DIFFERENCES IN ONSET TIMING OF MUSCLE ACTIVITIES DURING TWO TYPES OF JUMP LANDINGS

The purpose of this study was to determine the differences in onset timing of muscle activities between single leg landings and double leg landings. Healthy male college students participated in this study. All subjects performed two types of jump landings, single leg and double leg. The muscle activation during jump landings was measured using electromyography. Muscle activity onset occurred earlier during the single leg landing than during double leg landing, however, there were no significant differences between the onset of the quadriceps femoris muscles’ activities and that of the hamstring muscles’ activities. Results showed that the earlier muscle activation during motions such as the single leg landing may contribute to decreasing the impact to the joint

CONTRIBUTION OF MAXIMAL STRENGTH TO PEAK POWER AND RATE OF POWER DEVELOPMENT IN BENCH PRESS MOVEMENT USING FREE WEIGHTS

The purpose of the study was to demonstrate the relationships between peak power output, rate of power development (RPD) and maximal strength in the bench press movement with free weights. Eighteen healthy male subjects volunteered to participate in the study (mean age 21.1±1.4year, standing height 169.9±6.5cm, body mass (BM) 75.6±16.8kg). All subjects had moderate to extensive resistance training experience ranging from 1 to 5 years. The bench press movement was performed with a weight of 50% of one repetition maximum (1RM). Acceleration data were obtained with a uniaxial micromachined accelerometer attached to the centre of a barbell shaft. Based on the acceleration data, peak power output (W), time to peak power (TPP, s) and RPD (W/s) were computed. Significant correlations were found between peak power per body mass vs. 1RM/BM (r = 0.650, ) and RPD/BM vs. 1RM/BM (r = 0.557,. However, RPD/BM and TPP were not significantly different between the high-strength group and the low-strength group. The current findings indicate that increasing maximal strength may play a great role in the peak power improvement, but not on the RPD using free weights. Authors recommend mixed training strategy using a heavy weight and a light to medium weight to effectively improve the bench press performance

THE CORRELATIONS BETWEEN RECENT HISTORIES OF LOW BACK PAIN AND TRUNK STRENGTHS IN COLLEGIATE JUDOISTS

High occurrence of low back pain (LBP) in competitive judoists has been well documented. Since spine stability deficits could be associated with an incidence of low back injury, sufficient trunk strength is required for LBP prevention. Some studies have indicated that trunk strength weakness may be one of the risk factor for LBP in non-athlete population, yet there is little consensus on the correlation between LBP and trunk strength in competitive judoists. Therefore, the purpose of this study is to demonstrate the correlations between LBP experience and isometric strength of trunk flexion, extension and lateral flexion in collegiate judoists

MEASURING DYNAMIC KNEE MOTION DURING JUMP LANDING

The majority of anterior cruciate ligament (ACL) injuries in female athletes has been observed in noncontact situations such as jump landing. Theoretically, valgus and external rotation moments imposed to the knee joint will place ACL at high risk for injury (Olsen et al., 2004). Even though, it has been accepted that tibial and femoral rotation affects ACL tension, few studies have demonstrated tibial and femoral rotation angle in the relationship to neutral position. Therefore, the purpose of this study was to measure the tibial and femoral rotation angle during jump landing in female athletes

RELATIONSHIP BETWEEN ANTERIOR TIBIAL TRANSLATION AND ISOMETRIC STRENGTH IN FEMALE ATHLETES

The purpose of this study was to determine whether the isometric strength of the muscles around the knee and hip is associated with anterior tibial translation. Forty-four female high school basketball players participated in this study. Anterior tibial translation was measured with a Kneelax 3 arthrometer. The isometric strengths of knee flexion, knee extension, and hip abduction were determined with a hand-held dynamometer. In the case of both the legs, significant correlations were found between the anterior tibial translation, knee extension strength, and hamstring/quadriceps strength (H/Q) ratio. No significant correlations were found between the anterior tibial translation and the knee flexion and hip abduction strengths. Muscle imbalance between the quadriceps and hamstring muscles may lead to greater anterior tibial translation

RELATIONSHIPS BETWEEN THE MAXIMUM SHOULDER EXTERNAL ROTATION ANGLE DURING THROWING AND PHYSICAL VARIABLES

To our knowledge, excessive shoulder external rotation may increase elbow valgus stress during throwing (2005). Inhibition of the greater shoulder external rotation angle could prevent elbow injury during throwing. Thus the purpose of this study was to determine physical factors that would increase the maximum shoulder external rotation (MER) angle

Comparison of flexion and extension protocol for testing knee joint position sense

