Swarming while going backward ?

LaMotta's barrage of punches was more of a finishing move, sensing that his opponent was in a weak state and about to hold him. Prime Ali had the ability to fire off lightning jabs and combinations while backing up or being cornered. He was at his best when his opponents came forward. It wasn't swarming, but it was a high amount of offense from a defensive position. Short bursts released between intervals of slipping and moving. But a true swarmer presses forward with continual aggression during most of the fight. This is usually the fighter with a high amount of stamina. The motion must be forward because he's focusing on overwhelming the opponent with a high volume of punches, disrupting his rhythm, and not letting him recover.

Prime Ali had the ability to fire off lightning jabs and combinations while backing up or being cornered. He was at his best when his opponents came forward. It wasn't swarming, but it was a high amount of offense from a defensive position. Short bursts released between intervals of slipping and moving. But a true swarmer presses forward with continual aggression. This is usually the fighter with a high amount of stamina, or the fighter who believes his opponent is hurt. The motion must be forward because he's neglecting defense and focusing purely on overwhelming his opponent and not letting him recover.

You might be talking about the part where he was backing up so the opponent couldn't rest against him. A hurt opponent will clinch or rest against you, closing the distance so you can't get off punches. Jake gave him no place to rest and created space so he could continue the punishment.