From an injury prevention point of view, it is extremely important to complement your running with good strength work to counteract this decline in muscle mass and reduce your risk of developing injuries such as shin splints, calf strains, or low back pain.
This does not mean lifting massively heavy weights in the gym that you have no interest in. Shown in the vid is a resisted step up exercise for running mechanics and the development of hip extension and glute strength. Give it a try.
Riain Casey MISCP