Interesting research concerning running economy and muscle damage from researchers (and runners) at Georgia State: http://www.ncbi.nlm.nih.gov/pubmed/24531437
Last year, a colleague and I tried to collect some pilot data assessing ankle jerk/patellar reflexes and running economy following a brutal eccentric workout (drop jumps and leg press). The reflex results were unclear and a broken treadmill threw a wrench into our running economy analysis...
What implication(s) could this have for athletes?
It would be wise to avoid muscle damage (downhill running, eccentric resistance training) in the 2-3 days before major competitions. Could cross training that elicits less muscle damage than running (cycling, elliptical, swimming) in the days immediately prior to a race increase running economy?
Of course, if you have a race coming up that has a substantial amount of downhill, you may be able to attenuate some of the muscle damage that would be attained during the race by consistently training on downhills. The repeated bout effect would make you more resistant to muscle damage.