The purpose of this study was to investigate relationship between growth of body height and development of speed, agility, explosiveness and quickness in boys from childhood to adolescence. 3,863 boys aged from 3 to 22 years old were participated in this study. Height was used for physique and 20m dash, Pro agility test, side steps, standing long jump, vertical jump and rebound jump index were used for speed, agility, explosiveness and quickness. These items, along with the body height, were plotted on a logarithmic graph to obtain the allometric equation “y = bx^a”. As the results of calculating transition points, it was also shown by a linear function of the 4-phase with three transition points in any of the measurement items. Since the coefficient a from second transition point to third transition point was equal to or greater than 1, the development of muscle strength was speculated to contribute to the development of speed, agility, explosiveness and quickness. Further, since the coefficient a to the first transition point in all measurements showed a value of 1 or more, the improvement of the nervous system may contribute to the development of speed, agility, explosiveness and quickness.

View full abstract

The purpose of this study was to investigate the influence on post-activation potentiation (PAP) by performing isotonic muscle contraction using representative squat in resistance exercise. Subjects in this study were eight healthy male college students with training experience. In order to verify the effect of PAP, a counter movement jump (CMJ) was performed before and after the back-full squat (30%1RM× 3sets × 6reps, 60%1RM× 3sets×3reps, 90%1RM×3sets×2reps), and jump height, peak power, peak velocity, mean power, mean velocity were measured and analyzed. As a result, CMJ jump height (ES=0.68, 0.63), peak power (ES=0.80, 0.96), peak velocity (ES=1.03, 0.60) showed significantly high values after 60% and 90%1 RM conditions. This suggests that performing several sets of isotonic muscle contraction using medium and high intensity squats induce PAP and it can be an effective means as training to emphasize improvement of maximum power and speed.

View full abstract

The purpose of this study was to clarify relationship between sprint start variables which seemed to be affecting explosive acceleration ability and the muscle function of lower extremities. 25 male rugby players of a team which belonged to the Japan top league cub performed 5m sprint start, barbell squat, squat jump and rebound jump test. Average step velocity from the 1st to 4th step (V1-4Step) which play important role in explosive acceleration ability in sprint start was analyzed. Step length, flight time, and contact time showed significant correlations with V1-4Step, however, there was no significant relationship between V1-4Step and step frequency. V1-4Step showed significant correlations with body mass ratio of jump squat power for 20 kg, 30%1RM, 60%1RM, 80%1RM, respectively, and rebound jump index. Comparing the difference of sprint variables and the muscle functions of the lower extremities between the higher ranked group and lower rank group divided by the V1-4Step, higher ranked group showed significantly lager step length, flight time, body mass ratio of the power for 20kg and 60%1RM, and rebound jump index. There were insignificant but very large difference in the contact time, and the body mass ratio of the power for the 30% and 80%1RM, higher ranked group showed shorter contact time and higher body mass ratio of the power. From these results, to achieve shorter contact time while increasing a step length appeared to be important to improve V1-4Step. In addition, it seemed to be necessary to increase body mass ratio of the power for the loads ranged from light to heavy, and improve reactive leg strength performed in stretch shortening cycle muscle activities.

View full abstract