Scandinavian journal of medicine & science in sports
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Scand J Med Sci Sports · Apr 2000
Comparative StudyAntagonist muscle coactivation during isokinetic knee extension.
The aim of the present study was to quantify the amount of antagonist coactivation and the resultant moment of force generated by the hamstring muscles during maximal quadriceps contraction in slow isokinetic knee extension. The net joint moment at the knee joint and electromyographic (EMG) signals of the vastus medialis, vastus lateralis, rectus femoris muscles (quadriceps) and the biceps femoris caput longum and semitendinosus muscles (hamstrings) were obtained in 16 male subjects during maximal isokinetic knee joint extension (KinCom, ROM 90-10 degrees, 30 degrees x s(-1)). Two types of extension were performed: [1] maximal concentric quadriceps contractions and [2] maximal eccentric hamstring contractions Hamstring antagonist EMG in [1] were converted into antagonist moment based on the EMG-moment relationships determined in [2] and vice versa. ⋯ In consequence substantial antagonist flexor moments are generated. The antagonist hamstring moments potentially counteract the anterior tibial shear and excessive internal tibial rotation induced by the contractile forces of the quadriceps near full knee extension. In doing so the hamstring coactivation is suggested to assist the mechanical and neurosensory functions of the anterior cruciate ligament (ACL).
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Scand J Med Sci Sports · Oct 1998
Isokinetic knee extensor strength and functional performance in healthy female soccer players.
The aims of this study were to determine the relationship between isokinetic knee extensor muscle strength at 60 degrees/s and 180 degrees/s and five functional performance tests (one-leg-hop, triple-jump, vertical-jump, one-leg-rising and square-hop), to determine the relationship between the five different functional performance tests and to present normative data and limb symmetry index concerning healthy female soccer players. In total 101 female soccer players (X = 20.3 years) were tested. A limb symmetry index, using weak/strong leg, varied from 83.9 to 96.3 in the tests. ⋯ No differences were found between the right and the left leg or the dominant and the non-dominant leg. Using linear regression models corrected for body weight, height and age, there were low correlations between the isokinetic strength measurements and the functional tests. It is not recommended using functional performance testing and isokinetic testing interchangeably.
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Scand J Med Sci Sports · Oct 1998
Comparative StudyBody composition and cross-sectional areas of limb lean tissues in Olympic weight lifters.
The cross-sectional area (CSAs) of bone and muscle tissues in the forearm, upper arm, lower leg, and thigh and body composition were determined by B-mode ultrasound and underwater weighing methods, respectively for 56 college Olympic weight lifters and 28 age-matched non-athletes to investigate the magnitude of musculoskeletal development in the strength-trained athletes belonging to the weight-classified sports event. The average value of fat-free mass (FFM) for the weight lifters ranked 12.6 kg above the regression line of FFM on stature for untrained subjects. In the weight lifters, however, the percentage of fat mass to body mass was also highly correlated to body mass index. ⋯ The differences in lean (bone + muscle) CSA were still significant in all sites except for the lower leg even when the difference in body size was statistically controlled. The comparisons between the weight lifters and untrained subjects on the lean CSA ratios of site to site and muscle CSA ratios of flexors to extensors indicated that the weight lifters had achieved a high relative distribution of lean tissues in the arms and a dominant development in elbow and knee extensors. Thus, the present results suggested that participation in weight lifting exercises for a long period could increase bone CSA as well as muscle CSA, and induce in the participants a noticeable enlargement in given sites and muscle groups responsible for performing the Olympic lifts.
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Scand J Med Sci Sports · Jun 1998
Hyperextension trauma to the elbow joint induced through the distal ulna or the distal radius: pathoanatomy and kinematics. An experimental study of the ligament injuries.
Loads applied to the forearm result in hyperextension of the elbow. The pathomechanics of hyperextension trauma with load applied to the distal radius and ulna were studied in 10 macroscopically normal cadaver elbow joint specimens to reveal patterns of injury with radial traction (n = 5) compared to ulnar traction (n = 5). The mean age of the donors was 60.8 years (range 33-74). ⋯ In both groups, the changes were significant in joint flexion during forced valgus and external rotation, but were not significant in flexion during forced varus and internal rotation. In both groups, the same four lesions were produced: 1) Anterior capsule rupture, 2) L-formed rupture of the origin of the pronator muscle with elongation of the anterior bundle of the medial collateral ligament, 3) partial rupture of the lateral collateral ligament and 4) small cartilage damage to the posterior or anteromedial edge of the ulna. In conclusion, hyperextension trauma to the elbow joint induced through the distal ulna or the distal radius produced the same pattern of injury as reported in hyperextension of the elbow with traction to the forearm when free rotation of the radius relative to the ulna was allowed.