While I've not got shins 'o' steel I've always questioned the sort of conditioning that require people to hit bricks/tree/cement/steel etc. In MT we achieve conditioning by use of the heavy bag and the thai pads. Both of which are soft by comparison to any of the things I've listed above. If my understanding is correct the conditioning benefit from the heavy bag/thai pads comes from bone ossification - that is growth and improvement in bone density - due to repeated impact on the heavy bags. According to what I've read about ossification - it happens from the inside out.. so that bone becomes stronger by adding new bone material from the inside of the bone not from the outside. Even when shins are conditioned from much time on the heavy bags/thai pads it doesn't mean they're indestructable and it doesn't mean it doesn't hurt to check an incoming kick. It does and will always hurt... usually what people are seeing when someone checks a full blown kick is not conditioning a fighter that is immune to pain... but a fighter that knows how to keep a poker face in a fight to put the other fighter off his game... the fighter checking the kick will still feel pain... even if he's got the increased pain threshold that fighters have. Getting out of the way through good footwork is always the first option in a fight and decent trainer will tell you this. It's interesting because we don't do forearm conditioning per se in Muay Thai... yet when we hold the Thai pads for someone that's kicking... we are essentially absorbing much of that impact with the forearms. So I'd imagine there is some conditioning that takes place. If a kicker is a strong kicker I often end up with bruises on the forearm even when holding the Thai pads. It's not impossible to break someones forearms with a good solid roundhouse kick - as was shown in the 2005 Kings Cup in Thailand when a French fighter had no choice but to check his Thai opponents kick with his forearms and resulted in a broken forearm. For a bit there when we got different weather systems moving through I'd always be able to tell in advance... much like how old people do... it was because my shins would tell me. I'd had a rough year in the fights so my shins had checked a fair number of kicks..... but couldn't really be avoided - and so I focussed on a better massage/diet regimen and back to the heavy bag/Thai pads and it doesn't seem to happen anymore. But I think if you don' stay on top of it with rehabbing it... like any trauma it will effect you as you get older with more regularity. In terms of steel shot.. it's interesting in the bags of shot that I've seen they've got a fair bit of give in them... so maybe it's not all that disimilar from hitting a heavy bag or Thai pads. From both Boxing and Muay Thai we spend a huge amount of time punching so if anything I'd expect to see problems in my hands... but since we wrap properly and take care of them properly (massage etc.) I've never seen problems in my hands/wrists/shoulders from the Boxing and the Muay Thai. Anyhow - that was my long winded 2 cents.