1. Objective measurements of the maximal voluntary strength of triceps surae and the amount and speed of customary walking have been made in 56 men and 66 women aged over 65 years, who were living independently.
2. Strength was measured using a dynamometer based upon a hydraulic system (Bourdon tube). Walking was assessed, for amount using a mechanical accelerometer (pedometer) over a week, and for speed using a self-paced test for normal walking over 100 m on the level. The reliability and validity of these methods has been described.
3. The men were significantly stronger (1128 ± 206 vs 873 ± 177 N) even after adjustment for body weight; their amount of walking was similar to that of women, but they walked significantly faster (4.8 ±0.6 vs 4.2 ±0.6 km/h). Men were significantly more active in leisure pursuits (as assessed by questionnaire).
4. Significant associations between strength and chosen normal walking speed were found for both sexes (r = 0.41, P < 0.001 for men and r = 0.36, P < 0.01 for women). The amount of walking (daily stepscore as a mean from 7 consecutive days recorded) was significantly but less strongly correlated with strength (r = 0.30, P < 0.05) in the men only.
5. Multiple regression analysis showed that in men neither age nor amount of walking had any further effect in addition to speed, but in women age had an additional effect (multiple R = 0.48).
6. An association has been demonstrated which raises the possibility of reversing loss of muscle strength through increased daily activity.