Your body is one system, treat and train it that way. The brain doesn’t disassociate your hip from your shoulder, or your ankle from your low back. We are not multiple systems, we are only one. The brain, the nervous system, the gut, the lymphatic system, the musculoskeletal system, everything... it is all one unit. That unit is designed to function interdependently to ultimately produce actions and movements. Treat and train accordingly.