The heavy bag must be treated as what is meant to be – a simulated opponent. If you remember that, you will not get your guard down, and your shoulders will always be up going for the head. The heavy bag is not for you to develop those single punches that pound a face in, but it is meant for getting your body developed for efficiency with channel your energy in the right places, and the endurance to keep up with the performance. With that in mind the the fundamentals will be further enforced.
Vince Lombardi once said that the best football team is the one who is the best in its basics, and not in the flashy stuff. So here are 4 fundamentals to enforce each time you take on the heavy bag.
Take the bag seriously and not punch for the sake of it. Imagine that in front of you is your opponent himself or herself. Where are the eyes? Where are the shoulders? Where are the arms? The same principle of fighting in the ring should apply on the heavy bag – do not look on the ground, do not stare at where you are giving a go at, and yes, keep that fierce and focused look and practice how to scare the hell out of your opponent.
If it helps, put up duct tapes to mark these critical areas of the opponent. Or if you are a little creative, draw the opponent on your bag.
As though you are facing your opponent, keep your footwork in good shape (for a great footwork drill, see here), and do not lean on the bag. You know that if you do that in the ring, your opponent can just slide off, and cause you to lose balance. Worst is when you get so close that it becomes really easy for your opponent to throw an uppercut up your jaw. Move around the bag, practice your manoeuvres and your dodges, and keep your proper distances.
If you are strategic with your punches on your opponent, do the same to the heavy bag. Throw punches consistently (not periodically with 10 seconds of footwork dance!), and at the right spots (see above for Eyes Right) – the face, the shoulders, the ribs. Make sure that like in a real fight, that you are not skipping and hopping around. Make sure your feet are firm on the ground as you throw your punches. You want to hear solid jabs and not lifeless thuds as you land those punches.
I know it is very tempting to throw hard punches, especially because the heavy bag is not going to punch back at you! But if you get so used to this, you will tend to be very tempted to throw reckless punches in the ring. I cannot stress the importance over and over again – treat your heavy bag as your opponent, and be strategic with your punches. Take the opportunity to practice new combos, and new angles. When you meet an opponent in the ring, you basically execute the same moves, so treat the heavy bag with respect.
Your heavy bag is not going to punch back at you, but you are going to pretend that it might. Get a trainer, or film yourself attacking the heavy bag. There is a chance that you will be caught with your hands down, and you end up internalizing your habits in not keeping them up. This can become very fatal in the ring. Make sure your elbows are in the right places even when facing the heavy bag.
The bottom line is, respect the heavy bag, as it will help you develop irrefutable habits that help you win in the ring.