Intermittent Exercise with and without Hypoxia Improves Insulin Sensitivity in Individuals with Type 2 Diabetes

Context:
Hypoxia and muscle contraction stimulate glucose transport activity in vitro. Exercise and hypoxia have additive effects on insulin sensitivity in type 2 diabetics (T2D).

Objective:
The objective of the study was to examine the effectiveness of intermittent exercise with and without hypoxia on acute- and moderate-term glucose kinetics and insulin sensitivity in T2D.

Setting:
The study was conducted at a university research center.

Design, Participants, and Interventions:
Eight male T2D patients completed the following: 1) 60 min of continuous exercise at 90% lactate threshold in hypoxia (HyEx60); 2) intermittent exercise at 120% lactate threshold, separated by periods of passive recovery (5:5 min) in hypoxia [Hy5:5; O2 ∼ 14.7 (0.2)%]; and 3) intermittent exercise (5:5 min) at 120% lactate threshold in normoxia (O2 ∼ 20.93%).

Main Outcome Measures:
Glucose appearance and glucose disappearance, using an adapted non-steady-state one-compartment model were measured. Homeostasis models of insulin resistance (HOMAIR), fasting insulin resistance index (FIRI), and β-cell function were calculated 24 and 48 h after exercise conditions.

Results:
Glucose disappearance increased from baseline (1.85 mg/kg · min−1) compared with 24 h (2.01 min/kg · min−1) after HyEx60 (P = 0.031). No difference was noted for both Hy5:5 (P = 0.064) and normoxia (P = 0.385). Hy5:5 demonstrated improvements in HOMAIR from baseline [d 1, 6.20 (0.40)] when comparisons were made with d 2 [4.83 (0.41)] (P = 0.0013). HOMAIR and FIRI improved in the 24 h (HOMAIR, P = 0.002; FIRI, P = 0.003), remaining reduced 48 h after HyEx60 (HOMAIR, P = 0.028; and FIRI, P = 0.034).

Conclusion:
HyEx60 offered the greatest improvements in acute and moderate-term glucose control in T2D. Intermittent exercise stimulated glucose disposal and improved post-exercise insulin resistance, which was enhanced when exercise was combined with hypoxia (Hy5:5). The data suggest a use of hypoxic exercise in treatment of T2D.