beautiful, girl. reporter: the key of this paradox being kayla s determination and a nerve disease called multiple sclerosis. four years ago this one-time elite soccer player began to lose feeling in her feet and legs and was told that m.s. would likely leave her unable to move someday, period. i was mad. i was really mad. reporter: but kayla took that mad and decided she was going to run while she still could. although starting out she was, how fast? i was kind of slow. average, at best. reporter: that s patrick. the coach who took her on and watched her get faster and faster. fastest yet. reporter: and who was always there at the finish. here s why. when kayla runs, the natural increase in her body temperature temporarily gives the m.s. the edge again. in the last part of races, kayla has lost all feeling below her waist. she lacks the control to slow to a stop. the reason her cries are so