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

Abstract

Purpose The impact of physical impairment on Froude efficiency and intracyclic velocity fluctuation in Para swimmers is not well documented. Identification of differences in these variables between disabled and nondisabled swimmers could help develop a more objective system for assigning Para swimmers to classes for competition. This study quantifies Froude efficiency and intracyclic velocity fluctuation in unilateral forearm-amputee front crawl swimmers and evaluates associations between these variables and performance. Methods Ten unilateral forearm-amputee swimmers completed front crawl trials at 50- and 400-m pace; three-dimensional video analysis provided mass center, and wrist and stump velocities. Intracyclic velocity fluctuation was calculated as follows: 1) maximum-minimum mass center velocity, expressed as percent of mean velocity, and 2) coefficient of variation in mass center 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. Results Forearm amputees' intracyclic velocity fluctuation (400 m: 22% ± 7%, 50 m: 18% ± 5%) was similar to published values for nondisabled swimmers, whereas Froude efficiencies were lower. Froude efficiency was higher at 400-m (0.37 ± 0.04) than 50-m pace (0.35 ± 0.05; P < 0.05) 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 < 0.05). Neither intracyclic velocity fluctuation nor Froude efficiency was associated with swimming performance. Conclusions 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.