niall

 

Ukemi in judo and aikido are slightly different but I don't think either are tough on the body if you do them properly.

In aikido the ukemi is often forward - escaping into position for another attack or defence. So it is possible to do it softly and silently.

In judo the ukemi is often straight down. And in judo you learn yoko ukemi - a fast sideways ukemi - as well as ushiro (back) and mae (forward) ukemi and mae mawari (forward rolling) ukemi. That's the judo terminology.

Also in judo the thrower sometimes takes you to the mat as part of a dynamic throw so an aikido-style ukemi crossing your legs could be very dangerous (imagine hitting the tatami legs crossed with a 100kg tori landing hard on top of you).

Speed is an interesting point. Sometimes you don't have time to turn your body into a mae ukemi. A lot of beginners do an ushiro ukemi against kote gaeshi. Then as they become more experienced they naturally progress to doing a mae ukemi. But sometimes you just don't have the time - and you're back to doing ushiro ukemi again!