Swimming is anecdotally suggested as a suitable exercise for chronic low back pain. However, swimming involves different strokes that require different movement patterns and therefore may impact low back pain symptoms differently. The extent to which different swim strokes impact chronic low back pain differently is currently unknown.

This study compares and describes the intensity of pain experienced during and immediately after different swimming strokes in individuals with chronic low back pain.

We recruited 30 adults with chronic low back pain. Participants swam 100m of freestyle, breaststroke, and backstroke in a balanced, randomised sequence. The primary outcome was pain intensity during swimming, measured as average and worst pain (0-10 Numeric Pain Rating). Secondary outcomes included pain after swimming while standing and while completing an aggravating movement. Pain scores were compared between strokes using linear mixed-effects models that included a fixed effect of stroke and period, and a random effect for participant. Carry-over effects were investigated via a stroke by period interaction.

There was no evidence of carry-over effects for any outcome measure (p>0.15). Backstroke had lower average pain compared to breaststroke (mean difference [MD] -0.63 [-1.17 to -0.10]) but was not different to freestyle (MD -0.27 [-0.80 to 0.27]), and lower worst pain compared to breaststroke (MD -1.10 [-1.77 to -0.43]) but was not different to freestyle (MD -0.60 [-1.27 to 0.07]). Standing pain had a similar pattern to the primary outcomes, but pain with an aggravating movement showed no statistically significant differences.

Backstroke was the least painful swimming stroke during and immediately after swimming when compared to breaststroke, and to a lesser extent freestyle. The average differences were typically small but may be important to the long-term effects. Swimming stroke should be considered by health professionals when prescribing an individualised swimming program.