[halfcat]

>Or did people's being healthier cause them to be runners?

There was another study that showed that people who take up mixed martial arts in their late 40s are healthier than people of the same age who only walk [1]. No word on whether genetics plays a role.

[1]http://en.wikipedia.org/wiki/Herschel_Walker

[thesz]

Martial arts are 1) interval training in disguise and 2) strength endurance training in disguise.

Kata practicing is an exercise in explosive power over long period (several minutes), thus strength endurance training.

All MA training I attended interspersed action with rest. Thus interval training.