• activity monitoring;   • physical activity recommendations;
• activity recognition;   • locomotion  This study investigated
which aspects of the individuals' activity behavior determine
the physical activity level (PAL). Habitual physical activity of
20 Dutch adults (age: 26–60 years, body mass index:
24.5±2.7 kg/m2) was measured using a tri-axial accelerometer.
Accelerometer output was used to identify the engagement in
different types of daily activities with a classification tree
algorithm. Activity behavior was described by the daily duration
of sleeping, sedentary behavior (lying, sitting, and standing),
walking, running, bicycling, and generic standing activities.
Simultaneously, the total energy expenditure (TEE) was measured
using doubly labeled water. PAL was calculated as TEE divided by
sleeping metabolic rate. PAL was significantly associated
(P<0.05) with sedentary time (R=−0.72), and the duration of
walking (R=0.49), bicycling (R=0.77), and active standing
(R=0.62). A negative association was