Transient decrease in number of motor units after immobilisation in man.

AUTOR(ES)

Fuglsang-Frederiksen, A

RESUMO

On the day after the removal of a long leg cast, when the patient could just bend his knee, the electrical activity in the disused quadriceps muscle showed changes that indicated a reduction in the number of motor units. At 10 to 75% of maximum force the number of turns and the mean amplitude of the needle-recorded EMG were reduced in the disused muscle. Eight days later, when half the initial loss of force had been regained, the electrical activity was normal. The electrical activity produced during a constant force of 5 kg did not differ in the disused and in the contralateral muscle. From the findings in normal subjects it was deduced that the compensatory increase in turns in the EMG pattern to be expected from the decrease in cross-sectional area of the muscle fibres was within the error of the method. The transient decrease in the number of turns and in mean amplitude of the EMG of the disused muscle are an indication of the plasticity of the motor system.

Documentos Relacionados

• Recruitment of motor units in response to transcranial magnetic stimulation in man.
• Axonal refractory period of single short toe extensor motor units in man.
• Effects of prior activity on the conduction in single motor units in man.
• The effect of afferent stimuli on steadily discharging single motor units in man.
• Variation in the degree of synchronization exhibited by motor units lying in different finger muscles in man.