Q: “How do you feel about doing plyos in between sets of squat or deadlift?”

A: “The purpose of doing explosive training in between or after strength training is to take advantage of what’s called nervous system potentiation. The theory is that lifting heavy weights brings about more motor unit recruitment, more adrenaline, and more neural drive in general than any other activity. Basically it gets your nervous system really fired up. And by doing explosive training after strength, you can evoke better explosive performance. Of course this does not just apply to any strength training. Obviously if you do exhaustive lifting, it will not improve your explosive performance immediately. There are specific lifting protocols that people have developed to get a potentiation effect. But I’m actually not going to bother to cover those protocols, because I am not a believer in potentiation.

I have two theoretical beefs with potentiation.

1. If you warm up thoroughly, why would your nervous system not be fully up-regulated and able to produce the best explosive performance that you are capable of at that time? Why would you need to lift to get fully fired up?
Of course if you are not really warmed up, then, yes, some non-fatiguing lifting very well may improve your performance immediately. If you have not yet done any high effort activity, you probably need to do something with high effort to get fully fired up. Personally, I used to walk into the weight room cold and start snatching when I wasn’t in the mood for a typical warm up. There are a lot of ways to warm up. But do you need to do a heavy set of 3 squats in order to hit your best vertical jump?

2. My other theoretical beef with potentiation protocol has to do with reflexes. The myotatic stretch reflex plays an important role in explosive performance. The nervous system makes constant adjustments to the sensitivity of the muscle spindle fibers that signal the stretch reflex. When you perform a movement, your nervous system tunes your reflexes to that movement. For example, thorough stretching deadens a muscle’s stretch reflex temporarily. That is why you cannot jump well immediately after thorough stretching. Of course, lifting is not the same as stretching. It does not deaden the stretch reflex. But is a strength exercise going to tune your reflexes ideally for an explosive exercise? Absolutely not.

So we have conflicting theory. What happens in practice?

My final beef with potentiation is that I have never seen it work. Not once. I have tried a variety of protocols with a lot of different athletes, and I continue to keep trying. I have definitely seen performance drop after a strength exercise. Not once have I seen explosive performance improve. In my experience, potentiation does not exist. Warming up exists. Warming up works really well. But once you’re warmed up, attempting potentiation to improve performance is chasing after the wind.

So why do many people in sports training think potentiation works? I guess it is possible that it works for some people, just none of the athletes I have tried it with. But I suspect the real reason is that people rely too much on how they feel. After doing some cleans or some low rep squats, you very well may feel fired up. And that may lead you to believe that your bounds are quicker off the ground or your vertical is higher or whatever. But when you actually measure your performance, you will most likely find that it is the same or slightly down immediately after lifting compared to before.”