Effect of inspiratory muscle training on trunk control in patients with stroke: a systematic review of randomized controlled trials

Stroke is a leading cause of long-term disability worldwide and is associated with impairments in motor function, balance, and respiratory capacity. Trunk control is a key component of postural stability and functional mobility, and its impairment is commonly observed in stroke survivors. Inspiratory muscle training (IMT) has been proposed as an intervention that may improve both respiratory function and trunk stability due to the functional role of the diaphragm in core control. This systematic review aimed to evaluate the effect of inspiratory muscle training on trunk control in patients with stroke. A systematic search was conducted to identify randomized controlled trials investigating the effects of IMT in stroke populations. Studies were included if they examined IMT as an intervention and reported trunk control outcomes, primarily using the Trunk Impairment Scale (TIS), along with other measures such as balance, mobility, and respiratory function. Methodological quality was assessed using the PEDro scale. Five randomized controlled trials involving 189 participants were included. The methodological quality of the studies ranged from fair to high (PEDro scores: 5–8/10). Most studies demonstrated that IMT, when combined with conventional rehabilitation, resulted in greater improvements in trunk control compared with control interventions. Improvements were also reported in secondary outcomes, including respiratory muscle strength, balance, mobility, and functional independence. However, one study found no significant between-group differences. Considerable heterogeneity was observed across studies with respect to IMT intensity, duration, frequency, and progression strategies, which limited direct comparisons between interventions. IMT appears to be a promising adjunct to conventional rehabilitation for improving trunk control in patients with stroke. However, the evidence is based on a limited number of studies with relatively small sample sizes and substantial variability in intervention protocols. Therefore, the findings should be interpreted with caution. Larger, high-quality randomized controlled trials using standardized IMT protocols and long-term follow-up are needed to confirm these findings and inform clinical practice.