This study monitored the physical activity behavior of adolescent students over a ten month school year. Physical activity was assessed at two month intervals using selfreport and objective (Actical accelerometers) measures. Self-report results (n = 547) indicated a decline in physical activity throughout the school year for all grades and genders. The decline was attributed largely to a decrease in organized activity participation. Objective physical activity results (n = 40) revealed a significant decline in activity in the latter half of the school year (February to June). Declining physical activity was attributed to a decrease in vigorous activity which was consistent across grade and gender. Collectively, the results highlight the importance of promoting consistent opportunities for adolescents to be active throughout the school year.
Mark W. Bruner, Karen E. Chad, Jodie A. Beattie-Flath, M. Louise Humbert, Tanya C. Verrall, Lan Vu and Nazeem Muhajarine
Nicholas M. Brisson, Paul W. Stratford, Saara Totterman, José G. Tamez-Peña, Karen A. Beattie, Jonathan D. Adachi and Monica R. Maly
Investigations of joint loading in knee osteoarthritis (OA) typically normalize the knee adduction moment to global measures of body size (eg, body mass, height) to allow comparison between individuals. However, such measurements may not reflect knee size. This study used a morphometric measurement of the cartilage surface area on the medial tibial plateau, which better represents medial knee size. This study aimed to determine whether normalizing the peak knee adduction moment and knee adduction moment impulse during gait to the medial tibial bone–cartilage interface could classify radiographic knee OA severity more accurately than traditional normalization techniques. Individuals with mild (N = 22) and severe (N = 17) radiographic knee OA participated. The medial tibial bone–cartilage interface was quantified from magnetic resonance imaging scans. Gait analysis was performed, and the peak knee adduction moment and knee adduction moment impulse were calculated in nonnormalized units and normalized to body mass, body weight × height, and the medial tibial bone–cartilage interface. Receiver operating characteristic curves compared the ability of each knee adduction moment normalization technique to classify participants according to radiographic disease severity. No normalization technique was superior at distinguishing between OA severities. Knee adduction moments normalized to medial knee size were not more sensitive to OA severity.