Why do I get incorrect heart rate spikes while exercising (see screen shot)?

Make sure the watch is fastened snugly. During exercise, especially if you're using your hands and wrists (as you would on an elliptical, it can be helpful to move the watch up your arm a half inch or so toward your elbow.

Wearing your Apple Watch - Apple Support

Get the most accurate measurements using your Apple Watch - Apple Support

Is that at the start of your workout?

I get them as well, it is just that the watch is having problems getting a strong reading.

I find it happens usually at the beginning of my workout.

I go into the health app and delete the couple of numbers.

First off as seanfromllanelli mentioned above, when in doubt check with your doctor.

If you're sure it is the watch you can try re-calibration of the fitness data

From your iPhone>My Watch>Privacy>Rest Fitness Calibration Data

After that I would do a hard reset on the watch

Hold the side button and the crown in until you see the Apple logo and then release.

Branta_uk wrote:

I’m prepared to risk a beer bet on tightness of the band for the solution. With vigorous exercise the watch may move too much and get false results, usually high spikes.

Also, the bending and extending of the wrist on the handles of an elliptical would exacerbate the problem.

I would consult your Doctor, if you are concerned. As your heart rate will peak during exercise. My can go as high as yours at the peak of exercise

I’m prepared to risk a beer bet on tightness of the band for the solution. With vigorous exercise the watch may move too much and get false results, usually high spikes.