That's the truth! I learned it earlier this year when I made my first assault up GRM. Didn't have very many miles in my legs since the winter lay-off. When I came back down the hill, my hamstrings were "killing" me. Could hardly walk. They "hurt" for several days until finally I forced myself to get back out there on a bike and do a ride. It was hard for me to believe, but the pain/soreness went away ... totally.