新しい固有感覚測定装置使用のための基礎データを得る目的で膝関節の運動方向の違いが位置覚測定の結果に与える影響を調べた.対象は,膝関節疾患および外傷の既往がない大学生8名とした.位置覚測定は設定角度を膝屈曲15°として,設定角度まで膝屈曲30°から伸展させるタスクと,膝完全伸展位から屈曲させるタスクを行った.2つのタスク間で再現角度,定数誤差値および絶対誤差値の平均値に差があるかを確かめたが,いずれも有意差を認めなかった.その結果,運動方向の違いは,位置覚測定では測定結果に影響を与えないことが示唆された.これは,位置覚測定において運動方向を任意に選択しても結果に影響しないことを示している.膝関節構成体は運動方向の違い,即ち屈曲と伸展で異なった刺激を受けていると考えられるが測定結果に有意差を認めなかったことからメカノレセプターの機能を再考する必要があると考えた.今後はACL 損傷者と健常者とを比較することにより,位置覚測定で運動方向の違いがACL 中のメカノレセプターに与える影響を明らかにすることができると考える.It is reported that the anterior cruciate ligament (ACL) has a sensitive function that regulates proprioception. The partial or total rupture of ACL could reduce proprioception. In this study, we investigated whether the direction of joint motion has an affect on proprioceptive sensibility. Eight subjects (5 men and 3 women) who did not have any history of previous injury or surgery to either knee joint participated. Two kinds of tasks for knee joint position sense were examined using a specially made article to record target joint angles and to calculate reproduced angles after limb movement. Task A involved extension from a 30°flexed position and task B involved flexion from a totally extended position. The repositioning angle departed from target angle (15°) within one degree in each task. Mean real error indicated a tendency to underestimate reproduced joint angles in all tasks, although the magnitude of the error was small. Absolute error was around two degrees. No significant difference was found in repositioning angle, real error or absolute error between task A and task B. These data show that direction of joint motion does not affect knee joint position sense. It is suggested that joint direction can be chosen at will in the measurement of knee joint position sense. Further investigations may include measurements of ACL injured patients to clarify the influence of ACL mechanoreceptors by comparison with the present study as a control group

Discrimination of athletic characteristics based on exercise physiology and serum biochemistry

The purpose of the present study is to determine whether athletic characteristics can be discriminated by changes in serum components during exercise which are considered to reflect systemic endurance capacity, muscle strength, and the energy metabolism system. Thirteen male long-distance athletes and 8 male short-distance and field athletes performed an incremental exercise test, muscle strength, and endurance test. They were also observed for changes in serum components during exercise. According to data analysis, the discriminant function thus obtained was: Z=0.8220×peakVO2+0.0037×AT+0.0010×MVC+(-0.0276)×60deg/sec+0.2629×MVC500me+(-0.8715)×UN+36.1659(peakVO2: measured value of peak VO2, AT: 0xbfffa670eakVO2, MVC: measured value of the isometric muscle strength, 60deg/sec: peak torque of the isokinetic muscle contraction at 60deg/sec, MVC50-1230722560me: the time for the previously determined isometric muscle strength value to become less than 50%, UN: the increase rate of UN from the value at rest to the maximum value). Subjects were classified into the actual group correctly, while the erroneous discriminant rate was 0.73%.0 In particular, weighting of the discriminant coefficient of peakVO2 and UN was large, indicating that these are useful as parameters for discriminating athletic characteristics

Acute Effects of Selective Strength Exercise on the Peroneus Longus and Brevis

The peroneus muscles are muscles that mainly act in ankle eversion and can be divided into PL and PB, which have different but important roles in foot and ankle functions. Therefore, PL and PB dysfunction can lead to foot and ankle issues, making. selective strength exercise necessary. This study aimed to identify the effect of two different exercise techniques on PL and PB morphologies. Two interventions were performed on separate days: the PL intervention, in which a Thera-Band® was placed on the ball of the foot and pushed out from the contact point, and the PB intervention, in which the Thera-Band® was pulled from the base of the fifth metatarsal. Cross-sectional area (CSA) and thickness of the peroneus muscles at 25% (showing the PL morphology) and 75% (showing the PB morphology) proximal to the line connecting the fibular head and lateral malleolus, as well as ankle strength was measured before and immediately after the interventions and at 10, 20, and 30 min later. A repeated-measures two-way analysis of variance was conducted to identify differences in the effects of the interventions on the PL and PB. Main and interaction effects on CSA, thickness, and ankle strength, with a significant increase in CSA and thickness in the proximal 25% in the PL intervention and the distal 75% in the PB intervention immediately after implementation, were observed (p < 0.05). The transient increase in muscle volume due to edema immediately after exercise indicates the acute effect of exercise. The CSA and thickness of the proximal 25% in the PL intervention and the distal 75% in the PB intervention increased immediately after the intervention, indicating that these interventions can be used to selectively exercise the PL and PB