Abstract
Backstroke starts involve the athlete starting from a flexed position with their feet against the pool wall and then extending their ankles, knees, hips and back to push off; however, swimmers can start in different positions. The purpose of this study was to evaluate the performance impact of different knee extension angles in the setup position for a backstroke start. Ten backstroke swimmers completed maximum-effort starts in each of two setup positions: one with the knees maximally flexed, and one with the knees less flexed. The start handles and touchpad were instrumented with multi-axial force sensors. Activity of major hip and knee extensors was measured using surface electromyography. Body position in the sagittal plane was recorded using high-speed cameras. There was no overall difference in time to 10 m between the two conditions (p = 0.36, dz = 0.12), but some participants showed differences as large as 0.12 s in time to 10 m between start conditions. We observed that starts performed from a setup position with less knee flexion had an average 0.07 m greater head entry distance (p = 0.07, dz = 0.53), while starts from a setup position with maximal knee flexion had an average 0.2 m/s greater takeoff velocity (p = 0.02, dz = 0.78). Both head entry distance and takeoff velocity are related to start performance, suggesting each position may optimize different aspects of the backstroke start. Coaches should assess athletes individually to determine which position is optimal.
Highlights
In 2014, the backstroke ledge was approved by FINA (Fédération internationale de natation, or International Swimming Federation) for use in competition
This study investigated whether a specific lower-limb setup position was related to better start performance
The results revealed that there was no statistically significant difference in time to 10 m between start conditions, failing to support the hypothesis that setup with the lower-limbs in a more extended position would result in a shorter time to 10 m
Summary
In 2014, the backstroke ledge was approved by FINA (Fédération internationale de natation, or International Swimming Federation) for use in competition. Findings from previous studies where the backstroke ledge was not used may no longer be relevant. Since use of the backstroke ledge appears to offer a performance advantage [2,3,4,5], it has been almost universally adopted as the preferred starting surface. Two studies have analyzed the impact of different handgrip positions while using the backstroke ledge; one determined that it does not affect start time [4], and the other did not discuss start time [6]. No other analysis of setup technique has been performed on starts where the backstroke ledge is used
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