Locomotor activity in female rhesus monkeys: Assessment of age and calorierestriction effects

As a component of a long-term, longitudinal study of aging in this primate model, the objective of the current experiment was to assess age and diet e ffects on locomotor activity in a cross-sectional analysis. By attaching a motion detection device to the home cage, locomotor activity was monitored over a week in a group (N = 47) of female rhesus monkeys (Macaca mulatta) 6 -26 Srs of age. About half these monkeys composed a control group fed a nut ritionally fortified diet near ad libitum levels, whereas an experimental g roup had been fed the same diet at levels 30% less than comparable control levels for approximately 5 yrs prior to testing. Among control monkeys, a m arked age-related decline in activity was noted when total activity was con sidered and also when diurnal and nocturnal periods of activity were analyz ed separately. When comparing activity levels between control and experimen tal groups, only one significant diet effect was noted, which was in the yo ungest group of monkeys (6-8 yrs of age) during the diurnal period. Monkeys in the experimental group exhibited reduced activity compared to controls. Body weight was not consistently correlated to activity levels. In some ol der groups, heavier monkeys tended to show greater activity, but in younger groups the opposite pattern was observed.