Changes in muscle force following therapeutic electrical stimulation in patients with complete paraplegia

Changes in muscle force following therapeutic electrical stimulation (TES) in 5 patients with complete paraplegia were evaluated by computed tomography, Cybex II, a strain-gauge transducer, and manual muscle testing. The stimulation parameters included a frequency of 20 Hz, a pulse width of 0.2 ms, and an output voltage of -15 V. The cross-sectional areas of muscles, the muscle torques, and the muscle forces increased after TES, though the increased ratio differed in each muscle. The reasons why it differed are as follows: (1) The possibility of peripheral nerve injury; (2) The different patterns of nerve distribution in the muscles; (3) Implantation techniques; and (4) The possibility of breakage, movement, or changes in the impedance of electrodes. This study demonstrates that TES increases muscle force during electrical stimulation in paralyzed muscle, but that an initial TES-induced muscle force greater than a poor-minus level on manual muscle testing is necessary for practical use. TES treatment should be started as soon as possible after the onset of paralysis, in order to maintain muscle quality.