Effect of forced use therapy on posture in children with hemiplegic cerebral palsy: a pilot study.

OBJECTIVE: To evaluate the impact of forced use therapy on posture in children with hemiplegic cerebral palsy. DESIGN: Single group pre- and post-training assessments. SUBJECTS: Eight children (mean age 10.5 years (standard deviation 1.26 years)) with hemiplegic cerebral palsy Levels I and II on the gross motor function classification scale. METHODS: All participants underwent 12 days (6 h/day) of forced use therapy. Postural asymmetry as well as the centre of pressure range and peak velocity during quiet standing were evaluated before and after the therapy. Upper limb functional level was also assessed using the Bruininks Oseretsky test of Motor Proficiency and the Assisting Hand Assessment. RESULTS: Before forced use therapy, postural asymmetry tended to decrease when the participants wore the upper limb constraint. After forced use therapy, upper limb functional scores improved significantly, and postural asymmetry tended to decrease, compared with the pre-therapy values. Postural improvement was correlated with postural asymmetry before forced use therapy. No significant differences were observed on the centre of pressure displacement parameters during the quiet standing tests in all conditions. CONCLUSION: This pilot study showed that forced use therapy may be an efficient way to improve postural asymmetry in children with hemiplegic cerebral palsy.

Effects of fatigue of elbow extensor muscles voluntarily induced and induced by electromyostimulation on multi-joint movement organization.

To investigate the capacity of the central nervous system to integrate and differentiate two different muscular fatigue states, the present study examines the changes on multi-joint movement organization following muscular fatigue of elbow extensor muscles (triceps brachii) induced by voluntary versus electrically induced contractions. Twenty right-handed male volunteers performed throws in the horizontal plane before and after two fatiguing procedures. First, success rate of throws was not affected by fatigue neither after voluntary contractions, nor after electrically induced contractions. Despite similar reductions of the maximal voluntary isometric force and the median frequency of the electromyographic signal following both fatiguing protocols, voluntary contractions induced greater changes in muscle activation, kinematics and kinetics during throws than electrically induced contractions. The changes observed following voluntary contractions are interpreted as a compensatory strategy involving a greater contribution of the wrist. In contrast, the greater activation of the triceps brachii could compensate the weakness of this muscle induced by fatigue without any modification of the initial multi-joint movement organization.

Effects of distal and proximal arm muscles fatigue on multi-joint movement organization.

To investigate the strategies developed by the central nervous system to compensate for fatigue in muscles, we studied the changes in the relative mechanical contribution of the joint torques in a multi-joint movement following an isometric exhaustion test. Eighteen male subjects performed throws, moving the arm in the horizontal plane, before and after two fatigue protocols. Muscular fatigue was induced either in the distal (extensor digitorum communis) or in the proximal (triceps brachii) agonist muscle of the arm. The kinematic, kinetic and electromyographic parameters of the movement were analysed. The subjects produced two different coordinations following the fatigue protocols. In the distal fatigue condition, the wrist angular velocity was maintained by decreasing elbow active torque. In the proximal fatigue condition, the compensatory strategy involved increasing the contribution of the wrist. In fact, the control of elbow and wrist was modified in order to compensate for the different mechanical effects.

Effect of low gravitational stimulation on the perception of target elevation: role of spatial expertise.

To examine the interindividual differences in the judgment of the visually perceived eye level (VPEL-upright position) and of the visually perceived apparent zenith (VPAZ-supine position) when the subject is subjected to low gravitational-inertial force (GIF), we independently altered GIF in two different populations: control subjects and spatial experts. Subjects were instructed to set a luminous target to the eye level while they were in total darkness and motionless or undergoing low radial acceleration with respect to the threshold of the otolithic system (0.015-1.67 m/sec2 for the VPEL and 0.55-2.19 m/sec2 for the VPAZ, respectively). Results showed that (1) low GIFs, close to those met during daily life, induced an eye level lowering in the upright and supine positions for the control group, and (2) the spatial expertise modified the influence of low GIF. Whereas an oculogravic illusion was found for the control group, this phenomenon was absent (VPAZ) or weaker (VPEL) for the spatial experts. Thus, the relations that the subjects maintain with their spatial environment and the knowledge acquired through experience modify the processing of sensory information and the perceptive construction resulting from it. The interindividual differences in sensitivity to the oculogravic illusion are discussed in terms of sensory dominance and of a better efficiency in the use of the available sensory information.