Effects Of Moderate Versus Vigorous Intensity Exercise Training In Older Adults With Prediabetes

Abstract

PURPOSE: Aerobic exercise is recommended to improve glycemic control; however, the optimal intensity of exercise for older adults with prediabetes is unknown. The objective of this pilot study was to compare the effects of moderate vs. vigorous intensity aerobic exercise on glycemic control and non-exercise physical activity (NEPA). METHODS: 19 older adults (14F; 68.1 ± 5.8 yrs) with prediabetes (HbA1c 5.7-6.4% or fasting glucose 100-125 mg/dl) were randomized to 12-weeks of supervised aerobic exercise (45-min sessions 4 days/wk) at either moderate (MOD: 60-65% HRmax) or vigorous (VIG: 80-85% HRmax) intensity. Free-living glycemic control (24h mean; percent of day ≥140 mg/dL) was measured using continuous glucose monitors (CGM, Dexcom). NEPA (>1.5 METs, excluding exercise sessions) was assessed using a thigh worn accelerometer (ActivPAL v4). A 3h Oral glucose tolerance test (OGTT, 75g) was performed at baseline and following the exercise intervention (72-96h following the last exercise bout) to compare to free-living CGM and as measure of insulin sensitivity (Matsuda Index). Data are presented as mean±SE. RESULTS: Adherence rates to the exercise interventions were 85±9% and 89±3% in MOD and VIG with mean heart rates during exercise of 99±1 bpm (65% HRmax) and 123±4 bpm (79% HRmax), respectively. Mean 24h glucose (-8.4±6.4 vs. -2.2±6.7 mg/dl) and percent of day >140 mg/dL (-9.7±11.0% vs. 0.7±4.6%) did not significantly change in MOD or VIG, respectively. However, there was a significant group by time interaction (p=0.05) for change in insulin sensitivity in MOD (+2.4±1.1) and VIG (-0.6±0.8).There were no differences between groups for change in NEPA, fasting glucose, or 2h glucose. Changes in free-living CGM were not significantly correlated with changes in OGTT outcomes. CONCLUSION: In older men and women with prediabetes, both MOD and VIG had minimal effects on free-living glycemic control, but MOD induced greater improvements in insulin sensitivity. These preliminary results suggest that a more comprehensive lifestyle intervention combining dietary intervention and exercise may be needed to improve glycemic control in this population.