The images were analysed using Virtualdub software 1.8.8 by Avery Lee. Kinematic thereby data were obtained by one observer twice, with a two-month interval between observations. Internal consistency reliability for all the variables was determined using intraclass correlation coefficients (ICC 3.1), and the associated 95% confidence interval. The ICCs of the velocity and stroke rate were high, with a value of 0.99 in both cases. Data analysis The stroke rate (SR) was calculated in Hz (cycles ? s?1) by the number of frames taken to complete three stroke cycles within the central 10 meters of each 50 m length. The measurement started when the left hand of the swimmer first entered the water after the head had crossed the first reference line.

The average velocity (V) was obtained from the numbers of frames that each participant needed to cover the central 10 meters. The timing used the frames in which the head crossed reference lines at the start and end of the 10 meters. Finally, the stroke length (SL) was determined from the calculated stroke rate and average velocity: SL = V ? SR?1 (m ? cycle?1). Descriptive statistics including means and standard deviations were calculated. The normality of the variables was analysed with the Shapiro – Wilk test. Since the distribution was not normal, comparisons between conditions were performed with Friedman repeated measures analysis of variance. If differences were detected, post-hoc comparisons were made using the Wilcoxon signed-rank paired t-test to determine where the differences had occurred. The data were analyzed using SPSS 15.

0. The level of significance was set at p �� 0.05. Results Table 1 presents mean velocity, stroke rate and stroke length for each type of paddle condition in the central 10 meters of each 50 m length. The ANOVA analysis revealed significant differences (p < 0.05) in the main effect of kinematic variables among the paddle conditions. Table 1 Mean �� standard deviation of velocity, stroke rate and stroke length during freestyle swimming without hand paddles, with small and large hand paddles An increasing trend in the average velocity during the first 50 m was found, but no significant differences were observed between paddle conditions. Conversely, mean velocities in the second 50 m wearing both small and large paddles were significantly greater than without paddles (p < 0.01).

As for the stroke rate, no significant differences were detected either in the first 50 m or in the second 50 m. However, a decreasing trend was found as the size of the paddles was enlarged. Stroke length wearing small paddles was significantly greater than without paddles in the first 50 m (p < 0.05). Stroke length wearing large paddles was significantly greater than without paddles during both the first 50 m (p < 0.01) and the second 50 m (p < 0.05). AV-951 Figure 1 shows the relationship between the three kinematic variables for each partial simultaneously.