How do we convince the body to generate more force, or to generate force faster? Basically we need to make the body work near the limits of its force generating capacity. In other words, to convince your body to be able to push harder (with more force) you have to push something in such a way that it's very, very hard (for you). You can push lightly on something all day and you're not going to force much of an adaption.
How do you make a movement or position hard to do (require a lot of force)? Sometimes the weight of your own body provides enough resistance. Other times you need to load the movement or position (I'm just going to say movement from now on - the same basic ideas apply to holding a position). How do we load movements? There are various ways.
The most familiar way to load a movement is with weights of some kind. There are various forms of weight - dumbells, barbells, kettlebells, medicine balls, etc. Weights load movement in two distinct ways:
- Gravity pulls the weights downward, forcing you to exert a counteracting force upwards;
- The mass of the weights resists acceleration, forcing you to exert a force to get them moving or to change the direction of their movement.
This is why some people are find of throwing medicine balls. They have the same basic properties as dumbells, but they're meant to be thrown. You can do a bench press like movement where you throw the ball away at the top. All that does is prevent you from having to slow the weight down as you finish the move - you really end up free to push hard and accelerate the ball through the whole range of motion.
Bands are just what they sound like - heavy duty rubber bands that can be used to load a moment or position. You hold the band, or hold a handle attached to the band by a carabiner or something, and hook the other end of the band to something - maybe a specially designed something. Then you pull. Band provide a very different type of resistance for these reasons:
- Bands have very little mass, so they develop an inconsequential amount of momentum. The resistance at all parts of the movement will have nothing to do with how fast you're moving.
- Bands exert greater force the greater the stretch. Imagine someone bench pressing with two bands anchored to the floor instead of a bar - it will be relatively easy to start the motion, but the bands will really fight you as you get closer to lockout. This may or may not be a good thing depending on where you want the resistance.
- Since bands have so little weight they don't automatically exert a downward force. If the band is anchored behind or above you it won't exert any noticeable downward force at all (as opposed to weights, which are pulled down as long as you are working out close to the surface of the Earth).
If you use bands they will "fight you" at extension - where your punch will land - much more than near the chamber. This is probably bad - you probably won't ever be able to generate enough force near the end of a punch to make any difference in its speed - you want to be able to fire out of your chamber quickly.
If you use dumbells they'll want to fly across the room - you'll have to exaggerate the stopping, or pulling back, motion at the end of the punchso you don't throw the dumbells through your TV or wall or whatever.
The medicine ball will resist moving out of your chamber (which is good) and won't make you pull back at the end of the punch (which is also good). The downside to using a medicine ball is that you have to have something to throw it against - a wall, a rebounder, or just a big open space where it won't hit anything important - and you have to retrieve it after each rep, which might be impractical.
Okay, suppose you do decide to load a punch. The problem with throwing punches while holding a dumbell, band, or medicine ball is that you're changing the movement. Effectively, you're practicing a move that's very similar to a regular punch but not quite the same. If the resistance is too large - the band too tight or the weight too heavy - you'll alter the motion so much that you might make yourself worse at punching. In fact, you'll find plenty of coaches who will tell you that any loading will interfere with your skill at the movement. You'll also find evidence that as long as the load is light (think 2-3 lb. dumbells or light bands) you'll see some real benefits.
I'm a big fan of loading techniques with light weights this way, and I'm in a minority. I've seen research both in favor of and against that kind of training. I will say that you want to use relatively light weights - a punch holding a 35 lb. dumbell doesn't even resemble a real punch anymore. I will also say that you should use loaded technique practice in conjunction with unloaded practice. That is, practice punching with weights or bands, then throw punches without any extra load. In my experience I can sort of trick my body into throwing harder punches with the weights and then carry it over into naked practice.
I might do 10-20 punches while holding a dumbell, rest for a few seconds, then throw 10-20 punches without it. Don't ever go weeks or months training while always holding weights - you'll lose your skill at performing the movements. If you can find a 2-3 lb. medicine ball and a way to use it, do so - I haven't managed to find a way or place to do any quality medicine ball training myself.
Don't overuse this technique - it's fairly hard on your body. And let me know if you do try it and what happens. This falls into the category of "I think it works but the evidence is mixed and I might be wrong."