I did get a little help from some lucky shade in defining my calves 
So this is my first "real" mtb. It has a cute story: my dh bought it off a woman who had gotten all fired up at work about riding Birken with her colleagues, a very popular mtb event, 93 km long. They'd gotten a good deal on bikes, she trained 100 km altogether, did Birken, her knees hurt and she didn't want to ride anymore...
I've had a rigid mtb for years and mostly used it for commuting and riding on gravel roads. I've tried trails a few times, but mostly just got mightily frustrated at being bounced off roots, rocks and the like. But when this lovely thing turned up on my doorstep I had to go try it on a real mtb trail
Lesson 1: racing pedals (ie. one-sided) are useless on a trail, unless you plan on never unclipping. 
Lesson 2: mud slows you down. A lot. I actually learned that after a few tries.
Lesson 3: the nice smooth surface of a large puddle doesn't mean the bottom of it is equally nice and smooth... I tried just charging through a calf-deep puddle to avoid the gnarly root-mess on one side, and ended up getting my bike stuck in the very middle, tipping over and hitting a submerged rock with my knee.
I even managed to do it on the way back too
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett