STRENGTH, ENDURANCE, AND WORK CAPACITY AFTER MUSCLE STRENGTHENING EXERCISE IN POSTPOLIO SUBJECTS

Objective: To determine whether a 12-week home quadriceps muscle stren gthening exercise program would increase muscle strength, isometric en durance, and tension time index (TTI) in postpolio syndrome subjects w ithout adversely affecting the surviving motor units or the muscle. De sign: A longitudinal study to investigate the effect of a 12-week exer cise program on neuromuscular function and electromyographic variables . Setting: Neuromuscular laboratory of a university hospital. Subjects : Seven subjects were recruited from a cohort of 12 subjects who had p articipated in a previous exercise study. All subjects had greater tha n antigravity strength of the quadriceps. Upon completion of a postpol io questionnaire, all acknowledged common postpolio syndrome symptoms such as new fatigue, pain, and weakness; 6 of the 7 acknowledged new s trength decline. Intervention: On Mondays and Thursdays subjects perfo rmed three sets of four maximal isometric contractions of the quadrice ps held for 5 seconds each. On Tuesdays and Fridays subjects performed three sets of 12 dynamic knee extension exercises with ankle weights. Main Outcome Measures: Neuromuscular variables of the quadriceps musc les were measured at the beginning and completion of the exercise prog ram and included: isokinetic peak torque (ISOKPT, at 60 degrees/sec an gular velocity) and total work performed of four contractions (ISOKTW) , Isometric peak torque (MVC), endurance (EDUR, time subject could hol d isometric contraction at 40% of the initial MVC), isometric tension time index (TTI, product of endurance time and torque at 40% of MVC), and initial and final ankle weight (WGT, kg) lifted. Electromyographic variables included: fiber density (FD), jitter (MCD), and blocking (B LK) from single fiber assessment and median macro amplitude (MACRO). S erum creatine kinase (CK) was also measured initially and at 4-week in tervals throughout the study. Results: The following variables signifi cantly (p < .05) increased: WGT by 47%, ISOKPT, 15%, ISOKTW, 15%; MVC, 36%; EDUR, 21%; TTI, 18%. The following variables did not significant ly (p > .05) change: FD, MCD, BLK, MACRO, and CK. Conclusions: This ho me exercise program significantly increased strength, endurance, and T TI without apparently adversely affecting the motor units or the muscl e, as the EMG and CK variables did not change. (C) 1997 by the America n Congress of Rehabilitation Medicine and the American Academy of Phys ical Medicine and Rehabilitation.