At what point prior to a marathon does training stop impacting race performance? In other words how long does it take for various training to impact performance? I'm guessing that general aerobic runs, LT, and VO2 work takes diffferent amounts of time to produce results. I see marathon tapers typically starting 2 or 3 weeks out from a race. Understand that part of this is resting the body, but how much is that doing certain work over that 2 to 3 week period just not beneficial for race performance? Thanks in advance for any insight on this.