Background: Low back pain (LBP) is the leading cause of years lived with disability globally. Chronic LBP is associated with impaired function and morphology of the paraspinal and gluteal muscles. Although exercise therapy is recommended as a first-line conservative treatment for chronic LBP, many individuals struggle with fear-avoidance beliefs that hinder their participation in physical activities. Aquatic therapy offers a valuable alternative by reducing spinal loading, enhancing movement capacity, and facilitating exercises that may be challenging to perform on land. While research has explored the psychological benefits of aquatic therapy for individuals with chronic LBP, the effects of aquatic therapy on muscle health remain largely unexplored. This study aims to examine the effects of an aquatic therapy (AT) exercise intervention compared to standard care (SC) on: 1) the morphology and function of paraspinal muscles (i.e., multifidus [MF], erector spinae [ES]) and gluteal muscles; and 2) patient-oriented outcomes (i.e., pain, disability, psychological factors).
Methods: This study was a two-arm pilot randomized controlled trial. A total of 34 participants aged between 18 to 65 and with moderate-to-severe non-specific chronic LBP were randomized to the AT (n=16) and SC (n=18) groups. Both groups completed a 10-week supervised intervention program (2 sessions per week). Baseline and post-intervention assessments included lumbopelvic MRI, lumbar extension (MedEx) strength test, gluteal (hand-held dynamometer) strength test and various questionnaires (Oswestry Disability Index, Tampa Scale of Kinesiophobia, Pain Catastrophizing Scale, SF-12 Questionnaire, International Physical Activity Questionnaire, Hospital Anxiety and Depression Scale, Insomnia Severity Index). Two-way repeated measures ANOVA was used to assess the changes in muscle and patient-oriented outcomes within and between-groups.
Results: There was a significant increase in MF volume at L2-L3 (MD: 0.21, p=0.008) and L3-L4 (MD: 0.35, p=0.019), ES volume at L1-L2 (MD: 0.59, p=0.02) and MF % fatty infiltration at L2-L3 (MD: 0.80, p=0.001), with no significant changes in the SC group. Both groups showed significant improvements in lumbar extensor strength (AT MD= 26.64, p=0.012; SC MD=34.79, p=0.003), gluteus maximus strength (AT MD=51.78, p<0.001; SC MD=45.30, p<0.001) and gluteus medius strength (AT MD=66.41, p<0.001; SC MD=50.58, p<0.001) across timepoints. The aquatic exercise group saw a significant improvement in pain (MD=-2.95, p<0.001), disability (MD=-18.04, p<0.001), quality of life (MD=13.00, p<0.001), pain catastrophizing (MD=-9.21, p<0.001), kinesiophobia (MD = -4.84, p=0.002), anxiety/depression (MD=-3.97, p<0.001), insomnia (MD=-5.06, p=0.001). The standard care group saw a significant improvement in pain (MD = -3.19, p <0.001), disability (MD = -12.54, p<0.001), quality of life (MD=12.45, p<0.001), pain catastrophizing (MD = -8.34, p<0.001), and anxiety/depression (MD=-2.66, p=0.007) with no difference across groups for all self-reported outcomes. The gluteal muscle morphology results will be available by April 2025.
Discussion: This project provides valuable insight into the effects of aquatic therapy versus standard care on lumbopelvic muscle health, and patient-oriented outcomes. Notably, these preliminary results suggest that aquatic therapy may help improve lumbar paraspinal muscle volume, lumbopelvic strength and patient-oriented outcomes in participants with chronic LBP.