I would sometimes exceed my MHR on my Polar when really cranking up the treadmill for speed intervals. I'd heard from one coach that you could add 6 to the basic 220 minus age formula for when you were on a treadmill as compared to being on my bike. I think the following paragraphs made more sense to me though ...
"It's possible that the maximum heart rate theory that's widely used may not be as accurate as we've come to believe.'
"In an article that appeared in the New York Times on April 24, 2001, this very subject was addressed. Back in 1970, two doctors preparing for a meeting wanted to determine how strenuously patients with heart disease could exercise. They gathered information from ten studies using people of all different ages who had been tested for maximum heart rate. They plotted the subjects' maximum heart rates on a graph, drew a line through the points, and determined that the heart rate maximum seemed to be, on average, 200 beats per minute (bpm) for a twenty-year-old, 180 bpm for a forty-year-old, 160 bpm for a sixty-year-old, and so on. Based on these findings, they came up with the equation that MHR = 220 - age (in years). However, many subjects in these studies had heart rates that varied widely from the formula. Many variables also weren't accounted for. The tests used in determining this formula were far from perfect as well. Somehow, though, this equation, 220 - age, became entrenched in cardiology departments, fitness centers, and textbooks. According to Dr. William Haskell, one of the doctors who observed this relationship: "The formula was never supposed to be a guide to rule people's training." '
"So, what does this mean for you and others whose heart rates don't seem to fit into this equation? First, you need to discuss your observations about your heart rate with your primary health care provider. Let him or her assess any other conditions that could affect your heart. Barring any problems, you could focus your training in two other ways. One is by using a scale termed, "Rate of Perceived Exertion (RPE)," in which you rate how hard you feel you are exercising. It's recommended you assign a number from 0 to 10 to rate your exercise intensity, 0 being no exertion and 10 being most difficult. A major benefit of this system is that it gets you in touch with how you feel while you're exercising. Also, you don't need any special equipment or devices. If you already have a heart rate monitor or enjoy counting your beats, you can use RPE along with your heart rate. Try comparing your perception of exercise intensity to how hard you actually are working. This method will help you establish a new frame of reference for your exercise intensity.'
"Another useful measurement of fitness is how quickly one's heart rate falls when exercise is stopped. (Don't just stop completely — that can be dangerous.) This measurement is probably best done with a heart rate monitor. Check your heart rate while at the very end of a vigorous routine. Begin cooling down, and then check your heart rate one minute later. As a person becomes more fit, her or his heart rate returns to resting faster than an unfit person. This is called heart rate variability. Recent studies have shown that people whose heart rates fell less than 12 beats per minute after vigorous exercise had four times the risk of dying in the next six years compared to those whose heart rates dropped by 13 beats or more! Most healthy people's heart rates will drop about 20 beats in a minute. You can measure progress in a fitness program by improving the number of beats your heart rate goes down in one minute. Tracking this can help you chart the effectiveness of your aerobic training.'
"The moral of the story here is that we all don't fit into a neat package (or equation, as the case may be).'