sec bicycle exercise (intensity: 170% V˙O2max) with a 10-sec rest between bouts. Using a metabolic chamber, the oxygen uptake of ten men was measured from 10:30 am to 07:00 am the next day on two separate days with or without HIIE, with lunch (12:00) and supper (18:00) (Diet experiment). On two other days, the oxygen uptake of six different subjects was measured from 10:30 to 16:00 with or without HIIE, but without meals (Fasting experiment). Ten minutes of exercise at 50% V˙O2maxpreceded the HIIE in both experiments; EPOC (excess postexercise oxygen consumption) after HIIE was found to wear off before 12:00 in both experiments. In the Diet experiment, oxygen uptake during HIIE and EPOC were 123.4 ± 12.0 and 115.3 ± 32.3 mL·kg-1, respectively. Meals elevated resting oxygen uptake on both days, but those on the HIIE day were significantly higher than on the control day. This enhanced diet-induced oxygen uptake (difference in resting oxygen uptake from 12:00-23:00 between HIIE and control day: ΔDIT) was 146.1 ± 90.9 mL·kg-1, comparable to the oxygen uptake during the HIIE and EPOC The ΔDIT was correlated with subjects' V˙O2max(52.1 ± 6.6 mL·kg-1·min-1) (r = 0.76, n = 10, P < 0.05). We concluded that HIIE enhances diet-induced oxygen uptake significantly, and that it is related to the cardiorespiratory fitness.

New approach for weight reduction by a combination of diet, light resistance exercise and the timing of ingesting a protein supplement

We have reported that ingesting a meal immediately after exercise increased skeletal muscle accretion and less adipose tissue accumulation in rats employed in a 10 week resistance exercise program. We hypothesized that a possible increase in the resting metabolic rate (RMR) as a result of the larger skeletal muscle mass might be responsible for the less adipose deposition. Therefore, the effect of the timing of a protein supplement after resistance exercise on body composition and the RMR was investigated in 17 slightly overweight men. The subjects participated in a 12-week weight reduction program consisting of mild energy restriction (17% energy intake reduction) and a light resistance exercise using a pair of dumbbells (3-5 kg). The subjects were assigned to two groups. Group S ingested a protein supplement (10 g protein, 7 g carbohydrate, 3.3 g fat and one-third of recommended daily allowance (RDA) of vitamins and minerals) immediately after exercise. Group C did not ingest the supplement. Daily intake of both energy and protein was equal between the two groups and the protein intake met the RDA. After 12 weeks, the bodyweight, skinfold thickness, girth of waist and hip and percentage bodyfat significantly decreased in the both groups, however, no significant differences were observed between the groups. The fat-free mass significantly decreased in C, whereas its decrease in S was not significant. The RMR and post-meal total energy output significantly increased in S, while these variables did not change in C. In addition, the urinary nitrogen excretion tended to increase in C but not in S. These results suggest that the RMR increase observed in S might be associated with an increase in body protein synthesis.

Effect of exercise intensity on 24-h energy expenditure and nutrient oxidation

The aim of this study was to determine the effects of exercise at different intensities on 24-h energy expenditure (EE) and substrate oxidation. Sixteen adults (8 men and 8 women) were studied on three occasions [sedentary day (Con), a low-intensity exercise day (LI; 400 kcal at 40% of maximal oxygen consumption) and a high-intensity exercise day (HI; 400 kcal at 70% of maximal oxygen consumption)] by using whole room indirect calorimetry. Both 24-h EE and carbohydrate oxidation were significantly elevated on the exercise days (Con < LI = HI), but 24-h fat oxidation was not different across conditions. Muscle enzymatic profile was not consistently related to 24-h fat or carbohydrate oxidation. With further analysis, it was found that, compared with men, women sustained slightly higher rates of 24-h fat oxidation (mg x kg FFM(-1) x min(-1)) and had a muscle enzymatic profile favoring fat oxidation. It is concluded that exercise intensity has no effect on 24-h EE or nutrient oxidation. Additionally, it appears that women may sustain slightly greater 24-h fat oxidation rates during waking and active periods of the day.

Meal size and frequency: effect on potentiation of the thermal effect of food by prior exercise

Prior exercise potentiates the thermic effect of a carbohydrate meal. The purpose of this study was to determine if meal size or feeding pattern influences this response. Two groups of healthy, normal-weight young women exercised for 45 min on a cycle ergometer at 70% of maximal aerobic capacity. Once aerobic capacity returned to pre-exercise baseline, the thermic effect of food (TEF) was determined by indirect calorimetry over a 2-h period. One group of subjects ingested a 2510-kJ meal and the other a 5020-kJ meal. As a control, subjects ingested the test meal without prior exercise. In addition, subjects ingesting the 5020-kJ meal were studied for an additional 2 h. In a separate trial, these subjects ingested a 5020-kJ meal in two equal portions after a bout of exercise, the second portion 120 min after the first. TEF was less for the 2510-kJ meal compared with the 5020-kJ meal for both the control [mean (SE), 76 (17) vs 158 (19) kJ.2h-1, P < 0.01), and prior exercise [124 (23) vs 197 (24) kJ.2h-1, P < 0.01) trials. However, the same increment in TEF resulted from the prior bout of exercise [48 (9) vs 40 (8) kJ.2h-1 for 2510-and 5020-kJ meals, respectively). TEF was 31% lower when the 5020-kJ meal was given in two portions compared with one [281 (30) vs 369 (41) kJ.4h-1, P < 0.05]. No difference in TEF was found between the first and second 2510-kJ portion.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise prescription for individuals with metabolic disorders. Practical considerations

Regular exercise has been recognised as an important component in the management of patients with diabetes mellitus. In addition to acutely lowering blood glucose, exercise training improves glucose tolerance and peripheral insulin sensitivity, contributes to weight loss and reduces several risk factors for cardiovascular disease. When proper precautions are taken to prevent hypoglycaemia, individuals with diabetes can enjoy the same benefits from exercise as nondiabetic healthy individuals. As a guideline, moderate intensity, aerobic endurance activities should be performed for 20 to 40 minutes at least 3 times a week. Blood glucose should be monitored, and insulin dose and carbohydrate intake adjusted based on the blood glucose response to the type and duration of exercise. This review will summarise current understanding of the therapeutic role of exercise in the treatment of diabetes and will present guidelines for prescribing exercise in diabetic patients.