Froude Efficiency and Velocity Fluctuation in Forearm-Amputee Front Crawl: Implications for Para Swimming Classification

The impact of physical impairment on Froude efficiency and intra-cyclic velocity fluctuation in Para swimmers is not well documented. Identification of differences in these variables between disabled and non-disabled swimmers could help develop a more objective system for assigning Para swimmers to classes for competition. This study quantifies Froude efficiency and intra-cyclic velocity fluctuation in unilateral forearm-amputee front crawl swimmers, and evaluates associations between these variables and performance. Ten unilateral forearm-amputee swimmers completed front crawl trials at 50 m and 400 m pace; three-dimensional video analysis provided mass centre, wrist and stump velocities. Intra-cyclic velocity fluctuation was calculated as: 1) maximum - minimum mass centre velocity, expressed as % of mean velocity, and 2) coefficient of variation in mass centre velocity. Froude efficiency was the ratio between mean swimming velocity and wrist plus stump velocity during each segment's respective: 1) underwater phase, and 2) propulsive underwater phase. Forearm-amputees' intra-cyclic velocity fluctuation (400 m: 22 ± 7%; 50 m: 18 ± 5%) was similar to published values for non-disabled swimmers, whilst Froude efficiencies were lower. Froude efficiency was higher at 400 m (0.37 ± 0.04) than 50 m pace (0.35 ± 0.05; p < .05) and higher for the unaffected limb (400 m: 0.52 ± 0.03; 50 m: 0.54 ± 0.04) than the residual limb (400 m: 0.38 ± 0.03; 50 m 0.38 ± 0.02; p < .05). Neither intra-cyclic velocity fluctuation nor Froude efficiency were associated with swimming performance. Froude efficiency may be a valuable measure of activity limitation in swimmers with an upper limb deficiency and a useful metric for comparing swimmers with different types and severity of physical impairment.