I received a couple of interesting questions about max heart rate (HRmax) this week...
Question: Does declining max HR with age affect max performance?
First, there is no research I’m aware of on exactly this topic as it relates to aging. So this is my opinion only. Something related we do have research on has to do with short-term changes in HRmax due to performance changes (Zavorsky 2000). This is, in a way, a reverse of your question. We know, for example, that as VO2max (aerobic capacity) increases HRmax decreases—as much as 7% according to some research. The more aerobically fit you become the lower your HRmax becomes. And the other side of the same coin is that as aerobic fitness declines HRmax increases. In other words, it is not a foregone conclusion that a decrease in HRmax means a decline in performance. That’s a very common but unsupported view of athletes who are ill informed about the science behind heart rate. They assume a high HR means a high level of performance. Not true. For example, I once coached a cyclist in his 60s with a HRmax in the upper 140s. He broke the US record for the 40km time trial despite his relatively low HR.
But your question has to do with declines in performance related to changes in HRmax. First of all, we don’t know why HRmax changes with age. It appears to, but those studies were done almost entirely using aerobically untrained subjects. Not only had their HRmax changed but they also experienced many other changes with aging such as a loss of muscle mass. And since all the heart does during exercise is respond to the demands of the muscles (for O2 and fuel, primarily), if there's a loss of muscle power the demand will be low so the HRmax will also be low. Maybe. Again, no research.
So does performance decline with age? Definitely. Exactly why that happens is open to conjecture. One of the most common explanations is a loss of VO2max power as a result of the heart’s stroke volume (blood pumped per beat) declining. Why does that happen? We don’t know for sure. Perhaps, among the many possibilities, it has to do with a change in lifestyle as we age. As a young person the athlete may have done highly intense training. But as he/she ages there is often a shift toward long, slow distance exercise with less intense training. We know that such a shift causes a reduction in stroke volume (along with decreased muscle mass—the demand thing again). So the physiological process of aging may not be the culprit at all. It may simply be lifestyle.
My guess is that HRmax has nothing to do with performance. Unfortunately, that thought is totally rejected by athletes who see their heart rates as the end-all and be-all of training. That’s all they know how to measure (“for a hammer the whole world is a nail”). So it’s not a popular position to take if you want to win support for a different way of training—such as power- or pace-based training or something else.
Question: What considerations should a woman in her 50s, for example, have regarding the Fitbit training zones (which are based on set percentages of a 220-Age Max), compared to someone in her 30s (recognizing that the formula may be off due to individual differences, are there age-related differences as well?)
That's correct about such formulas. Research has shown the 220-age formula may be off by +11 to -11 (Robergs 2002), which makes the formula pretty much unusable. A 22-beat per minute range is gigantic. Personally, mine is off by about 33bpm. A guess would be at least as accurate—probably more so.
I believe it’s far better to base zones on anaerobic/lactate threshold HR as it is much more easily determined and less dangerous to discover. It also reflects more about one’s fitness (Faude 2009) than does HRmax. How fast or powerful one is at a sustained threshold HR speaks volumes about the person’s fitness. The gap between threshold and HRmax also indicates a great deal about aerobic fitness. If you and I have the same HRmax but you achieve threshold (go anaerobic) at 85% of HRmax and I do that at 65%, you are much more aerobically fit. I’ll be suffering at 75% while you are just cruising along. That's why I believe threshold is a better metric for setting zones than is HRmax.
Additionally, a true HRmax requires the motivation accompanying a gun to the head. Most people, including athletes, are unable to push themselves hard enough to see a true HRmax. It’s much too painful. They get a moderately high number after a few minutes of suffering and assume that’s it. They’re nearly always wrong as this commonly results in a much lower number than they are physiologically capable of producing under the right circumstances such as a short, all-out race or perhaps a clinical test. And not only that but it’s also dangerous to suggest to untrained people who aspire to set up HR zones that they exercise to a maximal HR. I would never suggest that.
Finally, there is absolutely no reason to compare HR zones. It tells us nothing about either person as far as fitness, health, or performance is concerned. It’s like comparing shoes sizes to determine how fit people are. There is little in the way of an absolute and direct relationship between the two.