Wrist-worn activity tracking devices have become increasingly popular in the last several years. These devices are commonly used to measure steps, heart-rate, and energy expenditure during physical activities. Walking and jogging are two of the most common activities for health and fitness, and are commonly assessed using these wearable devices. The accuracy of these devices for treadmill activities at different speeds and grades is debatable. Therefore, the purpose of this study is to evaluate the accuracy of energy expenditure and heart rate measures for two of the most popular devices (Garmin Vivoactive 3, FitBit Ionic) during walking and jogging at different treadmill grades. Participants will be recruited by word of mouth among apparently healthy, recreationally active adults. Approximately 15 participants will be recruited, both men and women. Participants will be asked to attend two laboratory sessions. During the first session, participants will be fitted with the two wrist-worn activity devices, one on each wrist. They will then be fitted with a Polar heart rate monitor (chest worn strap and receiver) as well as a face mask for collecting expired gases to determine energy expenditure. Participants will then complete three steady state walking intervals at three different grades (0%, 3% and 6% treadmill grades). They will be asked to walk at a brisk pace for approximately 10 minutes during each interval. The second laboratory session will consist similar measurements during jogging intervals at a “moderately hard” pace. For each participant, the treadmill grade order will be randomized for each session. Energy expenditure will be determined from gas exchange measures using indirect calorimetry. Heart rate values from the Polar heart rate monitor will be recorded. Accuracy of the devices for each exercise condition will be determined using ANOVA with significance set at p
