The definition of the dominant leg (lateral dominance) is not clear, and there has been little reporting related to lateral dominance in the legs. To uncover the practical factors influencing which leg to use as the takeoff leg in 1-legged jumping movements, this study aimed to investigate the subjective dominance side of fundamental movements and to examine the lateral dominance of motor functions between the takeoff leg and non-takeoff leg. The subjects consisted of 27 young men who exercised regularly. They had not trained particularly on unilateral jumping. Fifteen men are the athlete group (left-legged jumpers group [LG]) using a left leg and 12 men are the athlete group (right-legged jumpers group [RG]) using a right leg as determined by a preliminary survey related to takeoff leg during high jump. The fundamental motions of the subjective dominant leg were investigated and the differences between the motor functions of takeoff and lead legs, such as sole shapes, single-leg vertical jump, 20-m hopping, ladder hopping, single-leg balance, and isokinetic strength were examined. It was found that many RG subjects (83%) tended to select the right leg for hopping, and many LG subjects (87%) tended to select the left leg for 1-legged balance. It was suggested that skilled movements show right-leg dominance in both takeoff leg groups. In the LG subjects, the left leg showed a higher value than the right leg in sole shape. The RG subjects showed a higher value in the right leg than in the left leg in a single-leg vertical jump. However, marked dominance was not found in the takeoff leg. The lower limbs may not show marked lateral dominance such as in the upper limbs.

This study aimed to clarify the relationships between isometric squat (IS) using a back dynamometer and 1 repetition maximum (1RM) squat for maximum force and muscle activities and to examine the effectiveness of a 1RM estimation method based on IS. The subjects were 15 young men with weight training experience (mean age 20.7 ± 0.8 years, mean height 171.3 ± 4.4 cm, mean weight 64.4 ± 8.4 kg). They performed the IS with various stance widths and squat depths. The measured data of exerted maximum force and the action potential of the agonist muscles were compared with the 1RM squat data. The exerted maximum force during IS was significantly larger in wide stance (140% shoulder width) than in narrow stance (5-cm width). The maximum force was significantly larger with decreased knee flexion. As for muscle activity, the % root mean square value of muscle electric potential of the rectus femoris and the vastus lateralis tended to be higher in wide stance. As for exerted maximum force, wide stance and parallel depth in IS showed a significant and high correlation (r = 0.73) with 1RM squat. Simple linear regression analysis revealed a significant estimated regression equation [Y = 0.992X + 30.3 (Y:1RM, X:IS)]. However, the standard error of an estimate value obtained by the regression equation was very large (11.19 kg). In conclusion, IS with wide stance and parallel depth may be useful for the estimation of 1RM squat. However, estimating a 1RM by IS using a back dynamometer may be difficult.

This study aimed to clarify the relationship between upper-body strength and bat swing speed in high school baseball players and to examine physical characteristics of home run hitters (sluggers). The subjects were 30 male high school baseball players with national tournament experience at Koshien Stadium. Bat swing speed exerted by full effort was measured with a microwave-type speed measuring instrument. One repetition maximum (1 RM) of a bench press, bench press power (bench power) using a light load (30kg), and isokinetic chest press (0.4m/s, 0.8m/s, 1.2m/s) were measured as upper-body strength. The relationships between bat swing speed and upper-body strength values were examined. Additionally, the t-test was used to reveal the mean differences between 14 home run hitters (Group-A) and 16 mediocre hitters (Group-B) for each measurement value. The bat swing speed showed significant and middle correlations with the 1RM bench press (1RM BP) (r = 0.59), bench power (0.41), and isokinetic chest press (0.48-0.55). Group-A had significantly higher values in bench power and isokinetic chest press (high-speed) per kilogram of body weight than Group-B. The swing speed showed significant correlations (r=0.62) with 1RM bench press in Group-B, but not in Group-A. In conclusion, to improve the hitting power of high school baseball players, it may also be important to develop bench power with light loads in addition to 1RM BP.

According to dynamic analyses of muscle contraction, jump rope is a typical stretch-shortening cycle (SSC) movement. It has been reported that the relationship with SSC is higher in double unders than in single unders (basic jumps); however, the relationship between jump rope and sprint performances has not been extensively studied. To clarify this relationship in elementary schoolchildren, we compared the sprint speed and SSC ability of children who were grouped according to gender and ability. The subjects were 143 elementary fifth and sixth graders (78 boys, 65 girls). The consecutive maximal number of double unders, reactivity index (index of SSC ability) by Myotest, and 20-m sprint time were measured. According to the mean of jump rope records, the children were divided into a superior ability group (more than average + 0.5 SD) and an inferior ability group (less than average - 0.5 SD) for each gender. In both genders, a significant difference was found in the 20-m sprint time between the inferior and superior ability groups. The times for the superior ability groups (boys, 3.75 ± 0.23 seconds; girls, 4.02 ± 0.24 seconds) were excellent compared with the inferior ability groups (boys, 4.17 ± 0.32 seconds; girls, 4.23 ± 0.21 seconds). This effect size was higher in boys (1.44) than in girls (0.93). The reactivity index in the superior ability group was excellent compared with that in the inferior ability group. In conclusion, children who perform better in double unders are also faster during a 20-m sprint run. This tendency may be higher in boys. Classic jump rope training, such as double unders, should be effective as elementary plyometrics for improving the sprint ability of children.

Although jumping rope has been said to be a typical stretch-shortening cycle movement (SSC) from the dynamic analysis of muscle contraction, there are few research reports that focus on this point. Recently, the function of SSC of the legs with respect to the jumping movement has been evaluated using the rebound jump index (RJ-index). This study aimed to examine the possibility of using rope jumping in SSC training by comparing the RJ-index of the rebound jump (standard value) and the 2 different methods of rope jumping. The subjects included 76 healthy young men. Most subjects were involved in routine sports training 2-3 times per week. They performed the rebound jump (5 consecutive vertical jumps) and both a basic and a double-under jump with the jump rope, according to each participant's individual style (rhythm or timing). The RJ-index was calculated using the ground contact time and the jump height. The reliabilities of the RJ-index in the basic (intraclass correlation coefficient: 0.85) and double-under jump (0.92) were high, and the RJ-index of the latter (1.34 ± 0.24) was significantly higher than that of the former (0.60 ± 0.21). In the case of a group with inferior SSC ability, the RJ-index of the rebound jump only showed a significant correlation with the double-under but not with the basic jump. When using the RJ-index (1.97 ± 0.38) of the rebound jump as a criterion, the double-under-using about 70% of the SSC ability-may be effective for reinforcement of SSC ability.