Ech, you're giving me a coronary!

January 16, 2006 11:34 PM

The "new, state of the art" cardio machines at my gym always tell me my heart rate is unreasonably high (170 beats per minute) even though I'm working at a level where I can still maintain a breathy conversation. Occasionally, the machine will say my heart rate is something totally wacky, like 220.

The readout is never unrealistically low, always just scary high. It happens across both the treadmills and the elliptical machines, and on each machine of that type that I've tried.

Are these machines all crap, or is there something really scary going on with my heart?

(I'm a 29 year old woman in the low end of 'kinda in shape-ish' - I can jog comfortably for about 3km.)

posted by Kololo to health & fitness (9 comments total)

I've seen machines do this too, especially suddenly reporting a huge jump in heartrate. Generally it's due to interference from a nearby mobile phone, heartrate monitor, CD player, or other electronic device. Other times, it's just a wacky machine. Also, they take time to recalibrate. If you take your hands of the conducting handholds for a second and grab hold again, you'll notice it gives a heartrate indication much more quickly than when you first grab hold. So when it goes haywire, remove your hands for a good minute or so, wipe down hands and grips, then try again.

As for the new machine consistently reporting 170 bpm, if that's not what you normally read at the same level of perceived exertion on other machines, then the new state-of-the-art machine might be inaccurate. The only way to check that is to wear a heartrate monitor and doublecheck the monitor's reading against the machine's. But consider this: Very good cardio machines, especially good elliptical trainers, can indeed get your heartbeat up higher than you expect for the level of perceived effort. I suppose that's due to a smaller & smoother range of motion with less jarring of the joints than, say, jogging or rowing. In other words, you're getting a great workout but it doesn't feel like it. If so, you've got a dream machine and should shoo away anyone else who starts sidling up to it.
posted by mono blanco at 11:54 PM on January 16, 2006

Are these machines all crap

Yes. Take your pulse at your neck with your finger. Hold for 10 seconds, then multiply by six.
posted by frogan at 12:05 AM on January 17, 2006

Or, for a slightly more accurate (and easier to multiply) result, use frogan's method for 20 seconds, multiplying by 3. :)
posted by antifuse at 1:53 AM on January 17, 2006

My experience has been what mono blanco said. Putting my iPod on the machine causes the HR readout to spike. I've also used a Polar HRM with a chest strap and wristwatch display. The wristwatch will show my correct HR while the display on the machine shows some incredibly high number.
posted by fixedgear at 2:17 AM on January 17, 2006

These machines never get my heartrate right. I think that sometimes they even halve it or double it. I just assume I'm a freak, and go by perceived effort. It does make it impossible to do those "fat burn" settings where the machine alters the tension in order to keep my heart rate in a particular range. What happens is that the tension/level setting goes up and down like a yoyo as the machine guesses wildly.
posted by handee at 3:03 AM on January 17, 2006

Related Warning: If you are serious about monitoring your heart rate, you need to find out what your max heart rate is.

The correct way to do this is via your doctor and a cardiac stress test. The reason this is the correct way is that, every so often, you find out that while your heart can technically work at a heart rate of FOO, you have something go wrong at a heart rate of .9FOO. Being near doctors at the time helps.

Plus, with the ECG wired in, they can find out where your real max is, and if you have any impending problems, you'll get a warning.

As to the sensor failure. They work on picking up the very small current that triggers your heart contractions. This can easily be overwhelmed by other things, such as iPods and cellphones. Double-heart-rate is usually caused by something acting as an inductor, slowing the signal in one arm, so the sensor sees the pulse in the left arm (for example) then the right. Half-heart-rate is usually a conductivity problem, and it's usually not exactly half -- it's missing some pulses, so it is low.

The chest based sensors are much more accurate for this reason.

If you stop moving, you'll probably be able to get a good pulse from these machines. You need to have good electrical contact with the sensors -- however, the sweat from exercise is more than conductive enough for this.

And, yes, you're nowhere near max heart rate if you can easily talk. Then again, you *might* have a max heart rate of 260bpm, in which case, 170bpm isn't anywhere near that level. You can say "that's unpossible", but I know two people who, after cardiac stress tests, showed max rates well above 250bpm. No rule-of-thumb would ever tell them that. Of course, the real problem is the guy who, by the rule of thumb, thinks he has a max rate of 180bpm, but really is in trouble if he holds 160bpm for more than a minute....
posted by eriko at 5:36 AM on January 17, 2006

mono blanco, I'm glad you asked this because I have had the same problem. The machines seem so alarmed that I expect the to go ahead and call 911 for me. I switched to the "Random" setting instead of the "Cardio" setting and it quit.
posted by small_ruminant at 10:06 AM on January 17, 2006

During a cardiac stress test, I was nowhere near my max when the monitors suddenly showed a spike in the rate, the doctor yelled, "he's throwing PVCs!", and the nurse started punching buttons to shut everything off. I was completely bewildered by all this since I was in no discomfort at all and was barely breathing hard.

The cardiologist explained that the preventricular contractions had fooled the monitor into thinking I had a very high heart rate. (This didn't make sense to me because he explained that a PVC was like the heart skipping a beat, which would lower the rate, but he's the cardiologist, not me.)

Upshot of this is that your problem is most likely due to the failure of the monitors, but it wouldn't hurt to consider eriko's advice of getting a stress test.
posted by forrest at 8:45 PM on January 17, 2006

It could also be from vibration - if you put a pulse oximeter (the little finger clippy) on your finger, and shake your finger around, it'll say your heart rate jumped way up.
posted by IndigoRain at 12:56 PM on January 20, 2006