Is it necessary to practice falling on concrete to help prepare for a real life situation and build up endurance?

Training on mats is great as it may allow less risk of injury. However, it may not suffice to your needs of a real situation. For example, when you fall down on a surface that is concrete, you feel a hard impact unlike a mat that suppresses the fall because of the cushion that it has. You may even want to practice the impact of a fall that a concrete gives such as shock. A concrete impact is a shock to the body. It surprises you when you fall down because your brain and blood move out of place. To train for shock-like experience, be very attentive. React to your target practice as soon as possible. This will gain your ability to push through that shock of the ground.

In my experience, doing simple Ukemi over hard surfaces provides important feedback about any problems with your technique. You will boldly notice if your head, shoulder, arm, elbow, hip, knees, or ankles are hitting the floor.

There's no need to roll over concrete, though. The ground under a park's grass is hard enough, and a beach provides several densities of sand.

Yet as other's have said, it's best to polish your technique on the mat first. The fall should "spread" over the surface, with no impact to the head or joints.

If you're used to hitting the mat hard with your arm to take energy out of the fall, you probably need to find a different way, as any form of hitting a concrete floor is sure to cause injury.

Training on firm mats is probably sufficient for learning how to take a fall. There's a slight risk of picking up bad habits, not removing small inefficiencies in the fall (I know that I used to be bad about not distributing my impact along my side in situations where I knew I could fall flat without injury, whereas on wood or concrete, the point of my hip or elbow would be more likely to cause an injury on impact). But, on the other hand, it's usually enough that you'll only come away from a fall with bruises when, with perfect technique, you might avoid any injury, and without any training, you might have broken bones.

Fighting, in general, will be a rare thing. Falling, to be honest, happens more often, but you have to keep in mind that training can lead to more injuries than the average person will ever experience in a fight. I do feel that people ought to try occasional controlled rolls on harder surfaces so that they get used to avoiding pressure points on the surface, but consistently training on a hard surface is bound to create more injuries in the long run than it will save.

No, falling on concrete is not necessary, provided you train with mats as a safety mechanism and you do not rely on mats to protect you from unrealistic techniques.

Use mats for extra safety for techniques that work without mats

Mats provide an extra margin of error while you are learning but should not be used to protect you from bad technique. When you fall, you should be executing proper falling technique by supporting your head while trying to reduce pressure, impact, and the energy absorbed by your body. If you train like this on mats, practicing these elements carries directly into falls on concrete.

Drop knee seoi nage is an example of a technique that only works with mats. The thrower in this technique drops their knees directly into the ground while attempting to throw. While this may not injure the thrower on a mat surface, this is totally inadvisable for the thrower on concrete. The mat is protecting against behavior that relies upon the ground being soft. This should be obvious from using your imagination; no one should need to test this on concrete.

You can choose to train techniques like this in the sport context, but personally I think the punishment your body takes is too much even with mat protection.

You can see how well a person falls on any flat surface

For example:

• Head hitting the ground is an automatic failure. Do not allow the person anywhere near hard surfaces
• Is the impact spread over a large area?
• Is the impact over the large area at the same time?
• Is force directed into the joints (for example, bracing with a straight arm? This one is bad.
• If the fall allows it, is energy directed away from impact? This could be rolling, where you preserve kinetic energy rather than take it as impact, or raising the legs during a rear breakfall to convert the energy of the fall into potential energy.
• If there is a roll, how much energy does the person need to return to standing? If they exert their legs significantly to get up, this tells you they have absorbed the potential energy in their body when falling. It is obviously preferable to avoid absorbing more energy.

Proper falling practice reduces forces regardless of surface

Regardless of training surface, you should be continually trying to improve your falls. You cannot restrict yourself to thinking, "I don't get hurt on the mat, so I won't get hurt on concrete." This is also a general problem with training mindless repetitions, if you never think about what you are doing, especially "the basics", you will not get better.

It may be useful to fall on hard surfaces occasionally to give yourself feedback, but this really should not be necessary. You can feel how you make contact with the ground on a mat surface and adjust to improve your falling technique to support your head, reduce pressure, or keep your frame from collapsing. You still get this sensory feedback while falling on mat surfaces. Did your head hit the ground? Are you concentrating force in your shoulder that makes you uncomfortable? Is a roll continuous? Unlike getting punched in the face, which is very different from not getting punched in the face, falling on mats is very similar to falling on concrete. If you compare two ways of falling on the mat, and one reduces the forces on your body, this will continue to be true on harder surfaces.

Good falling technique works on hard surfaces

It is definitely worthwhile to know you can take a controlled fall on concrete without getting hurt. Some people get the idea that mats are necessary to fall safely. Malicious opponents are, of course, a different story.

Yes, I have taken unplanned falls (solo) on concrete with only superficial injuries. Yes, you will get scrapes from little pebbles on the ground. No, falling on concrete beforehand was not necessary to prepare.

Practicing on a mat is not sufficient.

If you do not progress to harder materials you will not have the feedback benefit harder surfaces provide. You might think you're doing well because it's (relatively) comfortable.

The phrase "safely fall" is nebulous. Will practicing breakfalls on forgiving surfaces transfer to concrete? Of course--you're learning how to fall well. Can you learn to fall better by progressing to harder surfaces? IMO yes.

Yes, the potential for "scrapes and cuts" is much higher--this is obvious. Of course, you're in a fight, so injuries are essentially unavoidable at that point.