2017, Volume 13, Issue 1

Relationship between age and expertise with the maximum impact force of a reverse punch by shotokan karate athletes

Vinicius Aguiar de Souza1, Andre M. Marques2

1Mechanical and Aerospace Engineering, Tohoku University, Japan
2Department of Economics, Federal University of Paraiba, Brazil

Author for correspondence: Vinicius Aguiar de Souza; Mechanical and Aerospace Engineering, Tohoku University, Japan; email: vinicius@m.tohoku.ac.jp

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Background and Study Aim: Karate is a Japanese martial art that traditional apparatus such as the punching board (makiwara) to improve, effectiveness (stroke precision) and physical strength. However, little is known about the magnitude of the impact forces, and its connection to anthropometric and biomechanical variables. To fill this gap, the cognitive goal of this study is the knowledge about two phenomena: (i) the maximum impact force on a punching board generated by a reverse punch (gyaku-zuki) in a front stance (zenkutsu-dachi) in conditions as close as possible to the regular practice, and (ii) the relationship between anthropometric (age) and biomechanical (expertise) variables with the maximum impact force.

Material and Methods: The maximum impact force was acquired by strain gauges for eight shotokan karate athletes male black belts: age 20.25 ±4.13 years; height 1.74 ±0.04 m; body mass 72.41 ±9.62 kg; expertise:7.64 ±4.33 years (mean, SD). The effect of two variables, i.e., age, and expertise, on the maximum impact force was analysed by a linear regression model based on the bootstrap resampling method.

Results: Both variables age and expertise present statistically significant correlation with the maximum impact force. However, this dependence manifests itself in a quadratic form, in which a decreasing effect is present and dictates the behaviour of the maximum impact force. The maximum impact force for all trial ranged from 1310.82 N to 2314.53 N with an average of 1812.01 N. A negative correlation was observed between the age and the standard deviation of the subject’s performance. This indicates that the expertise accumulated over the years may exert a stabilising effect.

Conclusions: It was found that age and expertise have relationships with the maximum impact force as documented in the literature. However, these influences have a critical point from which they have a decreasing effect on the maximum impact force. The critical point for the age is 31 years old and, the critical point for the expertise is 11 years of lifetime training. After these critical points, the karate athlete would be advised to search for ways to compensate for the decreasing marginal effects, such as nutrition or complementary practices under the guidance of a professional.

Key words: punching board (makiwara), reverse punch (gyaku-zuki), global science space