Tuesday, August 17, 2010

Slow Twitch, Fast Twitch

Yesterday I ran 5 miles of easy trails with strides in the morning. I felt good and wanted to do more. Instead, I channeled all that energy into crossing things off my dreaded errand list. I got a lot done! In the late afternoon, I pumped up the tires and brushed off the dust on my road bike. The poor thing has been neglected since early Spring because mountain biking is just so much more fun! It's kind of like comparing road running to trail running. On foot or on wheels, roads are boring and trails are fun.

I was curious to see how my mountain biking fitness would translate into road biking fitness. When I have road biked more in past years, I usually start off in the Spring with an average of about 15 MPH on these hilly country roads and get up to 17 and 18 toward the end of summer (I'm no bicycle racer). Yesterday I rode around the time of day when everyone was coming home from their jobs in Portland. The roads around here are only a single lane in each direction and most don't have paved shoulders. So I did a particularly hilly loop around the back roads of Porter and South Hiram to stay away from traffic. I felt fast! It seems that mountain biking the technical single track at a slow pace (necessary for me and my bike to stay upright) has actually made my legs very strong! I averaged over 17MPH on yesterday's road ride and wasn't pushing hard at all.

This is a lot different than the way trail running translates into road running. When I only run on single track trails I get very strong, but very slow. I guess it all has to do with fast twitch and slow twitch muscle fibers. To run fast you have to turn over fast and use those fast twitch fibers. And fast twitch fibers are like so many things in that you have to use them or lose them. On the bike, I can power through on the road or trail without a fast cadence (although you're supposed to turn over fast for efficiency on the road bike). In other words, On the bike I can compensate for my lack of speed with muscle.

Not so with running. I miss running fast. That is why I have started incorporating strides on my runs and have been moving off the technical single track and onto the tote roads and even the pavement for some of my runs. I even have plans to start a little speed work in a few weeks. This will be too late to help me for my goal race at Pisgah, but I might try to race something shorter later in the fall. Mostly, I just want to feel fast again, whether I race or not.


  1. I do nearly all my training runs on the road with a jogging stroller. I run between a 7 - 8:30 minute mile (depends the day/workout). I could never run that on tech trails! And to be honest I wouldn't want to. I enjoy trails for the challenge. I think as I get older I am worried less about speed and more about experinces.

  2. Laurel, I really appreciate your post as I need to be reminded that trail running is so much more vigorous than street running so I can't expect the same results. I sometimes get frustrated over my lack of speed on the trails but love the high I get from them so just have to accept that I can't run nearly as fast on the trails as I do on the streets.

    Good for you with the increased speed on your road cycling. It just goes to show how cross training really is a win/win situation.