Uso de células de carga para mensuração da força dos membros inferiores em nado ondulatório

Abstract

Considering the crescent utilization of the underwater dolphin kick (NOSB) techniques during the beginning and the turns of front crawl events, the main purpose of the present study was to determine the dol- phin kick force (FMINO) in tethered swimming and its correlations with the maximal performance determined in NOSB and in dolphin kick with a commercial board (NOSP). Nineteen male swimmers with mean age of 15.2±0.6 years and affiliated with Sao Paulo Aquatic Federation participated in the present study. The athletes were submit- ted a 30-s maximal effort of dolphin kick tethered to a dynamometer with strain gages (load cells) as a primary sensor element. The tension detected by the dynamometer due the swimmers’ efforts was amplified by an extensometer font. The results obtained during the efforts were sent to a computer using an interface and were stored in a data acquisi- tion program at 200 Hz. After these procedures, the results were smoothed using the “butterworth” filter of fourth order with 3-Hz fre- quency. Using the calibration straight line, the values were converted into force units (N) by the Matlab 5.3 program. This conversion allowed the determination of the dolphin kick mean force in tethered swimming (FMINO). Then, the swimmers performed a 15-m maximum effort of underwater dolphin kick (NOSB) and another 25-m maximum effort of dolphin kick using a commercial board (NOSP). The relation- ships between these three maximum efforts were analyzed using the Pearson’s correlation coefficient. A significance level of 5% was chosen. The mean ± standard deviation of FMINO, NOSB and NOSP were 53.85 ± 11.45 N, 1.19 ± 0.14 m.s-1, and 1.76 ± 0.26 m.s-1, respec- tively. The FMINO presented significant correlations with NOSB (r= 0.80) and NOSP (r= 0.76). According to the results of the present study, the use of FMINO to evaluate and predict the NOSB and NOSP of expert’s swimmers is suggested. However, more studies are necessary to verify the sensibility of the FMINO to specific effects into the swimming training