With respect to diurnal profiles , there were two peaks at @-@ AM ( mean -LSB- @ % - confidence interval -RSB- : @ -LSB- @-@ -RSB- steps ) and at @-@ pm ( @ -LSB- @-@ -RSB- steps ) interrupted by a period of lower activity with a low point at @-@ pm ( @ -LSB- @-@ -RSB- steps ) .