I've read a lot about iron hand training on the internet, and there is heavily conflicting advice. I want to try to clear that up here, as I started iron hand training 3 weeks ago and I'm not sure if I should continue. I'll try to make my question as organized as possible.

What I currently do:

This is my daily routine, for each hand:

  1. I punch downward into a bucket of sand with a closed fist so all my knuckles contact and dig into the sand, 300 times.
  2. I strike this canvas bag (filled with sand) with my palm, backhand, blade, and fingertips, 200 times (for each part of the hand listed).
  3. I strike this concrete brick just like in step 2, but 100 times only.

The total number of strikes for all parts of the hand combined is 1500 strikes per hand, daily. I don't hit so hard that it hurts, just enough so it's uncomfortable. By the end, my hands are red, superficially scratched up, and slightly swollen, but NOT painful or bloody.

Why do I train iron hand?

I stopped training martial arts (boxing and jiu jitsu) 2 years ago due to a serious heart condition, which I don't need to go into. Recently, I became very interested in the idea of toughening my hands so they don't hurt when I strike hard surfaces, and so I can break bricks with my bare hands. I also saw it as a way to get back into some form of martial arts training again. Also, on two separate occasions, someone tried to rob me but I was able to flee both times; I was lucky they weren't armed, but if I ever need to strike someone, iron hands would be useful. While I'm not a professional, I am serious about wanting to build tough hands.

My concerns:

I play piano almost everyday, and my job requires me to type on a keyboard all day. I have read online that improper iron hand training, or even proper training, could cause nerve damage over time. My main concern is avoiding this nerve damage, obviously, and other such long-term injuries like arthritis. So far, after 3 weeks of iron hand training, I haven't noticed any deficiency in my piano or typing ability.

Some of the sources I looked at:

Sources AGAINST iron hand:
Sources FOR iron hand:

I know these sources aren't medical studies, but honestly, I couldn't find anything that academic on iron hand training. Mostly anecdotal stuff.

My questions:

What is your advice about iron hand training? Based on what I've written here (and your knowledge), do you advise me to stop it? If not, do you think it's ok to continue my routine above or should I change my routine?

2 Answers 2


I would advise against some of what you are doing.

I sourced the Wolff articles in the "anti Iron fist" post you referenced, and so I won't source again, you do seem to understand the concept.

All that needs to be said about arthritis can be easily digested in this article:

National Institute of Arthritis and Musculoskeletal and Skin Diseases

Essentially, if you damage the cartilage, you are at high risk of osteoarthritis (OA). I have severe OA in the left hip and moderate in the right. I'm a lefty. My favorite kick was the side kick; I was quite good at it, I used it a lot in breaking, sparring, demonstration, and warming up.

The hip is a ball-and-socket assembly, and there is cartilage that surrounds both the ball and the interior of the socket.

I lost the cartilage at the base of the ball and rim of the socket, my doctor surmised, because of all the air kicking I did in practicing taekwondo.

What happens is newton's first law (inertia) - "a body in motion tends to remain in motion until a force acts upon it". Well, in my case, the force that acted upon the mass of the leg moving in the direction of a common side kick was the rim of the hip socket. That caused the deterioration of cartilage at that area on both the ball and socket.

I also lost cartilage at the top of the ball and at the back of the socket, my doctor again surmised, because of all of the bag kicking I did:

When you kick a bag via a side kick, newton's 3rd law predominates: "for every action, there is an equal and opposite reaction". When the bag is kicked, 1st law applies, as the bag wants to remain where it is. But also, 3rd law kicks in too: the bag exerts an equal and opposite force upon the foot, which transfers all the way back to the hip. (This could have been mitigated, but wasn't; and the details of how are out of scope for the question). Needless to say, I screwed up my hips pretty badly. As a lefty, my left hip is severely arthritic, and my right is moderately so.

So what I learned is that my injury was caused by the pinching of cartilage in the hips' ball and socket mechanics.

But the hand has no such ball and socket, and your exercises are not pinching any cartilage, except in the case of your fingertip strikes, and that places you at risk.

Ah, but "injury" is a broad term, and herein is where Wolff's law could lead to OA.

