I dont noe how to explain running mechanics...
But when u run, it does not use yr leg muscles only...
It uses most of the body muscle... In fact, it is the body muscles
tat gives u the momentum to slice thru the air...
We r not born to have heavy legs and thus our joints in legs have
their limit...
even if u want to use ankle weights , u have to use it progessively
... probably, every gram per day. Depends on scientific
calucalation... So tat, it is the muscle tat is building rather
than stress on joints...
But true enough, when u remove yr SBO , wear pt kit and start to
run, it is really like flying sia...