Spinal range of motion during different swim strokes in people with chronic low back pain: a randomised crossover trial

Background: The spinal biomechanics of different swim strokes may impact swimming's suitability for chronic low back pain patients, but this remains unexplored. Objective: Compare spinal range of motion between different swimming strokes in chronic low back pain patients. Design: Randomised crossover trial. Method: Chronic low back pain participants completed 100m of freestyle, breaststroke, and backstroke in a random order during one indoor pool session. Inertial measurement units were worn at T2 and S2 spinal landmarks. The primary outcome was inter-sensor range of motion (T2 and S2 sensor difference) for flexion/extension, rotation and lateral flexion. Mixed-effect models compared strokes. Results: Twenty-two females and 8 males participated (age: 43 ± 15, pain intensity: 2.9 ± 2.2). Flexion/extension range of motion was greatest for breaststroke (22.6 ± 11.3°); increases were small compared to freestyle (Mean difference [MD]: 3.6 [95 % Confidence interval: -2.1 to 9.2]; p = 0.29) and large compared to backstroke (MD: 8.8 [3.2 to 14.5]; p = 0.001). Rotation range of motion was greatest for freestyle (36.7 ± 23.3°); increases were trivial compared to backstroke (MD: 2.6 [-6.5 to 11.6]; p = 0.78) and large compared to breaststroke (MD: 27.1 [18.1 to 36.1]; p < 0.001). Lateral flexion range of motion was greatest for freestyle (32.6 ± 10.6°); increases were moderate to large compared to backstroke (MD: 6.7 [1.2 to 12.2]; p = 0.01) and breaststroke (MD: 25.2 [19.7 to 30.7]; p < 0.001). Conclusion: Freestyle produced the largest overall spinal range of motion, with the most rotation and lateral flexion. Breaststroke produced the most flexion/extension. Backstroke produced mostly rotation and lateral flexion.