Plyometrics and the women suckered into doing them

Something I’ve noticed over the last year or two is a trend towards including ‘plyometric’ exercises in workouts and other ‘information products’ geared towards women.

For those of you that don’t know, a plyometric exercise is a movement that’s rapidly loaded and then instantly reversed. Any jumping, bounding, or hopping movement falls into this category to some degree.

The idea is that some of the connective-tissue elements of the muscle complex can store energy from being rapidly loaded, and this energy can be reversed to provide a more powerful movement. The appropriate analogy here is a rubber band – when you land from a jump, the connective tissues around your muscle act in the exact same way. There’s a quick, powerful stretch which stores the energy.

This is labeled the stretch-shortening cycle (SSC), and it’s one of the most widely-studied phenomena in sports science. A lot of sports have a need for the ability to absorb and rebound force, and plyometrics have been repeatedly demonstrated to be very effective at training this ability.

The key thing to remember is that typical strength training doesn’t train the SSC; what plyometrics train, and how they train it, is a completely different thing from strength training. I’m reiterating this so you don’t get it in your head that it’s just a different kind of muscle exercise. Plyometric training is a dominantly neuromuscular effect – there’s little to no actual effect on the muscle fibers.

Now, don’t let this fool you. Plyometric work is still taxing on the body. Your joints and connective tissues still have to build up the ability to absorb high impacts. Even though you may just be using body weight, that can still add up to a significant force due to physics voodoo. That force doesn’t last long, mind you, but that’s not relevant – if it exceeds the tolerances of your tissues, then you’ve just injured yourself.

All that said, you still see plenty of women doing plyos and swearing by them. Women that aren’t playing any sports and supposedly have only physique goals. Claiming that plyos ‘gave them great results’ and ‘had them really working up a sweat’. Oh and the best one, that plyos really gave their muscles a ‘lean and defined’ look.

I’ve ranted before on why you can’t use ‘it worked for me’ as any kind of valid excuse. The bit about working up a sweat is a red herring argument: you can work up a sweat from doing housework. That doesn’t mean it’s training your body in a way that is moving you towards your goals.

As for the claim about ‘lean and defined’, I’ve been saying for years now that plyos don’t involve the muscles to any meaningful degree. Well the latest Journal of Strength and Conditioning was nice enough to provide some concrete evidence in study-form.

Muscle adaptations to plyometric vs. resistance training in untrained young men.

The purpose of this study was to compare changes in muscle strength, power, and morphology induced by conventional strength training vs. plyometric training of equal time and effort requirements. Young, untrained men performed 12 weeks of progressive conventional resistance training (CRT, n = 8) or plyometric training (PT, n = 7). Tests before and after training included one-repetition maximum (1 RM) incline leg press, 3 RM knee extension, and 1 RM knee flexion, countermovement jumping (CMJ), and ballistic incline leg press. Also, before and after training, magnetic resonance imaging scanning was performed for the thigh, and a muscle biopsy was sampled from the vastus lateralis muscle. Muscle strength increased by approximately 20-30% (1-3 RM tests) (p < 0.001), with CRT showing 50% greater improvement in hamstring strength than PT (p < 0.01). Plyometric training increased maximum CMJ height (10%) and maximal power (Pmax; 9%) during CMJ (p < 0.01) and Pmax in ballistic leg press (17%) (p < 0.001). This was far greater than for CRT (p < 0.01), which only increased Pmax during the ballistic leg press (4%) (p < 0.05). Quadriceps, hamstring, and adductor whole-muscle cross-sectional area (CSA) increased equally (7-10%) with CRT and PT (p < 0.001). For fiber CSA analysis, some of the biopsies had to be omitted. Type I and IIa fiber CSA increased in CRT (n = 4) by 32 and 49%, respectively (p < 0.05), whereas no significant changes occurred for PT (n = 5). Myosin heavy-chain IIX content decreased from 11 to 6%, with no difference between CRT and PT. In conclusion, gross muscle size increased both by PT and CRT, whereas only CRT seemed to increase muscle fiber CSA. Gains in maximal muscle strength were essentially similar between groups, whereas muscle power increased almost exclusively with PT training.

Now this is an interesting result. The statistical power is relatively weak, with a total sample of n = 15, but there’s some illumination here in any event. What’s telling to me is the gains in gross muscle size in both groups, whereas only the resistance-trained group showed any gains in muscle fiber. What that suggests is that something else was creating the size gains – but it wasn’t the muscle itself.

We have to be a bit careful here as well since untrained subjects means that getting off the couch will make them grow, but this is still telling – if plyos were a causal factor, you’d expect that they’d have created actual fiber hypertrophy. They didn’t.

My two cents? I think that plyometrics are being subbed in for high-intensity cardio in most of these fad programs. Think about it. The routines I’ve seen have been a lot of jumping, bounding, hopping, and so forth – which counts as high-intensity exercise. Keep up enough effort, or keep the rest times short enough (or both), and you’re going to be winded. You might even be working up a mad sweat.

Here’s the secret, though. That’s no magical plyometric effect. In light of the above study, and the simple fact that it’s been long known plyo work affects the elastic connective tissues, how could it be? Occam’s razor cuts away all that because there’s simply nothing to support it. The simplest answer that fits all the facts is that these ‘plyo’ routines are just subbing in as another form of high-intensity cardio.

I put that in quotes because from what I’ve seen a lot of stuff out there claiming to be plyometric is really…well, not. It’ll be really nothing more than a step class with some impact stuff. This is hardly a surprising move from an industry built on taking science out of context and jumping on bandwagons, but it’s something to be aware of – especially if you’re a woman and having plyometric exercises marketed at you as some new magic.