Abstract

PAPOTI, Marcelo et al. Use of load cells to measurements of underwater dolphin kicki force in swimming tethered. . Rev. Port. Cien. Desp. [online]. 2007, vol.7, n.3, pp.313-318. ISSN 1645-0523.

Considering the crescent utilization of the underwater dolphin kick (NO_SB) techniques during the beginning and the turns of front crawl events, the main purpose of the present study was to determine the dolphin kick force (FMI_NO) in tethered swimming and its correlations with the maximal performance determined in NO_SB and in dolphin kick with a commercial board (NO_SP). 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 submitted 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 acquisition program at 200 Hz. After these procedures, the results were smoothed using the "butterworth" filter of fourth order with 3-Hz frequency. 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 (FMI_NO). Then, the swimmers performed a 15-m maximum effort of underwater dolphin kick (NO_SB) and another 25-m maximum effort of dolphin kick using a commercial board (NO_SP). The relationships 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  FMI_NO, NO_SB and NO_SP were 53.85 ± 11.45N, 1.19 ± 0.14 m.s^-1, and 1.76 ± 0.26 m.s^-1, respectively. The FMI_NO presented significant correlations with NO_SB(r= 0.80) and NO_SP (r= 0.76). According to the results of the present study, the use of FMI_NO to evaluate and predict the NO_SB and NO_SP of expert’s swimmers is suggested. However, more studies are necessary to verify the sensibility of the FMI_NO to specific effects into the swimming training.

Keywords : dolphin kick; tethered swimming; force measurement.

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