The aim of this study was to investigate the relationship between changes in swimming velocity (SV), stroke rate (SR), stroke length (SL) and muscle activities during a 4×50m swimming test to simulate a 200m freestyle race. A total of 20 male collegiate swimmers participated in this study. The electromyography (EMG) signals of 11 muscles, 7 muscles in the upper half of the body and 4 muscles in the lower half, were recorded with surface electrodes. SV, SR and SL were analyzed for each 50m (S1, S2, S3 and S4) from side view recordings of swimmers taken with an underwater camera.SV and SR for S1 were significantly higher than for S2 and S3. SL for S1 was significantly longer than for S3. The averaged EMGs (aEMGs) for S1 were significantly higher than for S2 or for S3 in 5 muscles (flexor carpi ulnaris, biceps brachii, triceps brachii, deltoideus posterior and rectus femoris). There were no significant changes between S3 and S4 in SV, SR, SL and aEMG of all muscles except pectoralis major which showed the highest aEMG in S4. Significant correlations were observed between changes of (Δ) aEMG and ΔSV, especially in upper half muscles (r=0.485-0.939, p<0.05).These results suggested that decline in muscle activities of the five muscles mentioned earlier caused a decrease in SV from S1 to S3; and an increase in muscle activity of the pectoralis major led preventing a decline in SV by maintaining the SR in S4.

Pitching motion is made up by three-dimensional whole body movement. Pelvic and trunk rotation movement is important for the prevention of throwing injuries. Throwing is not a simple rotation movement. Evaluation should reflect muscle strength, coordination, and pitching motion characteristics. We have devised throwing rotational assessment (TRA) similar to throwing as the new evaluation of total rotation angle required for throwing. The purpose of this study was to introduce the new method and to examine the characteristics of players with throwing disorders. The subjects were 76 high school baseball pitchers who participated in the medical check. Pain-induced tests were elbow hyperextension test and intra-articular shoulder impingement test. Pitchers who felt pain in either test were classified as disorder group. TRA evaluation was performed as follows. In the positions similar to the foot contact phase, rotation angles of the pelvis and trunk were measured. In the position similar to follow through phase, the distance between the middle finger and the second toe was measured. All tests were performed in the throwing and opposite direction. Twenty five pitchers were classified as disorder group. All TRA tests in healthy group were significantly higher in the throwing direction than in the opposite direction, but there was no significant difference in the disorder group. Disorder group had significantly lower average rotation angles of the pelvis and trunk in the throwing direction and rotation angle of trunk in the opposite direction than the healthy group. Restrictions on TRA reflecting the complex whole body rotation movement may be related to the throwing disorder. This evaluation is a simple method. It would be useful early detection of throwing disorder and systematic evaluation in medical check, as well as self-check in the sports field.

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.

Abdominal draw-in is a functional transversus abdominal muscle exercise to acquire the contraction. However, it is difficult for even healthy subjects to selectively contract the deep transversus abdominal and internal oblique muscles without over-contraction of the superficial rectus abdominis and the external oblique muscles. This study examined whether the transversus abdominal muscle is selectively contracted by our taping method. The subjects were 20 healthy males. Using ultrasound, we compared the thickness of external oblique, internal oblique, and transversus abdominal muscle among no taping, kinesio taping and abdominal muscle activation taping in the standing position. The thickness of transversus abdominal muscle significantly increased in the activation taping more than the other methods. This study showed that abdominal musculature activation taping made it possible to contract the transversus abdominal muscle selectively.