Pros: Arras Citadelle to Roubaix, 156.5km, Cobbles
Me: 52km Z2, 3 x 5 x (1m Z3, 1m Z5, 1m Z1), 5m RI
The pros are riding a mini-Paris-Roubaix, featuring 15 cobbles sections. The dynamics of a cobble section are (very roughly) a fast run-in as the main guys want to be among the first few onto the section, the section itself is ridden at a hard pace and then things ease up when the section finishes. For me, that translates to 15 bouts of a minute Z3, a minute Z5 and a minute Z1, split into 3 groups of 5.