Changes in Strength over Time Among Polio Survivors

Objective: To study changes in the strength of different muscle groups in polio survivors over a period of approximately 9 months.

Design: Longitudinal study.

Setting: Moss Rehabilitation Research Institute.

Participants: One hundred twenty subjects (57 men, 63 women) were studied on three occasions, each 3 to 5 months apart. Subjects were recruited through the Einstein-Moss Post-Polio Management Program. newspaper advertisements, and polio support groups.

Main Outcome Measures: Isometric strength of 30 muscle groups (16 in upper extremities, 14 in lower extremities) was measured, using a hand-held dynamometer.

Results: Data were analyzed in two separate groups: upper-extremity muscles and lower-extremity muscles. Results for the upper-extremity muscles revealed evidence of a significant deterioration in strength. The amount of deterioration differed among muscles and increased with age. There was also evidence of deterioration in strength in the flexor muscles in the ankle, hip, and knee. However, the rate of deterioration in these muscles was not strongly related to age, time since polio, gender, symptom status, or history of residual weakness.

Conclusions: Strength is deteriorating among polio survivors at a rate higher than that associated with normal aging. This deterioration is not occurring in the extensor, or so-called "weight-bearing" muscles, but is occurring in many of the upper-extremity muscle groups and in the flexor muscles in the lower extremities.