When you run at a faster pace, your feet spend less time touching the ground as you move forward. This slight difference means that your muscles are activated differently. According to a study published in the October 2005 issue of the "Journal of Sports Sciences," your pace affects the activation of the muscles in your glutes, hamstrings, quadriceps, shins and calves. The study notes that the faster you move, the more your muscles are activated. The difference in muscle activation is obvious when you compare the physiques of long-distance runners with that of sprinters. Long-distance runners tend to look thin and underdeveloped, whereas sprinters have more muscular physiques.