Intermittent exercise with and without hypoxia improves insulin sensitivity in individuals with type 2 diabetes - Mackenzie et al. (2012)
Continuous exercise in moderate hypoxia improves glycemic control more than intermittent exercise in normoxia or hypoxia in type 2 diabetics
However, intermittent exercise in hypoxia increased insulin sensitivity and improved beta cell function in type 2 diabetics
The Breathing Diabetic Summary
This study was motivated by other studies (some of which we have reviewed here) that have found that hypoxia lowers blood sugar independent of insulin. However, this study wanted to focus specifically on intermittent exercise because it is often easier than continuous exercise (e.g., 5 min cycles versus 1 hour of continuous exercise). If intermittent exercise in hypoxia provides benefits in glycemic control, it might be a more acceptable, less time-consuming form of exercise treatment for diabetic patients.
The study had 3 groups performing different protocols. One group performed 1-hour of moderate, continuous exercise in hypoxia (O2 ~ 14.7%; well within the therapeutic range). Two other groups performed intermittent exercise of with more intense bouts of effort for 5 min, then 5 min of rest, for 60 min total. One group performed the intermittent exercise in normoxia and the other in hypoxia (O2 ~ 14.7% again).
The authors found that all three protocols lowered blood sugar post-exercise, with the largest improvements coming from the hypoxic continuous exercise. However, insulin levels and insulin resistance were both reduced in the hypoxic exercise programs, whereas they were unchanged in the normoxic group. Further, intermittent exercise in hypoxia improved beta cell function in measurements taken 48 h after the experiment.
Overall, this study found that continuous exercise in hypoxia provided the largest improvements in glycemic control for these type 2 diabetics. However, intermittent exercise in hypoxia also provided glycemic benefits and improved insulin sensitivity and beta cell function.
For us, this is another study supporting the use of intermittent hypoxia for 1) short-term glycemic control and 2) long-term improvements in insulin sensitivity. Obviously, we have to consider hormones and activation of the sympathetic nervous system, but simply doing some easy breath holds during a walk might be sufficient to improve glycemic control.
Abstract From Paper
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 nonsteady- state one-compartment model were measured. Homeostasis models of insulin resistance (HOMAIR), fasting insulin resistance index (FIRI), and beta-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.
R. Mackenzie, N. Maxwell, P. Castle, B. Elliott, G. Brickley, and P. Watt, (2012) Intermittent exercise with and without hypoxia improves insulin sensitivity in individuals with type 2 diabetes, J Clin Endocrinol Metab, 97(4), E546–E555.