Effects of high- versus moderate-intensity multimodal whole-body training to improve inspiratory muscle function in persons with chronic nonspecific low back pain

To compare the effects of a multimodal whole-body high-intensity training (HIT) program versus a moderate-intensity training (MIT) program on inspiratory muscle function in persons with chronic nonspecific low back pain (CNSLBP), and to investigate whether changes in inspiratory muscle function relate to changes in disability, pain intensity, anxiety, depression, and exercise capacity. In this randomized controlled trial, persons with CNSLBP followed a 12-week HIT or MIT program consisting of cardiorespiratory, general resistance, and trunk muscle strength training. Inspiratory muscle function outcomes, assessed pre- and post-intervention, included maximal inspiratory pressure (MIP), inspiratory muscle endurance (IME) time, exercise-induced inspiratory muscle fatigue (IMF), and surface electromyography amplitude of the sternocleidomastoid and scalene muscles during postural control tasks. Sixty-four participants were included (mean age: 44.9 ± 14.5 years, 38 males). MIP predicted increased after both HIT (∆9.0 ± 9.9%, p = 0.002) and MIT (∆10.8 ± 13.2%, p < 0.0001), with no significant between-group difference ( p = 0.558). IME time increased more after HIT (∆69.6 ± 78.6s, p < 0.0001) compared to MIT (∆20.0 ± 60.9s, p = 0.414; p = 0.010 for between-group difference). Exercise-induced IMF and inspiratory muscle activation during postural control did not improve in either group ( p > 0.05). Larger increases in MIP related to larger decreases in depressive symptoms (Adj R 2 = 0.07, p = 0.047) and smaller increases in exercise capacity (Adj R 2 = 0.08, p = 0.018), while larger increases in exercise-induced IMF related to larger decreases in trait anxiety (Adj R 2 = 0.10, p = 0.019). This study showed that both multimodal HIT and MIT improved MIP in persons with CNSLBP, while only HIT enhanced IME time. Exercise-induced IMF or inspiratory muscle activation during postural control did not improve after HIT or MIT. This trial was registered at ClinicalTrials.gov (NCT05384457) on May 11, 2022.