Kinematic Differences in Shoulder Roll and Hip Roll at Different Front Crawl Speeds in National Level Swimmers

ABSTRACTAndersen, JT, Sinclair, PJ, McCabe, CB, and Sanders, RH. Kinematic differences in shoulder roll and hip roll at different front crawl speeds in National Level Swimmers. J Strength Cond Res 34(1)20–25, 2020—Dry-land strength training is a common component of swimming programs; however, its efficacy is contentious. A common criticism of dry-land strength training for swimming is a lack of specificity. An understanding of movement patterns in swimming can enable dry-land strength training programs to be developed to elicit adaptations that transfer to improvements in swimming performance. This study aimed to quantify the range and velocity of hip roll, shoulder roll, and torso twist (produced by differences in the relative angle between shoulder roll and hip roll) in front crawl at different swimming speeds. Longitudinal torso kinematics was compared between sprint and 400-m pace front crawl using 3D kinematics of 13 elite Scottish front crawl specialists. The range (sprint78.1°; 400 m61.3°) and velocity of torso twist (sprint166.3°·s; 400 m96.9°·s) were greater at sprint than 400-m pace. These differences were attributed to reductions in hip roll (sprint36.8°; 400 m49.9°) without corresponding reductions in shoulder roll (sprint97.7°; 400 m101.6°) when subjects swam faster. Shoulder roll velocity (sprint190.9°·s; 400 m139.2°·s) and hip roll velocity (sprint75.5°·s; 400 m69.1°·s) were greater at sprint than 400-m pace due to a higher stroke frequency at sprint pace (sprint0.95 strokes·s; 400 m0.70 strokes·s). These findings imply that torques acting to rotate the upper torso and the lower torso are greater at sprint than 400-m pace. Dry-land strength training specificity can be improved by designing exercises that challenge the torso muscles to reproduce the torques required to generate the longitudinal kinematics in front crawl.