"Bite-size Exercise" - Energy Expenditure During Accumulated Exercise Compared To One Bout Of Equivalent Total Duration.

Abstract

Adopting a habit of multiple shorter duration bouts of exercise throughout the day may be beneficial, and it has been suggested that such a prescription may avoid the risks of unaccustomed, prolonged vigorous exercise. Equally, cardio-respiratory fitness improves to a similar degree with training regimens based on either long or short duration bouts of exercise. For example: when sedentary middle-aged women performed either one 30 min session of brisk walking or three 10 min sessions, five days per week over ten weeks - peak fitness increased by similar amounts. PURPOSE: To determine whether three short duration (10 min) bouts of physical activity have a similar energy expenditure compared to one continuous bout of 30 min. METHODS: On two separate days, 24 subjects (9 female) of mean [range] age 30 [18-58] years and BMI 25 [20-31] Kg/m2, were randomly assigned to either group A (3 × 10 min exercise bouts) or group B (1 × 30 min exercise bout) in a cross-over design. Indirect calorimetry during exercise, during recovery from exercise, and throughout the 8-h simulated working day (15 min epoch each hour) was used to estimate energy expenditure and metabolic fuel selection. RESULTS: Total energy expenditure was similar for both days (group A: 3459 kJ, group B: 3411kJ), with no differences in metabolic substrate utilization. During exercise, energy expenditure was higher during 1 × 30 min bout (831 kJ) compared to energy expenditure accumulated during 3 × 10 min bouts (787 kJ). During the 1 × 30 min exercise bout, higher total carbohydrate (36.3 g) and lower total fat (5.4 g) usage was estimated compared to that accumulated during 3 × 10 min bouts (carbohydrate 30.7 g, fat 6.7 g). During recovery from exercise, energy expenditure was the same for both conditions, although a different mixture of metabolic substrates contributed to this expenditure (group A: carbohydrate 11.7 g, fat 0.1 g vs. group B: carbohydrate 9.3 g, fat 1.1 g). CONCLUSIONS: This study provides empirical evidence that shorter bouts of exercise may offer comparable benefits to a single longer duration bout, particularly in terms of energy expenditure. "Bite-size" exercise may improve long term adherence to physical activity programmes, thus offering a further tool in the fight against inactivity related health problems. Supported by Sport and Recreation New Zealand.