Effects of aquatic high-intensity interval training on aerobic capacity in adults with rheumatic and musculoskeletal diseases: the AquaHigh randomised controlled trial

Objectives To examine the effects of 12 weeks aquatic high-intensity interval training (AHIIT) compared with aquatic moderate-intensity continuous training (AMICT) on aerobic capacity and lower limb functional strength in adults with rheumatic and musculoskeletal diseases (RMDs). Design An assessor-blinded randomised controlled trial. Setting Community-based setting. Participants 89 participants (91% female, mean age 62 (SD 13) years) with RMDs were randomly allocated to AHIIT (n=44) or AMICT (n=45). Interventions Both groups participated in group-based peer-led exercise programmes two times per week for 12 weeks. The AHIIT group included four intervals of 4 min at high intensity (Borg scale 14–18). The AMICT group maintained moderate continuous intensity level (Borg scale 12–13). Main outcome measures Peak aerobic capacity (VO 2 peak) was estimated by time to exhaustion and lower limb functional strength with the 30-second sit-to-stand test (30sSTS) at baseline, 3 months and 6 months. A linear mixed model for repeated measures estimated the mean difference with 95% CI in VO 2 peak and 30sSTS. Results Mean exercise intensity was Borg scale 15 (SD 2) and 13 (SD 2) in the AHIIT and AMICT, respectively. Mean improvement in VO 2 peak in AHIIT was 1.9 mL∙kg −1 ∙min −1 (95% CI 0.045 to 3.77) compared with AMICT after 12 weeks (p<0.05). There was no statistically significant difference between groups in VO 2 peak after 6 months or in 30sSTS at either 3 or 6 months (p>0.05). No adverse events during exercise were reported. Conclusions AHIIT demonstrated significant improvements in aerobic capacity after 12 weeks, and the intervention was well tolerated with no adverse events reported. However, there was no maintenance of aerobic capacity at 6 months. Trial registration number NCT05209802 .