Originally Posted by Jay Turberville

Zone 2 is a low to moderate exercise level where you use mostly Type 1 muscle fibers and burn mostly fat but also a bit of carbs. That's why you should be able to hold Zone 2 for very long periods of time.


Speed isn't the issue. The issue is the load you are putting on you body's various energy systems. Maybe that means 15 mph on level ground for you. For a younger and more fit rider, it might be 20 mph. That's where the "conversation" test comes in. It is a way of assessing how hard you are pushing yourself. That's the gauge. Not speed.



Changing terrain makes it harder to maintain a strict Zone 2 intensity. but if you resist the urge to charge up the hills and also keep some effort on the pedals going downhill, you should be able to get close. If you have some kind of HR monitor, it can help you see how much your effort is jumping around. I see you asked about 70% or 80% above. Use the conversation thing as the guide. If in doubt err toward 70% IMO.

Years ago, cyclists might have referred to this intensity a "long slow easy", or "building a base". For someone who is just starting out, and especially for someone in our age range starting out, I think it is important to let your body acclimate to this new stuff. You might also be able to discover more about how well your bike is fit to your body. Good bike fit helps to avoid injury as well. If you go too hard too early you increase the risk of injury or burnout. Riding should be fun (for the most part). You can shift more to "challenging" later on.

You'll find that your two laps will get easy pretty soon. So increase it to three laps when that happens. When that gets easier, start picking a day or two where you go harder. Maybe you go slow the first lap and then the second or third lap you go hard up the hills. The thing about training is that your body adapts to it. And once it does, it is important to increase the total work load if you want fitness to continue to increase. You'll have to spend either more time or shift more of the time you are riding to higher intensity - or both. And when/if you start doing rides 90 minutes or more, that's when you'll want to learn more about fueling before, during and after a ride.