Vigorous exercise?

Count Iblis

http://online.wsj.com/article/SB1000...243027174.html

Doesn't sound like vigorous exercise to me at all. How on earth can biking at a speed of 10 miles an hour be vigorous exercise?

berkeman

I think they are just setting an arbitrary limit to make it clear that it shouldn't be leisurely biking. But yeah, 10mph on pavement with a good road bike is pretty leisurely. 10mph in the dirt on a MTB can sometimes be taxing, though, depending on how soft the ground is.

I think they are trying to list activities that elevate the heart rate and respiration rate significantly. The gardening one threw me a bit, but there have been some ditches and such that I've dug that elevated my CV rate...

denverdoc

Agreed, as to why 10 mph--IIRC drag is pretty much negligible from 0 to 10, and then it gets quadratic. Likely a Reynolds number phenomenon.