Neuromuscular activities during increasing and decreasing force of isometric contractions

The object was to investigate muscle activities during increasing and decreasing force of isometric contraction. Ten male subjects performed elbow flexion and extension with isometric force increasing linearly from zero to 70% maximal voluntary contraction (MVC) and immediately decreasing from 70%MVC to zero. Surface electromyographic (EMG) activities from the biceps brachii (BB) and triceps brachii (TB) were recorded. Force tremor root mean square (rms), EMG rms, EMG mean power frequency (MPF), and the peak value of cross correlation coefficients between agonist and antagonist EMGs were calculated for each 1000 ms period. Force tremor rms in the decreasing phase were higher than that in the increasing phase,while no significant increase in agonist EMG rms was found between both phases. Antagonist EMG rms in the decreasing phase was higher than that in the increasing phase. The cross correlation levels between agonist and antagonist EMGs in the decreasing phase were higher than those in the increasing phase. These results suggest that the increase in force tremor rms in the decreasing phase is cause by the synchronization of firing of motoneurons, not by the recruitment of the motor unit, and that agonist-antagonist muscle pairs are controlled as a single unit by a common central drive especially in the decreasing phase

Central and peripheral visual reaction time of soccer players and nonathletes

Visual reaction time of 20 soccer players and 13 nonathlete university students was measured using three different sizes of stimulus in central and peripheral vision.The results were summarized as follows: 1) Central visual reaction time of soccer players increased significantly with a decrease in size of a stimulus, while peripheral visual reaction time of nonathletes increased significantly with a decrease in size of the stimulus.2) In soccer players the correlation between peripheral visual reaction time and central visual reaction time was higher when the size of the stimulus was small. In nonathletes，however，correlation of the same parameters was higher when the size of the stimulus was large. These results suggest that soccer players have a higher ability of peripheral visual perception to the smaller object than nonathletes，that might enable to make quick judgement and decision to the far distant ball in the soccer field

CORRELATION BETWEEN THROWING MOTION AND MAXIMUM ELBOW VARUS TORQUE IN FEMALE PROFESSIONAL BASEBALL PITCHERS

The purpose of this study was to identify the correlation between throwing motion and maximum elbow varus torque (MEV) in female professional baseball pitchers. Twelve pitchers without pre-existing pain were recruited. Ball velocity and pitching motion were measured. Ball velocity and, kinematic and kinetic data from each joint during the pitch were extracted to evaluate the correlation with MEV. There was no correlation between the fastest ball velocity and MEV. Sixteen kinematic and kinetic parameters were found to have significant correlations with MEV. Particularly, as trunk rotation angle to the non-throwing direction before lead foot contact (FC) increased, the MEV decreased. Rotating the trunk in the non-throwing direction before FC and immediately in the throwing direction after FC could be a key component of the throwing motion

Dynamic three-dimensional shoulder kinematics in patients with massive rotator cuff tears: a comparison of patients with and without subscapularis tears

Background Massive rotator cuff tears (MRCTs) with subscapularis (SSC) tears cause severe shoulder dysfunction. In the present study, the influence of SSC tears on three-dimensional (3D) shoulder kinematics during scapular plane abduction in patients with MRCTs was examined. Methods This study included 15 patients who were divided into two groups: supraspinatus (SSP) and infraspinatus (ISP) tears with SSC tear (torn SSC group: 10 shoulders) or without SSC tear (intact SSC group: 5 shoulders). Single-plane fluoroscopic images during scapular plane elevation and computed tomography (CT)-derived 3D bone models were matched to the fluoroscopic images using two-dimensional (2D)/3D registration techniques. Changes in 3D kinematic results were compared. Results The humeral head center at the beginning of arm elevation was significantly higher in the torn SSC group than in the intact SSC group (1.8±3.4 mm vs. −1.1±1.6 mm, p<0.05). In the torn SSC group, the center of the humeral head migrated superiorly, then significantly downward at 60° arm elevation (p<0.05). In the intact SSC group, significant difference was not observed in the superior-inferior translation of the humeral head between the elevation angles. Conclusions In cases of MRCTs with a torn SSC, the center of the humeral head showed a superior translation at the initial phase of scapular plane abduction followed by inferior translation. These findings indicate the SSC muscle plays an important role in determining the dynamic stability of the glenohumeral joint in a superior-inferior direction in patients with MRCTs

Practical research on sports mental training focused on coach in field

The purpose of this study was to examine the effects of sports mental training (SMT) focused on technical coaches. In case 1, a SMT was performed on a high school baseball team by a technical coach of baseball team. A content of the training was a basic psychological skill like the goal setting. Levels of psychological competitive ability were assessed by the Diagnostic Inventory of Psychological-Competitive Ability for Athletes (DIPCA) before and after the training. As a result, the training improved the confidence and strategy ability of the baseball players. These findings suggested that combination of the SMT and the practice for technical skills was effective for the confidence and strategy ability. In case 2, we assessed effects of a SMT for a high school volleyball team and its technical coach. As a direct approach method, the SMT was performed on all the players by a SMT coach once a month. Moreover, as an indirect approach method, the SMT was performed on the technical coach by the SMT coach everyday. As a result, the team was 3rd place in Kinki competition tournament. A style of coaching in the technical coach was changed. Although a next goal had been lost when losing a match before the training, the technical coach set the goal of the team again, aiming at the Kinki competition tournament. The team switched the feelings from the lost game. Moreover, a remarkable improvement of psychological skill was seen in confidence and strategy ability for technical coach. Therefore, these results suggested the effects of SMT by technical coach and the effects of SMT for technical coach

Direction and distance dependency of reaching movements of lower limb.

Efficient body movement is required in our daily lives, as it facilitates responding to the external environment and producing movements in various directions and distances. While numerous studies have reported on goal-directed movements in the frontal direction during gait initiation, there is limited research on the efficient movement of the lower limbs in multiple directions and distances. Therefore, we aimed to examine changes in the kinematics of lower-limb reaching movements to determine skilled motor ability in terms of direction and distance. Sixteen adults (10 male participants) were requested to reach targets projected on the floor in seven directions and at three distances for a total of 21 points. The reaching time slowed down for the contralateral side (right foot to left-sided target) and was caused by a slower start of the toe movement. To identify the cause of this delay, we analyzed the onset of movement at each joint and found that movement to the contralateral side starts from the hip, followed by the knee, and subsequently the toe. The time-to-peak velocity was also calculated, and the motion required to reach the target in the shortest time varied depending on direction and distance. These results suggested that movement kinematics vary with direction and distance, resulting in a slower reaching time on the contralateral side. The results of our study hold promise for potential applications in sports and rehabilitation