Note that this question is a mirror of this one on skeptics.se. Due to the lack of answers at the time of writing, I thought here might be a good place to seek more. Feel free to answer in either.

There is a fairly wide spread belief within the Aikido community that all joint locks and some throws (or rather their break falls) are harmful to children. I am looking for actual evidence-based medicine research1) on the medium to long term harm to the development of children's body. Adults can practice these locks for decades without any adverse effects as their bones, tendons, and so on are all finalised. On the other hand, kids bodies are still growing and might be much weaker to resist strain. That is the common view within the Aikido teaching world. I am looking for actual medical evidence of such.

For example, here are two common locks used in Aikido: kote gaeshi (supinating wrist lock) and kote hineri (rotational wrist lock). The former twists the wrist anti-clockwise, the latter clockwise if applied to the left hand.

kote gaeshikote hineri

Both can be very painful in the short term but once the lock is released the pain disappears. The goal of locks is to either cause the body to move in a predefined way (to set up for a throw) or to pin the target so they are disinclined to resist the pin. The locks are safe to practice on adults: they do not cause any short, medium, or long term damage if applied correctly. Of course, they could do grievous damage if applied in haste on unsuspecting targets. But damage is not the goal. Otherwise, we could not train! To be fair, pain is not the goal either.

1: Answers based on either anecdotes or hearsay will attract down votes.

  • I hope this does not break the asking for medical advise as I am not asking for advise, I am asking for medical research. However, this might break the "asking for reference material" which tends to be frowned upon. It works well as a skeptic question. Not sure if it fits here... Commented Aug 7, 2014 at 8:57
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    You're asking for medical data, not advice. Big difference. The difference is between asking "what is <X>" and "should I <X>" Commented Aug 7, 2014 at 12:16
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    Have you considered asking a medical professional? Commented Aug 7, 2014 at 14:04
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    @JuannStrauss: Yeah but WHY!!!. Curious mind want to know! ^_~ Commented Aug 8, 2014 at 7:01
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    @ jacefarm I rejected your edit on the simple basis that we are not a forum. We are a Q&A site. It might seem trivial but is actually a really important distinction to make. Commented Nov 1, 2017 at 8:53

2 Answers 2


I don't have medical studies, but I can at least point you in the right direction of what to look up, based on kinesiology and adult biology.

Tendon Plasticity

"Tendon Plasticity" (Viscoelastic tissue) - Tendons work somewhat like rubber bands - they have some stretch to them, but if you over-stretch them, just like a rubber band, it ends up loose and destabilized and doesn't ever come back to normal:

If the recovery time between successive exertions is not long enough for a given force and duration, the recovery will not be complete and the tendon will be stretched further with each successive exertion.

(If you want to go further in-depth, check out Chapter 2 of Tendon Injuries Basic Science & Clinical Medicine, which goes into the issues of mechanical loading and stress failure points for tendon tissue)

Joint locks often use the limits of a person's muscle/tendon length to get the "lock" - the wrist lock being a prime example - and you'll notice from doing wrist locks, some people have a lot more range of motion before they have to go with it - that's a matter of having more muscle/tendon length.

Regularly stretching (or having it stretched for you, via joint lock) can result in that permanent tendon deformation and joint destabilization.

Tendon Strengthening

Too much load, or too much stretching, is bad. Too little load, is also bad. The key to strengthening tendons is months of regular resistance/load, high rep or long holds, to increase tendon thickness:

Chart of Tendon Therapy vs Injury based on load/stress levels

What this means about adults vs. children

I'm not a pediatrician, but based on what I know above, the argument for kids to not do joint locks has some solid basis:

  1. Adults have had more tendon strength from natural thickening of tendons based on long term loading, whereas children it is easier to overpower their tissue strength.
  2. Tendon overstretching is effectively permanent damage (short of surgery and stapling), and opens you up for other injuries for the rest of your life

There's also a 3rd factor which is that joint locks rely either on end length of tendons, or compressing joint capsules, which, if done with too much force or repetition, permanently damages cartilage.

If you want more science or specific studies, I suggest looking for people who are versed in pediatric sports injuries, as you're likely to find more relevant information there.

