As you're on a bike, it would be a lot better to get a power meter, take an FTP test and then ride 20% above your FTP to properly ride in an anaerobic zone. You

As you're on a bike, it would be a lot better to get a power meter, take an FTP test and then ride 20% above your FTP to properly ride in an anaerobic zone. You'll quickly find that long anaerobic exercise isn't possible Heart rate is too affected by other factors like hydration, temperature, stress etc to be reliable.