# Max HR not reached

I’m 5’6. 54kg. Do HIIT 4x week & spin/combat 2x week. My Max HR (220-45=175bpm) but I NEVER reach it. Ever! My RHR is 44-45bpm. VO2max is 48.9. I push myself to absolute max but I just don’t get into my MHR zone. What am I doing wrong?

• Why do you want to reach your max heart rate zone? (This is a leading question. The optimal working zone is below your max heart rate, somewhere in the 70-85% area).
– C. Lange
Feb 23 at 19:35
• So I should be working in 70-85% of my max heart rate? Based on the formula of 220-45(age). 70%-85% would be 122bpm-148bpm. Is this what I should be aiming for? Feb 23 at 20:10
• What do you do wrong? You concentrate on whatever your gadget is showing you, instead of the exercise. Feb 23 at 22:24
• 220 - age is a very bad myth. The only way to know your max HR is to do a maximal test in a lab. Otherwise you need to use predictive models which have large variances.
– JohnP
Feb 24 at 14:44

The maximum heart rate formula is just a predictive model. It aims to give an approximation of the average maximum heart rate for people by age, and it certainly isn't guaranteed to be accurate for individuals.

Here is what actual individual max heart rate measurements look like. The dots and circle are individuals, and the lines are the predictive models. You can see that in this population, the max heart rates for people in their 40s vary from around 160 to 200.

Source for image: Tanaka, H., Monahan, K. D., & Seals, D. R. (2001). Age-predicted maximal heart rate revisited. Journal of the American College of Cardiology, 37(1), 153–156. https://doi.org/10.1016/s0735-1097(00)01054-8

If you really want to know what your max heart rate is, just use the maximum value you've ever measured when pushing yourself to your absolute max.