Intensity Over Effort: Exercise Prescription Strategies for Glycemic Control

ABSTRACT Resistance exercise (RE) is effective in mitigating the development of type 2 diabetes (T2D) and prediabetes, but long-term adherence is low in these populations. Continuous glucose monitoring (CGM) devices are important tools in clinical practices to assist glycemic control. Previous meta-analysis shows the functionality of CGM devices among different exercise modalities but mentions the lack of studies with controlled diet and physical activity levels in free-living conditions. PURPOSE: To examine whether perceived effort during RE influences glycemic control and psychological outcomes in individuals with prediabetes and T2D using CGM under free-living conditions. METHODS: In randomized order, 25 individuals (11 with prediabetes, 14 with T2D) performed a control (CTRL) and 3 RE session targeting the major muscle groups: a high-load (HI; 3 sets per exercise, 8 repetitions per set, 120 seconds of rest between sets, with a load of 75% 1RM), a rest redistribution (RR; 6 sets per exercise, 4 repetitions per set, and 59 seconds of rest between sets, with a load of 75% 1RM), and a low-load (LL; 3 sets per exercise, 16 repetitions per set, 103 seconds of rest between sets, with a load of 37.5% 1RM). Sessions were matched for total volume-load. Psychological responses were recorded during and post RE sessions. CGM collected ~48 hours of blood glucose. Diet was controlled for, and physical activity levels were assessed by accelerometry. RESULTS: Perceived effort was greater in HI compared to all situations (p=0.0001), but no changes in self-efficacy, enjoyment, or discomfort (p>0.05) were noted among RE sessions. Average 24h post-session glucose levels were not different (p=0.56). CTRL had higher afternoon glucose levels in baseline (p=0.002) but not in HI, RR, or LL (p>0.05). Nocturnal glucose levels were lower in HI and RR (p0.05). LL saw an increase in glucose levels from baseline to the next morning (p=0.04). CONCLUSION: In matched total volume-load RE, perceived effort was not associated with improvements in free-living glycemic control, nor with psychological outcomes in individuals with prediabetes and T2D.