Quick 101 on injury from muscle imbalance

In this short article I'll show how the action of throwing a punch taxes your chest and back muscles in different ways and how this is involved in the development of injuries and how therefore to help prevent them. The action of throwing a punch is a very similar action to others used in sports and has similar effects for the muscles and joints involved those actions. Similar actions include

• throwing a ball
  
• playing a shot in a racquet sport
  
• taking a kick in football and rugby

When you throw a punch your chest will be involved in pulling your shoulder joint and your humerus (arm bone) forward. All the while your Latissimus Dorsi (your big back muscle) and a bunch of the smaller back muscles like the Rhomboids and Trapezius will be counteracting and keeping in check the pull of the chest muscle. Once the humerus is almost in front of you the chest has done it's work but the punch isn't finished. It's actually just beginning because the biggest, most important part is controlled by the back muscles. They determine how hard your punch is because they start slowing down the shoulder joint and the humerus down right at this point. Reason: if they don't the humerus will pop out of the shoulder joint and dislocate. So they protect the shoulder joint by managing and containing the force of the chest muscles.

This is called antagonistic pairing and is just as relevant in your biceps/triceps pair in your arm, your quads/hamstrings in your leg and your abs/lower back along with several other muscle groups.

So the story doesn't end there. Now that you see that the back muscles protect the shoulder joint from the excesses of the chest muscles and vice versa you'll begin to be aware that if your chest muscles are too strong then your back muscles are at a disadvantage. If you do lots of punching movements then your back muscles are likely to tire first. Leaving your shoulder joint exposed and meaning that both the shoulder joint and humerus are likely to be pulled too far forward resulting in stretching of the ligaments and tendons and ultimately injury.

Let's add to this and point out that it's easier for a muscle to pull things towards it (concentric action) than to stop something moving away from it (eccentric action). Therefore when punching or throwing (which is basically the same thing) your chest muscles are not working very hard but your back muscles are. So they're also at a disadvantage meaning that they need to be at least as strong as the chest muscles. I'd recommend they be stronger but then this would put the shoulder joint out of whack when doing the reverse (bringing the fists back).

Summary
So in summary you should now see why it's absolutely imperative to have balance in all muscle groups above all things. If you're too strong in one area you can bet that you'll be prone to injuries in a related area. To add to this though it's not just pure strength or stamina that you need to prevent an injury.

Not only will you need both e.g. The strength to control a really big punch and the stamina to do this time and time again without injury. You'll also need good coordination in the muscles being used to control this movement so that they are good at applying just the right amount of force. A muscle that doesn't have much coordination will either try too hard to stop the action or two little. Either way they'll put stress on either themselves or the support structure which isn't good.

How do you achieve this? Training. Keep doing the movements at different speeds, as part of different combinations and with other kinds of variety. Coordination comes from you nerves and brain learning how to control the muscles appropriately. This comes just like strength develops from doing the action regularly and with lots of variation. At slower speeds your muscles and brain get to learn the movement without risk of injury and allows you to focus on good technique. Higher speeds risk more injury but also tax the muscle, nervous and connective/support tissue to strengthen and improve. So a mix of these types of training is the best medicine to both prevent injury increase punching/ throwing power or the power from any antagonistic muscle pairing.