Originally Posted by atwl77

Z2 definitely feels too easy at the beginning, and there's always the temptation to push harder especially if other people are passing you, or you're on some familiar road going 30km/h and think "hey, I can usually go around 33-34km/h here". But keep at it and your legs will thank you for it at the end of the day (or the next day, for multi-day rides).

But... I consider 4 hours too short for Z2. Z2 is called your "all day riding pace", but 4 hours isn't riding all day (unless you're specifically doing base or endurance training) and I typically go Z3 for these.

Besides the overall zone, you also need to pay attention to specific riding efforts at various parts of the ride. When people say ride a Z2 (or Z3), it doesn't mean you're consistently at that pace like a robot all the way. There'll be short climbs where you push a bit more, downhills, some long straits where you occasionally want to push a bit (or recover). For longer rides, as someone mentioned above you want to avoid burning matches and going Z4-Z5 (or more), even if it's just a little 30-second power-up-that-little-bump-of-road, for example. Those things add up. Even standing starts from traffic lights, you want to ease in instead of rushing back up to your comfortable speed.

But regardless of the actual riding pace, you need to listen to your body and throw in some blocks of active recovery (i.e. Z1) if you're starting to feel it.