Changes

The evidence from the [[Glycogen]] depletion patterns may give some insight into the long run. We see that glycogen is depleted from some fibers before others<ref name="selective"/>. This pattern suggests that some slow twitch fibers are used first, and as these become exhausted, other fibers are recruited in their place. Slow twitch fibers are used first, but over time more and more fast twitch fibers are recruited. This may be one mechanism behind the benefits of the long run; it exhausts the most accessible fibers and therefore trains the other fibers. It is possible that without the long run, only the same, easily recruited fibers are trained. It is also conceivable that by using fast twitch fibers for endurance exercise, the long run will change the nature of these fibers. The level of Glycogen depletion will depend on a number of factors, including:* The initial level of Glycogen stores. ** A higher carbohydrate intake will tend to increase stored Glycogen.** Prior exercise will decrease stored Glycogen. * Carbohydrate taken during the run will tend to spare Glycogen.* The longer the run, the more Glycogen will be used.* The faster the pace, the more Glycogen will be used.The last two factors, distance and pace are considered in my Long Run difficulty calculator that is part of my [[VDOT Calculator]].