Purpose: Although closed (CKCE) and open (OKCE) kinetic chain exercises are used in athletic training and clinical environments, few studies have compared knee joint biomechanics while these exercises are performed dynamically. The purpose of this study was to quantify knee forces and muscle activity in CKCE(squat and leg press) and OKCE (knee extension). Methods: Ten male subjects performed three repetitions of each exercise at their 12-repetition maximum. Kinematic, kinetic, and electromyographic data were calculated using video cameras (60 Hz), force transducers (960 Hz), and EMG(960 Hz). Mathematical muscle modeling and optimization techniques were employed to estimate internal muscle forces. Results: Overall, the squat generated approximately twice as much hamstring activity as the leg press and knee extensions. Quadriceps muscle activity was greatest in CKCE when the knee was near full flexion and in OKCE when the knee was near full extension. OKCE produced more rectus femoris activity while CKCE produced more vasti muscle activity. Tibiofemoral compressive force was greatest in CKCE near full flexion and in OKCE near full extension. Peak tension in the posterior cruciate ligament was approximately twice as great in CKCE, and increased with knee flexion. Tension in the anterior cruciate ligament was present only in OKCE, and occurred near full extension. Patellofemoral compressive force was greatest in CKCE near full flexion and in the mid-range of the knee extending phase in OKCE. Conclusion: An understanding of these results can help in choosing appropriate exercises for rehabilitation and training.

Study Design Prospective single-group repeated-measures design. Objectives To quantify electromyographic (EMG) muscle activity of the infraspinatus, teres minor, supraspinatus, posterior deltoid, and middle deltoid during exercises commonly used to strengthen the shoulder external rotators. Background Exercises to strengthen the external rotators are commonly prescribed in rehabilitation, but the amount of EMG activity of the infraspinatus, teres minor, supraspinatus, and deltoid during these exercises has not been thoroughly studied to determine which exercises would be most effective to achieve strength gains. Methods and Measures EMG measured using intramuscular electrodes were analyzed in 10 healthy subjects during 7 shoulder exercises: prone horizontal abduction at 100° of abduction and full external rotation (ER), prone ER at 90° of abduction, standing ER at 90° of abduction, standing ER in the scapular plane (45° abduction, 30° horizontal adduction), standing ER at 0° of abduction, standing ER at 0...

As golf grows in popularity, golf related injuries have increased. The purpose of this study was to calculate and compare upper body kinematics of healthy male golfers from different skill levels. Kinematic data were obtained from 18 professional, 18 low handicap, 18 mid handicap and 18 high handicap golfers with an optoelectronic system at 240 frames per second. Ten displacement parameters were calculated at address, peak of back swing and ball contact. Angular velocity parameters and respective temporal data were calculated during the downswing phase. Most parameters were significantly different between the higher skilled golfers (professional, low handicap) and the least skilled golfers (high handicap). At the peak of the swing, professionals produced the largest magnitudes for left shoulder horizontal adduction (125 ± 6°), right shoulder external rotation (66 ± 11°), and trunk rotation (60 ± 7°). During the downswing, the professionals produced the largest angular velocities for the club shaft (2413 ± 442°/s), right elbow extension (854 ± 150°/s), right wrist (1183 ± 299°/s) and left wrist (1085 ± 338°/s). The results of this study show that improper mechanics of golf swing existed in middle and high handicap groups. These improper mechanics may contribute to golf related injuries.