Effects of inspiratory muscle training in older adults

Manifield, James Richard (2022) Effects of inspiratory muscle training in older adults. Doctoral thesis, Northumbria University.

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Abstract

Background: Respiratory muscle strength is reduced during the healthy ageing process, which can contribute to impaired exercise tolerance in older adults. Inspiratory muscle training (IMT) may improve respiratory muscle strength and thus exercise capacity in this population. Whether IMT is associated with changes in the action of the respiratory muscles during exercise currently remains unknown. Technological advances allow breath-by-breath assessment of compartmental thoracoabdominal volumes during exercise via optoelectronic plethysmography (OEP). Changes in the volumes of the rib cage (RC) compartment represent the action of the intercostal muscles and the diaphragm, whereas abdominal volume changes are reflected by the action of the muscles of the abdominal wall.

Objectives: 1) To perform a systematic review and meta-analysis on IMT in healthy older adults, 2) to determine the age-related differences in acute thoracoabdominal volume responses during inspiratory muscle loading at low, medium, and high intensities, 3) to determine whether an 8-week IMT programme improves respiratory muscle strength, exercise capacity, and the relative contribution of the different respiratory muscle group to tidal volume (VT) expansion during sub-maximal exercise, and 4) to explore older adults’ perspectives and views towards the IMT both immediately following IMT and at 3-months post-IMT.

Methods: OEP was employed to assess thoracoabdominal volume regulation during tapered flow resistive loading (TFRL) acutely but also before and after 8 weeks of IMT (30 breaths, twice daily, at 50% maximal inspiratory pressure; PImax) or SHAM-IMT (30 breaths, twice daily, at 10–15% PImax) in healthy older adults. Interviews were conducted in a subgroup of participants following the training programme.

Results: The meta-analysis found that IMT significantly improves inspiratory muscle strength, reflected by an increase in PImax of 24.7±22 cmH2O, and results in a non-significant, albeit minimum clinically important difference (MCID), in six-minute walk distance (6MWD) equivalent to 24.7±22.1 m in older adults. During acute application of TFRL at high intensities (50% and 70% PImax) older adults exhibited significantly lower RC VT expansion compared to their younger counterparts suggesting reduced intercostal muscle activation.

Following an 8-week IMT intervention, PImax was significantly increased by 20.0±11.9 cmH2O in older adults within the experimental group (p=0.001), which was not the case in the control (SHAM-IMT) group (by 2.4±9.3 cmH2O; p=1.000). Breathing discomfort was significantly reduced following IMT during a bout of training at 50% PImax (from Borg scale ratings of 3.5±0.9 to 1.7±0.8). Furthermore, IMT-induced significant improvements in the 6MWD in the experimental group (by 18.8 ± 28.4 m; p=0.042) with no change in the SHAM-IMT group (change of −0.5 m; p=0.956). During constant work rate (CWR) cycling reproducing external work rate and minute ventilation (

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