Multiple short bouts of exercise over 12-h period reduce glucose excursions more than an energy-matched single bout of exercise

Abstract

Objective: Long, uninterrupted bouts of sedentary behavior are thought to negatively influence postprandial glucose and insulin concentrations. We examined the effects of a 1-h bout of morning exercise versus intermittent walking bouts of short duration on glucose excursions and insulin secretion over 12-h.

Materials/methods: Eleven young, obese individuals (18-35 years, BMI>30kg/m(2)) with impaired glucose tolerance were studied on three 12-h study days: 1) sedentary behavior (SED); 2) sedentary behavior with 1-h morning exercise (EX) at 60%-65% VO2peak; and 3) sedentary behavior with 12-hourly, 5-min intervals of exercise (INT) at 60%-65% VO2peak. Meals (1046kJ/meal) were provided every 2-h. Blood samples were collected every 10 min and measured for glucose, insulin, and c-peptide concentrations.

Results: Glucose iAUC (12-h) was attenuated in the INT and SED conditions compared to the EX condition (P<0.05). Glucose concentrations were higher in the EX compared to the SED condition for ~150min (20% of the study day), and comparison of the EX-INT study days revealed that glucose concentrations were greater for~240min (~1/3 of the 12-hday). In the SED condition, the 12-h insulin iAUC was ~15% higher (P<0.05) compared to the INT and EX conditions. Insulin production rate was found to increase ~20% with INT exercise vs. the SED and EX condition (P<0.05).

Conclusions: Short, frequent periods of exercise attenuated glucose excursions and insulin concentrations in obese individuals to a greater degree than an equal amount of exercise performed continuously in the morning.

Keywords: Glucose; Insulin; Obesity; Physical activity; Sedentary.

Figure 1

A: Pattern of glucose response over the 12 h study day by condition. ⬇ Indicates meals. 1-h Exercise. Intermittent exercise condition; hourly 5-minute walking bouts. B: Two-hour glucose incremental area under the curve (iAUC) across the 12 h study day. Mean±SEM. *P<0.05 vs. 0700–0900h. †P<0.05 vs. 1100–1300h

Figure 2

A: Pattern of insulin glucose response over the 12 h study day by condition. ⬇ Indicates meals. 1-h Exercise. Intermittent exercise condition; hourly 5-minute walking bouts. B: Two-hour serum insulin iAUC across the 12 h study day. Mean±SEM. ‡P<0.05 between conditions (SED vs EX P=0.01, SED vs INT P=0.015); no significant difference between the 2-h time intervals; 0700–0900 *P=.007 SED vs EX, †P=0.06 SED vs INT.

Figure 3

The comparison of the exercise-sedentary day for A. glucose and B. insulin concentrations over 12-h. The solid line represents the difference between study days and simultaneous 95% confidence limits (dotted line) are shown. Significant stimulation of glucose or insulin release by exercise over the sedentary day conditions occurred when the lower 95% confidence limit was more than zero. Significant suppression of glucose or insulin release occurred when the upper 95% confidence limit was less than zero.

Figure 4

Comparison of the magnitudes of the A. glucose and B. insulin response to intermittent exercise over sedentary conditions for the 12 h period. Refer to Fig 3 for more detail.

Figure 5

The differences in response between the exercise and intermittent exercise day for A) glucose and B): insulin concentrations over 12-h. Refer to Fig 3 for further details.