Ultrastructural events following acute muscle trauma.

The purpose of this study was to determine the ultrastructural events occurring in skeletal muscle following acute blunt trauma. Male rats weighing 250 g were subjected to a single impact trauma to the medial gastrocnemius muscle while under general anesthesia. Hemorrhage, inflammation, non-necrotic degeneration, and later regeneration were observed. In the short term following impact (6-24 h), the damaged segments showed gross tearing and degeneration. A large number of mononuclear cells were seen in the intercellular connective tissue and within the damaged muscle cells. By 24-48 h, there was an increase in the number of sarcolemmal nuclei, some of which were likely of satellite cell origin. By day 3, regenerating muscle cells displayed central nuclei and reorganizing sarcomeres. By day 6, further progression of regeneration was seen. Moreover, focal interstitial collagen formation suggested minimal to mild scar formation. On days 14, 21, and 30 after trauma, the muscle appeared to have healed and no abnormalities could be found at the site of injury. In parallel with the ultrastructural events noted, the injured muscles underwent a marked catabolic response and showed a reproducible fall (-27%, P less than 0.001) in total protein content within 48 h. Muscle protein accumulation commenced after day 3; however, complete repletion of the loss did not occur until day 21 post-injury.

Comparison of voluntary and electrical stimulation contraction torques*.

Informed male volunteers completed maximal isometric knee extension efforts under each of three contraction conditions: 1) voluntary, 2) electrical stimulation (ES) only, and 3) superimposed (ES superimposed onto voluntary). Ten subjects completed the three contraction conditions using each of the following current formats: 1) asymmetrical biphasic rectangular wave, 2) asymmetrical biphasic spike wave, and 3) symmetrical monophasic square wave. Under the voluntary and the superimposed contraction conditions no significant differences in mean torque were observed between the three current formats. However, under the ES contraction condition, the torque associated with the symmetrical monophasic square wave was significantly less than that associated with the other two current formats. As well, the torque associated with the asymmetrical biphasic spike wave was significantly less than that associated with the asymmetrical biphasic rectangular wave format. No significant difference was observed between the maximum voluntary contraction (MVC) and the superimposed contraction conditions for the groups receiving the asymmetrical biphasic spike and the symmetrical monophasic square wave current formats, or between all three contraction conditions for the group receiving the asymmetrical biphasic rectangular wave format. However, the ES condition was associated with significantly less torque than were the MVC and the superimposed conditions for the asymmetrical biphasic spike and the symmetrical monophasic square wave formats. In response to a posttest questionnaire, 18 of 30 subjects felt that the ES contraction produced greater torque than did MVC, and 26 subjects selected the superimposed condition as having produced greater torque than the ES condition. The different current formats, resulting in different levels of sensation and preception, and the different output capabilities of each electrical stimulator are considered to have been jointly responsible for the ES only torque discrepancies. It is suggested that ES does not recruit more motor units, resulting in a greater force of contraction, than are recruited under MVC.J Orthop Sports Phys Ther 1984;5(6):324-331.

Electrical stimulation as a strength improvement technique: a review.

The dominant philosophy within rehabilitation has been that electrical stimulation is a valuable kinesthetic muscle reeducation technique, but voluntary exercise is of greater benefit in restoring voluntary muscular control and improving the strength of injured muscle. Much publicized Soviet research has suggested that this preference for voluntary exercise may be inappropriate and that electrical stimulation is the technique of choice for strengthening normally innervated muscle. This position has not been supported by the limited non-Soviet research. Whether this lack of support is attributable to an inability to duplicate the Soviet current format and/or application technique, or simply that electrical stimulation programs are not more effective than voluntary exercise programs, is presently unknown. To date, neither the voluntary exercise philosophy nor the nonvoluntary exercise (electrical stimulation) philosophy has overwhelming scientific support. Electrical stimulation programs must be compared with traditional voluntary exercise programs before practitioners are in a position to confidently accept or to refute either method. Until an adequate number of research studies have been conducted, practitioners cannot meet their obligation to know what the most effective strength improvement techniques are and to make such treatment available.J Orthop Sports Phys Ther 1982;4(2):91-98.