POLAR S720i - Manual (Page 93)

H. PRECAUTIONS
H 91
Using the Polar heart rate monitor in a water environment
Your Polar heart rate monitor is water resistant to 20 metres/ 60 feet. To
maintain the water resistance, do not operate the buttons of the wrist
receiver under water.
Heart rate measurement in a water environment is technically demanding
for the following reasons:
• Pool water with a high chlorine content and seawater may be very
conductive and the electrodes of Polar transmitter may get short
circuited and ECG signals cannot be detected by the transmitter unit.
• Jumping into the water or strenuous muscle movement during
competitive swimming may cause water resistance that shifts the
transmitter on the body to a location where it is not possible to
pick up ECG signal.
• The ECG signal strength varies depending on the individual’s tissue
composition and the percentage of people who have problems in heart
rate measuring is considerably higher in a water environment than in
other use.