Study Design <p>Single-center, retrospective analysis of real-world clinical data.</p> Objectives <p>To quantify the influence of personal, lesion-, and training-specific parameters on improvements in inspiratory training resistance during a respiratory muscle training period in persons with SCI.</p> Setting <p>SCI rehabilitation hospital in Switzerland.</p> Methods <p>Men and women with traumatic or non-traumatic SCI, 18 years or older, who performed at least 10 inspiratory training sessions with a preliminary measurement of maximal inspiratory muscle strength (MIP) were included. Inspiratory resistance training was conducted in a group setting of the physiotherapy department. Training prescription: 7 × 10 repetitions per training session at the highest possible intensity, 3–5 times a week during the inpatient rehabilitation stay. Demographic data and training parameters were summarized by median with 25 and 75% percentiles or absolute and relative frequencies. Most important parameters (personal and lesion characteristic as well as training volume and intensity) for improvement of inspiratory training resistance were analyzed by a random forest and an explanatory linear model.</p> Results <p>Training intensity and the total number of training sessions have a much greater impact on improvements in inspiratory training resistance than personal or lesion characteristics. Our model showed an adjusted R² of 0.50.</p> Conclusions <p>While performing respiratory muscle training in persons with SCI, therapists should focus on a high training intensity, i.e. setting the inspiratory resistance as high as possible, and motivating patients to perform the training for as long as possible, preferably more than 3 months.</p> <p></p>