It's also clear that the basic foundation of the last month should be intensity, not volume. Running lots of miles and fitting in last-second long runs would further stress already wounded muscles. It's better to let muscle fibres recover by gradually reducing their weekly dose of impact forces. Although at first glance the principle of running intensely during a recovery period seems peculiar (why wouldn't rapid running also stress the muscles?), it works well for several reasons. First, research has demonstrated that intensity is a much more potent producer of fitness than mileage. Since you are trying to boost your fitness dramatically in the last month, intensity is the more attractive option
-Marathon training: planning a 30-day running programme
MY COMMENT: Interesting!