Testing your max heart in 30 seconds

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It’s widely known that the old “220 minus your age” equation isn’t very good at determining your maximum heart rate. So what’s better? A new study from the University of Hawaii, recently published online at the Journal of Strength and Conditioning Research, tested nine different prediction equations, along with a surprisingly accurate way of determining your true max heart rate in about 30 seconds (sort of).

The study looked at 96 volunteers with an average age of about 22. That’s the first caveat: these results are only relevant for people in that general age group. And the volunteers were phys ed students, which means they’re likely to be more physically active than the general population.

I’ll start with the less interesting part of the study. Here’s the data from the equations they tested for all 96 subjects:

“CHRmax” is basically the “real” max heart rate. So they conclude that Gellish2 (191.5 – 0.007*age^2) and Fairbarn (201 – 0.63*age for women, 208 – 0.80*age for men) are the most accurate for this population. Maybe so — although trying to fit a function of age to data taken from subjects who are all virtually the same age seems a little weak to me. But the bigger problem is something they themselves note in their introduction:

The most commonly used Fox equation [i.e. 220 minus age] has been reported to have an SD [standard deviation] between 10 and 12 b/min. Thus, when estimating HRmax using the Fox equation, approximately 66% of the population should fall within +/-10 beats of the actual HRmax, but for the remaining population, the actual HRmax could differ by as much as 12–20 b/min or more.

I don’t know why they’re saying this is a property of the Fox equation. This is a fundamental property of human physiology: heart rate varies between individuals, so ANY equation based only on age will be more than 10 beats off for at least a third of the population. So for practical exercise prescription purposes, who cares which equation is more accurate?

Much more interesting is the way they calculate HRmax. They did the usual graded treadmill test to exhaustion to determine “true” max for 25 of their volunteers. Then they tested two other protocols. One was the Wingate test, which is basically 30 seconds all-out on an exercise bike. It was a crappy predictor, more than 10 beats below the actual average.

The second test was really simple: they had the subjects sprint as hard as they could for 200 metres on a standard track, with a running start. That’s it. And they measured their heart rate during the sprint. The average from the treadmill test was 190.0; the average determined from the 200m sprint (which takes a little over 30 seconds for most people) was 190.1. Pretty darn good.

Now, there are some caveats. The fact that the averages were close doesn’t mean everyone got identical values on the two tests. In fact, the “mean absolute error” was 5.8 bpm — but since the treadmill test was higher about half the time and the sprint was higher the other half, the averages balanced out.

Also, they didn’t do just one 200 sprint. They actually did two, but separated by at least three days. Each individual sprint, on average, underestimated the HRmax. The first sprint produced an average of 187.9; the second sprint produced an average of 186.3. So this test wasn’t as reliable at getting right up to HRmax. But when they gave people two tries, most people seem to have nailed at least one of the tries. Presumably if you gave them five tries (spread over several weeks), you’d get an even higher average max value. Of course, the same is true of the treadmill test: not everyone will execute it perfectly, so if you do it twice, the average value will probably creep up a bit. But what this study tells us is that, for this group of subjects (and remember, these are young phys ed students who are capable of sprinting 200 metres all out without pulling up lame halfway), give them two cracks at sprinting 200 metres and then take the highest heart rate they produce, and you’ll have a very good estimate of maxHR. It’s a heck of a lot cheaper and quicker than a graded exercise test — and a billion times more useful than any equation based only on your age.

14 Replies to “Testing your max heart in 30 seconds”

  1. “but since the treadmill test was higher about half the time and the sprint was higher the other half, the averages balanced out”

    That would seem to indicate that even the treadmill test doesn’t necessarily give your true maximum heart rate.

  2. I’m going out to the local HS track tomorrow to try this one! How could such a simple test have only been “discovered” in 2011? I guess it’s too simple. No expensive technology involved or needed. Another reason age related HR guesses are inaccurate: they assume that aging=lower HRmax. More and more evidence suggests that this just isn’t true at all in individuals who maintain physical fitness.

    Dave L.

  3. All of these equations under-predict my demonstrated safe heart rate in tough interval training and especially in races. Talking to my running colleagues I find that my experience is commonplace.

    I’d read of an alternative means of establishing one’s “maximum” heart rate (caveat – this test requires that one has a very high level of underlying fitness, as the test is quite strenuous):
    Run ten very tough uphill repeats with the absolute minimum recovery time between each repeat. During the tenth and final uphill repeat measure one’s heart rate (THIS measured value is probably the best estimate of one’s actual MHR).

  4. @Scott: Yes, the treadmill test is also imperfect: it’s always possible that the subject stops early for some reason (e.g. just not feeling good that day), or is dehydrated or sick, and as a result doesn’t quite reach max. This data suggests that a single treadmill test is still more reliable than a single 200m sprint, but no better than two 200m sprints.

    Another point worth bearing in mind: the only reason most people really care about HRmax is for “exercise prescription.” We want to follow training plans that tell us to run at, say, 80% of HRmax. But these percentages aren’t fundamental constants of nature! The training guidelines have been developed based the experience of subjects whose HRmax was determined with a progressive treadmill test. So in that sense, the treadmill max is the “true” value we’re interested in — and the actual physical max, which might be a couple of beats higher on average, is irrelevant.

    @David: Cool, let us know how the test turns out (and how it compares to any other estimates you have)!

    As for whether HRmax really does decline with age, I thought that was pretty well established — but I’m certainly open to hearing about other evidence. I’ve had two VO2max tests done, eight years apart, and the HRmax registered in the second test was eight beats lower than the first test. My fitness was the same — if not better — in the second test.

