Effect of inspiratory muscle training on respiratory muscle strength and functional capacity in patients with type 2 diabetes mellitus: A randomized clinical trial

Abstract

Background Type 2 diabetes mellitus (T2DM) is usually associated with respiratory manifestations including inspiratory muscle weakness which affects exercise capacity. The present study aimed to determine the effect of inspiratory muscle training (IMT) on inspiratory muscle strength and exercise capacity in patients with Type 2 diabetes mellitus (T2DM). Methods This was a randomized controlled trial in patients with type 2 diabetes mellitus with no previous cardiopulmonary or neuromuscular diseases. Patients had no back pain. Patients were randomized into interventional or placebo groups. Sniff nasal inspiratory pressure (SNIP), maximum inspiratory pressure (MIP), and six‐minute walking test (6MWT) were measured at baseline and 8 weeks post incremental inspiratory muscle training. Results At baseline, interventional and placebo groups were similar in age, body mass index, sex inspiratory muscle strength, and exercise capacity. After 8 weeks of incremental inspiratory muscle training at 40% of MIP, the interventional group had a significant increase in the SNIP (mean difference: 18.5 ± 5.30 cm H2O vs 2.8 ± 4.8 cm H2O) and MIP (mean difference: 19.4 ± 4.3 Vs 5.4 ± 3.6 cm H2O) compared to the placebo group, respectively. The interventional group showed improvement in the 6MWT (mean difference: 70 ± 29 m vs 34 ± 24 m) compared to the placebo group, P < .05. Conclusion Incremental inspiratory muscle training increased the diaphragm strength in patients with T2DM and improved exercise capacity.

Effects of Inspiratory Muscle Training in Type 2 Diabetes: A Systematic Review

“…In the protocols, IMT loads ranged between 30% and 75% of the maximum inspiratory pressure (MIP) for at least eight weeks, with a frequency between three and seven times a week ( Table 3 ). Considering six RCTs, three showed an increase in MIP and did not assess muscle endurance [ 13 , 19 , 24 ] . One showed an increase in MIP and endurance [ 25 ] and one obtained an increase only in muscular endurance, with no difference in MIP after the protocol [ 26 ] .…”

“…In one study, there was a reduction in glycemic levels in eight weeks of protocol [ 26 ] . Two studies demonstrated that IMT increased functional capacity, which was assessed by the six-minute walk test (6WT) [ 24 ] , and VO2max, assessed by the cardiopulmonary exercise test [ 13 ] . They were considered high-quality (> 7 points) and moderate-quality (6 or 5 points) studies, respectively ( Table 4 ).…”

“…Regarding the evaluated outcomes, one study demonstrated to reduce the glycemic levels of patients with T2DM [ 26 ] and one study verified the reduction of the normalized low frequency (LFn) (sympathetic component) [ 19 ] . Four studies analyzed the IMT effect on functional capacity of patients with T2DM, where two RCTs showed an increase in functional capacity [ 13 , 24 ] .…”

“…Due to this, patients with T2DM may have reduced inspiratory muscle strength [ 7 ] . When we analyzed the ventilatory strength and endurance, we found that among the six RCTs, three showed an increase in MIP after IMT, without endurance assessment [ 13 , 19 , 24 ] . One RCT did not assess MIP [ 28 ] , and another one found an increase in muscle endurance with no difference in MIP [ 26 ] .…”

Rehabilitation of Individuals With Diabetes Mellitus: Focus on Diabetic Myopathy

“…Given this, some safe and viable assessment tools can be used, mainly in T2DM, such as the six-minute walk test and the step test. As important as aerobic exercise is strength training, which can be based on 1-repetition maximum assessment, as demonstrated by studies with individuals with T1DM and T2DM ( 62 – 64 ).…”