The major intervention in the LIFE pilot study for participants assigned to the exercise group will be walking. According to the treatment protocol, during the first six months as much as half of their increase in walking will be carried out ?at home? or in a non-supervised setting. During the second six months, at least 75% of the assigned walking will be non-supervised for most participants. To know if this intervention was accomplished, LIFE investigators need documentation that a significant increase in walking took place in the exercise participants versus the healthy aging class participants. Currently the protocol includes the use of pedometers, logs and the CHAMPS questionnaire to inform the investigators about the activity profile of each study participant. While all of these measurement tools are likely to provide useful data, none have been proven to provide an accurate and objective assessment of the daily physical activity profile of older, somewhat frail persons. The Actigraph is a small solid-state accelerometer/recorder (6.6 x 4.3 x 2.5 cm., 70 grams) that can store the number of times it moves x the rate of movement change (acceleration) on a continuous basis for up to a month (approximate battery life). It stores these ?counts? for specified times intervals, usually set at one-minute. For LIFE, this monitor will be worn on the right hip of each participant. The specific aims of this project are to determine the capability of the Actigraph accelerometer activity monitor to detect a significant difference in the physical activity level in a subset of subjects assigned to the LIFE exercise group versus the healthy aging class controls at six months into the study, (2) compare the assessment of amount of physical activity performed by a subset of subjects in the two treatment groups as determined by the CHAMPS physical activity questionnaire administered at 6 months and the Actigraph monitor using average number of ?accelerometer counts? per hour and number of minutes per day spent above a conditioning threshold, and (3) determine if data collected by the Actigraph monitor during the 400-meter walk at the 6-month evaluation can be used to help ?calibrate? or individualize the analysis of the Actigraph recorded during the 7 days of usual living.