For sedentary people, I would say "At least a reasonable emergency." Preferably an unreasonable one. Near-falls, getting stuck, whatever, people get in situations where they get hurt because they were too weak or fat or slow to protect themselves or their kids. I've had two falls where catching myself on my way though the floor saved me from probably very serious injury. My brother's alive because when he was a kid he had a trail biking accident, seriously cut his head, and his uncle picked him up and ran three miles for medical attention rather than walking and having him bleed to death. I think lots of people have scenarios where they could have been hurt if they hadn't reacted appropriately, and where others would fail due to their physical condition.Strong for what? That’s always my question.
Anyway, Steve's obviously out there in some respects, but he's definitely put a lot of time into combining yoga mobility with strength, and his perspective is probably worth considering.