As I noted in my answer to the previous question you linked, Wolff works kind of like this: osseous pressures cause microfractures. The body responds by cementing those fractures in order to heal. The cement it uses is calcium. In bone, calcium exists primarily in the form of hydroxyapatite (Ca10 (PO4)6 (OH)2), and bone mineral is almost 40% of the weight of bone. Bone is a dynamic tissue that is constantly undergoing osteoclastic bone resorption and osteoblastic bone formation. You can read about that in more detail here.

Osteoclastic refers to a large multinucleate bone cell which absorbs bone tissue during growth and healing. Bone resorption is the process by which osteoclasts break down the tissue in bone and release minerals resulting in transfer of calcium from bone tissue to blood. Osteoblast is the same, but in the reverse direction.

In other words, there are specific kinds of bone cells which receive or transfer calcium.

Osteoclasts are responsible for aged bone resorption and osteoblasts are responsible for new bone formation. The resorption and formation is in stable at physiological conditions. However, when the balance is disturbed, bone architecture or function will be abnormal.

OK, so what this all means is, under normal conditions osteoclasts and osteoblasts maintain normal bone formation, until this balance is disturbed - as in injury.

All this is stating what Wolff said, although he did not describe it in these terms since he did not have the science we now have today: he merely observed what we today explain.

Back to you:

When you condition, you create these microfractures which disturb this osteoclast and osteoblast imbalance, and bone architecture becomes abnormal. The result is different for each person, due to the available hydroxyapatite in the body and the amount, duration, and repetition of injury to the hand. But several things are possible: if the microfractures occur in the bones of the hand where there is cartilage (see a description of the hand here) OA can result here if the uneven bone formation injures cartilage.

Equipotentially, bone malformation can cause soft tissue (specifically, nerves) to rub against the malformations resulting in painful or numb sensations.

Now, as to your workout, I have several observations.

Nix the bucket of sand. Not that it's dangerous, but you're wasting time. Just hit a punching bag instead because it's more realistic.

Next, nix the fingertip conditioning. There is a myth that fingertips are used to yank spleens out of the gut or disgorge the larynx out of the throat. That's not what the fingertip is for. You would never use this technique in self defense this way due to the damage it could cause you if you don't do it right. (Which is that you're hand would be rendered useless)

For everything the fingertip is purported to be used against, there is always a safer and stronger body part you should be using instead. (You didn't ask, but the fingertip you see in forms is actually a throw, and the manifestation of the fingertip shows the position of the hand in that throw).

If you want to increase hand strength, as for grappling, then carrying heavy clay pots would be perfectly safe and fine - and realistically appropriate.

Next, piss or get off the pot: break the damned brick or put it in your garden to tell the world you weren't strong enough to break it with palm or elbow. But slapping the thing a hundred times is an exercise in futility. Just use the punching bag. (Then you won't have to admit to not being able to break it). You can punch it, slap it, kick it, or whatever fancies your mood that day.

Last. Don't try to condition the back of the hand. You shouldn't be using it to break skulls, and with no conditioning at all, you can certainly use it to smack the nose or solar plexus to a very effective result. If you condition the backhand, I can assure you that Wolff's and Davis' laws will condemn you to painful hand movements. Your typing days would end, and good luck trying to impress with Mozart's K545 Piano Sonata 16 1st Movement.

