Shortening of muscle relaxation time after creatine loading.
The effect of creatine (Cr) supplementation on muscle isometric torque generation and relaxation was investigated in healthy male volunteers. Maximal torque (Tmax), contraction time (CT) from 0.25 to 0.75 of Tmax, and relaxation time (RT) from 0.75 to 0.25 of Tmax were measured during 12 maximal isometric 3-s elbow flexions interspersed by 10-s rest intervals. Between the pretest and the posttest, subjects ingested Cr monohydrate (4 x 5 g/day; n = 8) or placebo (n = 8) for 5 days. Pretest Tmax, CT, and RT were similar in Cr and placebo groups. Also in the posttest, Tmax and CT were similar between groups. However, posttest RT was decreased consistently by approximately 20% (P < 0.05) in the Cr group from the first to the last of the 12 contractions. In addition, the mean decrease in RT after Cr loading was positively correlated with pretest RT (r = 0.82). It is concluded that Cr loading facilitates the rate of muscle relaxation during brief isometric muscle contractions without affecting torque production. (+info)
Electromyographic study of the elbow flexors and extensors in a motion of forearm pronation/supination while maintaining elbow flexion in humans.
Activities of the elbow flexors (biceps brachii, BB; brachialis, B; brachioradialis, BR) and extensors (triceps brachii, TB) in a motion of forearm pronation/supination with maintenance of elbow flexion (PS-movement) in nine healthy human subjects were studied by electromyography (EMG). The subject performed the PS-movement slowly or quickly with or without a load extending the elbow. In the slow PS-movement, an increase and decrease of EMG activities during supination and pronation, respectively, were seen in BB and the reverse was in B. A clear increment of EMG activities in BB accompanied with a reduction of EMG activities in B and/or BR, and the reverse were often observed. The contraction level and gain with the forearm supine were higher and larger than those with the forearm prone, respectively, in BB and the reverse was in B and BR. In a series of the quick PS-movement, alternating increases of EMG activities between BB and the other flexors (B and BR) were seen. Since TB showed no EMG activities throughout the experiment, it is suggested that reciprocal contractions between BB and the other flexors, which produce a complementary force in flexion direction, enable motions of pronation/supination with maintenance of flexion. Contraction properties of the flexors were discussed. (+info)
Extensor carpi radialis brevis. An anatomical analysis of its origin.
We studied the origin of extensor carpi radialis brevis using 40 fresh frozen human cadaver specimens. Ten were stained with haematoxylin and eosin and trichrome which showed the collagenous structure of the extensor tendons at their origin. Gross anatomical observation showed that there was no definitive separation between brevis and communis at the osseotendinous junction. The histological findings confirmed the lack of separation between the two tendons. The extensor tendons were in close proximity to the joint capsule but trichrome staining showed no interdigitation of the tendon with the capsule. The validity of ascribing the pain of lateral epicondylitis to extensor carpi radialis brevis must be questioned. It appears to arise more from the 'common extensor' origin. (+info)
Common extensor tendon rupture following corticosteroid injection for lateral tendinosis of the elbow.
Corticosteroid injections are commonly administered to athletes to relieve symptoms of lateral elbow tendinosis. This report presents a case of almost total rupture of the common extensor origin in a 45 year old female squash player secondary to such a procedure. (+info)
Impaired response of human motoneurones to corticospinal stimulation after voluntary exercise.
1. Activation of descending corticospinal tracts with transmastoid electrical stimuli has been used to assess changes in the behaviour of motoneurones after voluntary contractions. Stimuli were delivered before and after maximal voluntary isometric contractions (MVCs) of the elbow flexor muscles. 2. Following a sustained MVC of the elbow flexors lasting 5-120 s there was an immediate reduction of the response to transmastoid stimulation to about half of the control value. The response recovered to control levels after about 2 min. This was evident even when the size of the responses was adjusted to accommodate changes in the maximal muscle action potential (assessed with supramaximal stimuli at the brachial plexus). 3. To determine whether the post-contraction depression required activity in descending motor paths, motoneurones were activated by supramaximal tetanic stimulation of the musculocutaneous nerve for 10 s. This did not depress the response to transmastoid stimulation. 4. Following a sustained MVC of 120 s duration, the response to transcranial magnetic stimulation of the motor cortex gradually declined to a minimal level by about 2 min and remained depressed for more than 10 min. 5. Additional studies were performed to check that the activation of descending tracts by transmastoid stimulation was likely to involve excitation of direct corticospinal paths. When magnetic cortical stimuli and transmastoid stimuli were timed appropriately, the response to magnetic cortical stimulation could be largely occluded. 6. This study describes a novel depression of effectiveness of corticospinal actions on human motoneurones. This depression may involve the corticomotoneuronal synapse. (+info)
Irreducible lateral dislocation of the elbow.
