Fin type and swimming performance: Energy cost, muscle activity and kinematic analysis

• Fin type impacted oxygen consumption up to 22 % and heart rate up to 11 % • Different fin type led to different muscular work • Fin type influenced kicking frequency and ankle amplitude The aim of this study was: 1) to characterize the properties or specificities of commercially available fins, 2) quantify the extent to which these fins influence energy expenditure, muscle activation patterns and the kinematics of fin swimming in professional divers, 3) evaluate how fin properties affect these parameters. A principal component analysis was used to select three fins with markedly different characteristics from a larger set of commercially available models. Eight professional military divers performed 3 underwater swims for 30 min in a counter-current pool at a constant pace of 4 minutes per 100 meters (i.e., 0.42 m.s -1 ). Energy cost, electromyography activity, and lower limb kinematics were assessed during the fin swimming trials. Significant differences in oxygen consumption (p<0.01) of up to 22% were observed between fins. Fin type also had a significant effect on heart rate (p<0.01) and perceived exertion (p<0.05), with variations of up to 11% and 15% respectively. Differences in fin design led to substantial variations in muscular work, particularly in the rectus femoris (p=0.002), vastus lateralis (p=0.012), biceps femoris (p=0.005), and semitendinosus (p=0.024). Fin type influenced only kicking frequency (p=0.015) and ankle amplitude (p=0.023). Overall, commercially available fins can substantially affect energy cost, muscle activation patterns and kinematics of fin swimming.