Discussion: zone 4?

This looks like a classic z4 workout to me. Would you have been able to continue doing several more of these at the same speed?

nope was pretty tired at the end and super happy when the cool down happened. I thought it was zone 3 because of the heart rate.

Sounds like z4. Typically your HR only goes into the zone for ~ the last minute. Assuming your zones are correct, if your hr doesn't go into the zone then you could either be not pushing hard enough ( doesn't sound like it) or you haven't recovered from previous workout or pehaps getting sick. maybe give me a call