Make sure the running computer is no further than 1 m / 3 ft from the transmitter.
Make sure the transmitter belt has not loosened during exercise.
Make sure the textile electrodes in the sports apparel fit snugly.
Make sure that the electrodes of the transmitter / sports apparel are moistened.
Make sure the transmitter / sports apparel is clean.
Make sure that there is no other heart rate transmitter within 1 m / 3 ft.
Strong electromagnetic signals can cause erratic readings. For further information, see
Precautions.
If the erratic heart rate reading continues despite moving away from the source of disturbance, slow down your speed and check your pulse manually. If you feel it corresponds to the high reading on the display, you may be experiencing cardiac arrhythmia. Most cases of arrhythmia are not serious, but consult your doctor nevertheless.
A cardiac event may have altered your ECG waveform. In this case, consult your physician.
