hi im quite new to the conditioning and would like some advice ,ive been doing press ups on my knuckles since istarted karate 4 years ago but only last year strted breaking ive only done it once and only 6 tiles ,january this year ive bought a straw makiwara and also a spung wall makiwara and i always use a heavy bag the problem i have is the middle knuckle on my right hand really protrudes much further than my first knuckle so when i strike unless i kink my wrist im only striking with the middle knuckle ,my first break my middle knuck swelled quite a bit and im thinking its perhaps when i broke i hit with the middle knuckle only ,is there anything i can do or should be doing to correct this any advice welcome ,i know a lot of people do not like conditioning but its something i want to do as ive got quite a few breaking sessions coming up this year and also my next grading i need to break
many thanks

The hand is a very complicated "machine". You can't just beat your hand against something hard & expect that you fist will automatically become a sledge hammer. It's obvious that you're not "conditioning" correctly.

Ask your sensei because he can SEE what your mistakes are.

From my personal training, I never trained like you described. I punch & kick Impact Pads regularly to develop my "shock" not brute strength.

Well, my first reaction to your question is concern. You are attempting to train for something without any real understanding of the methodology. And the fact you have put out there, you are basically changing your body to match the technique, not adapting the technique to your body. A fundamental mistake that will result in injury.

First, if you are kinking your wrist to make contact with 2 knuckles, you will either lose power or injure your wrist. You need the wrist to be supported correctly otherwise it will bend. Energy seeks the path of least resistance, if it can bend the wrist, it will. If it can't it will continue until it finds the weakest outlet, elbow, shoulder etc. This is one of the reasons when you hit correctly you transfer the power without injury to yourself, and when you hit incorrectly, you hurt yourself.

Moral, use good technique.

The harder the object you hit, to more important this becomes. A mitt or a bag has give and absorbs a lot of the energy, makiwara less, a wall much less.

As for your knuckles, your middle knuckle will injure for 2 reasons. One, because force is inversely proportional to the area of contact, meaning if you hit with one knuckle instead of two, it's absorbing double the force. (it's also transferring double the force so that's good). This is easy to demonstrate in person but to give you an idea all you have to do is slap yourself in the chest, then using the same amount of power poke yourself in the chest. Because of the much larger area, the slap doesn't hurt much if at all, where the poke is much less comfortable. Same thing is happening to your middle knuckle when it's out there all by itself.

There are all kinds of ways to toughen up the callous on your knuckles to reduce injury, but in my mind that is trading one 1 injury for another. You can punch sand, or pebbles and be all old school Kung Fu, the makiwara would help as well...but as the previous poster says you should ask your Sensei. Hopefully he knows what he's talking about (many do not sadly).

Another, and IMO more sane approach is the break with your hammer fist or palm heal. The added area of impact and natural padding between the striking surface and the bone will go along way to protect you from injury, and you can still break a lot of stuff.

I came up in the ITF so we broke alot. I would caution you to be careful with your hands. I have a mangled middle knuckle on my right hand from improper alignment on a break. Actually the index finger knuckle should take about 80% of the impact. If the middle knuckle is taking the brunt of the impact you are having an alignment problem. One knuckle over and you have a broken hand. Be careful.
Keep it up man. I have fond memories about breaking in my past. It is a fun way to test focus.

keep it up, Mark

For learning karate what should be the initial condition of the body? I mean only people who are physically fit can learn it?

The beginning condition of the body shouldn't be the a stumbling block. That is the great thing about martial arts. Most classes will only ask that you try your hardest. Everyone is on their own personal journey. We aren't keeping score.
In the beginning you might think that there is no way that your body can be trained to execute the advance techniques that upper belts perform.
I have witnesed people in terrible shape start working out and in time become very profitient in the arts. If you are thinking of joining a class I would encourage you to do some research on the schools in your area.
I like the martial arts. There is a disipline there added with the physical activity that I couldn't get in any other activity I have attempted.

good luck, Mark