Kinematic and kinetic analysis of push-up exercise.
ABSTRACT The purpose of this study was to experimentally measure and analytically determine the load across the wrist, elbow, and shoulder joints during push-ups to better understand the nature of this exercise. A piezoelectric force platform was used to measure the vertical and two shear forces as well as the moment and the location of the center of pressure on the hand during a push-up. The electromagnetic tracking system was utilized to associate the force and moment measurement on the hand to the joints of the upper limbs. Factors which affect the intersegmental loads on the joints during push-ups include the location of the palm relative to the shoulder joint, the plane of arm movement, and the relative foot positions. In addition, the speed of push-ups also affects the amount of inertial load on top of the base static load.
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ABSTRACT: Conclusions about normal and pathologic shoulder motion are frequently made from studies using skin surface markers, yet accuracy of such sensors representing humeral motion is not well known. Nineteen subjects were investigated with flock of birds electromagnetic sensors attached to transcortical pins placed into the scapula and humerus, and a thermoplastic cuff secured on the arm. Subjects completed two repetitions of raising and lowering the arm in the sagittal, scapular and coronal planes, as well as shoulder internal and external rotation with the elbow at the side and abducted to 90°. Humeral motion was recorded simultaneously from surface and bone fixed sensors. The average magnitude of error was calculated for the surface and bone fixed measurements throughout the range of motion. ANOVA tested for differences across angles of elevation, raising and lowering, and differences in body mass index. For all five motions tested, the plane of elevation rotation average absolute error ranged from 0-2°, while the humeral elevation rotation average error ranged from 0-4°. The axial rotation average absolute error was much greater, ranging from 5° during elevation motions to approaching 30° at maximum excursion of internal/external rotation motions. Average absolute error was greater in subjects with body mass index greater than 25. Surface sensors are an accurate way of measuring humeral elevation rotations and plane of elevation rotations. Conversely, there is a large amount of average error for axial rotations when using a humeral cuff to measure glenohumeral internal/external rotation as the primary motion.Journal of Biomechanics 03/2012; 45(7):1161-8. DOI:10.1016/j.jbiomech.2012.02.003 · 2.50 Impact Factor
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ABSTRACT: Malrotation of the humeral component of the capitellocondylar total elbow replacement is thought but not proved to be one of the major causes of postoperative dislocation. The purpose of this study was to quantitate the effect of malrotation of the humeral component on the kinematics and laxity of the capitellocondylar total elbow prosthesis. Eleven fresh previously frozen elbows were used. With the humeral component in optimal position, external rotation, or internal rotation, movements of the elbow with neutral, valgus, and varus loading were monitored with an electromagnetic tracking device. When the humeral component was positioned in external rotation, the ulna was more valgus and supinated than when the component was in optimal position, and when the component was in internal rotation the ulna was more valgus in extension and more supinated in flexion. Malrotation in external rotation decreased valgus-varus laxity, and malrotation in internal rotation increased rotational laxity. Only one elbow became dislocated, despite constant severe maltracking between the components in all of the specimens. We concluded that although malrotation of the humeral component influences the laxity and causes maltracking, it is not the primary cause of postoperative dislocation. The contribution of other factors should be investigated.Journal of Orthopaedic Research 09/1994; 12(5):665-71. DOI:10.1002/jor.1100120509 · 2.97 Impact Factor