Effect Of Trunk Rotation Research Articles

Is early trunk rotation really hazardous for shoulder biomechanics in baseball throwing?

Early trunk rotation (ETR), which is a unique kinematics of the trunk that occurs during baseball throwing, is thought to be related to shoulder injuries. Pelvic rotation is a confounder when studying the effects of trunk rotation on shoulder biomechanics. The purpose of this study was to understand the "pure" effects of trunk rotation on shoulder biomechanics, with pelvic rotation under control. Our hypotheses were as follows: (1) throwers with ETR have a different shoulder kinematics pattern compared with throwers without ETR; (2) throwers with ETR have a lower ball speed performance than do throwers without ETR; and (3) throwers with ETR have a greater value of shoulder forces and moments, which may increase risks of shoulder injury, than do throwers without ETR. Fifty-seven elite throwers were enrolled and divided into 2 groups (non-ETR and ETR) using an outdoor motion analysis. Several kinematics and kinetics parameters of the shoulder were analyzed and compared between the 2 groups. Ball velocity was faster in the non-ETR group (127 km/h) compared with the ETR group (120 km/h). The shoulders of throwers in the ETR group showed pathokinematics of "horizontal adduction lag" and "dropped elbow." The increases in maximal posterior force, inferior force, horizontal abduction moment, and vertical adduction moment were 9.2%, 13.6%, 21.3%, and 24.3%, respectively, in the shoulders of throwers in the ETR group. These results indicate that ETR may be hazardous for the throwing shoulder. With lower ball velocity and higher shoulder joint loading, ETR is not a proper pitching pattern for kinetic energy transfer. Improper pitching mechanics among baseball throwers, such as ETR, may result in higher shoulder joint loading and increased risk of shoulder injuries. When treating throwers with shoulder injuries, it is important not only to address shoulder anatomy and pathology but also to understand the possible pathomechanics and pathogenesis of the shoulder caused by ETR. Furthermore, special training programs focusing on trunk flexibility and core muscle strengthening should be implemented to prevent ETR and decrease the risk of shoulder injuries. Motion analysis is useful for the screening and early detection of improper pitching mechanics in throwers.

Effects of trunk rotation on scapular kinematics and muscle activity during humeral elevation

Trunk rotation often accompanies humeral elevation, during daily activities as well as sports activities. Earlier studies have demonstrated that changes in spinal posture contribute to scapular motion during humeral elevation. However, the effect of trunk rotation on scapular kinematics during humeral elevation has received scant attention. This study aimed to clarify how trunk rotation affects scapular kinematics and muscle activities during humeral elevation. Electromagnetic motion capture and electromyography were used to assess scapular and clavicular motion and muscle activity in the right and left sides of 12 healthy young men. The subjects were seated and instructed to elevate both arms with the trunk in neutral, ipsilaterally rotated, or contralaterally rotated position. Ipsilaterally rotated trunk position decreased the internal rotation (by 5°, relative to neutral trunk position) and increased the upward rotation (by 4°, relative to neutral trunk position) of the scapula. Trunk position did not affect clavicular motion during humeral movement. Electromyography showed that contralaterally rotated trunk position increased the activity of the upper trapezius and serratus anterior muscles and decreased the activity of the lower trapezius. Therapists should consider the importance of trunk rotation, which may be the key to developing more efficient rehabilitation programs.

The effect of patient positioning during radiographs on the resulting Cobb angle measurements

BackgroundStanding spinal radiographs have been the primarymethod of spinal deformity evaluation in patients withscoliosis. During periods of patient surveillance, the clin-ician compares radiographs over a period of time toassess the progression of the deformity [1-3]. One of thepotential problems in comparing one radiograph toanother is difference in positioning [4-6]. The goal ofthis study is to quantify the effect of trunk rotation onCobb angle measurements, and provide an algorithm todescribe this relationship.Material and methodsCT scans of three patients with Adolescent Idiopathic Sco-liosis were used retrospectively. Three-dimensional recon-structions of the images were created by CT scan software.Cobb angles were drawn for scoliosis curves in the anteriorplane. The 3-D image was then rotated two degrees to theright, and Cobb angle measurements were repeated. Thisprocedure was repeated through 14 degrees of right rota-tion, and then subsequently through 14 degrees of leftrotation.ResultsThe effect of trunk rotation on Cobb angle measure-ments is directly related to the location of the scoliosiscurves, the magnitude of those curves, and the magnitudeof lumbar lordosis and thoracic kyphosis. In general how-ever, a two degree rotation of the patient’s trunk whilepositioning results in a one degree change in themeasured Cobb angle (in patients with larger scoliosiscurves, and in the first six degrees of trunk rotation).ConclusionsPatient positioning can have a significant effect on thecalculation of scoliosis measurements, and this needs tobe considered when evaluating the progression of spinaldeformity.

Effect of trunk rotation and arm position on gross upper extremity adduction strength and muscular activity

The aim of the experiment was to determine the impact of axial trunk rotation and arm position on upper extremity adduction force and muscle activity. Ten healthy male subjects performed graded maximum voluntary contractions under isometric conditions in seven upper extremity positions and three trunk postures (neutral and 90°left/right rotated) in a simulated manual materials handling task. A custom built lightweight force-measuring device was held between the palmar surfaces of the hands and subjects compressed the lateral surfaces of the device. Muscle activity was recorded bilaterally over the muscle bellies of the anterior deltoid, the long head of the biceps brachii and over the flexor carpi radialis. The activity of the right pectoralis major was also recorded unilaterally. Descriptive, multivariate analysis of variance (MANOVA) and post-hoc Scheffé comparisons were performed on the mean and peak force as well as the EMG [electromyographic] data. Further analysis was performed on the force-EMG relationship at 20% intervals of maximum voluntary contraction (force). Both upper extremity adduction force and EMG were significantly affected by position (p<0.01) but not by trunk rotation. The muscle activity increased and force decreased with flexion of the upper extremity. Pearson correlation coefficients between force and EMG were low. The biceps and flexors were the most active muscles depending upon upper extremity position, and the right pectoralis major muscle activity expressed the highest correlation with force. The present findings confirm earlier hypotheses that upper extremity adduction strength is not significantly affected by trunk rotation.

Effects of tonic neck reflex on optokinetic nystagmus in rabbits.

In this study, rabbits with black-pigmented eyes were suspended in air with none of their limbs touching the ground, and surrounded by a full-field optokinetic drum. The drum was rotated counterclockwise at 60 degrees/s. Horizontal eye movement was recorded by electronystagmograph with the animals in three postures: 1) initial posture, head and trunk aligned along the same body axis, 2) trunk rotated clockwise by 60 degrees with head stationary, and 3) trunk rotated counterclockwise by 60 degrees with head stationary. The recordings were repeated after cervical nerve roots were sectioned unilaterally. The speed of the slow phase of nystagmus was significantly faster in the second than in the initial posture, but significantly slower in the third than in the initial posture. These effects of trunk rotation on the speed of the slow phase were not seen when the side of cervical nerve section was extended. The results indicate that smooth following eye movement is influenced by the neck reflex. It is accelerated when the head turns in the same direction as the visual field, whereas it is inhibited when the head turns in the opposite direction. Proprioceptors of the extended neck appear to account for the effects observed.