Cycling is co-operation between the cyclist and the bike. The Polar Power Output Sensor, optional for the Polar s625x, Polar s725, Polar s720i and Polar s710i Heart Rate Monitors, contains different measuring aspects that inform how the cyclist works with the bike and enables the cyclist to control the intensity of exercise. The Polar Power Output Sensor gives all information in one device only. It combines heart rate monitoring and power output measurement.

Together with the Polar s625x, s725, s720i or s710i the Power Output Sensor measures the actual, average and maximum power values. With the Power Output Sensor you can analyze the L/R Balance
(balance between left and right foot) and Pedaling Index (shows how even the power is distributed during one crankarm rotation). The Power Output Sensor also measures cycling speed, distance and cadence. You can easily download the data to the Polar Software for further analysis.

All of the drive force of the bike is transmitted through the chain, allowing the Polar Power Output Sensor to calculate power accurately. The sensor positioned on the rear pulley works magnetically and measures the speed of the chain. The chain stay sensor (power sensor) calculates the tension of the chain by measuring the vibration as the chain passes over the sensor. The Polar Power Output Sensor also has built-in cadence and speed sensors. The information is then transmitted to the heart rate monitor, which is mounted to a bracket on the handlebars.

How does Power Output help cycling?

With regard to training it can give much more precision than heart rate and perceived exertion. Power meters also have a number of other users, including working on bike position and determining efficiency at different cadences among them.

FAQ

How Does this System Measure Power?
The Power Output Sensor measures power direct from the chain, unlike other models that use the crank or hub. This precision system combines measures from two key factors:
Chain Tension – using a sensor on the chain stay
Chain Speed – using a sensor on the rear pulley

How Quick Is the Set-Up?
It couldn’t be easier. All you have to do is enter – once, when setting up the unit – a set of key factors: chain length, chain weight and the length between the bottom bracket and rear wheel axles. And then away you go. Or, you may use the default settings to get started (Chain weight 304 g and length 1473 cm and Span length 420 cm). Precision pedal power – every time!

Does Chain Slap Affect the Results?
No. Because the chain is taut as you pedal, the Power measurement is unaffected by chain slap. The only time excessive chain slap occurs is when you’re not pedaling – and no power is generated.

What About Pedaling Efficiency?
Together the Polar S720i/S710i and Power Output Sensor let you track your pedal-stroke efficiency, in real time, by measuring two indexes, L/R Balance and Pedaling Index.

L/R Balance
L/R Balance is an index of the power output balance between the left and right strokes making up one rotation. The Polar S720i/S710i then compares the peak power produced during the left stroke against the peak produced during the right stroke. If you press hard on the right, the L/R balance will be skewed on the right side (i.e. L 37, 63 R). The Polar S625x/S725/S720i/S710i display information helps you achieve balance between each push, avoid premature fatigue in either leg and contributes to improved pedaling efficiency with each rotation.

Pedaling Index
Pedaling Index (PI) measures the evenness of power output throughout each pedal rotation by comparing your power output at its minimum and maximum levels. A higher PI score shows that your power was produced more evenly throughout the pedal rotation –so your peak power for a rotation will be lower, even though your average power output remains the same.

How Does this System Measure Pedaling Efficiency?
A pedal stroke generates peak power as the foot pushes down on the pedal. In one rotation there are two power peaks: the first as you push down with the right foot and pull up with the left, and the second when you push down with the left foot and pull up with the right. In between, your power output is decreased. The Power Output Sensor measures the maximum and minimum power values and calculates your L/R Balance and Pedaling Index, using a cadence sensor on the right pedal to mark the right side.

Why Choose the Polar Power Output Sensor?
No hub, wheel or crank change: The system measures power direct from the chain – no need to change hubs, wheels or cranks unlike other models.

Right price for total system: The Polar Power Output Sensor option for the Polar S625x/S725/S720i/S710i Heart Rate Monitors is an additional module, separate from the heart rate monitor itself. An athlete who already has the Polar 625x/S725/S720i/S710i with its many heart rate monitoring features adds a whole new series including wattage, cadence and a pedaling index. The ability to incrementally buy into this power meter is one of its primary advantages.

Polar - the lightweight choice: The Polar 625x/S725/S720i/S710i Heart Rate Monitor and the bike sensors weighs in at just 318g grams when installed - compared to over 550 grams for other models.