The ASSIST Trial: Acute Effects of Manipulating Strength Exercise Volume on Insulin Sensitivity in Adults Living With Obesity: A Randomized Controlled, Crossover, Clinical Trial

Abstract

Aims

To investigate the influence of exercise volume on the transient increase in insulin sensitivity and β-cell function that occurs in the hours following an acute bout of strength exercise.

Materials and methods

Fifteen (14 females) adults living with obesity (47.4 ± 9.7 years, 44.3 ± 4.1% body fat) performed three randomized sessions separated by at least four washout days: (1) high volume (21 sets); (2) low volume (7 sets), and (3) control. An oral glucose tolerance test (OGTT) was performed the following morning, and indexes of insulin sensitivity and β-cell function were calculated using glucose, insulin, and C-peptide assessed during the OGTT. Every participant completed each arm of the experiment and was included in the data analysis (n = 15). Researchers who conducted data and statistical analysis were blinded to individuals and sessions.

Results

One-way repeated measure analysis of variance followed by Tukey as post hoc showed that indexes of insulin sensitivity improved after the high-volume session (p < 0.05) but not after the low-volume session (p > 0.05) (effect size [EF] for high and low volume, respectively): insulin area under the curve (AUC) [−0.53 and −0.05], C-peptide AUC [0.58 and 0.18], Cederholm index [0.59 and 0.11], skeletal muscle index [0.89 and 0.60], Gutt index [0.78 and 0.20], Stumvoll index [0.81 and 0.18], and the simple index [0.52 and 0.16]). β-cell function showed a strong tendency to improve (p < 0.06) after the high-volume session (EF for high and low volume, respectively): C-peptidogenic index [0.58 and −0.20], C-peptide oral disposition index [0.72, −0.33]. No adverse effects were observed during data collection.

Conclusions

These results suggest that adults living with obesity who are seeking to improve insulin sensitivity should perform high-volume strength exercises.