[dundarious]

For longevity, AFAIK you don't need that degree of cardiofitness, and walking is sufficient. It's possible to reduce longevity through running too fast, for example. Cultures that have noted longevity are not known for having an exercise culture either, rather they are moderately active throughout/several times a day.

Unfortunately I can't find my sources right now, so take that as just something some guy said on the Internet.

[randcraw]

Two guys. I've seen a lot of confirmation from medical researchers that moderate rate walking (easy to converse meanwhile) does provide some aerobic benefit as well as improve strength and balance. Faster walking (difficult to converse) delivers more aerobic benefit still, to the extent that for folks over 55, it's suggested that fast walking is sufficient to get aerobic benefits.

And if that's not enough, you can always speedwalk.

[novok]

Walking up hills is the gentle-to-the-body challenge increaser, and makes sense since even tribesmen of 50k years ago needed to walk up hills and mountains regularly.