ABSTRACT

I. Introduction................................................................................. 226 II. Definitions .................................................................................. 226

III. Conceptual Framework for Quantifying Energy Expenditure .................................................................... 231

IV. Methods of Assessing Physical Activity and Energy Expenditure .................................................................... 232 A. Measuring Energy Expenditure ........................................... 233

1. Direct Measures of Energy Expenditure ....................... 234 a. Doubly Labeled Water................................................. 234 b. Labeled Bicarbonate .................................................... 235

2. Indirect Measures of Energy Expenditure ..................... 235 a. Oxygen Uptake ............................................................ 235 b. Heart Rate .................................................................... 236 c. Body Temperature and Ventilation ............................ 237

B. Measuring Physical Activity ................................................ 237 1. Direct Measures of Physical Activity ............................. 237

a. Physical Activity Records ........................................... 237 b. Physical Activity Logs................................................. 238 c. Physical Activity Recalls ............................................. 239 d. Motion Detectors ......................................................... 242

2. Indirect Measures of Physical Activity........................... 246 a. Physical Activity Questionnaires ............................... 246 b. Body Composition ....................................................... 250

V. Summary...................................................................................... 251 References ............................................................................................. 251

Regular, moderate to high-intensity physical activity confers substantial health-related

and performance-related

benefits. The specific activityrelated physiologic adaptations and the degree to which these adaptations occur is dependent on the interaction of the frequency, duration and intensity of the activity being performed.