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A small (28 g) mechanical accelerometer has been tested by subjecting it to controlled bench tests consisting of repetitive vertical oscillations on two designs of test rig. The accelerometer's 3-digit display provided a cumulated score with a maximum of 99.9 units. This score was compared with an independent count of the imposed oscillations and found to be linear with time (r = 0.996) and reproducible on retest (coefficient of variation = +/- 1.5%). The sensitivity ranged from 6.2 to 7.4 units/10,000 oscillations. The response was related to the maximal applied acceleration (calculated from the amplitude and frequency of the oscillations on the assumption that they were sinusoidal) and independent of the amplitude and frequency used. The threshold maximal acceleration was less than 2 m s-2 and the response had reached a plateau at 4 m s-2. During field studies the accelerometer was firmly attached over the hip in a waistband where it responded to the vertical accelerations produced by walking. When compared with an independent count of footsteps from a heel-mounted resistance pad the accelerometer score (after calibration) was not significantly different. The mean difference was (0.29 +/- 0.67, S.D.) 10(3) "steps" in a younger group (n = 8, mean age 39 years) and (0.46 +/- 1.08, S.D.) 10(3) "steps" in an older group of women (n = 6, mean age 65 years). Scores of around 10 X 10(3) "steps" can be expected in a day in moderately active young subjects and 40 X 10(3) "steps" in a week in the elderly. Simultaneously recorded scores from both right and left hips wee not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

This paper describes a controlled study of the effects of an unsupervised walking-programme in 108 volunteers from among 580 middle-aged employees in a Nottingham light industrial company. Objective measurements of physical condition and of customary activity were made on four occasions at 12-week intervals. The subjects were randomly allocated to three groups and encouraged to follow a walking-programme in the first, second or third periods of the study: no activity was prescribed in the other periods. Compliance with the programme was estimated from log-cards and from a week's pedometer record. Although there were no significant differences between the changes seen in subjects following the walking-programme and those in control subjects, there were significant small improvements in physical condition and modest increases in customary activity in a) those subjects actually completing the programme, and b) the subjects measured before and after their programme, pooled without regard to the period of measurement. At least some of the increased activity is maintained for 12 weeks after the programme. The marginal changes suggest that the intensity of the training-programme as experienced by the subjects was close to the threshold for maintenance of physical condition in this age-group of workers.

SUMMARYAn objective method for assessing customary physical activity has been described, based on heart rate and footfall signals recorded on magnetic tape using small body-borne recorders. Computer analyses were used to obtain indices of the intensity and duration of periods of physical activity using both biosignals. Threshold values were set for each individual at a heart rate related to a standard walking speed of 4 8 km . h-1 (3 miles per hour). Four activity indices were defined in terms of time spent above this threshold and the intensity of the heart rate elevation above it, applying criteria relating to the duration of periods of activity or the concurrent activation of the walking signal. The choice and validity of these indices are discussed, and results for several groups of subjects presented. Three groups of subjects aged over 60 years were studied before and after retirement: twenty-five were steel-workers and thirty-nine were factory-workers (men and women). Rather low levels of activity were recorded. After one year of retirement the female factory workers showed a significant decrease in activity. In men this was found only after several years of retirement had elapsed.

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