Underwater dolphin kicks of young swimmers – evaluation of effectiveness based on kinematic analysis

Abstract

Purpose. The aim of the study was to distinguish the kinematic indicators influencing the average horizontal velocity of swimming (v cOM ) with underwater dolphin kicks (UDK). Methods. The study involved 15 boys and 20 girls (mean age, 11.5 ± 1.00 years; height, 1.57 ± 0.09 m; training experience, 2.5 ± 1.00 years) practicing swimming 7 times a week. We determined the body height (H), the length of the body with the arms lifted (L b ), and the best result in the 50-m freestyle (pbt); characteristic anthropological points were marked on the body. The subjects performed UDK after a water-start for a distance of ca. 8 m (without a push-off from the wall). Movements were recorded with an underwater camera. The recordings were kinematically analysed with the SkillSpector program. On this basis, we calculated v cOM , frequency of movement (f), amplitude of movement (A), horizontal displacement in one cycle (D pk ), maximum flexion in the knee joints (KF max ), the product of f and A (I Af ), the Strouhal number (St), and relative amplitude of toe movement (A rEL ).Results. The movements of the subjects were characterized as follows: v cOM = 1.08 ± 0.13 m/s, f = 2.00 ± 0.

Gender effect on underwater undulatory swimming technique of young competitive swimmers

“…The camera lens was set perpendicularly to the direction of movement of the subjects. The described arrangement of the measurement line was consistent with previous research by the authors of this study [21].…”

“…In this study, the relationship between maximal flexion of the ankle joints (A FLEX ) and the horizontal velocity of swimmers was negative, although the strength of these correlations was different for girls and boys (r = -0,501 and r = -0.206, respectively). The fact that maximising the extension of the ankle joints at the expense of flexion of the ankle joints is an effective strategy in increasing the velocity when performing underwater undulatory swimming was indicated by Wądrzyk et al [21]. This study also showed that the range of motion in the ankle joints did not significantly affect v COM .…”

“…In turn, in boys, the relationship between K ROM and v COM was weak (r = -0.281). It has already been documented that excessive flexion in the knee joints has a negative effect on the velocity of underwater undulatory swimming [2], [21]. According to Higgs et al [10], higher efficiency of underwater undulatory swimming can be obtained by increasing the range of motion in the hip joints during the upward movement of the feet.…”

“…However, changes in the frequency of movements should be monitored with the DPC measurement. It may turn out that maximising the distance per cycle may considerably extend the cycle time [21]. This, in turn, being synonymous with a decrease in the frequency of movements, may negatively affect the velocity of the swimmer [7].…”

“…The significance of differences between the mean values of these variables (tests for independent samples) was also assessed. The research method was similar to that described in earlier study [21]. Before the measurements were performed, the centers of rotation of the: upper, knee, hip, shoulder, elbow and radial-wrist joints were marked with a waterproof marker on the left, lateral side of the body.…”