You may be getting interference with another device in the environment, or you may have a faulty or discharged battery in chest strap.
Try the following and see if heart rate reading returns to normal/expected rates:
- Replace the battery in the chest strap (if it is the style of strap where you can do this; some batteries are ‘built-in’).
- Check the area and remove any devices that might be interfering, such as wireless phones, remote controls, or other exercise equipment with wireless heart rate capability.
- If you are using the digital contact grips, make sure you are grasping the grips firmly and keeping your hands steady and in place.
- Also, some individuals have a body chemistry that is not fully compatible with heart rate telemetry. Try the chest strap on another person to see if they are able to get a reading.