Impact of Sprints on Effectiveness of Zone 2 Aerobic Endurance Rides 

Sprint intervals can also increase MCT1 lactate transporter, but results vary wildly with the individual.

What I like with CTS is structured explanations! This coach is no exception and he goes very simple with all the stuff!

I don't know why so many people don't get it or don't want to get it. I've been using polarized training for years, which only uses 3 zones, and I do the vast majority (80-90%) of my training in zone 1. Once a week I go out and hammer some hill repeats or some sprint intervals, but that's it. Endurance zone, zone 1, or zone 2 for those who use 5 zones is just that, and if you can't keep your testosterone in check for the benefit of your overall training, then don't complain when the 60 year old guy drops you because his overall aerobic fitness is greater than yours. By the way I've had that happen on so many occasions I can't even count. Guys think they drop you on a group ride because they went hard for a few minutes, and they look back and see you on their wheel just tooling along and they can't believe it. Then, when they've burned their matches, I come off their wheel and leave them behind. I train to improve my overall health, but I'm not out there to waste my time. I want to get the best results from all the time I spend in the saddle. Also, I don't want to get burned out because every ride is a sufferfest and I no longer look at my bike as a fun thing to ride, but more as a torture device. Keep your ego in check, train the long hours in zone 1, do your intervals once or twice a week, and you'll see the vast improvements.

By going over z2 for any duration, you're activating the glycolitic pathway and switching off fat burning and it takes time to switch back.

If he has time to ride 2 to 3 hours after sprints, he's not time crunched. Wouldn't the sprints pre-fatigue the fast twitch fibers, which would make them act like slow twitch later in the ride?

4-5 out of 10 with some 6 is too high for z2! 3-4 is where you want to be and don't spend all your time at 4! 60% FTP will work for most people. If you're on a trainer with limited time 65% FTP is fine if you keep it strict and watch your HR, it should not go above 180 minus age and also shouldn't stay dead on 180 minus age for long!

I would think it would be optimal for a time crunched cyclist to do sprints during zone 2 sessions If the sprints are kept below 10 secs at maximal power with around 10mins between them they have no noticable effect on your ability to hold zone 2 power at a zone 2 heart rate and the zone 2 has noticable effect on the sprint performance You can effectively hit a max power session and a zone 2 session at the same time The question becomes can the body adapt to the two different stimuli as effectively as it can to doing them separately

Bs.. boys feel free to throw your short sprints here and there during your long ones