Effects of aquatic exercise in adults with rheumatic and musculoskeletal diseases

Sammendrag

Background: Rheumatic and musculoskeletal diseases (RMDs) affect millions worldwide, causing pain, and reduced quality of life. In Norway, nearly one in four adults report chronic musculoskeletal complaints. Despite advances in treatment, many continue to experience persistent symptoms. Exercise is key in managing RMDs, yet barriers such as pain and fatigue often hinder participation. High-intensity interval training (HIIT) is a time-efficient and effective alternative. However, evidence on aquatic HIIT (AHIIT) remains limited. This study was conducted in collaboration with the Norwegian Rheumatism Association (NRF), whose peer-led structure enabled AHIIT delivery through community services. Aligned with national health policy promoting decentralised, user-centred support, the intervention was guided by the International Classification of Functioning, Disability and Health (ICF) framework. To the best of our knowledge, this is the first study to investigate peer-led AHIIT in a community setting.

Aims: The overall aim of this thesis is to enhance knowledge and understanding of the effects of aquatic exercise in adults with RMDs. Specifically, it addresses: i) the effects of AHIIT on exercise capacity in people with chronic conditions, ii) the effects of AHIIT compared with aquatic moderate-intensity continuous training (AMICT) on aerobic capacity and lower limb functional strength in adults with RMDs, and iii) the effects of AHIIT compared with AMICT on patient-reported outcome measures (PROMs) in adults with RMDs, including disease activity, fatigue, pain, physical- and social activities, health-related quality of life (HRQoL), and quality-adjusted life years (QALYs).

Methods: We adopted a quantitative design guided by the Medical Research Council’s framework for complex interventions. In Paper I, we conducted a systematic review and meta-analysis. Eligible participants were adults (≥18 years) living with one or more chronic conditions. The AquaHigh trial (Papers II and III) was a pragmatic, two-arm randomised controlled trial (RCT) conducted across four Norwegian municipalities. The 12-week exercise programmes were supervised by experienced peer leaders. Outcomes were measured at baseline, three and six months. The primary outcome was VO₂peak; secondary outcomes included lower limb functional strength, PROMs, and estimated QALYs. Data were analysed using linear mixed models according to the intention-to-treat principle.

Results: Paper I: We searched six databases. Eighteen RCTs (n = 868) were included. AHIIT significantly improved exercise capacity compared to control (standardised mean difference (SMD) = 0.78, p < 0.00001) and showed a small, significant effect when compared to AMICT (SMD = 0.45, p = 0.01). Effects were comparable to land-based HIIT (SMD = 0.28, p = 0.08). Adherence was high (84–100%). Paper II: Included 89 participants (mean age 62 years, 91% women). A significant between-group difference in VO₂peak was shown in favour of the AHIIT group at three months (1.9 mL·kg⁻¹·min⁻¹, 95%CI 0.45 to 3.77), though this was not sustained at six months. Both groups improved lower limb functional strength, with no significant between-group differences. No adverse events were reported. Paper III: No significant between-group differences were observed at any time point. Both groups showed improvements in PROMs and HRQoL. The AHIIT group demonstrated statistically significant within-group improvements in disease activity, and health utilities.

Conclusion: This thesis supports the use of aquatic exercise as a tolerable and effective intervention for adults with RMDs. AHIIT may improve aerobic capacity and contribute to symptom relief and enhanced HRQoL. The findings highlight the therapeutic potential of aquatic environments and the value of peer-led exercise in community settings. By applying the ICF framework and the biopsychosocial model, the study may demonstrate how improvements in aerobic capacity can positively impact function and social participation. These results add to the evidence base for sustainable, accessible strategies in the management of RMDs and align with national policy goals for decentralised, user-centred support.