A rare case of an irreducible post-traumatic lateral dislocation of elbow is presented. The mechanism of injury was fall on a flexed elbow with trauma on its medial aspect resulting in pronation of the forearm. At open reduction, the brachialis muscle was in the form of a tight band which prevented reduction. The ulnar nerve was entrapped in the joint. (+info)
Hemorheologic variables in critical limb ischemia before and after infrainguinal reconstruction.
PURPOSE: Plasma and whole blood viscosity are elevated in patients with intermittent claudication. The objectives of this study were to investigate whether critical limb ischemia influences hemorheologic variables and whether the rheologic variables in blood from the affected limb differ from the general circulation. We also intended to study whether successful infrainguinal reconstruction improved hemorheologic variables. METHODS: Ten consecutive patients with critical limb ischemia (CLI) underwent arterial reconstruction, one patient with profundaplasty and nine patients with bypass procedures. Venous blood was sampled from the antecubital vein (arm) and the femoral vein (leg) of the affected limb 1 day before and 1 month after surgery. Ten control subjects (matched according to age, sex, diabetic status, and renal insufficiency) were also sampled. Whole blood viscosity, plasma viscosity, erythrocyte aggregation tendency, and erythrocyte fluidity (the latter variable describing the deformability of the erythrocytes) were measured by means of rotational viscometry. Erythrocyte volume fraction was also determined. Fibrinogen was measured in the patients with CLI. RESULTS: Erythrocyte fluidity, blood viscosity, and erythrocyte volume fraction were lower in patients with CLI than in control subjects (P <.01, P <.01, and P <.05, respectively). No major differences between cubital and femoral vein blood were seen before or after the operation in patients with CLI or in control subjects. Successful revascularization did not influence the hemorheologic variables, except for a decrease in blood viscosity in femoral vein blood (P <.05). CONCLUSION: Hemorheologic properties was impaired in patients with CLI. Because no differences were seen between the systemic and local circulation and because no major improvement occurred 1 month after arterial reconstruction, other mechanisms besides local tissue ischemia may play a role. (+info)
Plasticity in the distribution of the red nucleus output to forearm muscles after unilateral lesions of the pyramidal tract.
It has been hypothesized that the magnocellular red nucleus (RNm) contributes to compensation for motor impairments associated with lesions of the pyramidal tract. To test this hypothesis, we used stimulus triggered averaging (StTA) of electromyographic (EMG) activity to characterize changes in motor output from the red nucleus after lesions of the pyramidal tract. Three monkeys were trained to perform a reach and prehension task. EMG activity was recorded from 11 forearm muscles including one elbow, five wrist, and five digit muscles. Microstimulation (20 microA at 20 Hz) was delivered throughout the movement task to compute StTAs. Two monkeys served as controls. In a third monkey, 65% of the left pyramidal tract had been destroyed by an electrolytic lesion method five years before recording. The results demonstrate a clear pattern of postlesion reorganization in red nucleus-mediated output effects on forearm muscles. The normally prominent extensor preference in excitatory output from the RNm (92% in extensors) was greatly diminished in the lesioned monkey (59%). Similarly, suppression effects, which are normally much more prominent in flexor than in extensor muscles (90% in flexors), were also more evenly distributed after recovery from pyramidal tract lesions. Because of the limited excitatory output from the RNm to flexor muscles that normally exists, loss of corticospinal output would leave control of flexors particularly weak. The changes in RNm organization reported in this study would help restore function to flexor muscles. These results support the hypothesis that the RNm is capable of reorganization that contributes to the recovery of forelimb motor function after pyramidal tract lesions. (+info)