Well, perhaps it’s really an awareness of my heartbeat while doing CrossFit. A couple weeks I mentioned that I had purchased some new toys for monitoring my heart rate during my workouts. It is an issue that has captured my curiosity for some time.
The truth of the matter is that I am always conscious of any appreciable stress I place upon my heart. Having had several episodes in the Emergency Room for heart issues over the past twenty years has made me vigilant about paying attention to how I feel.
In the past, this has manifested itself in a fear of any type of exertion. However, at this time I am perhaps in the best physical condition I have been in over 40 years. So my fear is abated, but my vigilance remains.
Over the past few weeks, I have tried to note which exercises or movements in our WODs affect me the most. I have often declared that I hate WODs that are heavily into MetCons. I now have conclusive evidence to support my disdain for 200m and 400m runs and high volume Box Jumps.
Both running and box jumps drive my heart rate past 85% of my maximum heart rate. Rowing is demanding cardio effort for me, but not a big concern. Likewise for jumping rope. So how does one determine what is reasonable? I have located two formulas, a popular one from the 1960’s which may be outdated, and the Tanaka Study from 2001.
Regarding the former, the Mayo Clinic says, “For vigorous exercise, aim for a target heart rate of 70 to 85 percent of your maximum heart rate (MHR). Your MHR (roughly calculated as 220 minus your age) is the upper limit of what your cardiovascular system can handle during physical activity.” For me, the range was from 111-134 beat per minutes.
Several types of medications can lower your maximum heart rate and, therefore, lower your target heart rate zone. By what percentages, God only knows. For me, Beta Blockers and Calcium Blockers fall into this category. Even if it is only ten percent, that would reduce my range to 100-121. The Tanaka Study’s formula is 208 minus .7 x age, or in my case: 208-43.4=164.6. So my Maximum Heart Rate is 7 BPM higher with Tanaka’s formula.