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I like to ride my bike on trips with other people. I notice I can outlast anyone for the long haul but I can never sprint fast for very long like some folks do. Why is that?

You are noticing the difference between speed versus endurance. Muscle power generated for each type of activity differs based on muscle fiber type. There are some muscle fibers that fire just to give you the speed you need. Other muscle fibers come into play when staying power is what you want. These two muscle types are called slow and fast twitch fibers. Another name for these are Type I and Type II fibers.

Some people tend to have more of one type compared to the other. Athletes with the greatest power and speed tend to have more type II muscle fibers. These are the fast twitch fibers. There are even several types of fast twitch fibers. Some are designed to kick into high gear.

You probably have more type I fibers. They are considered "fatigue resistant". Type I fibers are made for activities with lower intensity and longer duration. Endurance athletes seem to have more type I fibers -- this is not due to training but rather from genetic factors.

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