Context: Glycemic control improves with physical activity, but the optimal exercise mode is unknown. Objective: To determine whether interval-based exercise improves postprandial glucose tolerance and free-living glycemia more than oxygen-consumption and time-duration matched continuous exercise. Design: Cross-over, controlled with trials performed in randomized order. Setting: Hospitalized and ambulatory care. Patients: Diagnosed with type 2 diabetes (T2DM; n=10, no withdrawels). Interventions: Subjects performed three 1-hour interventions: 1) interval-walking (IW; repeated cycles of 3 minutes of slow and fast walking); 2) continuous-walking (CW); 3) Control (CON). Oxygen consumption (VO2) was measured continuously to match mean VO2 between exercise sessions (∼75% VO2peak). Main Outcome Measures: A mixed meal tolerance test (MMTT; 450 kcal, 55% carbohydrate) with stable glucose isotopic tracers was provided after each intervention and glucose kinetics were measured during the following 4 hours. Free-living glycemic control was assessed for ∼32 hours following the MMTT using continuous glucose monitoring (CGM). Results: VO2 was well-matched between the exercise interventions. IW decreased mean and maximal incremental plasma glucose during the MMTT when compared to CON (Mean: 1.2±0.4 vs. 2.0±0.5 mmol/l, P<0.001. Maximal: 3.7±0.6 vs. 4.6±0.7 mmol/l, P=0.005) and mean when compared to CW (1.7±0.4 mmol/l, P=0.02). No differences in mean or maximal incremental plasma glucose values were seen between CW and CON. Metabolic clearance rate of glucose during the MMTT was increased in IW compared to CW (P=0.049) and CON (P<0.001). CGM mean glucose was reduced in IW compared to CW for the rest of the intervention day (8.2±0.4 vs. 9.3±0.7 mmol/l, P=0.03), whereas no differences were found between IW and CW the following day. Conclusions: One interval-based exercise session improves glycemic control in T2DM subjects when compared to an oxygen-consumption and time-duration matched continuous exercise session.
Journal of Clinical Endocrinology and Metabolism, 2014, Vol 99, Issue 9, p. 3334-42