3 Rounds On The Heavy Bag. Great Conditioning Workout. Tom Yankello of the World Class Boxing Channel is back with another great conditioning workout that he refers to as the 21 Drill. This video consists of 3 rounds on the heavy bag. If you have a trainer, you can have your trainer mimic the drill for you. And if you don’t have a coach, watch this video and follow along and use Tom as your trainer! Tom provides you with different intensities for each round. He focuses on building up your aerobic capacity, your lactic threshold, and your maximum threshold. Use Tom as your coach and follow along and do the drill. The first round is performed at 50% intensity. Round 2 consists of you picking up the tempo to 70%. During this round you are getting yourself in punch shape by improving your lactic threshold. The last round focuses on high intensity hard punches. Tom teaches you tosit on your punches while throwing the punch with high intensity. It is incredibly difficult to make it all the way through 1-21 and 21 -1 during this round. Make sure you don’t sacrifice great technique!