I think there are a lot of younger runners who also become overly fatigued from a lot of VO2max, but are in a program that has an aggressive approach and does a lot of hard vo2max workouts on a very regular basis. My son's program races weekly and has a weekly vo2max workout (ex. 6x800 at 3200 pace), along with another threshold workout. Half way through the season, his legs are heavy and his times slow. His fastest times are always coming off base, when doing thresholds and tempos with just a little bit of speed.[/quote]
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The weekly 6 x 800 should actually be run at current tempo pace and the second threshold workout would be replaced
with a short, sharp workout like 8 x 200 at current mile pace if there is room to fit it in......the 6 x 800 at tempo pace will yield excellent results......