Case Report: Impact of dolphin kick implementation during backstroke finishes on swimming performance. From regional to olympic-level swimmers. A comparative case study.

According to the World Aquatics (WA) an updated swimming regulation (SW) concerning the backstroke finish has been implemented, allowing, the swimmers to fully submerge their bodies at once when some part of their head pass the 5-meter mark immediately before touching the wall. Therefore, the present comparative case study aims to apply the new regulation on backstroke finish, examining the swimming efficiency and underwater kinematics of an elite Olympic-level swimmer, and comparing the data with the published ones from a previous study on regional-level swimmers. A 19-year-old male Olympic-level backstroke swimmer performed three all-out 20 m backstroke swims: (i) touching the wall, breaking the water's surface with one part of their body (Classic), (ii) touching the wall with one hand, submerging the body two strokes after passing the last 5 m (Dive-One Hand) and (iii) touching the wall on streamline position, submerging the body two strokes after passing the last 5 m (Dive-Streamline) Kinematic analysis of the intermediate 10 m and the last 5 m was conducted using a digital video camera. Descriptive statistics and the Crawford-Howell t-test were utilized for the comparisons between elite and regional-level swimmers. Based on the swimmer's analysis, intermediate 10 m were faster than that in regional level swimmers (Elite vs. Regional: 1.68 ± 0.1 vs. 1.29 ± 0.1 m·s^-1, p = 0.00). Also, the elite-level swimmer increased his transition swimming speed (SS) (from 10 to the last 5 m) in all backstroke finishes (0.05 ± 0.03 vs. -0.07 ± 0.03 m·s^-1). Also, in the last 5 m showed an extreme increase in velocity at the sink- to-finish speed (SFS), 2.16 and 2.28 m·s^-1 for Dive-One hand, and Dive-Streamline, respectively. However, the tendency in velocity between backstroke finishes was similar between regional and elite-level swimmers. The elite swimmer can utilize the two variations of backstroke finishes more effectively compared to the regional-level swimmers. The swifter dolphin kick ability appears to play a significant role in achieving a successful backstroke finish, However, further investigations involving elite swimmers, differentiating the sinking approach and improving the speed before sinking (SBS) factor, could potentially provide more insights.