RECENTLY, WHILE TRAINING WITH MY COACH ON THE HEAVY BAG, I STARTED TO BECOME SUPER TIRED AFTER 1 1/2 ROUNDS, WHEN BEFORE I COULD GO AT LEAST 4 PLUS ROUNDS W/O A PROBLEM. I AM COMPLETELY DRAINED AFTER 1 1/2 ROUNDS ON THE BAG. I AM DYING. I NEED HELP.