mr jones----7 1/2 months ffs he's still growing , knacker it's growth plates and it'll cripple the f****r, let it learn to walk before you force it to run, it's a hard life for dogs , without entering them too young, dont say i have'nt warned you of the possible dangers
my puppys 4months and im running im on the lamp he loves it all most pulls my arm off when he see a rabbit