Hi, college junior here. PR's of 31:48 and 15:12 for 10k and 5k. I have also run 8:47 for the 3k and 4:29 for the mile, but those PRs are 3+ years old. Since I have gotten to college, my coach has had me doing high mileage and lots of tempo-type work, with the only speed being done within the last month of the season. I doubt I could run a 60 sec 400 with a gun to my head right now. Also, all the slow mileage has made my stride feel much less powerful; I almost feel like my fast muscles have atrophied. My coach tells me that strides and hill sprints are enough speedwork to keep me in touch with fast twitch muscles, but I often feel so sluggish and slow doing these that I wonder if I am getting any benefit. Is it possible that nearly all of my fast twitch muscles have converted to slow twitch? In my last XC race, I stayed aerobic the entire time, but could not get my legs to move faster than 5:10 pace...