Beneficial Impact Of Respiratory Muscle Training On Postprandial Glycemic Control In Healthy Individuals: A Pilot Study

Respiratory muscles are metabolically active and thus could be an effective metabolic sink for glycemic control, particularly in populations where typical locomotor muscle activity is limited. However, the extent to which respiratory muscle training (RMT) can improve glycemic control has not been fully evaluated. PURPOSE: The purpose of the study was to determine the effectiveness of a session of RMT on postprandial glycemic control in healthy individuals. METHODS: Five healthy adults (age 47.4 ± 17.8 years; BMI 23.3 ± 2.6 kg/m2) were tested for maximal inspiratory pressure (MIP) to set the RMT intensity. Subjects performed three RMT trials: control (CON; 0% resistance), moderate (MOD; ~30% MIP), and high-intensity (HIGH; ~50% MIP). There was at least a 72-hour washout period between trials and the order was randomized. After baseline measurement including estimated work of breathing (eWOB), oxygen consumption (VO2) and fasting blood glucose level (GLU, via finger prick), subjects had 45 g of D-glucose with GLU obtained after 15 min (post-GLU/pre-RMT). Subsequently, they performed RMT that consisted of 6 episodes (4 min RMT and 1 min resting, 30 breaths/min) while eWOB and VO2 were assessed. After completion of RMT, GLU was obtained (5 min post-RMT). RESULTS: D-glucose intakes elevated GLU levels from baseline in all conditions (Baseline vs. Post-GLU; HIGH: 103.88 ± 8.99 vs. 166.47 ± 33.59; MOD: 98.18 ± 6.90 vs. 153.73 ± 23.40; CON: 101.27 ± 8.42 vs. 157.92 ± 29.59 mg/dL, p = 0.0001), with no significant differences observed between the conditions (p > 0.05). During RMT, VO2 increased, and it was the highest in HIGH followed by MOD and CON, respectively (8.09 ± 0.80, 7.29 ± 0.31 and 5.55 ± 0.62 mg/kg/min, respectively, p = 0.0031). Likewise, eWOB was the highest in HIGH followed by MOD and CON, respectively (106.23 ± 38.78, 89.42 ± 45.77 and 4.48 ± 3.92 J/min, p = 0.0079). After RMT, HIGH significantly decreased GLU levels and MOD relatively maintained GLU levels, however, CON continuously increased GLU levels (160.06 ± 41.61, 190.54 ± 34.10, 211.74 ± 27.54 mg/dL, respectively, p = 0.0288). CONCLUSION: RMT effectively increased VO2 and WOB and in turn it suppressed an elevation of postprandial glucose levels. Furthermore, the higher intensity was more beneficial as a therapeutic strategy.