Influence Of Approach And Arm Swing On Takeoff Velocity In Swimming Relay Exchanges.

Abstract

Exchanges are crucial in relay swim race performance. Previous research has partially supported an advantage for a start using a one or two step-up approach (1ST and 2ST) with arm swing to add impulse. However, this research has been limited and, to date, no studies have reported these effects on relay exchanges for intercollegiate female swimmers. PURPOSE: To quantify and compare takeoff impulses and velocities by swimmers when employing no step (NST), 1ST, and 2ST relay exchange techniques. METHODS: Twelve intercollegiate female swimmers executed NST, 1ST, and 2ST exchanges on a custom starting platform with a mounted force plate positioned identically to a standard starting block. Data from the plate were collected at 400 Hz. Time of impulse (tIMP) was calculated for each trial. Forces in the force plate frame of reference were projected into the world frame of reference using the angle between the plate’s surface and true horizontal. Time-series force data were integrated over tIMP to calculate starting impulses in the forward and upward directions. These were divided by swimmer mass to compute the components of takeoff velocity (vHOR and vVERT). Paired t-tests were used to compare means for takeoff velocities and times of impulse for the three relay starts (α = 0.05). RESULTS: NST, 1ST, and 2ST starts had mean vHOR of 3.33 ± 0.20, 3.42 ± 0.30, and 3.34 ± 0.24 m/s respectively, all statistically equivalent. Values for vVERT were 0.31 ± 0.24, 0.38 ± 0.30, and 0.26 ± 0.28 m/s respectively, with 1ST greater than 2ST (p = .02). Values for tIMP were 1.14 ± 0.15, 1.22 ± 0.17, and 1.35 ± 0.23 s for NST, 1ST, and 2ST respectively, and were statistically greater from technique to technique (p < .03, p < .03) CONCLUSIONS: No advantage for vHOR existed between techniques, but the time of impulse grew from technique to technique. Therefore, the average force of impulse decreased from technique to technique. There may be limitations in 1ST and 2ST techniques on the generation of horizontal force due to foot placement. Achieving bigger horizontal forces with increased times would yield bigger horizontal takeoff velocities. Future research should investigate ways to achieve this, and examine other starting techniques that may combine bigger forces with increased time of impulse.