Takeo Matsubayashi

Kinematics of transition during human accelerated sprinting

ABSTRACT This study investigated kinematics of human accelerated sprinting through 50 m and examined whether there is transition and changes in acceleration strategies during the entire acceleration phase. Twelve male sprinters performed a 60-m sprint, during which step-to-step kinematics were captured using 60 infrared cameras. To detect the transition during the acceleration phase, the mean height of the whole-body centre of gravity (CG) during the support phase was adopted as a measure. Detection methods found two transitions during the entire acceleration phase of maximal sprinting, and the acceleration phase could thus be divided into initial, middle, and final sections. Discriminable kinematic changes were found when the sprinters crossed the detected first transition—the foot contacting the ground in front of the CG, the knee-joint starting to flex during the support phase, terminating an increase in step frequency—and second transition—the termination of changes in body postures and the start of a slight decrease in the intensity of hip-joint movements, thus validating the employed methods. In each acceleration section, different contributions of lower-extremity segments to increase in the CG forward velocity—thigh and shank for the initial section, thigh, shank, and foot for the middle section, shank and foot for the final section—were verified, establishing different acceleration strategies during the entire acceleration phase. In conclusion, there are presumably two transitions during human maximal accelerated sprinting that divide the entire acceleration phase into three sections, and different acceleration strategies represented by the contributions of the segments for running speed are employed.

Bilateral Asymmetry in Joint Torque During Squat Exercise Performed by Long Jumpers

Kobayashi, Y, Kubo, J, Matsuo, A, Matsubayashi, T, Kobayashi, K, and Ishii, N Bilateral asymmetry in joint torque during squat exercise performed by long jumpers. J Strength Cond Res 24(10): 2826-2830, 2010-This study aimed to examine the bilateral differences in movement and joint torques during the squat exercise by using kinematic and kinetic analyses. Eighteen long jumpers participated in this study. They performed 3 repetitions of the squat exercise with loads of 50, 70, and 90% of their 3 repetition maximum (3RM). During the exercise, their movement was recorded using a Vicon motion capture system. Ground reaction forces (GRFs) were simultaneously measured by 2 force platforms, one under each foot. On the basis of these position and force data, joint angles and torques for the hip, knee, and ankle were calculated using inverse dynamics. Results showed that the peak vertical and horizontal GRFs did not differ between the takeoff and non-takeoff legs in any loading condition. However, the maximal flexion angle and peak torque at hip showed significant differences between the limbs under all loading conditions (p < 0.05). In addition, the peak ankle torque in the takeoff leg was larger than that in the non-takeoff leg under a load of 90% of 3RM. These results indicate that joint torques may be bilaterally asymmetric when long jumpers perform the squat exercise, which should be considered when attempting to decrease the risk of injury.

Comparison of the snatch technique for female weightlifters at the 2008 Asian championships.

Abstract Ikeda, Y, Jinji, T, Matsubayashi, T, Matsuo, A, Inagaki, E, Takemata, T, and Kikuta, M. Comparison of the snatch technique for female weightlifters at the 2008 Asian Championships. J Strength Cond Res 26(5): 1281–1295, 2012—The purpose of this study was to compare the snatch techniques of Japanese and international female weightlifters. Two high-speed cameras operating at 250 Hz were used to record the snatch lifts of the 5 best weightlifters in the snatch and 5 Japanese weightlifters during the 2008 Asian Weightlifting Championships held in Japan. The results revealed that the forward velocity of the barbell for the Japanese weightlifters during the second pull was significantly greater than that for the best weightlifters and that barbell trajectories of Japanese weightlifters except for the 53-kg class crossed the vertical reference line with great forward displacement of the barbell. In addition, the best weightlifters extended the knee and hip joints during the second pull earlier than the Japanese weightlifters did. These findings indicate that it is important to improve the way of pulling the barbell during the second pull for Japanese female weightlifters.

Ultrasonographic measurement of tendon displacement caused by active force generation in the psoas major muscle.

The purpose of this study was to examine the validity of using ultrasonography for detecting the force generated by the psoas major muscle, a muscle positioned in the deep trunk. We measured the displacement of central tendon on B-mode ultrasound images of two different longitudinal sections of the muscle during passive hip flexion-extension and isometric hip flexion at varied hip angles. In both tasks, the values of tendon displacement obtained independently from each section coincided well, indicating that tendon displacement took place along a straight trajectory, i.e., close to the nodal line between two scanned planes. It was strongly correlated with both the hip angle (R(2) = 0.98) and the hip-flexion torque (R(2) = 0.83). In the second set of experiment, we measured the tendon displacement during dynamic movements with the combination of ultrasonography and VICON-based motion analysis. From the tendon displacement during dynamic thigh lifting and walking, the force generated by the muscle could be estimated by extracting the force-related component. These results indicate that ultrasonography of the psoas major muscle can measure the displacement of its central tendon accompanied with either length change of the muscle or the elongation of tendon. Although much attention has to be paid to the limitations of this methodology, ultrasonography may be useful for detecting the force generation of the muscle during a variety of dynamic movements.

Effects of systemic hypoxia on human muscular adaptations to resistance exercise training: Reply from the authors

This study investigated the effect of resistance exercise training performed under systemic hypoxia or normoxia on biochemical and molecular muscular adaptations in healthy male subjects. Our findings demonstrate that resistance training under systemic hypoxia led not only to muscle hypertrophy, but most interestingly, to a greater increase in muscular endurance. This increase in muscular endurance was potentially caused by the increased angiogenesis as determined by capillary‐to‐fiber ratio.

Alteration of swing leg work and power during human accelerated sprinting

ABSTRACT This study investigated changes in lower-extremity joint work and power during the swing phase in a maximal accelerated sprinting. Twelve male sprinters performed 60 m maximal sprints while motion data was recorded. Lower-extremity joint work and power during the swing phase of each stride for both legs were calculated. Positive hip and negative knee work (≈4.3 and ≈−2.9 J kg−1) and mean power (≈13.4 and ≈−8.7 W kg−1) during the entire swing phase stabilized or decreased after the 26.2±1.1 (9.69±0.25 m s−1) or 34.3±1.5 m mark (9.97±0.26 m s−1) during the acceleration phase. In contrast, the hip negative work and mean power during the early swing phase (≈7-fold and ≈3.7-fold increase in total), as well as the knee negative work and power during the terminal swing phase (≈1.85-fold and ≈2-fold increase in total), increased until maximal speed. Moreover, only the magnitudes of increases in negative work and mean power at hip and knee joints during the swing phase were positively associated with the increment of running speed from the middle of acceleration phase. These findings indicate that the roles of energy generation and absorption at the hip and knee joints shift around the middle of the acceleration phase as energy generation and absorption at the hip during the late swing phase and at the knee during early swing phase are generally maintained or decreased, and negative work and power at hip during the early swing phase and at knee during the terminal swing phase may be responsible for increasing running speed when approaching maximal speed. Summary: The roles of respective swing leg joints intricately change with increases in running speed during accelerated sprinting.