The purpose of the present study was twofold: (i) to compare the kinematic characteristics of individual and relay swimming starts; and (ii) to relate the kinematic variables to 5 m performance for both starts. Twelve elite-level swimmers performed 2 × 25 m at maximal effort (one with an individual and one with a relay start randomly). Two-dimensional direct linear transformation algorithms were used to calculate swimmers' centre of mass (CM) kinematics during each subphase. The results indicated moderate to much faster 5 m, 10 m 15 and 15 m times (29.4, 10.7 and 6.5%) for relay than individual starts as well as the differences at specific parameters, but no differences in take-off horizontal velocity between start techniques. Large correlations to performance times were found in block time, horizontal takeoff velocity, take-off velocity and entry angle (r = 0.77 to 0.83) 20 for individual start, but in changeover time, take-off height and entry distance (r = 0.69 to 0.90) for relay start. Differences on swim start regulations between individual and relay events were in line with different key parameters related to start performances in each event. This should be considered by swimmers and coaches when addressing the starting improvement.

Despite changes in the underwater sections of swimming races affecting overall performance, there is no information about the effects of the apnea-induced changes on the physiological state of competitive swimmers. The aim of the present research was to examine the effect of changes in the underwater race sections on the physiological [blood lactate concentration, heart rate, and rating of perceived exertion (RPE)] and biomechanical (underwater time, distance, and velocity) parameters of competitive swimmers. Twelve youth competitive swimmers belonging to the national team (706 ± 28.9 FINA points) performed 2 × 75 m efforts under three different conditions, while maintaining a 200 m race pace: (1) free underwater sections, (2) kick number of condition 1 plus two kicks, and (3) maximum distance underwater. Overall performance was maintained, and underwater section durations increased from condition 1 to 3 as expected according to the experimental design. Heart rate and blood lactate concentration values did not show differences between conditions, but the RPE values were significantly greater (F2, 36 = 18.00, p = 0.001, η2: 0.50) for the constrained (conditions 2 and 3) vs. the free underwater condition. Underwater parameters were modified within the 75 m efforts (lap 1 to lap 3), but the magnitude of changes did not depend on the experimental condition (all lap × condition effects p > 0.05). Controlled increases of underwater sections in trained swimmers can led to optimizing performance in these race segments despite small increases of perceived discomfort.

In swimming relay races, various start techniques are performed by swimmers, but it remains unclear which technique leads to a better start performance. Therefore, the purpose of the present study was to compare the kinematic characteristics of different relay start techniques with the new starting block Omega OSB11. Eleven international youth swimmers were filmed during 1) no step with parallel feet, 2) no step with separated feet and 3) one-step starts and their centre of mass kinematics calculated with 2D-DLT algorithms. Results indicate that differences between techniques were detected in the spatiotemporal parameters of the block and aerial start phases (e.g., initial and take-off positions, entry height, preparation and changeover times) and in selected parameters of the underwater phase (e.g., emersion time and distance, underwater time and distance). However, no statistical effects were found in 5 m, 10 m and 15 m start times, nor in horizontal take-off velocity, despite an observed trend for the one-step start to be superior to the non-step techniques. These results suggest that differences between relay techniques could rely more on the swimmer's body posture (angular kinematics) on the block, flight and underwater phases than on the centre of mass linear kinematics.