The acute effects of interval- Vs continuous-walking exercise on glycemic control in subjects with type 2 diabetes: a crossover, controlled study

CONTEXT: Glycemic control improves with physical activity, but the optimal exercise mode is unknown.

OBJECTIVE: The objective of the study was 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: This was a crossover, controlled study with trials performed in randomized order.

SETTING: The study was conducted in hospitalized and ambulatory care.

PATIENTS: PATIENTS diagnosed with type 2 diabetes mellitus (n=10, no withdrawals) participated in the study.

INTERVENTIONS: Subjects performed three 1-hour interventions: 1) interval walking (IW; repeated cycles of 3 min of slow and fast walking); 2) continuous walking (CW); and 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 approximately 32 hours after the MMTT using continuous glucose monitoring.

RESULTS: VO2 was well matched between the exercise interventions. IW decreased the mean and maximal incremental plasma glucose during the MMTT when compared with the CON (mean 1.2 ± 0.4 vs 2.0 ± 0.5 mmol/L, P < .001; maximal 3.7 ± 0.6 vs 4.6 ± 0.7 mmol/L, P = .005) and mean when compared with CW (1.7 ± 0.4 mmol/L, P = .02). No differences in the mean or maximal incremental plasma glucose values were seen between the CW and CON. The metabolic clearance rate of glucose during the MMTT was increased in the IW compared with CW (P = .049) and CON (P < .001). Continuous glucose monitoring mean glucose was reduced in IW compared with CW for the rest of the intervention day (8.2 ± 0.4 vs 9.3 ± 0.7 mmol/L, P = .03), whereas no differences were found between IW and CW the following day.

CONCLUSIONS: One interval-based exercise session improves glycemic control in type 2 diabetes mellitus subjects when compared with an oxygen consumption- and time duration-matched continuous exercise session.