This study found that lower body muscle groups recovered from damaging isolation movements more quickly than upper body muscles. For bodybuilders, isolation days can be important for bringing up lagging muscle groups, and this study shows that you can add in more isolation days for the lower body than the upper body. This means that you can add in lower body isolation days between heavy leg workouts to boost growth, but probably shouldn’t do that for upper body muscles.
▪️ Source: Chen, T. C., Yang, T. J., Huang, M. J., Wang, H. S., Tseng, K. W., Chen, H. L., & Nosaka, K. (2019). Damage and the Repeated Bout Effect of Arm, Leg and Trunk Muscles Induced by Eccentric Resistance Exercises. Scandinavian Journal of Medicine & Science in Sports.