|Original paper: Moritani T and deVries HA (1979) Neural factors versus hypertrophy in the time course of muscle strength gain. American Journal of Physical Medicine 58(3):115-130|
Here are three ways to think about muscles. Runners are, of course, in the 'Neural' category. Like I said, skinny runners don't increase muscle mass so much as muscle recruitment.
|Runners have skinny legs, but not always the same kind of skinny. Bekele on far right has bigger quads than the Kenyan in centre. Far left is Bekele's younger brother, also fast.|
What's interesting is that distance runners don't want to recruit ALL of their muscles in one go. This would be bad. A 'perfect' distance run would use a selection of muscles per set of strides, as chosen by your brain. Muscle recruitment is something you only have indirect control over, based on training. If you spend most of your time running it is unlikely you'll induce hypertrophy (muscle enlargement). But extreme mileage may induce some muscle enlargement to prevent injury. It all depends on the training.
|Triathletes are more muscular even though they work longer than runners. It makes sense if you think about it|