  5. I’m just back from the track 3 x 5 x 200meters, 5 minutes rest between reps and 200 meter cool down each sprint… I was tired and slightly asthmatic but not sure I really maxed out. My HR maxed 171, my 220-age is 177 an my usual recorded max is 183.

    So the best test is really to just check your max over time on your hr watch, that should also be a good measurement (after all, this is 2011…)

  6. The problem with a workout like 3 x 5 x 200m is that you’re not going absolutely all out in the first few intervals, and by the end of the workout you’re too fatigued to reach your true max (i.e. your legs hold you back before you reach your heart’s limits). That’s why treadmill tests are “progressive” — they start slowly and gently ramp up the pace so that you’re not sprinting until the last stage of the test.

    The authors of this new study argue that the 200m sprint works because it’s long enough to fully exhaust your anaerobic energy sources. But that requires the single sprint to be truly all-out, not just part of a workout. You have to be highly motivated to run that single interval as if your life depended on it.

  7. I have to confess that until I read this, I thought that 30s was not long enough to achieve maximum HR. Is it possible that older athletes might require a longer duration of effort? Also, this piece seems to imply that maximum HRs are more stable than I had supposed. How do they compare in that respect with minimums?

  8. Did they test the HR at the end of the intervals or during them (with some kind of equipment)?

  9. @Phil: I had the same reaction: I would have maintained quite firmly that you need ~10 minutes to take a proper max. We should bear in mind that this is just one study — and of course, it’s possible that the researchers were really bad at administering the graded treadmill test (e.g. failed to properly motivate the participants) and thus obtained a falsely low value. But assuming the results are valid, then consider me as surprised as you.

    We should also bear in mind the subject group, and not assume that it applies to other ages and groups. As a guess, I would speculate that the protocol might be more likely to apply to older athletes than to sedentary people of any age: you have to have to some reasonable level of fitness to be able to deliver maximal exertion for ~30 seconds. It’s also interesting to note that the Wingate test — essentially 30 seconds of all-out cycling — didn’t perform as well as sprinting. This could be because running recruits more large muscle groups than cycling — but it underlines the fact that simply breathing hard for 30 seconds isn’t enough.

    Re. stability: my understanding is that HRmax is stable and relatively repeatable (other than the gradual decrease with age); i.e. the assumption is that scatter in repeated measurements is caused by the limitations of the measurement rather than changes in the actual maximum. Unlike resting heart rate, HRmax remains essentially unchanged as you go from unfit to fit and back. (There are some papers which hint that the training of elite athletes may cause their HRmax to get slightly lower, but the evidence for this is circumstantial at best.)

    @John: They just used ordinary Polar HR monitors, which record the heart rate throughout the interval. From what I can tell, they just took the highest value recorded.

  10. @alex “Unlike resting heart rate, HRmax remains essentially unchanged as you go from unfit to fit and back”

    This may be true, but it relies on your ability to achieve HRmax in the sport specific test, as a mostly cyclist who occasionally gets into some run training. I find it very easy (well painful) to hit my HRmax on the bike, but on the run I can only do it during the times when I’m run training, if I do a graded treadmill test or any other protocol it always comes in a large number of beats down. Essentially fitness does limit your ability to attain it, particularly if you have high CV fitness from another activity, but low sport specific fitness.

  11. As to the heart rate estimates: Perhaps it is not such a good idea to test age dependent formulas for heart rate, when there is hardly any age variation in the sample but considerable variation in heart rate (SD 2.8 versus 8.3). You’re basically testing only one point on the regression line. Small wonder that the formulas that are least dependent on age and just happen to have their ‘base rate’ (the 201 minus…, the 191.5 minus…) close to the real mean HRmax, are the most accurate.

    On the other hand and to the credit of the authors, young age is where the predictions of these formulas differ most, so this is were differences in predictive power will show.

  12. @Jim: Interesting points. Not to splits hairs, but I’d still say that what you’re describing isn’t variation of HRmax with fitness (in the sense of your physiological ability to circulate oxygen to working muscles and so on), but rather a varying ability to attain HRmax depending on the modality — which is a very good point, of course, but not the same thing.

    Along those lines, I have to admit I’m surprised that you don’t reach HRmax in graded treadmill tests (which I assume are to exhaustion, with suitable motivation and encouragement in the later stages of the test). I’d always thought of running as a sort of “sport-agnostic” testing protocol, in that virtually everyone has basic competence in running (unlike, say, cycling). But that was just an assumption on my part, not backed up by any data or experience (since I’m a runner myself).

    @RH: I couldn’t agree more. As I said in the blog post, “trying to fit a function of age to data taken from subjects who are all virtually the same age seems a little weak to me.” While the two equations they highlight happen to line up with their particular data set, I’d have very little confidence in applying that result to any other group of subjects — even within the same age range.

  13. They might be right, yet I think Jim Ley has a more significant point. In a power test or HPM-max test on a ‘bike’ I get scores that don’t even come close to what my body can deliver in running.

    In two groups of runners that I currently train (N=18) only two are able to reach HPMmax in 300 or 200 mtr runs. The classic test 3 or 4 (6 minute runs with increasing speed and all out at least the last 80 seconds; with a minute or so rest in between) scores best in achieving HPMmax that is not achieved in any other way for these athletes.

    Then there is the statistical stuff… these articles are usefull research, yet the conclusions are presented as sensationally simple… and are not as useful as assumed. The variation is highly underestimated and yet celarly visible in the data.

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