In order to evaluate how mechanical power relates to athletic performance in weight lifting, specific movement power (SMP) was investigated using a newly developed dynamometer. Four simulated pull movements in weight lifting were measured: weight lifting pull (WL), second pull, back strength pull, and shoulder shrug pull. Subjects included 12 elite (EL) and 14 district (DI) level Japanese weight lifters. Athletic performance was defined as the highest total combined weight (snatch plus clean and jerk) lifted during competition. The highest SMP was observed in the WL. Force, velocity, and power relations were derived from the WL, showing higher velocity and power values in EL than DI at an identical force level. SMP in WL was found to be significantly correlated to athletic performance. SMP measured as a simulated pull movement in weight lifting employing the present dynamometer appears useful in evaluating athletic performance. Furthermore, this dynamometer provides force-velocity relationships during multiarticular explosive movements.
Kazuo Funato, Akifumi Matsuo and Tetsuo Fukunaga
Ryu Nagahara, Mirai Mizutani, Akifumi Matsuo, Hiroaki Kanehisa and Tetsuo Fukunaga
We aimed to clarify the mechanical determinants of sprinting performance during acceleration and maximal speed phases of a single sprint, using ground reaction forces (GRFs). While 18 male athletes performed a 60-m sprint, GRF was measured at every step over a 50-m distance from the start. Variables during the entire acceleration phase were approximated with a fourth-order polynomial. Subsequently, accelerations at 55%, 65%, 75%, 85%, and 95% of maximal speed, and running speed during the maximal speed phase were determined as sprinting performance variables. Ground reaction impulses and mean GRFs during the acceleration and maximal speed phases were selected as independent variables. Stepwise multiple regression analysis selected propulsive and braking impulses as contributors to acceleration at 55%–95% (β > 0.72) and 75%–95% (β > 0.18), respectively, of maximal speed. Moreover, mean vertical force was a contributor to maximal running speed (β = 0.48). The current results demonstrate that exerting a large propulsive force during the entire acceleration phase, suppressing braking force when approaching maximal speed, and producing a large vertical force during the maximal speed phase are essential for achieving greater acceleration and maintaining higher maximal speed, respectively.
Toshimasa Yanai, Akifumi Matsuo, Akira Maeda, Hiroki Nakamoto, Mirai Mizutani, Hiroaki Kanehisa and Tetsuo Fukunaga
We developed a force measurement system in a soil-filled mound for measuring ground reaction forces (GRFs) acting on baseball pitchers and examined the reliability and validity of kinetic and kinematic parameters determined from the GRFs. Three soil-filled trays of dimensions that satisfied the official baseball rules were fixed onto 3 force platforms. Eight collegiate pitchers wearing baseball shoes with metal cleats were asked to throw 5 fastballs with maximum effort from the mound toward a catcher. The reliability of each parameter was determined for each subject as the coefficient of variation across the 5 pitches. The validity of the measurements was tested by comparing the outcomes either with the true values or the corresponding values computed from a motion capture system. The coefficients of variation in the repeated measurements of the peak forces ranged from 0.00 to 0.17, and were smaller for the pivot foot than the stride foot. The mean absolute errors in the impulses determined over the entire duration of pitching motion were 5.3 N˙s, 1.9 N˙s, and 8.2 N˙s for the X-, Y-, and Z-directions, respectively. These results suggest that the present method is reliable and valid for determining selected kinetic and kinematic parameters for analyzing pitching performance.
Yuji Kobayashi, Junjiro Kubo, Takeo Matsubayashi, Akifumi Matsuo, Kando Kobayashi and Naokata Ishii
The aims of the study were to investigate the differences in kinematics and kinetics between the dominant and nondominant leg during single-leg jumps without arm swing, and to determine the relationship between bilateral asymmetry in isokinetic knee strength and the single-leg jump. Isokinetic knee strength and single-leg jump kinematics and kinetics were measured in 11 male participants. The bilateral asymmetry index was calculated for each parameter. For isokinetic knee strength, there were no significant differences between the dominant and nondominant legs. Significant correlations were observed for the bilateral asymmetry index for isokinetic knee strength at 180 degrees per second and the bilateral asymmetry indexes for maximum flexion angle and the mean knee joint torque during the single-leg jumps. In conclusion, the findings of the current study suggest an association between knee strength imbalances and the joint angle, as well as the torque produced in single-leg jumps, although no relationship between knee strength and jump height was observed.
Ryu Nagahara, Yohei Takai, Miki Haramura, Mirai Mizutani, Akifumi Matsuo, Hiroaki Kanehisa and Tetsuo Fukunaga
Purpose: We aimed to elucidate age-related differences in spatiotemporal and ground reaction force variables during sprinting in boys over a broad range of chronological ages. Methods: Ground reaction force signals during 50-m sprinting were recorded in 99 boys aged 6.5–15.4 years. Step-to-step spatiotemporal variables and mean forces were then calculated. Results: There was a slower rate of development in sprinting performance in the age span from 8.8 to 12.1 years compared with younger and older boys. During that age span, mean propulsive force was almost constant, and step frequency for older boys was lower regardless of sprinting phase. During the ages younger than 8.8 years and older than 12.1 years, sprint performance rapidly increased with increasing mean propulsive forces during the middle acceleration and maximal speed phases and during the initial acceleration phase. Conclusion: There was a stage of temporal slower development of sprinting ability from age 8.8 to 12.1 years, being characterized by unchanged propulsive force and decreased step frequency. Moreover, increasing propulsive forces during the middle acceleration and maximal speed phases and during the initial acceleration phase are probably responsible for the rapid development of sprinting ability before and after the period of temporal slower development of sprinting ability.