About reloading while running it's not so difficult, the only risk is to fire on yourself if u stumble.
( at least I do it without problems with my beretta 9mm - with a rifle I don't know, never had one ).
For what concernes jumping.... I don't know if people would abuse of it, but in real like you're able to jump.......
Of course it should have limitations like running, and should be considered that jumping while transporting a law, a rifle, a pistol, anfibius shoes and an helmet shouldn't be the same than jumping with nike shoes on foot and just a pair of shorts......