Abstract
The current study investigated body roll amplitude and timing of its peak in backstroke and compared them with front crawl swimming. Nineteen anatomical landmarks were digitised using 80 swimming trial videos (ten swimmers × two techniques × four intensities) recorded by two above- and four below-water cameras. One upper-limb cycle was analysed for each trial, and shoulder and hip roll, whole-body roll (WBR), and WBR due to the buoyant torque (WBRBT) were obtained. Main effects of intensity and technique on the amplitude and timing to reach the peak in those variables were assessed by two-way repeated-measures ANOVA. Swimmers decreased their WBRBT amplitude with an increase in the intensity in both techniques (p ≤ 0.005). The same result was observed for the amplitude of WBR, shoulder roll, and hip roll only in front crawl (p ≤ 0.017). Swimmers maintained the timing of peak WBRBT in both techniques, while they shifted the timing of WBR and hip roll peak toward the beginning of the cycle when increasing the intensity in front crawl (p ≤ 0.017). In conclusion, swimmers maintain the amplitude of WBR, shoulder roll, and hip roll in backstroke when the intensity increases, whereas they reduce the amplitude of all rolls in front crawl.
Highlights
The current study investigated body roll amplitude and timing of its peak in backstroke and compared them with front crawl swimming
A significant main effect of intensity was observed in all those variables, and the main effect of technique was significant in vx and stroke frequency (SF) (p < 0.001 and 0.002, respectively) that were both larger in front crawl than in backstroke
Swimmers reduced the amplitude of wholebody roll (WBR), shoulder roll, and hip roll with the increase in the intensity in front crawl but it was not the case in backstroke
Summary
The current study investigated body roll amplitude and timing of its peak in backstroke and compared them with front crawl swimming. It has been reported that shoulder roll amplitude decreased when the velocity increased[11]; a recent study showed no difference in this variable between sprint and distance pace swimming[12]. It has been reported that swimmers did not change their shoulder and hip roll amplitude during a 200 m backstroke trial despite changes in the swimming velocity[13]. This finding is different from a study in 200 m front crawl in which swimmers increased their hip roll amplitude throughout the trial when the velocity d ecreased[10]. Similar results have been reported in a previous study in which swimmers show consistent shoulder roll and hip roll amplitude at four different swimming velocities[14]
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