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    Well, OP asked for medical science, so I gave it to him. Even then this is a very watered down version. I can break it down in more layman's terms, but I've found most people tend to think you're "making things up" when you simplify past a point, even if it's true as far as function goes.
    – Bankuei
    Commented Aug 8, 2014 at 20:05
  • As the OP, I think there could me more to this but as it stands, it's a great answer. Many thanks! Commented Aug 9, 2014 at 14:36
  • My training is in kinesiology & physical therapy, so I have a baseline level of the science behind it, but not specific to children. If you do find deeper science sources, do you think you could link it back in this question? I'd be happy to see more myself.
    – Bankuei
    Commented Aug 9, 2014 at 16:04
  • @Bankuei: I have asked several members of the medical profession. I am waiting results. Clearly, as soon as I have something, I will post it here and on skeptic. Commented Aug 14, 2014 at 11:00
  • @Bankuei - Admittedly it has been a long time since my kinesiology degree, but tendons connect muscle to bone and ligaments connect bone to bone. I am aware of the destabilizing effect of stretching ligaments, but was not aware of the same effect in tendons? In addition, all your links are either broken or lead to infected sites.
    – JohnP
    Commented Oct 24, 2017 at 22:39

I'll give an answer from a completely different point of view. A child who undergoes the stresses of joint locks are subject to the manifestations of injury as described in Bankuei's answer, I have no doubt. But the injury to a child is not relegated to the child, and for different reasons:

Children who engage in joint locks should be considered from both nage/tori point of view, as well as uke's point of view.

As nage, inexperienced children are at more risk of hurting (a minor) uke, because they are not experienced in the technique as well as recognizing when to stop. I often see youngsters perform what they think they see, and overexaggerate the technique; they do it too fast, and don't recognize the signs given by uke to stop. Either they don't recognize the sign at all, or they recognize it too late. For this reason, I see many a martial art school - not just aikido, but other styles as well - have very young and/or inexperienced kids do many of the techniques with tegatana - an open hand. Without the grip, there is virtually no chance of injury, since uke can slide out. Of course, this changes the dynamics of the technique, often to the point it is not useful or practical. But the exercise for these kids at this level is less about practicality, and more about the shape of the technique, an issue to deal with which is outside the scope of this question.

On uke's side, children sometimes cannot exhibit pain: either they don't know how, or they don't react in time. I have seen first hand an instructor bring a child into sankyo, and (accidentally) not realize the child bent over with tears streaming out of his eyes because he was too scared, too startled, or inexperienced to indicate he was in pain. A child being held in kotegaishi can be more easily seen in pain from a facial grimmace than one who is in sankyo, due to the fact that they are more or less facing each other.

Well, these aren't really medical considerations or studies, they are simply observations lending to the idea that children engaging in join locks and wrist bends should be watched with particular care.

However, there is more. When a child is injured - even if not noticeably so - they can have injuries show up later in an x-ray for an unrelated injury. For example, a child sustains a minor spiral metaphyseal fracture because of a joint lock, sankyo, or kotegaishi in class last week might experience minor pain which might not even be reported, or might be mistaken from injury sustained from football or hockey that same afternoon. Then this week, he falls off his bike (whether or not that fall is related to his fracture), and gets an x-ray which shows the other underlying injury. Bike falls, hockey, and football don't usually exhibit spiral fractures, while child abuse often does.

Now the parents have a lot of explaining to do - sometimes to child protection services.

Yes: an instructor who is not careful with his minor students can wrap his student's parents up in a child protective services investigation.

Here are some sources which may be of interest which describe fractures relating to child abuse. Note they are somewhat graphic and unsettling to those not experienced with the subject, caveat lector:

Diagnostic Imaging in Child Abuse: Non Accidental Trauma

Fractures Caused by Child Abuse

Does this happen often? No, not at all, or else the Surgeon General would be calling for a war on Aikido. But this subject comes up from time to time as a defense when a case goes to a formal investigation and/or court. Parents who are innocent and are accused of abuse in these cases must consider all of the activities their children have done which might have caused the injury. It is not uncommon for horseplay among peers, sports, and martial arts to be blamed.

So, hopefully this isn't outside the scope or spirit of your question. But the subject should cause people to think hard about the training their children get: the injuries their children can receive, the injuries their children can cause, and the (legal) injuries an injured child's parents can receive.

Having said that, there are diseases classified for repetitive use injuries in children, seen here:

Overuse Injuries in Children

Well, you DID ask for studies. In this article, the recommendations and articles are from none other than the American Academy of Orthopedic Surgeons, hardly a group to challenge their recommendations for sources.

I would venture that the US National Library of Medicine and National Institutes for Health falls under a similar category, although, they do source their articles:

The child and adolescent athlete: a review of three potentially serious injuries

Peri-epiphyseal and Overuse Injuries in Adolescent Athletes

As in the AAOS and NIH, the concern here is harm in growth plates and growth spurt. In both articles, the issue is of repetitive action, not the legal issues as mentioned before.

I guess I'm throwing in this one for no other reason than to show that, while the content of the article has nothing to do with Aikido or joint locks, the implication is that with proper and repetitive training, injuries can actually be reduced:

Nine year longitudinal retrospective study of Taekwondo injuries

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    Bounty was awarded. Many thanks indeed for taking the time to answer the question. Commented Nov 6, 2017 at 8:40
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    @Sardathrion - Thank you for your kind words!
    – Andrew Jay
    Commented Nov 6, 2017 at 16:25

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