Paul Pei-Hsi Chou

Effect of forearm axially rotated posture on shoulder load and shoulder abduction / flexion angles in one-armed arrest of forward falls

BACKGROUND Falling onto the outstretched hand is the most common cause of upper extremity injury. This study develops an experimental model for evaluating the shoulder load during a simulated forward fall onto one hand with three different forearm axially rotated postures, and examines the shoulder abduction angle and shoulder flexion angle in each case. METHODS Fifteen healthy young male subjects with an average age of 23.7 years performed a series of one-armed arrests from a height of 5 cm onto a force plate. The kinematics and kinetics of the upper extremity were analyzed for three different forearm postures, namely 45° externally rotated, non-rotated, and 45° internally rotated. FINDINGS The shoulder joint load and shoulder abduction/flexion angles were significantly dependent on the rotational posture of the forearm. The shoulder medio-lateral shear forces in the externally rotated group were found to be 1.61 and 2.94 times higher than those in the non-rotated and internally rotated groups, respectively. The shoulder flexion angles in the externally rotated, non-rotated and internally rotated groups were 0.6°, 8.0° and 19.2°, respectively, while the corresponding shoulder abduction angles were 6.1°, 34.1° and 46.3°, respectively. INTERPRETATION In falls onto the outstretched hand, an externally rotated forearm posture should be avoided in order to reduce the medio-lateral shear force acting on the shoulder joint. In falls of this type, a 45° internally rotated forearm posture represents the most effective fall strategy in terms of minimizing the risk of upper extremity injuries.

Surgical treatment of complete acromioclavicular separations.

A retrospective study of fifty-two patients (48 cases followed up), with Allman-Tossy grade III acromioclavicular separations, who were treated with coracoclavicular reconstruction by Mersilene prosthetic substitute (Mersilene tape with polyester suture, 5 mm wide, 30 cm, Ethicon), was carried out. The average follow up was 38 months, with the longest being 10 years, and the shortest being 8 months. The average age of the patients was 32 years, with a range from 20 to 62 years. Two groups were divided by age. Although the younger age group showed better results than the elder one in pain, range of motion and return to previous occupation or sports, the overall outcome was satisfactory in 41 of 48 (86%) followed patients. For the grade III acromioclavicular separation patients, surgical reconstruction with Mersilene looping provides a reliable result including use of the arm for sports or repetitive work.

Change in Pitching Biomechanics in the Late-inning in Taiwanese High School Baseball Pitchers

Abstract Pei-Hsi Chou, P, Huang, Y-P, Gu, Y-H, Liu, C, Chen, S-K, Hsu, K-C, Wang, R-T, Huang, M-J, and Lin, H-T. Change in pitching biomechanics in the late-inning in Taiwanese high school baseball pitchers. J Strength Cond Res 29(6): 1500–1508, 2015—Repetitive overhead throwing may result in overuse injuries and a change in the pitching mechanics of a baseball pitcher. Accordingly, the purpose of this study is to quantify the changes in the muscle strength and pitching motion kinematics in the late-innings stage of a baseball game. Sixteen healthy baseball pitchers (16.77 ± 0.73 years) recruited from a high school, which won the National High School Baseball Championship in Taiwan in 2011; each performed 100 pitches in a bullpen throwing session. Isometric muscle strength measurements and joint kinematic data were obtained before and after the throwing session. The mean Borgs Rating of Perceived Exertion index was found to have a value of 14.14, indicating a medium-to-large degree of perceived tiredness. The results showed that the ball velocity and horizontal abduction angle decreased significantly as the pitchers became tired. Moreover, the upper torso forward tilt and knee flexion angle both increased significantly at the moment of ball release. Finally, the muscle strength of the upper extremity remained decreased 2 days after the bullpen throwing session. Overall, the results suggest that an adequate amount of rest and specific strengthening programs for the shoulder external rotator, shoulder internal rotator, shoulder flexor, shoulder extensor, shoulder adductor, and shoulder abductor muscles are recommended to the coaches and for adolescent baseball pitchers. In addition, the changes in pitching mechanics noted in this study should be carefully monitored during the course of a baseball game to minimize the risk for overuse injuries.

Effects of glenohumeral internal rotation deficit on baseball pitching among pitchers of different ages

BACKGROUND Previous studies have reported that glenohumeral internal rotation deficit (GIRD) may increase the risk of shoulder injury. However, the effects of GIRD on baseball pitching among pitchers of different age groups are still unclear. METHODS The study participants were 24 high school and 24 university pitchers. For each age group, the pitchers were evenly divided into a GIRD group and a normal group. The pitching motion of each participant was captured using a motion analysis system at a sampling frequency of 300 Hz. The kinematics and kinetics of the throwing shoulder and trunk were quantified, and statistical differences between the groups were examined by 2-sample t tests. RESULTS For both age groups, significant differences were observed in shoulder external rotations of the GIRD and normal groups. Compared with the university pitchers in the normal group, the university pitchers with GIRD exhibited a greater shoulder loading and did more internal rotation work in the acceleration phase. The high school pitchers with GIRD showed a larger trunk tilt and less trunk rotation than the university pitchers with GIRD. However, the university pitchers with GIRD exhibited a larger shoulder posterior force and horizontal adduction torque than the high school pitchers with GIRD. CONCLUSION Pitchers with GIRD do change their pitching motions, and the greater resulting shoulder joint loading predisposes them to a greater risk of shoulder injury, especially among university pitchers.

Elbow Joint Fatigue and Bench-Press Training

CONTEXT Bench-press exercises are among the most common form of training exercise for the upper extremity because they yield a notable improvement in both muscle strength and muscle endurance. The literature contains various investigations into the effects of different bench-press positions on the degree of muscle activation. However, the effects of fatigue on the muscular performance and kinetics of the elbow joint are not understood fully. OBJECTIVE To investigate the effects of fatigue on the kinetics and myodynamic performance of the elbow joint in bench-press training. DESIGN Controlled laboratory study. SETTING Motion research laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 18 physically healthy male students (age = 19.6 ± 0.8 years, height = 168.7 ± 5.5 cm, mass = 69.6 ± 8.6 kg) participated in the investigation. All participants were right-hand dominant, and none had a history of upper extremity injuries or disorders. INTERVENTION(S) Participants performed bench-press training until fatigued. MAIN OUTCOME MEASURE(S) Maximal possible number of repetitions, cycle time, myodynamic decline rate, elbow-joint force, and elbow-joint moment. RESULTS We observed a difference in cycle time in the initial (2.1 ± 0.42 seconds) and fatigue (2.58 ± 0.46 seconds) stages of the bench-press exercise (P = .04). As the participants fatigued, we observed an increase in the medial-lateral force (P = .03) and internal-external moment (P ≤ .04) acting on the elbow joint. Moreover, a reduction in the elbow muscle strength was observed in the elbow extension-flexion (P ≤ .003) and forearm supination-pronation (P ≤ .001) conditions. CONCLUSIONS The results suggest that performing bench-press exercises to the point of fatigue increases elbow-joint loading and may further increase the risk of injury. Therefore, when clinicians design bench-press exercise regimens for general athletic training, muscle strengthening, or physical rehabilitation, they should control carefully the maximal number of repetitions.