Going into my third summer of cycling, been spinning indoors all winter, feel like I have a good base. Uploaded my Garmin data to Strava, analysis showed that I've done virtually NO work in the anaerobic zone, so I figured time to add interval training to the mix.
I'm 46, so 220-age = max heart rate of 174, so anaerobic zone should be somewhere north of 168 bpm. Today, did first attempt at intervals on bike. Pushing for as hard as I could, as long as I could, legs searing, chest exploding, I found it VERY hard to get my heart rate even past 155, and I only briefly went over 160. Most of the time during the hard intervals I was in the 149-153 range. What does this mean?