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    I would just like to point out that it's not like the amount of hydroxylapatite in the body was fixed. Up to a certain age, the body has no problem whatsoever with building up more bone mass (instead of merely restructuring existing bone). That only becomes increasingly difficult as red bone marrow is replaced by yellow (fatty) marrow. Less osteoblasts produced (which become osteozytes when they finish building bone structure around them), less minerals resorbed through digestive tract...in short, it's not like a healthy, sportive human could not increase bone density and mass. Commented Oct 13, 2022 at 6:22
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    Also, the three main contributors to cartilage damage are lack of full-range motion (parts of the cartilage not experiencing change of pressure and thus not being nurtured which has to happen by being pressed and this pressure being released, repeatedly), ruptures due to non-physiological stress (like strong pulls and pushes that are not mitigated by muscular tension), and dietary habits. Generally, pressure, even huge pressure, as such is no problem. It's what cartilage is made for. Commented Oct 13, 2022 at 6:29
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    This is a pretty comprehensive answer, thanks a lot. I'm convinced I should stop the fingertip & backhand strikes as per your and @PhilipKlöcking's advice. One thing I'm unclear about is why I should revert to punching bag; I've been striking punching bags on and off for 7 years and I've seen the wonderful conditioning of the wrist and knuckles provided by the bag. However a punching bag seems too soft at this point; I can punch it all day. A sandbag or brick seems to be the "next level" hard surface on which to toughen my hands. I'm no expert, so tell me if this is not a logical next step.
    – SNN
    Commented Oct 15, 2022 at 16:00
  • Also, since the discussion has been more about bone rather than skin, I should clarify that one benefit of the bucket of sand is that it calluses the skin way better than a punching bag. For this purpose, I think I'll continue striking the sand since you said it's not dangerous.
    – SNN
    Commented Oct 15, 2022 at 16:07
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    I could be wrong on this, so take it with a grain of... sand, if you will. But bucket sand conditioning was once de rigeur in order to callous the hands, as you say. If you really want to do it the ancient Chinese way, heat the sand, that'll give you calluses. And that's more sanitary. But the ancient Koreans used beans - mung beans, if I am not mistaken - because they have oils that can, well, preserve the skin. I dunno if any if this is true, but I do know you get more mileage out of one punching bag than you get out of a punching bag and a cauldron of hot sand. I'd nix the sand.
    – Andrew Jay
    Commented Oct 18, 2022 at 2:34

From a medical standpoint, I would advise against doing this daily and would also put the same amount of vigour on joint mobility. If you want your body to be both durable and mobile, you need to provide it with the corresponding stimuli. It will adapt functionally automatically.

What you want to achieve is that your structures adapt to a certain stimulus. That takes time. If it is swollen, that speaks for inflammations and a lot of lymph in the hands to get rid of that and breakdown products of damaged structures. Doing that the next day, again, means this can add up. This is what will probably, over time will lead to arthritis and chronic joint pain because it leads to stiffening and contraction of the extracellular matrix in your fascies and that makes it harder to properly nourish the cartilage of the joints so that it ultimately degenerates.

Therefore, the first point will be to give your body 2-3 days between routines, just as you would (sorry, should) with sore muscles.

This directly leads us to mobilisation. Mobilisation includes the activation before the routine by moving all joints (especially fingers and wrist, but generally the whole body), streaking of the hand after the routine (towards the heart!) to activate perfusion and move the lymph, and stretching of the joints on off-days within functional angles (hypermobility in hand joints is not desirable). All this helps to preserve and/or improve the smoothness of fascial structures gliding on one another and moving undesirable metabolic products away, both of which are necessary for a healty extracellular matrix that, in turn, is necessary for proper nourishment of cartilage and healthy adaption of the structures to the stimulus.

That being said: If you punch hard things a lot, you will force your body to form calcaneus structures to protect the joint. There are always small "boney" structures in the cartilage near the joint and if there is consistent stress, part of the cartilage will start to calcify. Trabeculae will eventually form boney calusses. Those will eventually impair joint mobility, no matter how careful you are with the management of stimulus amplitude.

Therefore, you will, over the course of years, impair your mobility and fine motor skills of your hands. There is no way around it. The slapping is different here as there is no direct pressure stress into the joint itself and it will improve bone density (up to a certain age) and the resilience of fascial structures. Too dense a fascial structure can also impair cell and cartilage nutrition that can, in part, be mitigated by the means I described but punching hard things, over years, will definitely have unwanted consequences, even if you do the mitigating stuff I described.

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    Written with the background of (ongoing) training as physiotherapist having read relevant literature and being a certified fascial training instructor. Commented Sep 27, 2022 at 17:08
  • This is a very thorough answer, thank you. Some questions: 1) What is "streaking of the hand" toward the heart? 2) What kind of hand mobility exercises do you recommend for before/after the routine? 3) It seems like the highest risk for motor impairment comes from punching or direct stress into the joints; if I only do punching once per 2-3 days, is it safe to do the slapping motions daily? 4) Would you include the backhand slap and the blade strike in the "slapping" category, as you distinguished it from the punching category?
    – SNN
    Commented Oct 2, 2022 at 1:56
  • And what about the fingertips strike, is that considered "direct pressure stress into the joint"?
    – SNN
    Commented Oct 2, 2022 at 2:10

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