Does incremental inspiratory muscle training provide additional benefits over minimal‑load training for respiratory muscle strength, diaphragm thickness, and diaphragmatic excursion in patients with pre‑dialysis chronic kidney disease? A randomized clinical trial

Purpose To compare the effects of incremental-load inspiratory muscle training (IMT) versus fixed minimal-load IMT on respiratory muscle strength, diaphragm thickness, and excursion in patients with non-dialysis chronic kidney disease (CKD).Methods In this randomized, controlled, blinded clinical trial, patients with CKD stages G3a–G5 were allocated to incremental-load IMT, with progressive loading up to 60% of maximal inspiratory pressure (MIP), or fixed minimal-load IMT at 5 cmH2O. Both interventions were performed daily for 8 weeks. Respiratory muscle strength was assessed by manovacuometry, while diaphragm thickness, excursion, and thickening fraction were evaluated using ultrasonography before and after the intervention.Results Inspiratory and expiratory muscle strength increased in both groups, with no significant between-group differences in MIP (adjusted mean difference [AMD] = 32.97 cmH2O, 95% CI: −4.44 to 12.37; p = .344) or maximal expiratory pressure (AMD = 1.52 cmH2O, 95% CI: −6.81 to 9.85; p = .712). Diaphragm thickness and excursion also increased within both groups, without significant between-group differences (thickness: AMD = 0.10 mm, 95% CI: −0.17 to 0.37; p = .461; excursion: AMD = 0.22 mm, 95% CI: −0.46 to 0.90; p = .514). No significant between-group difference was observed in diaphragm thickening fraction (AMD = 6.74% points, 95% CI: −3.03 to 16.51; p = .170).Conclusion In patients with pre-dialysis chronic kidney disease, 8 weeks of progressive-load inspiratory muscle training did not result in additional benefits over fixed minimal-load training in respiratory muscle strength, diaphragmatic thickness, or excursion. Although both groups showed improvements, these findings suggest that progressive loading may not confer superior short-term benefits in this population. Larger, adequately powered trials are warranted to clarify the effects of training intensity and determine the optimal inspiratory muscle training protocol.