High- vs. low-intensity inspiratory muscle training in asthma: effects on respiratory muscles, exercise performance, dyspnea, and health-related quality of life.

OBJECTIVE

To compare the effects of high- and low-intensity Inspiratory Muscle Training (IMT) combined with standard pulmonary rehabilitation on respiratory muscle function, exercise capacity, dyspnea, and quality of life in asthmatic patients.

METHODS

Forty asthmatic patients were randomized into high-intensity IMT (H-IMT, n = 20) and low-intensity IMT (L-IMT, n = 20) groups. The H-IMT group trained at 80% of maximal inspiratory pressure and the L-IMT group at 30%, with 5% weekly load increases. Both groups followed an 8-week exercise program including breathing, strengthening, and walking exercises. Respiratory functions, pulmonary function test, respiratory muscle strength, maximum inspiratory and expiratory pressure measurement, peripheral muscle strength, 6-min walk test (6MWT), modified Medical Research Council (mMRC) dyspnea and Asthma Control Test (ACT), Asthma Quality of Life Questionnaire (AQLQ), Saint George Respiratory Quality of Life Questionnaire (SGRQ) and International Physical Activity Questionnaire (IPAQ) scores were assessed pre- and post-intervention.

RESULTS

Baseline characteristics were similar. Both groups improved in most outcomes except spirometric values. The L-IMT group showed significant gains in IPAQ-SF walking (p = .03) and total scores (p = .02). 6MWT distance, mMRC, and ACT scores improved significantly more in the H-IMT group compared to the L-IMT group. There was no statistically significant difference between the groups (p > 0.05). Similarly, when the groups were compared, AQLQ-Environmental, AQLQ-Total, SGRQ-Impact, SGRQ-Total scores showed more improvement in the H-IMT group.

CONCLUSION

Both IMT intensities improved respiratory function, exercise capacity, and quality of life. High-intensity IMT was more effective for asthma control, while low-intensity IMT enhanced physical activity. Tailoring IMT intensity may optimize outcomes for asthmatic patients.

REGISTRATION NUMBER: NCT06516848.