This study developed an isochronous substitution model and used 30 minutes to explore the correlation between physical behavior and physical health of college students, and established a sports intervention plan to verify the accuracy of the isochronous substitution model. A total of 124 college students were recruited from four freshman classes at a university in Tianjin, and were randomly divided into an experimental group (31 males and 31 females) and a control group (31 males and 31 females). We measured the physical activity and sedentary behavior of all subjects using Actigraph GT3X and speedometer; measured the height, weight, waist to hip ratio, body fat percentage, lung capacity, maximum oxygen uptake (VO2max), grip strength, standing long jump, 1-minute sit ups, and sitting forward bending of the subjects; developed an isochronous substitution model and conducted a substitution analysis of physical behavior for 30 minutes to evaluate the substitution benefits; and established an exercise intervention plan based on the isochronous substitution model and verified the accuracy of the isochronous substitution model. The study revealed the following results: the LPA time and MVPA time of males were significantly higher than those of females (P<0.05); the BMI, waist to hip ratio, body fat ratio, lung capacity, VO2max, grip strength, and standing long jump of males were significantly higher than those of females (P<0.01); the forward bending of females sitting posture was significantly higher than that of males (P<0.01); after controlling for age and gender, replacing SB with MVPA for 30 minutes per day had the greatest benefits, with a significant decrease in BMI and body fat percentage (P<0.05), and a significant increase in grip strength, standing long jump, sit ups, forward bending, lung capacity, and VO2max (P<0.05); the benefits generated by MVPA replacing LPA were greater than those generated by LPA replacing SB; after 8 weeks of exercise intervention, the BMI and body fat percentage of the experimental group significantly decreased (P<0.05), while lung capacity, grip strength, standing long jump, and VO2max significantly increased (P<0.05). This study successfully established an isochronous substitution model for the relationship between physical behavior and physical health of college students and verified it. This study found that: (1) while maintaining the total activity time unchanged, using 30 minutes of MVPA instead of SB will have a significant improvement effect on the physical health of college students; (2) The health benefits generated by exercise intervention are basically consistent with the predicted results of the isochronous replacement model; (3) Improving the BMI, body fat percentage, and waist circumference of college students requires dietary control to achieve the predictive effect of the isochronous replacement model. |