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I've always loved triathlon because it forces me to continue trying new things. New things are scary! Change is uncomfortable. That is why I make myself embrace it; it keeps me young. I'm not an "adrenaline junkie" by any means; I just love that point when you become comfortable enough in a new sport/hobby/profession (insert favorite new thing here) to shift from "Oh my God, I'm going to die!" to "Oh my God, this is so fun!"
I've owned a mountain bike for a few years now (read: owned, not used). It sat for a long time in the previous owner's basement. After procuring my Trek (aptly named "Rocky"), she then continued to sit, this time in my garage. I continued finding excuses not to ride her. "I'm tapering," I don't want to get injured before my A race," "I don't know how," "I don't have anyone to go with," and then, "I don't have anyone to go with who isn't going to take me over some cliff and kill me." True, I took her out for a few measly spins on simple, flat pedals, jumping off and walking more times than riding. In the end, I preferred to hit the trails in my running shoes rather than on wheels.
I'm still in the steep learning curve part of mountain biking but I get a little better each time I go out. It's getting more and more fun as I gain confidence. Here's what I've learned so far:
1. It's a lot more technical than road biking. You shift your position around. A lot. Weight forward, back, side-to-side; all depending on the terrain.
2. Objects look bigger than they actually are. Usually, I freak myself out and either jump off or hesitate, resulting in a fall (normally without injuries). When I can actually relax and go over the rocks (or other obstacles), they're usually not nearly as big as I've built them up to be in my head. Hmmm. A perfect analogy to life here? 'nuff said.
3. You fall a lot. But unlike in road biking, most falls are at slow speeds and on softer terrain. Usually, I just pick myself and keep riding (unlike on the road where you end up in the hospital or worse).
4. You go a lot slower than in road biking but still get a great workout. I like to gauge my workouts by time out on the trail, rather than mileage. I still am gasping for breath and dripping with sweat at the end. It's great for building power, short bursts of speed, and anaerobic endurance.
5. Your cadence is much slower than in road biking and you rarely get out of the saddle to climb. (Instead, shift your weight forward and bend from the hips so your chest is almost touching the top bar. For downhill, shift weight back behind the saddle).
6. Relaxation is key. When I'm tense, every shock bounces me around, threatening to unseat me. When I'm relaxed, the shock is absorbed by the bike and not me. I can get out of the saddle and let my the vibrations transfer to my feet instead of my core. Then, my head is looking up and forward, where I want to go, instead of down, bug-eyed in widened fear at the huge rock I'm about to bounce over.
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--proudly displaying my injuries after taking a tumble.
--bruises from my death-grip on the frame the day after mountain biking. Rookie mistake.
There's a great instructional video on mountain biking by Ned Overand (http://www.amazon.com/Performance-Mountain-Biking-Ned-Overend/dp/B0002J8PME).
Other great sites for beginners:
http://www.outdoor.com/skills/mountain-biking-skills/basic-mountain-biking-skills/
http://www.extreme-adventure-sports.com/mountain-bike-technique.html
http://www.myra-simon.com/bike/trail.html
http://www.mountainzone.com/how-to-articles/category.asp?cid=100145