Objectives We investigated the effect of inspiratory muscle training (IMT) on inspiratory muscle strength, functional capacity and respiratory muscle kinematics during exercise in older adults.

Methods 24 older adults (age: 68.3±2.5 years) were evenly randomised into an experimental (IMT) or control (SHAM-IMT) group. Both groups performed 30 breaths, twice daily, for 8 weeks, with the IMT group training at an intensity of ~50% maximal inspiratory pressure (PImax) and the SHAM-IMT group training at an intensity of <15% PImax. Measurements of PImax, breathing discomfort (Borg scale ratings) during a bout of IMT at 50% PImax, 6MWT, accelerometry-assessed physical activity levels, and balance (mini-BEST), were assessed pre- and post-intervention. Furthermore, respiratory muscle kinematics were assessed via optoelectronic plethysmography (OEP) during constant work rate cycling at the same absolute intensity (75% predicted peak work rate) before and after training. Participant views towards the intervention were explored via interviews.

Results Inspiratory muscle strength (reflected by an increased PImax) was significantly improved in the IMT group (by 20.0±11.9 cmH₂O; p=0.001) but not in the SHAM-IMT group (by 2.24±9.3 cmH₂O). Breathing discomfort ratings significantly decreased (from 3.5±0.9 to 1.7±0.8) following IMT but did not change (3.6±1.0 to 3.3±1.2) in SHAM-IMT. The 6MWD increased by 18.8±28.4 m (p=0.042) in the IMT group with no change (-0.4±29.0 m) in SHAM-IMT. Sedentary time was decreased following IMT (by 28.0±39.8 min; p=0.042), and the reactive component within the mini-BEST balance was improved (by 1.2±0.8; p<0.001) in the IMT group only. OEP measures showed a significantly greater contribution of the pulmonary and abdominal rib cage compartments to the total tidal volume (V_T) expansion only in the IMT group. Older adults reported positive experiences with IMT, highlighting facilitators such as ease of use and sessions not being time-consuming.

Conclusions IMT significantly improved inspiratory muscle strength, IMT-induced breathing discomfort, and functional capacity in this population. Observations of respiratory muscle kinematics during exercise suggest greater expansion of the rib cage compartment following IMT, potentially due to a greater contribution of intercostal muscles and the diaphragm. Qualitative measures revealed that IMT is well-tolerated in healthy older adults.