The WATER study: Which AquaTic ExeRcises increase muscle activity and limit pain for people with low back pain?

Objective: Aquatic exercise therapy is used for chronic low back pain (CLBP) treatment and management. However, there are currently no data comparing muscle activity between different aquatic exercises performed by people with CLBP. We assessed and compared muscle activity, pain, perceived exertion and exercise intensity, between different rehabilitative aquatic exercises. 
Design: Cross-sectional. 
Setting: A 25m indoors swimming pool within a university building.
Participants: Twenty participants with non-specific CLBP. 
Assessment: Twenty-six aquatic exercises at shallow water (1.25m depth). We quantified muscle activity bilaterally for erector spinae, multifidus, gluteus maximus and medius, rectus abdominis, external and internal oblique.
Main outcomes: Mean and peak muscle activity, pain (visual-analog scale), perceived exertion (Borg scale) and exercise intensity (heart rate). 
Results: Hip abduction/adduction and extension/flexion exercises produced higher activity for gluteal muscles. Variations of squat exercises increased activity of back extensors. Higher abdominal muscle activity was produced with exercises that made use of buoyancy equipment and included leg and trunk movements while floating on the back, and with some proprioceptive and dynamic lower limb exercises. Pain occurrence and intensity were very low, with 17 exercises being pain free. 
Conclusions: The present study provides an evidence base on trunk and gluteal muscle activity, pain, intensity and perceived exertion for people with CLBP performing aquatic exercises. The findings are very useful in programme prescription for rehabilitation, as physiotherapists seek to implement progression in effort and muscle activity, variation in exercise type, and may wish to target or avoid particular muscles.
Contribution of the paper:
-The first study to compare trunk or gluteal muscle activity between 26 different aquatic rehabilitative exercises performed by people with chronic low back pain.
-Pain occurrence and intensity of aquatic exercises are very low, with most exercises being completely pain free.
-The following aquatic exercises are particularly effective in increasing muscle activity: a) for gluteus maximus and medius, hip abduction/adduction and extension/flexion exercises; b) for back extensors (erector spinae and multifidus), squat exercises; c) for abdominals (rectus abdominis, external and internal oblique), exercises that make use of support buoyancy equipment and include leg movements while floating on the back.