how long can I run at maximum heart rate?

Pretty simple… say I start running, and gradually speed up until after about ten minutes I reach my maximum heart rate of 194 bpm. How long can I last at this heart rate regardless of speed? (It is OK to slow down, just so long as I keep my heart at 194)

In other words, how long can someone last at 100% heart rate, regardless of speed, or deceleration?

Until you pass out or die.

Or quit.

Or ninja pirates pull up beside you in their ship and steal your heart to sell on the French black market.

Ain’t no such thing as “maximum”…at least not in the absolute sense. That “220-(age)” formula is based on exercise theory, not physiological limits.

I have absolutely no medical training or knowledge, so this is a completely WAG, but I’d assume that (provided the rest of your body could keep doing everything) you could keep it up for quite some time, but eventually your heart (being a muscle after all) would start to tire. Then you would have to either slow up, or you’d pass out. Or maybe your legs would stop getting sufficient blood, and either slow by them selves (is that possible?) or cramp.

I think this question is kind of like asking “how long can I hold my breath?” Nobody can answer that for you.
When I run (I’m currently training for my 3rd marathon), sometimes I use a heart monitor. Using the 220-age formula seems to work for me (many people advise that that’s only a rough guess, however). I never deliberately run at an effort greater than 90%, for me, that’s about 160 bpm. At that rate, I can pretty comfortably cover a mile in about 8:15. After three miles, I’d be slowing to about 8:30/mile, and be pretty much looking for a break.

My guess would be that if I ran to “max heart rate” I’d only be willing to hold up for about 6 minutes, maybe a little more.

I can’t imagine why I’d want to do that, however.

Theoretically, you can keep going as long as you suck in enough oxygen to keep up with muscular oxygen consumption. Once you use more than you consume, your muscles switch to anaerobic metabolism, you build up lactic acid, and you will stop! With painful muscle cramps.

In reality, other factors come into play, such as fatigue, painful joints, low blood sugar, and a full bladder. These will make you stop too.

QtM, MD

My understanding of “Max V02” is that it is when you reach the greatest rate of 02 uptake. It’s the most 02 your body can process, therefore taking in more 02 wouldn’t help at this point even if you could. When one reaches Max V02 anaerobic energy systems must take over to supply any further energy.

Have I misunderstood this, or just phrased it differently?

My exercise physiology textbook here says Max V02 correlates strongly with maximum effort (as most people who have taken this test on a treadmill will surely agree - no question of that when I did it!). So I’m doubtful one could prolong exercise at max heart rate for very long. My textbook has no figures on this, however.

Oh, and meant to include in my post that Max V02 and max heart rate generally occur simulataneously according to my text.

You’re correct. But the predicted max heart rate is just an estimate. I’ve done literally over a thousand exercise stress tests in my career, and I’ve seen people pass their max predicted heart rate, their predicted METS, and still keep on trucking. It’s when they hit their personal wall, whatever that is, that they go anaerobic and have to stop. The predicted values are just guidelines.

How would you try to predict MHR?

I was under the impression that the average person could not reach his/her MHR, for lack of conditioning. Is this true in any way?

MHR standard formula is 220 minus age (alternate formulas exist). Therefore if you’re 40, your target is 180.

In a graded exercise test (stress test), the results are generally considered valid if you get within 90 percent of that number. So if you’re 40, you need to hit a rate of 162 to get a “diagnostic” test (warning: I am oversimplifying).

And many people have no trouble reaching or exceeding 100% of predicted heart rate.

Hell, one guy went into ventricular tachycardia when I tested him, and hit a rate of 300! Gosh, that was exciting! He lived and I later got the stains out of my shorts!

O, the old 220-age is the “prediction”? I was expecting some in-depth studies and blood tests and stuff.

QtM, how high can some old marathon runners get up to? Or, what is the highest you have seen for someone over 70?

fuel, we usually don’t push the patient, especially the over 70 crowd, too far. To do otherwise is to use the “test to destruction” principle. This principle, while interesting to observe, tends to interfere with the smooth practice of medicine.

Once you’ve seen the runner stumble, and go down on the treadmill, you do not want to see it again. Unlike George Jetson, the patient does not go 'round and 'round on the treadmill. Generally he just gets sucked underneath it, where he remains until physically removed. And treadmills are heavy to lift. And the paperwork afterwards is time consuming.

Old marathon runners can generally hit their predicted target, as can young ones. And even marathon runners cannot beat the treadmill. Keep in mind, the treadmill goes faster up a steeper grade every 3 minutes. At 28 minutes into the protocol, the testee is going 12 miles an hour up a 28% grade. I never had a patient reach 28 minutes. I think my longest testee was about 25 and a half minutes. And this was a guy that ran 3 marathons a year.

From Lore of Running, by Tim Noakes, MD (1991), pages 39 and 40: “For reasons that are not absolutely clear, it is not possible to run at 100% VO[sub]2[/sub] maximum for more than a few minutes. This concept has been most clearly researched by C.T.M. Davies and Thompson (1979), two eminent British physiologists who found that trained athletes could maintain an average of 94% (range: 89 to 100%) of the VO[sub]2[/sub] max values for a 5-km race, 82% range…for the standard marathon, and 67% range…for the 85-km London-to-Brighton race.” These authors also collected data on four elite ultramarathoners who ran for 24 hours. The sustainable exercise intensity fell progressively with increasing exercise duration (no suprise, there). At the end of 24 hours, it was at 45% max VO[sub]2[/sub].