Physical activity declines from childhood to adolescence. Affective factors may partially account for this decline. The present study investigated whether within-person changes in children’s enjoyment of physical activity are associated with the age-related decline in physical activity. Children (N = 169, 54% female, 56% Hispanic; 8–12 years old at enrollment) took part in a longitudinal study with six assessment waves across 3 years. At each wave, enjoyment of physical activity was reported, and moderate to vigorous physical activity (MVPA) was measured with an accelerometer across seven consecutive days. MVPA and enjoyment of physical activity both declined across waves. Multilevel analyses revealed that within-person changes in enjoyment moderated the effects of age on within-person changes in MVPA. Enjoyment appeared to be a dynamic factor that buffered against the age-related decline in physical activity in youth. These findings call for health promotion interventions that encourage enjoyable physical activities.

体育活动从儿童期到青春期就下降了。情感因素可能部分解释了这种下降。本研究调查了儿童在体育锻炼中的人际变化是否与年龄相关的体育锻炼下降有关。儿童（N = 169，女性为54％，西班牙裔为56％；入学时为8-12岁）参加了一项纵向研究，历时3年，共进行了6次评估。在每一波中，都报告了身体活动的乐趣，并且连续七天使用加速度计测量了中度到剧烈的身体活动（MVPA）。MVPA和体力活动的享受都随着海浪而下降。多层次分析显示，人际享受的变化减轻了年龄对​​MVPA人际变化的影响。享受似乎是一个动态因素，可以缓解与年龄有关的青年体育活动的下降。这些发现要求采取健康促进干预措施，鼓励人们进行愉快的体育锻炼。