Trunk muscle activity during dynamic exercises on land and in water for participants with and without chronic low back pain

Purpose
Aquatic exercise is beneficial in managing Chronic Low Back Pain (CLBP), however information is lacking as to which exercises are appropriate for targeting specific muscle groups. Whilst there is greater understanding of trunk and hip muscle activation patterns on land, few studies have quantified activation patterns during aquatic rehabilitation exercises, and no studies have measured trunk muscle activity in adults with CLBP in an aquatic environment. The purpose of this study is to evaluate muscle activity in people with CLBP and controls in water and on land when they perform exercises involving dynamic upper and lower limb movements with a stable trunk and pelvis.

Methods
20 males with CLBP and 20 healthy controls (18–45 years, BMI < 28) performed 20 aquatic and 20 land exercises commonly used for trunk stabilization at a predetermined cadence. Waterproof wireless surface electromyography synched with video analysis measured 7 muscles bilaterally (multifidus, erector spinae, internal oblique, external oblique, rectus abdominis, gluteus maximus and gluteus medius). For each exercise participants recorded pain on a Visual Analogue Scale (VAS). Group characteristics were compared using independent t-test. Comparisons between CLBP/control and water/land environments were made using 2-way analysis of variance.

Results
There were no significant differences in mean and peak activity found for any muscle or exercise between CLBP and control group in both land and aquatic exercises. For exercises with the same movement patterns on land and in water, several significant differences in muscle activity were found such as higher mean gluteal activity on land (P < 0.01) for unilateral hip movements. Muscles exhibiting highest mean muscle activity were identified for each exercise in water and on land for all exercises. Although not significant, the incidence of pain was lower (2.8%) during water exercises, but up to 3 times higher during some exercises on land (7.5%).

Conclusion(s)
For mild to moderate CLBP, exercises performed at a controlled pace demonstrate that motor recruitment strategies at an individual muscle level are similar both in water as they are on land suggesting that not only is it a suitable environment for exercising the same muscle groups, but lower incidences of pain in water suggest it may be an appropriate environment for rehabilitating individuals with even higher levels of chronic disability.

Future studies should aim to investigate similar exercises in water using different speeds/types of equipment. From this information a longitudinal cohort study with groups categorized with low, moderate and severe CLBP should be investigated to assess which individuals are most responsive to these aquatic exercises.

Implications
The current study provides an evidence base for specifying which aquatic exercises recruit specific muscles, with comparable movement patterns on land exhibiting similar muscle activation. This can provide managers’ justification for providing a cost effective aquatic therapy service in their clinics similar to land based programmes, and gives health professionals the autonomy to inform exercise prescription for people with CLBP or other musculoskeletal disorders where it is beneficial to recruit trunk and hip muscle stabilizers to be carried out in either environment dependent on each individuals’ requirements.