We begin to lose skeletal muscle mass in our mid-20s. But it turns out this loss is mostly confined to our faster (speed and strength) muscle fibers, with our slow-twitch (endurance) fibers resistant to atrophy. Since faster fibers power our race stride, the result is reduced stride length and a slower pace. But faster muscle fiber loss is not a fait accompli. This is a case of use it or lose it. Unfortunately, most masters runners don’t “use it.” That’s because workouts like distance runs and tempo barely touch faster fibers. To recruit 100 percent of your available faster (and slower) muscle fibers—and to teach your nervous system to use them simultaneously and efficiently—you’re going to have to include sprint workouts. And no sprint workout is more effective than hill sprints. The workout:Find a hill that’s steep, but not so steep that you can’t manage an approximation of your normal stride. Sprint uphill for 6-10 seconds at 95% effort, then walk slowly down the hill for recovery. Do 4-8 reps. Next, sprint downhill for 8-15 seconds at a controlled 85-90 percent effort, walking slowly up the hill for recovery. Do 4-6 reps.
Read more at http://running.competitor.com/2014/09/training/fast-40-master-stride_113559#t4TxAv4I3Ve4ZTDX.99