Purpose: Cognitive load theory focuses on providing appropriate cognitive engagement to facilitate knowledge learning. The purpose of this study was to determine the contributions of cognitive load on high school students' in-class physical activity. Method: A stratified random sample of high school students (N = 150) who participated in a large curriculum intervention study provided the data. A path analysis and Hayes' PROCESS analysis were used to test a correlation model and moderation effect from gender and race. Results: The results showed that the reasoning learning tasks directly contributed to their in-class physical activity (path coefficient = 0.54, p < 0.01) and the gender and race factors were not significant moderators (p > 0.05). Conclusion: The findings imply that high cognitive load tasks can facilitate in-class physical activity. The findings suggest the power of the concept-based physical education curriculum in providing productive learning opportunities to all students.