I know nothing about what the 520 recommends. The improvement in capability that comes from training occurs during recovery. Based on your training stress, individual physiology, and riding goals, there is an optimum amount.
It's been said that the large majority of riders ride too much at moderate and moderately high intensities and would be better off riding less at higher intensities and recover more. Recovery allows hitting higher stress during the next session.
Last edited by Looigi; 04-17-16 at 05:23 AM.