another option wrote:
I also am a middle distance guy who struggled throughout XC in college. Another thing that you could think about and that I found helped me to run my best cross races was race strategy. I found that I ran my best races when I went out conservative and then worked up after 2 miles or so. I talked to my coach and we started running all my races this way, I found that the positive feelings of always passing people helped me to stay focused and positive myself during the whole race which had been a problem before. It also left me with enough in the tank the last mile to use some of my middle distance abilities and really hammer home well. You may want to look at this sort of strategy and discuss it with your coach.
Different things work for different people. This approach works for a lot of mid-distance guys who are running college cross.
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The OP has experimented with higher mileage and not benefited from it. While aerobic work is important, it need not (all) come from running; for instance, instead of the long run on Sunday, some mid-distance types have done an endurance tetrathlon (or triathlon or pentathlon), e.g. 20-30min run, 20-30min bike, 20-30min elliptical, and 20-30min pool (swim and/or water running). Your heart gets that aerobic work; your legs avoid the pounding.
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To a mid-distance guy, the opening pace in cross is going to feel very easy; it's *maintaining* the pace that's hard. Related to that, it's tough for a lot of MD runners to maintain mental focus throughout a 25-30min race. In some contrast to the advice quoted above, what works for some is to run the race in a more fartlek fashion, say by doing this:
1) Going out at a good pace, maybe for 600-1000m, then easing back from it *before* you're forced to do so;
2) Finishing strongly, say the last 800-1200--"No one can live with me here!";
3) In between, running well in spurts of 1-2mins, verying with the course--if you have good turnover, for instance, just try to keep a moderate pace as you go uphill, but then crest the hill well and let yourself roll on the downhill, staying perpendicular to the slope instead of leaning back. Or if there's a point ~500m away, saying "I'm going to pass these three guys by the time I get there." In other words, give yourself smaller chunks to focus on, while accepting that the focus will not be constant and that you'll get some "breathers."
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It's a bit too late for this year, but a lot of MD guys seem to benefit from doing a set of 200s or 400s or 600s, about once a week in their summer training. Shouldn't be a gut-buster workout--you don't even have to time the repeats--but it gives you a chance to turn the legs over and feel like the fast runner you are.