How do exercise machines determine heart rate?

It’s reading the pulse in your thumb.

There are two ways these machines can read your heart rate. It can read the actual surge of blood, caused by the heart pumping, or the electric pulse your brain creates, which causes your heart to beat.
With me, the second is very inaccurate, since my heart occasionally beats before it receives the electric pulse, causing it to appear to skip beats.

Incorrectly.

The heart rate monitors on cardio machines are just as inaccurate as the calorie expenditure meters.

The ones at our gym apparently use your pulse.

It’s not the electrical impulse in your brain, but the actual electrical impulse of your heart. When your heart beats, there is an electrical impulse that starts at your right atrium and then travels through the heart in a coordinated fashion. ECG machines read that electrical impulse.

The treadmill has two metal pads, and it’s reading the same electrical impulses from your heart. It is inaccurate because you’re moving around.

@Rarebear I noticed that the machines give a reading only when I hold BOTH handles. Does this mean that there must be an electrical impulse traveling from one hand to the other?

@2davidc8 No. It’s measuring a voltage difference between the two hands. Normal heart signals point from the upper right to the lower left. So that’s what it’s measuring.

Thanks for your reply, @Rarebear. “Upper right to lower left”: do you mean the heart, or from upper right hand to lower left hand?

http://www.youtube.com/watch?v=8aLufvkRw-k

@Rarebear Great video, and I could see the entire cycle. But how does that translate to a voltage difference that the exercise machine can pick up? Does just this electrical activity in the heart create a voltage difference between your right and left hands?

@2davidc8 Yes.