Background: Considering that many diabetic patients have poor exercise tolerance, alternatives to conventional exercise modalities, such as inspiratory muscle training, should be sought. Preliminary data showed similar reduction of glucose and glucose variability when comparing inspiratory muscle training with conventional training (aerobic and resistance). Aim: To evaluate the effect of an acute session of inspiratory muscle exercise (IME) on glucose and glucose variability through continuous glucose monitoring, in patients with type 2 diabetes on oral antidiabetics. Methods: Baseline clinical assessment and evaluation of maximal inspiratory pressure (PImax) using a pressure transducer were performed in 14 diabetic subjects. They wore a continuous glucose monitoring system (CGMS) for three days, and the protocol was held in the second day. Subjects were randomly assigned to an IME session with 2% (placebo) or 60% (intervention) of PImax. The protocol began at 10:00 AM, after breakfast and usual medication intake (including antidiabetic agents metformin and sulfonylureas), and followed the sequence: 10 min of resting, 10 min of controlled ventilation, 40 min of resting, 10 min of IME against an inspiratory load of 2% or 60% of PImax until task failure. Glucose and glucose variability [glucose variance (VAR), glucose coefficient of variation (CV%), glucose standard deviation (SD), all normalized by the mean glucose on each period (6h before and 18h after, in blocks of 6 hours)] were evaluated. Two-way ANOVA for repeated measures was used, comparing placebo and intervention loads. Results: Subjects were 53.6 ± 7.4 years, baseline HbA1c was 8.8 ± 0.9%. Both protocols determined a glucose reduction 5 min (60% PImax - 174  8.9 mg/dL and 2% PImax - 177.5 ± 15.2 mg/dL), 60 min (60% PImax - 184.2  8.7 mg/dL and 2% PImax 179.1 ± 13.5 mg/dL) and 120 min (60% PImax- 205.8  13.2 mg/dL and 2% PImax 198.5 ± 8.5 mg/dL) after exercise [p<0.001 vs.1h before exercise (60% PImax- 261.8  10.9 mg/dL and 2% PImax 261.0 ± 16.8 mg/dL)], with no difference between different loads (p=0.804). This reduction was observed in all moments of the protocol (controlled ventilation, interval, IME, recovery). The intervention (60% of PImax) determined higher glucose variability (CV%, SD, VAR, p<0.001 for all comparisons) when comparing 6h after the exercise session with baseline. After 12h of the exercise session, this increase remained in CV% and VAR in the 60% PImax group. After 18h of the exercise session, VAR remained increased as compared to baseline in the 60% PImax group. In the placebo group (2% of PImax), no differences were found in CV%, SD and VAR evaluated 6h and 12h after the exercise, when compared to the same baseline parameters. After 18h of the exercise session, SD decreased from baseline in the 2% PImax group. No differences between groups (intervention vs. placebo) were observed in any of the glucose variability parameters (CV%- P =0.580, SD- P=0.559 and VAR- P=0.394). Discussion: An acute session of inspiratory muscle exercise with 60% of PImax is similar to the placebo session (2%) in reducing glucose levels in type 2 diabetic patients. Glucose variability increased after IME in the 60% PImax group. The changes observed in glucose levels and glucose variability might have occurred in response to insulin secretion in response to the meal and because of the expected effect of the antidiabetics received early in the morning of the protocol.

Glucose and glucose variability after and acute session of inspiratory muscle exercise in patients with type 2 diabetes