Inspiratory muscle training improves exercise performance and breathing pattern during six-minute walking test in systemic sclerosis-associated interstitial lung disease

Systemic sclerosis-associated interstitial lung disease (SSc-ILD) significantly impacts exercise capacity and contributes to morbidity and mortality in affected individuals. Inspiratory muscle training (IMT) has demonstrated benefits in improving inspiratory muscle strength and respiratory efficiency in various cardiopulmonary conditions, including ILD. This case-control study hypothesises that IMT can enhance inspiratory muscle strength and exercise capacity in patients with SSc-ILD, likely through improved ventilatory patterns during exercise. In this randomised, placebo-controlled trial, 24 patients with SSc-ILD (4 males, 20 females) were randomly assigned to the IMT (n=12) or Sham (n=12) groups. The IMT group performed training at 60% of maximal inspiratory pressure (MIP) for five weeks, while the Sham group received a placebo intervention at 5% MIP. Baseline and post-intervention assessments included pulmonary function tests, six-minute walk test (6 MWT) with combined wearable metabolic system to measure minute ventilation (V̇E), respiratory frequency (Rf), tidal volume (Vt), and ventilatory equivalent for CO 2 (V̇E/V̇CO 2 ). At rest, IMT increased MIP and prolonged expiratory time. The IMT group showed significant improvements in six-minute walking distance, and oxygen uptake during 6 MWT. An increasing of minute ventilation was observed primarily through an enhanced Vt. These improvements are likely mediated by optimised breathing patterns, potentially reducing physiological dead space thanks to increased tidal volume during exercise. Further studies are needed to evaluate the long-term effects of IMT on functional outcomes.