Effects of exercise intensity on postprandial improvement in glucose disposal and insulin sensitivity in prediabetic adults

Abstract

Background: A single bout of exercise improves postprandial glycemia and insulin sensitivity in prediabetic patients; however, the impact of exercise intensity is not well understood. The present study compared the effects of acute isocaloric moderate (MIE) and high-intensity (HIE) exercise on glucose disposal and insulin sensitivity in prediabetic adults.

Methods: Subjects (n=18; age 49±14 y; fasting glucose 105±11 mg/dL; 2 h glucose 170±32 mg/dL) completed a peak O2 consumption/lactate threshold (LT) protocol plus three randomly assigned conditions: 1) control, 1 hour of seated rest, 2) MIE (at LT), and 3) HIE (75% of difference between LT and peak O2 consumption). One hour after exercise, subjects received an oral glucose tolerance test (OGTT). Plasma glucose, insulin, and C-peptide concentrations were sampled at 5- to 10-minute intervals at baseline, during exercise, after exercise, and for 3 hours after glucose ingestion. Total, early-phase, and late-phase area under the glucose and insulin response curves were compared between conditions. Indices of insulin sensitivity (SI) were derived from OGTT data using the oral minimal model.

Results: Compared with control, SI improved by 51% (P=.02) and 85% (P<.001) on the MIE and HIE days, respectively. No differences in SI were observed between the exercise conditions (P=.62). Improvements in SI corresponded to significant reductions in the glucose, insulin, and C-peptide area under the curve values during the late phase of the OGTT after HIE (P<.05), with only a trend for reductions after MIE.

Conclusion: These results suggest that in prediabetic adults, acute exercise has an immediate and intensity-dependent effect on improving postprandial glycemia and insulin sensitivity.

Figure 1.

Study time line.

Figure 2.

Mean(±SE) plasma glucose (A), insulin (B), and C-peptide (C) response profiles by sampling time point (every 5 to 10 min intervals) at baseline, during exercise (or rest), during recovery, and during the 3-hour, 75-g OGTT.

Figure 3.

Mean (±SE) incremental AUC for the glucose (A), insulin (B), and C-peptide (C) responses to a 3-hour OGTT performed 1 hour after the cessation of acute isocaloric moderate and HIE, compared with a no-exercise control condition. AUC values represent first-phase (first hour during the OGTT) and late-phase segments (second and third hour of the OGTT). *, Significantly different from control (P < .05). †, significantly different from MIE (P < .05).

Figure 4.

Mean (±SE) minimal derived estimates of insulin sensitivity in response to acute isocaloric high and MIE compared with a no-exercise control condition. *, Significantly different from control (P < .05).