I bike once a week on a stationary...so it's completely flat and I control the resistance completely. I go with very little resistance and keep a high cadence (about 90-100 rpm). I guess I do 13 miles in about 40 minutes or so, I can't really say for sure, as I don't place a lot of emphasis on the distance:time. I'm pretty sure that a couple of weeks ago I did a half-marathon on the bike and it was right at 45ish minutes.
@Shue, 3:10 would give me a hard on. That's next after I hit 1:30.
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