Effect of a wearing overlap length change of the knee joint supporter during a stop-jump task / 体力科学

The purpose of this study is to show the kinetic effect on the stop-jump movement in wearing overlap length change of the knee joint supporter. Ten young health males volunteered as subjects for this study. Three-dimensional videographic and ground reaction force data in a stop-jump task were collected in three conditions. Overlap length of supporter, peak ground reaction force, peak knee flexion angle, peak knee extension torque at landing, peak jump height, peak jump velocity at takeoff were compared among conditions: high pressure condition, middle pressure condition and no supporter. The high pressure condition significantly increased peak knee flexion angle and peak knee extension torque at landing. It is considered that the high pressure condition enlarged the knee joint angle and the knee joint extension torque in stop task because the rigidity of the supporter increased. On the other hand, it was suggested that the pressure change of wearing the knee joint supporter don’t affect jump performance.

EFFCT OF WALKING SPEED ON THE COMPLEXITY OF THE CYCLE OF HEAD FLUCTUATION DURING WALKING USING APPROXIMATE ENTROPY / 体力科学

The purpose of this study is to show clearly whether the complexity of the cycle of head fluctuation during walking is influenced with walking speed. Thirty young healthy males and females volunteered as subjects for this study. Subjects walked 40 m, and they were instructed to walk “slowly”, “a little slowly”, “usual speed”, “a little fast” and “fast” depending on their subjectivities. The head fluctuation of the right-and-left direction during a walk was measured by using an accelerometer. In addition, the complexity of the head fluctuation of the right-and-left direction cycle was calculated by utilizing Approximate Entropy (ApEn). After the value of ApEn was standardized at the walking speed, each walking speeds were compared. As a result, the value of ApEn increased at the slowly speed, and decreased with the increases in the walking speed. And the value of ApEn showed plateau or decrease at a little faster than free walking speed. From our results, it thought a possibility that Central Pattern Generator is optimized at the free walking speed. In conclusion, it is clear that walking speed have influenced on the complexity of the walking cycle.

Effect of Different frequencies of Skipping Rope on Elastic Components of Muscle and Tendon in Human Triceps Surae / 体力科学

The purpose of this study was to clarify the effects of different frequencies of skipping rope on the elastic components of muscle and tendon in human triceps surae. Six male subjects performed ten rounds of skipping rope. Skipping tempos were with in a range of 100-170 skips per minute (SPM) . The vertical ground reaction force and the surface EMG of triceps surae muscles were recorded during each skipping round. Elastic components of muscle and tendon were estimated by Residual Time (RT : lag time difference between the vanishing point of muscle discharge and disappearance of EMG, and the end of the ground reaction force wave) and RTintegrate (integration of ground reaction force while RT still appears) . RT and RTintegrate at 100 SPM were the smallest values for all jump frequencies. On the other hand, integrated EMG (iEMG) at 100 SPM was the largest value for all jump frequencies. Although RT and RT<SUB>integrate</SUB>progressively increased as SPM was increased, iEMG correspondingly decreased. Rate in utilization of elastic components of muscle and tendon assessed by RT<SUB>integrate</SUB>at 170 SPM corresponds to 150% at 100 SPM. These results suggest that the rate in utilization of the elastic components of muscle and tendon while skipping rope, depend on jump frequency.

Stress in the Lower Extremities Due to Walking Stairs One Step at a Time / 体力科学

The purpose of this study was to determine the differences between walking stairs one step at a time versus using alternating feet by evaluating muscle tensions and joint forces. This quantitative basic knowledge will be useful in setting safe guidelines for stair walking in rehabilitation programs. Five healthy young males participated as subjects. Ascending and descending motions were measured by utilizing a 3 D motion analysis system, a force platform and an EMG telemetry system. Measurements were made for three conditions : 1) Both limbs during alternating feet walking (normal stair walking : NW), 2) The leading limb (LL) and 3) The trailing limb (TL) when walking stairs one step at a time. Moments of force on the joints, muscle tensions and joint forces were calcu-lated using two mathematical models (the link segment and musculoskeletal models, Yamazaki (1992) ) . When ascending, maximum flexion angles of three joints in the TL were smaller than during NW. Also, quadriceps tension in the TL and soleus tension in the LL were smaller than during NW. Except for joint force, which was directed toward the anterior of the tibia, knee joint forces in the TL were smaller than during NW. When descending, maximum flexion angles of the three joints of the LL were smaller than during NW. The quadriceps tension and the soleus tension in the LL were smaller than during NW. Knee joint forces in the LL were smaller than during NW. The results suggested that : 1) When ascending, if a patient has a failure in the system of knee extension, the unaffected side should be made the LL and the affected side the TL. Also, if there is a failure in the system of plantar flexion, the unaffected side should be the TL and the affected side the LL. 2) When descending, if there is a failure in one limb, the unaffected side should be the TL and the affected side the LL.