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If you are in the strength training profession, be it medical provider, coach or athlete, it is likely that you are aware of the the Jefferson Curl. Perhaps more than any other exercise, the Jefferson Curl conjures strong feelings and is shrouded in controversy. On one side you have medical professionals yelling about how loaded flexion is bad for you and on the other you have social medial influencers - often with a proclivity for being controversial - touting how this exercise is not bad for you. Here we go.
As you all know, I am a medical professional. Instead of starting out by attacking the Jefferson Curl as foolish, I wanted to start with the fact that Jefferson Curls do work; if the didn’t, you would not hear so much about them. If so many people are talking about how great them make their backs feel, it must have some utility. I don’t think one can dispute the fact that they do make your back feel better. I myself have felt these effects. The question is not about its efficacy, it's about the mechanism of action. The answer has to do with the every popular posterior chain.
You wouldn’t have to spend much time in a weight room or at a strength training conference before you heard someone talk about “training their posterior chain” or the importance of the posterior chain. While there is no doubt that having a highly function and powerful posterior chain is important, essential even, the strength training profession tends to over-emphasize its development. We bias our exercise prescription for it and we encourage technique that overloads it. Glance at any strength training program and you will notice that more than 50% of the exercises target the posterior chain - squats, deadlifts, cleans, swings, snatches, RDLs, good mornings, the list goes on and on. Because of this proclivity to (over) emphasize the posterior chain, athletes often have over-active erector spinae.
This over-activity produces lower back pain both directly and indirectly. It directly contributes via a “tight back”. Lower back pain has many causes, a tight back is one of them. It contributes indirectly via axial compression of the spine. (*Axial compression is squishing the spine, similar to putting a heavy sandbag on your head.) Increased axial compression indirectly causes lower back pain via the intervertebral disc, what I would consider THE most common cause of lower back pain. When axial compression is increased, there is a concomitant increase in the pressure within the disc, aka intra-discal pressure. The greater the intra-discal pressure, the greater the strain (tension) on the annulus fibrosis (the collagenous rings that surround the nucleus pulpous, (a toothpaste-like liquid in the middle of the disc). Strong as they are, these fibers can only handle so much tension. Once that limit has been reached, they start to stretch and distort. They don’t like this so much. Once they have stretch too much, it causes pain. As an experienced clinician, I will tell you that the disc causes the vast majority of lower back pain. So, the posterior chain indirectly causes lower back pain via the intervertebral disc. Enter the Jefferson Curl…
Because it places the spine in a flexed position, the Jefferson Curl is a powerful way to reduce the hyperactivity of the posterior chain. Given that traditional strength training tends to over-emphasize the posterior chain and over-activity of the posterior chain produces lower back pain, any reduction of the pathological load the posterior chain places on the spine will “help” reduce lower back pain…potentially. This is why it’s effective. Via this mechanism, with some athletes (likely young), I have no doubt that it makes the back of the athletes using this movement feel better.
The problem with the Jefferson Curl is the position in which it puts the lumbar spine, flexion - loaded flexion at that. Loaded flexion is the main mechanism of injury for the disc. There are 4 main factors that contribute to damage to the disc: 1) the length of time one is in flexion; 2) the magnitude of the flexion; 3) the load; and 4) the speed of the flexion (momentum).
Jefferson Curls are essentially slow, loaded, potentially heavy, maximal segmental flexion of the spine, most notably the lumbar spine. If you load this exercise up, you are maximizing 3 of the 4 factors involved with injury to the disc. This is why the medical profession cringes when we see athletes performing this exercises.
While maximal flexion is potentially dangerous, it all comes down to load. If you crank up the weight on this exercises, because it “feels good, I think you are testing your luck and just asking for an injury to the disc. If, however, you keep the weight light, this exercise might actually be useful. Yes, I said that. What I did not say is that this is a “phenomenal exercise that you should all be using in your training/programming”.
Jefferson Curls may be an effective way to reduce hyperactivity of the posterior chain, but it brings with it a high risk of injury. I’m not sure it’s worth it, actually, I’m sure it’s not. If the goal is to reduce hyperactivity of the posterior chain, there are tons of exercises out there that are at least as effective at Jefferson Curls to accomplish this that do not carry with them the high risk of injury. (A topic for another time.)
If you insist on using this controversial exercise, here is what I suggest:
1) Keep the weight light. While the spine is in a dangerously flexed position, I think load is the main culprit. Keep the weight around 1/3 body weight, 1/2 body weight at the absolute most, and you “should” be okay.
2) Program this exercise at the end of your training session. I don’t like the idea of massively reducing the activity of the posterior chain. While I do not like over-emphasizing the posterior chain, I realize its importance in many of the classic lifts we all use (e.g. back squats, cleans, and snatches). Over stretching/relaxing the posterior chain will hinder the athlete’s performance and may increase their risk for acute injury to the disc.
Final thoughts:
While the Jefferson Curl may be an effective way to reduce the potentially pathologically pathological force of a hyperactive posterior chain, and see its potential utility to this end, I think there are better ways to accomplish this - ones which do not bring the same risk of injury. So, if you insist on programming/using Jefferson Curls in your trining, you’d better know why you are using them and why you are not choosing another, equally effective exercises instead.
- Dr. Richard Ulm