Head Depth and Head Speed During Competitive Backstroke Ledge Starts

Abstract

Recently, a commercially available starting ‘ledge’ designed to reduce foot slippage during the execution of the backstroke start was introduced in competitive swimming. For the purpose of identifying potential safety consequences, the present study investigated the effect of ledge use on head depths, speeds, and distances in backstroke starts of athletes with no prior or only novice familiarity of the ledge. Competitive backstroke starts were performed with and without ledges by high school-aged (14.5 to 19.2 yr, N = 61) swimmers in 1.52 m of water during a closed testing session. A SIMI Reality Motion System in a calibrated space using three cameras was employed for filming starts. Dependent measures were initial head height (Y _set ), distance from wall at entry (X _entry ), entry angle (Angle _entry ), horizontal velocity at head entry (XVel _entry ), resultant velocity at entry (ResVel _entry ), maximum depth of the center of the head (Y _mhd ), resultant velocity at maximum head depth (ResVel _mhd ), and distance from the wall at maximum head depth (X _mhd ). The ledge (L) condition showed significant increases compared to the non-ledge (NL) condition in X _entry (L 1.61 ± 0.59 m, NL 1.50 ± 0.53 m, p < .001), ResVel _entry (L 3.44 ± 0.97 m·s ^-1 , NL 3.08 ± 1.00 m·s ^-1 , p < .001), Angle _entry (L 43.13 ± 16.97°, NL 39.66 ± 18.11°, p = .030), X _mhd (L 4.18 ± 0.58 m, NL 4.09 ± 0.63 m, p = .008), and Y _mhd (L 0.54 ± 0.21 m, NL 0.49 ± 0.18, p