He is fighting in an extremely smart way, conserves energy and just looking at him feels like his brain in working on 200% capacity focus/tactics wise. Just look at him and nigsrael in the end, he has a lot less sweat on him but acts as if he is completely mentally and emotionally burnt out. I always finnish my weight training sessions with 5 x 5 min 1 min rest in between rounds on the bag. It easy to build up endurance in it if you are consistent.