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The effects of inspiratory muscle training on physiological and sensory responses to exercise in healthy males

University of British Columbia

Inspiratory muscle training (IMT) is an efficacious intervention to reduce dyspnoea in health and disease. Growing evidence also suggests that IMT can improve whole body exercise performance. However, the physiological mechanisms for these improvements are not well understood. We sought to examine the effects of IMT on dyspnoea, respiratory muscle electromyography (EMG), and respiratory and locomotor oxygenation to examine potential mechanisms of action for any IMT-related improvements in dyspnoea and exercise performance. 25 recreationally active healthy men completed two maximal incremental cycle exercise tests separated by 5 weeks of randomly assigned pressure threshold IMT or sham control training (SC). The IMT group (n = 12) performed 30 inspiratory efforts twice daily against a 30 repetition maximum intensity. The SC (n = 13) group performed a daily bout of 60 inspiratory efforts against 10% maximal inspiratory pressure (MIP), with no weekly adjustments. EMG electrodes on the sternocleidomastoid (SCM) and scalene muscles measured changes in muscle activity, and near-infrared spectroscopy (NIRS) optodes on the SCM, parasternal intercostals, 7th intercostal space, and vastus lateralis muscle measured changes in oxygenated and deoxygenated haemoglobin during each exercise test. Dyspnoea was measured throughout exercise using the modified Borg scale. Finally, a subset of participants (IMT: n = 11; SC: n = 11) were instrumented with a multi-pair oesophageal electrode catheter containing two balloons, to measure diaphragm EMG and respiratory pressures. IMT significantly improved MIP (pre: -138±45 vs. post: -160±43, cm H₂O, p<0.01) whereas the SC intervention did not. A between group analysis determined the increase in MIP in the IMT group was greater than the change in the SC group (p<0.05). Moreover, after IMT, dyspnoea was significantly reduced at the highest equivalent work rate (pre: 7.6±2.5 vs. post: 6.8±2.9 Borg units, p<0.05), but not in the SC group with no between-group interaction effects. Finally, there were no significant differences in respiratory muscle EMG or respiratory and locomotor muscle oxygenation in either the IMT or SC intervention. Together, these findings suggest that while IMT can reduce dyspnoea, it is likely unrelated to changes in EMG or NIRS derived measurements.

Text

2016-08-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/58884

Rehabilitation Sciences

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/