Roy J. Shephard

Habitual Physical Activity and Physical Fitness in Older Japanese Adults: The Nakanojo Study

Background: Optimal patterns of habitual physical activity to ensure healthy aging remain unclear because of measurement limitations; most investigators have used either subjective questionnaires, or accelerometer or pedometer measurements limited to a single week, despite evidence of both the limited reliability/validity of questionnaires and seasonal changes in activity patterns. Objective: This study explored possible associations between indicators of physical fitness (walking ability, upper- and lower-extremity isometric strength, and static and dynamic balance) and yearlong pedometer/accelerometer assessments of the quantity and quality of habitual physical activity in ostensibly healthy older adults. Methods: Subjects were 76 male and 94 female Japanese aged 65–84 years. Each participant wore a pedometer/accelerometer for 1 year; measurements included the average number of steps taken each day and the duration of activity at an intensity of >3 metabolic equivalents (METs). Compliance was good, the instrument being removed for intervals of >3 h on <5% of days; data for such intervals were excluded from analysis. At the year’s end, traditional laboratory techniques assessed preferred and maximal walking speeds, peak handgrip force, peak knee extension torque, total body sway, and maximal functional reach. Results: After controlling data for age and/or sex, lower-extremity function (walking speeds and knee extension torque) showed significant positive relationships with the daily step count and daily duration of activity at >3 METs, especially in individuals ≥75 years of age. On the other hand, handgrip force and body sway were unrelated to pedometer/accelerometer measurements. Linear and exponential regressions showed positive associations between walking speeds and pedometer/accelerometer scores up to the observed maxima of 13,700 steps/day and 62 min/day at >3 METs. However, when data were categorized into quartiles, walking speeds were not significantly greater in persons exceeding 7,000–8,000 steps/day and/or 15–20 min/day at >3 METs. With a few exceptions, subjects meeting these levels of habitual activity had walking speeds above the threshold predicting the development of functional dependence. Conclusion: The present data suggest that fitness is well maintained in elderly people who take >7,000–8,000 steps/day and/or spend >15–20 min/day at >3 METs. Nevertheless, the direction of this association merits exploration by longitudinal prospective studies and/or randomized controlled trials.

Steps per day: the road to senior health?

In older adults, as in younger individuals, habitual moderate-intensity physical activity is associated with a reduced risk of various chronic health conditions, including certain types of cardiovascular and musculoskeletal disease and certain forms of cancer. However, the pattern of physical activity associated with such benefits remains unclear. One problem is that most investigators have examined patterns of physical activity using either subjective questionnaires or accelerometer or pedometer measurements limited to a single week, despite clear evidence of both the unreliability/invalidity of questionnaires and seasonal changes in activity patterns.Since 2000, we have thus conducted an interdisciplinary study examining the habitual physical activity and health of elderly people living in a medium-sized Japanese town (the Nakanojo Study). In about one-tenth of some 5000 available subjects aged ≥65 years, physical activity has already been assessed continuously for 24 h/day for >8 years using a specially adapted pedometer/accelerometer. This device has a storage capacity of 36 days and can distinguish >10 intensities of physical activity (expressed in metaboliwc equivalents [METs]). Data have to date been summarized as daily step counts and daily durations of activity of <3 and >3 METs, averaged over a 1-year period. This article provides a detailed overview of both factors influencing habitual physical activity and relationships between such activity and health in an elderly population.To date, analyses have been cross-sectional in type. Substantial associations have been noted between the overall health of participants and both the daily duration of effort undertaken at an intensity of >3 METs and the daily step count. In men, the extent of health is associated more closely with the daily duration of activity of >3 METs than with the daily step count, whereas in women, the association is closer for the step count than for the duration of activity >3 METs. In both sexes, the threshold amount of physical activity associated with better health is greater for physical than for mental benefits: >8000 versus >4000 steps/day and/or >20 versus >5 min/day at an intensity >3 METs, respectively. In other words, better physical health is seen in those spending at least 20 min/day in moderate walking (at a pace of around 1.4 m/s [5 km/h]) and a further >60 min of light activity per day. In contrast, better mental health is associated with much smaller amounts of deliberate physical activity.The daily step count and the daily durations of activity of <3 and >3 METs are all influenced by meteorological factors, particularly precipitation and mean ambient temperature. Activity decreases exponentially to about 4000 steps/day as precipitation increases. Excluding the influence of rainfall, the daily step count peaks at a mean outdoor temperature of around 17°C; above and especially below such readings, physical activity decreases as a quadratic function of temperature. Seasonal changes in microclimate should thus be considered when designing interventions intended to increase the habitual physical activity of elderly people.The observed associations between physical activity and health outcomes point to a need for longitudinal analyses; these should examine potential causal interpretations of the current findings and elucidate possible additional mediating variables.

How Many Days of Pedometer Use Predict the Annual Activity of the Elderly Reliably

PURPOSE Daily variations of physical activity in the elderly remain unclear. We thus used a uniaxial accelerometer/pedometer to examine the variability of step counts for 1 yr, determining the minimum number of days observation needed to obtain reliable estimates of annual physical activity. METHODS Subjects were 37 males and 44 females, healthy Japanese, aged 65-83 yr. The pedometer was worn on the waistband throughout 1 yr, accumulating information on the individuals daily step count. RESULTS The step count spectrum showed peaks with periods of 2.3, 3.5, and 7.0 d and an aperiodic component that had a greater power at low frequencies (i.e., non-white noise). These characteristics were absent in randomly resequenced data. To ensure that 80% of total variance was attributable to between-subjects variance, 25 and 8 consecutive days of observation were needed in male and female subjects, respectively. To achieve 90% on this same measure of reliability, 105 and 37 consecutive days of observation were required. In contrast, 4 d of randomly timed observations yielded 80% reliability for both men and women, and 11 and 9 d gave 90% reliability in men and women, respectively. If sampling also took account of season and day of the week, the respective observation periods for men and women were reduced to 8 and 4 d (i.e., 2 and 1 consecutive days of sampling every 89 d) for 80% and to 16 and 12 d (i.e., 4 and 3 consecutive days every 89 d) for 90% reliability. CONCLUSION When estimating annual step counts, seasonal and/or random sampling of data allows collection of reliable data during substantially fewer days than needed for consecutive observations.