What do eating chips with queso and cardio have in common? Two very important things. First, if you have too much of it, your body will be mad at you. If you’re lactose intolerant, the queso will really mess you up. If you’re lactate (the metabolized form of lactic acid) intolerant, the cardio will. But for real, controlling how much volume you’re logging is one of the most important things you can do for injury prevention. The second thing they have in common is you shouldn’t double dip.
Double dipping while training for a sport or activity is when you use a movement from your sport for resistance training. So this would be like instead of doing bench press and rows to work out your arms for tennis, you just swing a weight tennis racket. I see people do this most often at the cable machines at the gym because the cable gives them the freedom to do any movement they want with added resistance. If you swing your tennis racket hundreds or thousands of times at practice during the week, then go to the gym and do essentially the same thing just with weight, you’re going to be pushing into overtraining and a possible repetitive movement injury. There are other flaws as well.
A big one is that movement carryover is velocity dependent. This means that if you train at a certain speed, you get better at that speed. But you don’t really have much carryover to other speeds. So if you’re using weight, you’re obviously going to go slower. Which is great if your goal was to slow down your swing or stroke. Except that no one wants to get slower and less powerful…
Another flaw is that you’re likely missing much of the benefit of using weights or resistance to work out on your strength training days. Most people’s goal is to improve their power – whether it’s how fast they hit the ball, how far each step propels them, or any other sport movement. Strength training is meant to improve your overall capacity. It builds a bigger engine with more horsepower. Practice and sport-specific drills are what allow you to access that improved power. So using a cable machine to work out in a swing pattern using 20 lb. is not going to improve your overall strength near as much as doing movements like the bench press and pull-down, where most people could lift in excess of 100 lb. Let your strength training be your strength training, and your sport be your sport. Get the most of each of them, and no double dipping!
There are 2 exceptions. First, some people use a weighted racket/club/bat to prime their nervous system immediately before a game so that their normal equipment feels lighter and they can swing faster. This is fine because the volume of this primer is so low. The second exception is to know when to break the rules! After all, what about sled sprints or even hill sprints (the hill being a form of resistance)? These are classic tools for athletes. So can you do these types of training that are similar to your sport? Yes, but it’s important to realize that these significantly contribute to your training volume. You can’t just throw them in randomly. Make sure you consider their contribution to your overall training volume and, if you’re new to sprints, add them in slowly. If you’re truly interested in gaining overall strength, you should also have multiple strength exercises. This is because any one exercise, even a compound movement like sprinting or squatting, will be limited by its weakest link. So if you do hill sprints and your quads are burning (your limiting factor), then you will probably want to make sure you do some deliberate hamstring, calf, core, and other muscle group work.