Low-intensity, alternate-day exercise improves muscle performance without apparent adverse effect in postpolio patients.

The purpose of this study was to examine the effect of a low-intensity, alternate-day, 12 wk quadriceps muscle-strengthening exercise program on muscle strength and muscle and motor unit integrity in 12 postpolio patients. Patients performed six to ten repetitions of a 5-s duration knee extension exercise with ankle weights. After completing six repetitions, patients rated the perceived exertion (RPE) in the exercised muscle. The patient continued repetitions until RPE was >/= 17 or ten repetitions were performed. The weight was increased the next exercise day whenever the RPE was < 17 after ten repetitions. Before and after the training program, median macroamplitude as well as jitter and blocking were determined electromyographically (EMG), serum creatine kinase (CK) was measured, and quadriceps muscle strength was assessed. The ankle weight lifted after 2 wk of training and at the end of the program were also recorded. Although the ankle weight lifted at the end of the program significantly (P < 0.05) increased from a mean +/- SD of 7.1 +/- 2.7 to 11.2 +/- 4.7 kg, the dynametrically determined muscle strength measures did not significantly (P > 0.05) increase. The EMG and the serum CK variables also did not significantly (P >0.05) change as a result of the exercise program. We conclude that performance was improved, as demonstrated by an increase in the amount of weight the patients lifted in the exercise program. No evidence was found to show that this program adversely affected the motor units or the muscle as the EMG and CK did not change.

Electromyographic and neuromuscular variables in post-polio subjects.

OBJECTIVE: Post-polio subjects experience functional deterioration many years after developing acute poliomyelitis and have been shown previously to have a deficit in strength recovery after isometric activity. This study characterized the size and stability of the motor units in a group of post-polio subjects with macro and single fiber electromyography (EMG) and correlated these variables with isometric strength, endurance, "work capacity," and strength recovery after fatiguing isometric exercise. DESIGN: A cohort of 12 post-polio subjects was tested for neuromuscular function. Electromyographic variables were determined on a separate day. SETTING: Volunteers were recruited from the community and tested in our neuromuscular research laboratory. SUBJECTS: A volunteer sample was obtained from advertisements. All subjects acknowledged post-polio syndrome symptoms. MAIN OUTCOME MEASURES: Neuromuscular variables were isometric knee extension peak torque, endurance (time to exhaustion) at 40% of maximal torque, tension time index, and recovery of torque at 10 minutes. Electromyographic variables were macro EMG and single fiber EMG (percent blocking and jitter). RESULTS: Macro EMG amplitude was ninefold the control value, and both jitter and blocking were greatly increased in comparison to control values. Isometric strength significantly (p < .05) correlated negatively with macro EMG amplitude. CONCLUSIONS: The weakest subjects had the greatest number of muscle fibers within the motor unit (as measured by macro EMG amplitude). Jitter and blocking did not correlate with neuromuscular function.