Kids Fitness Physiology
by Dr. Kwame M. Brown
This article will by no means be an exhaustive discussion of the evidence, but I look forward to elaborating as we get responses.
Installment #476 in things I keep hearing people say:
“You should lock out the joints at the end of a (bench press, squat, etc)”. The joints need stress to get stronger.”
By this logic I should do the following:
1. Beat my head against a wall to protect myself from brain injuries (After all I am putting my cranium under much needed stress, right?
2. Yell at kids all the time and berate them to improve their self esteem
I think we can agree that just because something needs to get stronger, this doesn’t mean that all stress on that thing is good!
I could just simply say that this is wrong, but it’s better for all concerned (especially kids) if we address the real problem. The real problem is a combination of a lack of understanding of how joints work combined with a pretty loose application of terminology.
First, let me explain (quickly) what locking out a joint does with regard to hinge joints. What happens is what’s called a “screw home” mechanism. The smaller bones lock into place with the larger bone. This is true at the knee and elbow, which aren’t identical but are very similarly constructed (two small bones connecting to a larger bone).
Second, let’s talk about what most people think they are talking about when they say “lock out”. What they really mean (and I think maybe some don’t realize it) is “lock out the lift”. This involves full joint extension, a completely different thing than locking out the joint. This is healthy and should be done on a regular basis. The difference is that the muscles are involved in extension. They are not involved as much in a lockout, meaning therefore that the joints are at risk.
Lock out your knee joint by letting the joint go as straight as it can. You will find that the muscles are quite lax. You may also feel that you have to expend some effort to unlock the knee. What do you think is happening inside that joint? You are likely wearing away the lubricating structures.
This means most of the stress is being borne by the joints, in a way that is rubbing the very structures responsible for lubricating them. Yes, is true that there is more contact in a knee flexed position, but the difference is that the stress is on the muscles!
Now extend the legs all the way as if you are pushing the floor away. Extend your upper body. The muscles are engaged, the joints are getting good strengthening stress, instead of the potential wearing away stress.
Most people who lock out their joints during a lift are trying to get a rest. Well, if you have an external weight, the stress / force has to go somewhere! Where, you ask? The stress is likely travelling to your spine.
A member recently asked me did I have any evidence that locking joints out will cause injuries in young athletes: I don’t. Do you want to know why?
Because proving this would require me to purposely put kids fitness at risk to prove my point.
But we can certainly extrapolate things from what we know about biomechanics (a discipline that applies the laws of physics to the tissues in the body).
Now, if you want to lock out your joints, I say go for it. But please don’t instruct kids to do this for a couple of reasons:
1) They don’t understand the nuanced difference between lockout and extension. They will likely lock the joints when you tell them to lock out the lift. Case in point: Every time I have seen someone instruct kids to “lock out”, I have seen a hyper extended lumbar spine. Every time – because it is the natural reaction.
2) Now the second part of the logic is: Well, why is lockout bad? The reason: Most agree that those with hyper-mobile joints should avoid locking the joints, because it promotes further laxity. Guess what young kids often have? Yes, that’s right, you guessed it: hyper-mobile joints! Guess what else they have issues with: Control over their muscles. Did you guess that one too? Now, why would we want to take that individual and instruct them to lock out their immature joints? Furthermore, why would we need to?
And to the detractors of my statements here, I will say that you are the prosecution here, not I. In the face of a risk to a body part, the onus is on the one taking the risk to prove it’s safe. Where is your evidence that this is a necessary thing? Where are the people that are getting injured and not realizing their potential just because of not locking out joints?
Kwame is just one of several international superstar Youth Fitness Specialists who will be taking the stage at the 2nd Annual IYCA International Summit next month in Louisville.
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