Characteristics of Relative Age Effects and Anthropometric Data in Japanese Recreational and Elite Male Junior Baseball Players.

Background: The mechanisms underlying the relative age effect (RAE), a biased distribution of birth dates, in sport events have been investigated for more than two decades. The present study investigated the characteristics of the RAE in baseball and anthropometric data (height and weight) among recreational junior baseball players as well as elite players, using data extracted from national surveys.

Methods: Birth and anthropometric data were obtained from 4464 Japanese students as elementary school, junior high school, and high school players.

Determinant of leg stiffness during hopping is frequency-dependent.

Identifying the major determinant of leg stiffness during hopping would be helpful in the development of more effective training methods. Despite the fact that overall leg stiffness depends on a combination of the joint stiffness, it is unclear how the major determinants of leg stiffness are influenced by hopping frequency. The purpose of this study was to identify the major determinant of leg stiffness over a wide range of hopping frequencies.

Leg stiffness adjustment for a range of hopping frequencies in humans.

The purpose of the present study was to determine how humans adjust leg stiffness over a range of hopping frequencies. Ten male subjects performed in place hopping on two legs, at three frequencies (1.5, 2.

Knee stiffness is a major determinant of leg stiffness during maximal hopping.

Understanding stiffness of the lower extremities during human movement may provide important information for developing more effective training methods during sports activities. It has been reported that leg stiffness during submaximal hopping depends primarily on ankle stiffness, but the way stiffness is regulated in maximal hopping is unknown. The goal of this study was to examine the hypothesis that knee stiffness is a major determinant of leg stiffness during the maximal hopping.

Differences in lower extremity stiffness between endurance-trained athletes and untrained subjects.

An understanding of lower extremity stiffness is important for evaluation of sports performance and injury prevention. The aim of this study was to investigate whether stiffness regulation during hopping differed between endurance-trained athletes and untrained subjects. Eight endurance-trained athletes and eight untrained subjects performed two-legged hopping at 2.

Determinants of difference in leg stiffness between endurance- and power-trained athletes.

Understanding the leg and joint stiffness during human movement would provide important information that could be utilized for evaluating sports performance and for injury prevention. In the present study, we examined the determinants of the difference in the leg stiffness between the endurance-trained and power-trained athletes. Seven distance runners and seven power-trained athletes performed in-place hopping, matching metronome beats at 3.

Effects of muscle cooling on the stiffness of the human gastrocnemius muscle in vivo.

Background/aims: The effects of muscle cooling on the stiffness of the human gastrocnemius muscle (GAS) were examined in vivo.

Methods: The knee joint was passively extended from 90 to 0 degrees (0 degrees = full knee extended position) with a constant ankle angle of 10 degrees dorsiflexed position (0 degrees = the sole of the foot is approximately perpendicular to the anterior margin of the shaft of the tibia) in a control condition (room temperature of 18-23 degrees C) and a cooling condition (muscle temperature decreased by 5.8 +/- 1.

Influence of muscle cooling on the passive mechanical properties of the human gastrocnemius muscle.

The purpose of the present study was to examine the influence of muscle cooling on the passive mechanical properties of the human gastrocnemius muscle (GAS) in vivo. In a thermoneutral (a room temperature of 18-23°C) and a local cooling (placing the right lower leg into cold water with a temperature of 5-8°C for 60 min) conditions, the change in passive plantarflexion force (F), which is produced only by the GAS length change, was taken in five subjects during passive knee extension from 90° to 0° with a constant ankle joint angle of 10° dorsiflexion. To evaluate an elastic component of the passive plantarflexion force of GAS, the subject held full knee extended position for 1 min (i.