Although being tough in boxing is an important trait, it is only one aspect that is necessary to succeed in the squared circle. No matter what exercise you are doing in the gym, positioning plays a crucial role. That means not only your position in the ring, in relation to your opponent, but also during training. In order to be effective from different heights and angles, you have to train with variety.
Aside from the muscles you use most, there are supporting muscles that surround and help strengthen the ones you place the most demands on. To train in a more well-rounded fashion, you need to occasionally change up your body position to strengthen these stabilizers, the muscles around the ones that you rely on most to do the heavy lifting.
One way of strengthening these surrounding muscles can be done on a heavy bag. Of course it's always important to punch straight and get there faster than your opponent, but when working out, especially on the bag, you can mix that up and get some muscular gains from it. To begin with, try your first round from a crouched position, even more than you would usually bend down. Fight the entire round from that position. Not only will it strengthen the muscles in your hips and thighs, it will also strengthen your back, your triceps and the back of your shoulder muscles because you’ll be punching from an angle you don’t typically fight from. By constantly having to punch upward you're adding extra strength to lower muscles that surround your shoulders and those in your upper back.
Next round, take just the opposite approach. Stand taller than you normally would and punch down on the bag. This will also work the muscles in your shoulders in a different way. It will focus more on the upper part of your shoulder, your chest muscles and it will allow you to get full rotation on every punch. Again, this places an emphasis on the muscles surrounding the (front) anterior deltoid muscle, which is the central shoulder muscle you use most. After the first grueling round for your legs, standing more upright takes your legs out of the equation for this round. This forces you to “arm punch” more and work a little harder to get your punches off and landed squarely. Of course, arm punching is not something you want to get in the habit of doing or to use on a regular basis, but for muscle-strengthening, and in this situation, it helps. Both from a lower and higher position, punching from various heights strengthens your back, your legs, your shoulders, your neck muscles and places different demands on your core.
The variety will also make you more adaptable. As a fighter, you never know when you will be forced out of position or out of your comfort zone. Although you may be used to and feel most comfortable fighting from one position, such as a crouched, bobbing-and-weaving style of fighting, you are limiting your ability to land the most powerful and effective blows when you consistently fight from one angle. Training for what you might experience in a fight is the only way to be prepared.
Periodically adding these variations to your routine may help you feel a little more familiar, in terms of how you use your muscles. Plus if you ever find yourself facing a much taller or shorter opponent, this type of exercise will have helped strengthen the muscles you will calling on to land effective blows.
Practice does make perfect and positioning should play a part in your preparation. And that's way too many Ps in one sentence, but it makes the point.