  We investigate long-duration time series of human physical activity under
three different conditions: healthy individuals in (i) a constant routine
protocol and (ii) in regular daily routine, and (iii) individuals diagnosed
with multiple chemical sensitivities. We find that in all cases human physical
activity displays power law decaying temporal auto-correlations. Moreover, we
find that under regular daily routine, time correlations of physical activity
are significantly different during diurnal and nocturnal periods but that no
difference exists under constant routine conditions. Finally, we find
significantly different auto-correlations for diurnal records of patients with
multiple chemical sensitivities.
