Identification of key somatic features that are common and the ones that differ between swim strokes through allometric modeling.

Introduction: The aim of this study was to explore which key somatic features are common to four swim strokes and medley, and specifically to identify which characteristics benefit only specific strokes. Methods: The sample was composed of 130 swimmers (95 males aged 19.5 ± 2.9 years and 35 females aged 18.4 ± 2.8 years). A set of anthropometric variables was used to predict swimming speed in the four swimming strokes and medley. Results: A multiplicative model with allometric body size components was used to identify the demographic and anthropometric predictors of swimming speed. Trunk height and waist circumference were the only variables significantly different among swimming strokes (p < 0.05). Associations between swimming speed and arm length were similar in breaststroke and medley, and in freestyle, backstroke and butterfly (R2 = 60.9%). The model retained as swimming speed predictors the age2, upper body circumference, hand breadth, waist circumference, and subscapular skinfold thickness (these last two had negative associations). Conclusion: All these predictors were common to all four swim strokes and medley. Arm length was also retained as a significant predictor, but this one varied significantly between the four different swim strokes and medley. These findings highlight the importance of having a "V-shape" trunk, longer upper limbs, and large hands as predictors of swimming performance.

The kinematic profile of ventral swimming start: sex diversity.

It has been suggested that sex distinctions in physiology may affect the swimming performance of each sex differently. Yet, sex-based performance dependency has not been taken into consideration by most of the researchers evaluating swimming start. Therefore, the purpose of this research was to determine the effect of sex heterogeneity on the spatiotemporal characteristics of swimming start by investigating the determinants of its performance. A total of fifty-two international-level swimmers (thirty females and twenty-two males) performed three repetitions of the kick-start up to the 15-m mark. During trials, data were collected using video cameras and instrumented starting block. To search for evidence of differences between the two groups, the one-way ANOVA was conducted. Pearson's correlation coefficients were calculated between measurements widely used to describe overall starting performance and selected kinematical variables of swimming start. A sex effect was exposed for temporal variables describing all swimming start phases (p ≤ 0.015). Male swimmers, by spending less time during the push-off from the starting block (p = 0.002; η p 2 = 0.18), reaching higher take-off velocity (p < 0.001; η p 2 = 0.29), traveling longer distances during flight (p < 0.001; η p 2 = 0.40), and swimming faster in the water phase (p < 0.001; η p 2 = 0.40), took starting advantage over their female counterparts. Consequently, performance measures such as 5-m, 10-m, and 15-m start times indicated that male participants were faster than females (p < 0.001; η p 2 ≥ 0.40). Only in the group of male swimmers a significant correlation between variables describing overall starting performance (5-m, 10-m, and 15-m times), and variables commonly highlighted as starting performance determining factors (block phase duration, take-off horizontal velocity, and flight distance) was found. The current study shows that the spatiotemporal variables of swimming start, the relation between them as well as overall starting performance, vary by sex. Consequently, the requirement of sex factor and its heterogeneity effect should be included not only in detailed characteristics of separate variables but also in all approaches undertaken. Those findings seem to play a crucial role mainly in swimming start evaluations in post-pubertal age groups of swimmers.

Does the Back Plate Position Influence Swimming Start Temporal Characteristics?

The current study examined the back plate position impact on the block phase movement pattern and total starting performance with a distinction for sex. Thirty-eight swimmers performed starts changing the back plate position (preferred position, one position forward and one position backward), with the data being assessed using a 3D dynamometric central and a video camera. In males, the 15 m start time was 0.1 s shorter for the preferred position compared with the backward position (p < 0.05). Regardless of the back plate positioning, the swimmers spent a similar time on the block. A more forward position of the back plate postponed the rear foot take-off and consequently reduced the front foot stand duration. A back plate position effect was revealed for those variables with a larger effect size in males whereas in females, a change of about two positions was needed to reach a significance level. Probably due to the specification of physical domains, a greater impact on the changes introduced was noted for males. Therefore, whilst searching for the optimal starting position, adjustments to the back plate placement might affect a greater number of males than females. To reinforce the starting optimization during the training process and its monitoring, the effect of personal preference toward the starting block setting was also considered.

Anthropometric predispositions for swimming from the perspective of biomechanics.

PURPOSE: Early identification of anthropological potential in swimmers is considered important to the recruitment and selection of children and adolescents to perform extensive and strenuous training. The aim of the research was a comparative analysis of the anthropometric parameters and indicators of adult, elite swimmers with people who had never trained for swimming. It was assumed that the specific characteristics of the swimmers' somatic composition referred to the laws of swimming biomechanics. METHODS: Anthropometric measurements were taken in a group of elite male swimmers (N = 28), aged 17-24. The same set of measurements was taken in a homogeneous control group of students of physical education. An anthropometric profile significantly differentiating swimmers from the control group was constructed. Next, a linear forward stepwise discriminant analysis was conducted to investigate which indices can be used to distinguish the two groups. RESULTS: It seems significant that a specific somatic composition trait of swimmers in the form of a relatively long shank was observed, which had not been observed in earlier studies. Additionally, indices of relatively slim hand dimension, and indices describing a "reversed triangle" shape of trunk, were the most powerful discrimination variables between the two examined groups. CONCLUSION: The results obtained cannot be generalised to the entire population of swimmers, however referring them to the laws of biomechanics of swimming allows for the continuation of research into identifying the prognostic traits desirable for success among young swimmers.

Assessing the impact of a targeted plyometric training on changes in selected kinematic parameters of the swimming start.

PURPOSE: The aim of this study was to analyse changes taking place within selected kinematic parameters of the swimming start, after completing a six-week plyometric training, assuming that the take-off power training improves its effectiveness. METHODS: The experiment included nine male swimmers. In the pre-test the swimmers performed three starts focusing on the best performance. Next, a plyometric training programme, adapted from sprint running, was introduced in order to increase a power of the lower extremities. The programme entailed 75 minute sessions conducted twice a week. Afterwards, a post-test was performed, analogous to the pre-test. Spatio-temporal structure data of the swimming start were gathered from video recordings of the swimmer above and under water. RESULTS: Impulses triggered by the plyometric training contributed to a shorter start time (the main measure of start effectiveness) and glide time as well as increasing average take-off, flight and glide velocities including take-off, entry and glide instantaneous velocities. The glide angle decreased. CONCLUSIONS: The changes in selected parameters of the swimming start and its confirmed diagnostic values, showed the areas to be susceptible to plyometric training and suggested that applied plyometric training programme aimed at increasing take-off power enhances the effectiveness of the swimming start.