This study investigated how the human CNS organizes complex three-dimensional (3D) ball-throwing movements that require both speed and accuracy. Skilled baseball players threw a baseball to a target at three different speeds. Kinematic analysis revealed that the fingertip speed at ball release was mainly produced by trunk leftward rotation, shoulder internal rotation, elbow extension, and wrist flexion in all speed conditions. The study participants adjusted the angular velocities of these four motions to throw the balls at three different speeds. We also analyzed the dynamics of the 3D multijoint movements using a recently developed method called "nonorthogonal torque decomposition" that can clarify how angular acceleration about a joint coordinate axis (e.g., shoulder internal rotation) is generated by the muscle, gravity, and interaction torques. We found that the study participants utilized the interaction torque to generate larger angular velocities of the shoulder internal rotation, elbow extension, and wrist flexion. To increase the interaction torque acting at these joints, the ball throwers increased muscle torque at the shoulder and trunk but not at the elbow and wrist. These results indicates that skilled ball throwers adopted a hierarchical control in which the proximal muscle torques created a dynamic foundation for the entire limb motion and beneficial interaction torques for distal joint rotations.

Healing of osteochondritis dissecans lesions of the elbow can be achieved after fragment fixation with pull-out wiring and a bone grafting technique.

In order to determine whether there is a different susceptibility of muscle fiber types in the m. vastus lateralis (VL) in knee-joint disorders, histochemical studies were performed on 112 cases. Anterior cruciate ligament (ACL) injuries affected 51 patients; ACL injuries associated with meniscus (ACL + M) injuries affected 29. Twenty-five patients had sustained meniscus injuries and seven had injuries of the collateral ligaments (CL). Fifty-two were athletic and 60 were not. On each biopsy, fiber-type distribution was obtained and the degree of atrophy of each fiber type was estimated from two parameters, the mean diameter and the percentage of atrophied fibers. The distribution of type-1 fibers averaged 38.0% +/- 12.0%. There were no significant differences among disorders in the distribution of type-1 fibers. Both parameters of fiber atrophy revealed a difference in susceptibility between type-1 and type-2 fibers. Atrophy of type-1 fibers was found only in ACL and ACL + M injuries. Type-2 fibers were atrophied in all four disorders. Atrophy of type-2 fibers could be a nonspecific change due to the inactivity of the VL, but type-1 fiber atrophy may relate specifically to the condition of ACL insufficiency.

This study analyzes patient participation in athletic activities after meniscectomy. Seventy simple meniscus lesions in 68 patients without ligamentous insufficiency were studied by means of a detailed questionnaire and clinical and radiological examinations. Follow-up ranged from 1 to 18.4 years, averaging 4.5 years. These cases are classified into two groups, depending on the intensity of athletic activities. Group 1 consisted of international class athletes and Group 2 consisted of both competitive and recreational athletes. None of those studied have given up sports following meniscectomy. Results were worse in Group 1 than in Group 2 in both clinical and subjective evaluation. In Group 1 volleyball players presented results worse than those of football (American style) players and wrestlers. In Group 2 there was no significant difference in results among athletes of various sports. We conclude that the results after meniscectomy are influenced by the quality and frequency of postoperative athletic activities.

The purpose of this study was to test quantitatively the hypothesis that, as runners run along a more sharply curved track, greater torsional moments act on their tibiae. Six male participants were asked to run along a straight track and along counterclockwise curved tracks with turn radii of 15 m (gentle) and 5 m (sharp) at 3.5 m s–1. Data were collected using two high-speed cameras and force platforms. Each participant’s left (corresponding to the inside of the curves) foot and tibia were modeled as a system of coupled rigid bodies. For analysis, net axial moments acting on both ends of the tibia were calculated using free-body analysis. The torsional moment acting on the tibia was determined from the quasi-equilibrium balance of the tibial axial moments based on the assumption that the rate of change of the angular momentum about the tibial axis was negligible. The results showed that the torsional moments, which were in the direction of external rotational loading of the proximal tibiae, increased as the track curvature became sharper. Furthermore, the mean value of the maximum torsional moments, while running on a sharply curved track (28.5 Nm), was significantly higher than the values obtained while running on a straight track (11.0 Nm, p < .01) and on a gently curved track (12.2 Nm, p < .01). In conclusion, the present study has quantitatively confirmed that as runners run along a more sharply curved track, greater torsional moments act on their tibiae. The findings imply that athletes prone to tibial running injuries such as stress fractures should avoid repetitive running on sharply curved paths.

No abstract

[Purpose] The purpose of this study was to evaluate the relationship between malalignment and lower-extremity injury and to determine the optimal dynamic alignment of the lower extremity with wall squats. [Subjects and Methods] Healthy individuals from one therapy school were enrolled and assigned to a wall squat normal or abnormal group based on their forms during wall squats. The abnormal group was found to be more prone to lower-extremity injury on three-dimensional motion analysis. Eight students from each group were randomly chosen for the study. The effects of single-leg landing movements were assessed using three-dimensional motion analysis. [Results] In the sagittal plane, significant flexion of the hip and knee joints occurred 0.02 and 0.04 seconds after initial foot contact with the ground in the normal and abnormal groups, respectively. In the frontal plane, significant adduction of the hip joint occurred at 0.07 seconds in the abnormal group. [Conclusion] The abnormal group tended to display later flexion of the hip and knee joints and narrower hip, knee, and ankle range of motion than the normal group, suggesting that dynamic alignment of the lower extremity in the abnormal group likely made them susceptible to injury.

No abstract