From How to Box pages 96-97. "Few people realize that the reason a tired fighter's legs begin to wobble is usually because his thigh muscles are exhausted. Yet it is true. Here is the plan I adopted to strengthen these: I procured an eighty-five pound punching bag. This bas was of much the same size, shape, and general appearance as a lather mail pouch. I began punching it regularly, every other day. I used on it the blows I would use in a fight; hitting heavily and only keeping up this work until slightly tired, never allowing myself to become exhausted. I gradually increased the length of time of punching this bag, as my muscles grew more and more accustomed to standing such violent work. At last I could punch it any number of rounds without fatigue or ache. But first it was anything but easy. The exercise 'caught' my in the legs and thighs. It didn't bother the upper part of my body to any extent. This proved my theory as to the effect on the thighs of heavy hitting. I kept it up, an found my thighs increased an inch in girth during a single month. Moreover, the old-time jar and fatigue were utterly absent. Punching the eighty five pound bag had another beneficial result. It helped my footwork along and made me cleverer in ducking and side-stepping. When you punch a bag it naturally comes back at you and comes back with express-train speed. That's all right when it's a light bag, an occasional tap on the face from it doesn't matter. But an eighty five pound bag traveling at that rate is a different proposition. It forces you to be quick as lightening keeping out of its way. Thus my work with it served a double purpose. When I met Jeffries I hit him throughout the fight without once feeling the old-time weariness and wabbly tendency of the legs. Moreover, I kept out of his way for the most part, just as I had avoided the terrible recoil of the eighty-five pound bag."
I remember hitting such a heavy bag back in my late teen years. As crazy as it sounds I would punch that bag full power for 30 minutes straight alternating between a dancing side stepping jabbing distance attack and a aggressive punchers attack bobbing under the bag after every punch. I would then skip rope 10,000 times without stopping (an occasional miss skip although rare). When I was done skipping I would be standing in a pool of sweat. Finally I'd run 3-5 miles. Today my workout is just a 2-3 mile run 4-5 times a week.....but only in the warm months of the year! Back in the days of my crazy exercise regimen I weighed 152 pounds with very low body fat. Today I am 215 but am usually told I look 180.
