Golden ratio and self-similarity in swimming: breast-stroke and the back-stroke.

Introduction: Dynamics-on-graph concepts and generalized finite-length Fibonacci sequences have been used to characterize, from a temporal point of view, both human walking & running at a comfortable speed and front-crawl & butterfly swimming strokes at a middle/long distance pace. Such sequences, in which the golden ratio plays a crucial role to describe self-similar patterns, have been found to be subtly experimentally exhibited by healthy (but not pathological) walking subjects and elite swimmers, in terms of durations of gait/stroke-subphases with a clear physical meaning. Corresponding quantitative indices have been able to unveil the resulting hidden time-harmonic and self-similar structures. Results: In this study, we meaningfully extend such latest findings to the remaining two swimming strokes, namely, the breast-stroke and the back-stroke: breast-stroke, just like butterfly swimming, is highly technical and involves the complex coordination of the arm and leg actions, while back-stroke is definitely similar to front-crawl swimming. An experimental validation with reference to international-level swimmers is included.

Specificity of weightlifting bench exercises in kayaking sprint performance: A perspective for neuromuscular training.

Several studies showed significant differences between bench lift exercises without investigating which is more related, in biomechanical and neuromuscular terms, to improve the sprint flatwater kayak performance. This study aims to compare the power-load and velocity-load neuromuscular parameters performed in prone bench pull (PBP), and bench press (BP) exercises to identify which of them meet the gesture specificity in sprint flatwater kayak performance. Ten elite kayakers participated in this study. Power-load, velocity-load relationships, the maximum dynamic strength, and the kayak sprint performance test were assessed. The power-load and velocity-load relationships showed significant differences between the PBP and BP for each considered load. The kayakers showed a significant correlation between maximum power performed on the PBP and the maximum velocity reached in the kayak sprint (r = 0.80, p < 0.01) and the stroke frequency (r = 0.61, p < 0.05). Conversely, the maximum power performed on the BP did not correlate with the kinematic parameters analyzed. In addition, the maximum dynamic strength in the PBP and BP did not correlate with the maximum velocity and stroke frequency. Furthermore, no significant difference was observed in both the bench exercises for the maximum dynamic strength (p > 0.05). The results of this study suggest that the maximal muscular power expressed in PBP exercise only seems to be more specific in kayak velocity performance compared with maximal dynamic strength and with all dynamic parameters recorded in the BP. This will allow coaches and trainers to use specific bench exercises for specific neuromuscular kayakers' adaptations during the whole competitive season.

Paddle propulsive force and power balance: a new approach to performance assessment in flatwater kayaking.

This study aims to determine the propulsive force (Fp) and its timing of application during the paddle stroke confirming the dynamic balance between propulsive and drag powers (Pp = Pd) in kayaking performance. Ten male sub-elite paddlers participated in the study. The athletes carried out three trials of 50 m at three different velocity ranges: 2.70 - 3.00 m/ s; 3.01 - 3.50 m/s and 3.51 - 4.00 m/ s. A constant velocity during each trial was maintained and the section between 15 and 40 m of the total pool length was considered for further analysis. Data were collected using the E-kayak system provided of an instrumented paddle and 2D video analysis. It was observed that the propulsive force increases in intensity (up to 90% of the peak force) as the velocity increases. The dynamic balance between Pd and Pp was confirmed with a Bland and Altman plot (estimated bias: 0.2; LoA: 12.8 and 13.3 W). The related comparisons between the power parameters showed no significant difference (p > 0.050) in each of the considered velocity. By applying the dynamic balance theory between Pp = Pd on the data obtained from the interaction among GPS, force on the paddle and 2D video analysis, it is possible to acquire essential information (Fp, Pp) to monitor the flatwater kayaking performance.

Kinematic Analysis of Water Polo Player in the Vertical Thrust Performance to Determine the Force-Velocity and Power-Velocity Relationships in Water: A Preliminary Study.

BACKGROUND: To date, studies on muscle force and power-velocity (F-v and P-v) relationships performed in water are absent. AIM: The goal of this study is to derive the F-v and P-v regression models of water polo players in water vertical thrust performance at increasing load. METHODS: After use of a control object for direct linear transformation, displacement over the water and elapsed time was measured, by using a high-speed 2D-videoanalysis system, on 14 players involved in the study. RESULTS: Intra-operator and player's performance interclass correlation coefficient (ICC) reliability showed an excellent level of reproducibility for all kinematic and dynamic measurements considered in this study with a coefficient of variation (CV) of less than 4.5%. Results of this study have shown that an exponential force-velocity relationship seems to explain better the propulsive force exerted in the water in lifting increasing loads compared to the linear one, while the power and velocity have been shown to follow a second-order polynomial regression model. CONCLUSION: Given the accuracy of the video analysis, the high reliability and the specificity of the results, it is pointed out that video analysis can be a valid method to determine force-velocity and power-velocity curves in a specific environment to evaluate the neuromuscular profile of each water polo player.

A Pilot Study on the e-Kayak System: A Wireless DAQ Suited for Performance Analysis in Flatwater Sprint Kayaks.

Nowadays, in modern elite sport, the identification of the best training strategies which are useful in obtaining improvements during competitions requires an accurate measure of the physiologic and biomechanical parameters that affect performance. The goal of this pilot study was to investigate the capabilities of the e-Kayak system, a multichannel digital acquisition system specifically tailored for flatwater sprint kayaking application. e-Kayak allows the synchronous measure of all the parameters involved in kayak propulsion, both dynamic (including forces acting on the paddle and footrest) and kinematic (including stroke frequency, displacement, velocity, acceleration, roll, yaw, and pitch of the boat). After a detailed description of the system, we investigate its capability in supporting coaches to evaluate the performance of elite athletes' trough-specific measurements. This approach allows for a better understanding of the paddler's motion and the relevant effects on kayak behavior. The system allows the coach to carry out a wide study of kayak propulsion highlighting, and, at the same time, the occurrences of specific technical flaws in the paddling technique. In order to evaluate the correctness of the measurement results acquired in this pilot study, these results were compared with others which are available in the literature and which were obtained from subjects with similar characteristics.