Functional Electrical Stimulation, a Two-Year Study (1992)

Introduction Vrbova (1963); Brown, Cotter, Hudlicka & Vrbova (1976); Peckham, Mortimer & Marsolais (1976); Petrofsky & Phillips (1983); Petrofsky, Phillips & Hendershot (1985); Petrofsky & Smith (1988, 1991); and Van der Meulen (1974) all examined the use of electrical stimulation as a means of reversing the atrophy of skeletal muscle associated with paralysis. The ultimate goal of this research, including later work on computer-aided movement (Marsolais & Kobetic, 1982; Petrofsky, Glaser, Phillips & Gruner, 1982; Petrofsky, Phillips & Hendershot, 1985; Petrofsky & Smith, 1992) was to restore lost motor function (Guttman, 1976) and reverse some of the secondary medical problems associated with spinal cord injury such as pressure sores, kidney and bladder infections, and bone fractures (Young, 1982; Foege, 1985). In fact, these secondary medical problems are the most significant problems associated with spinal cord injury in terms of both cost and medical complications. It is not uncommon for a paralyzed individual to expend between thousands and tens of thousands of dollars in medical costs each year (Guttman, 1976; Burke, 1975; Young, Burns, Bowen & McClutcheon, 1982). Pressure sores, for example, have a yearly rate of incidence of over 30% (Young, Burns, Bowen & McClutcheon, 1982). Freehafer and Mast (1965) have shown that bone fractures have an incidence of 9.3%. It is hoped that functional electrical stimulation (FES) may offer a means of reversing some of these secondary medical problems through exercising paralyzed muscle and increasing the blood delivery to the legs. However, questions arise as to the safety of the technology. In weak, osteoporotic bone, can powered muscle stimulation cause bone fractures in itself? What is the incidence of electrode burns with continuous FES use? Further, the compliance of a patient population for this technology must be examined. This was the purpose of the present investigation. Subjects The subjects in these studies were 109 volunteers. Eighty-three of the subjects in these studies volunteered to participate in research. These individuals were asked to participate for a minimum of a two-year period. Twenty-six subjects were involved in a broad-based clinical program involving FES and conventional therapy. The average age of the research group was 26 +/- 3 years, whereas the average age of the clinical group was 29 +/- 9 years. Of the research group, 40 were persons with quadriplegia and 43 were persons with paraplegia. All were diagnosed as having complete injuries. All protocols were shown to each subject. All procedures were approved by the committee on human experimentation. Methods Four exercise modalities were used here as described below: Weightlifting Upper body conditioning of non-paralyzed muscles (weightlifting) was accomplished on specially designed equipment. Special handles and arm grips were used so that persons with quadriplegia could accomplish upper body weightlifting. FES Weightlifting Functional Electrical Stimulation (FES) weightlifting involved electrical stimulation of the paralyzed muscles in the body. Electrodes were applied above the muscle, and transcutaneous electrical stimulation was used to excite the motor nerves to elicit a muscle contraction. To exercise a given muscle, a weight was applied that would resist the movement of that muscle through loading of its joint. Electrical stimulation was then applied with biphasic, square-waves at a pulse width of 350 microseconds and a stimulation amplitude, which was variable, from 0 to 150 milliamps. The frequency of stimulation was 35 Hz. As current was increased through the stimulation electrodes, the muscle contracted. Current was adjusted so that the muscle lifted a weight over a period of three seconds, held the weight for one second, and then slowly reduced the amount of force in the muscle over another period of two seconds; six seconds were allowed between the contractions. …