One of the unique features of the GymAware Power Tool, is its ability to measure angle of lift, see the fact sheet here. This overcomes one of the main limitations of LPT based performance measurement with the popular Olympic lifts.
To get the most out of this feature it helps to understand the basics of the technology, its strengths and its weaknesses.
How it works
The Power Tool 4 and 5 measure angle of the tether by measuring tilt with a biaxial accelerometer. This means the measurement is made with respect to gravity as opposed to the orientation of the unit. This is good because the lift calculations require all measurements to be referenced to gravity. As detailed in this fact sheet, the power tool reports both distance and angle in every measurement. It then uses the angle to correct the distance so that only vertical movements are used in calculations.
Measuring distance with an encoder is much easier to do accurately than measuring the angle of the tether with accelerometers. This means distance measurements are many times more accurate than angle readings. So to get the best accuracy, a protocol that limits change in angle during the lift is desired. To explain this see the three different setups below.
The first setup is ideal. By placing the GymAware unit directly under the bar, the only changes in angle will be due to horizontal components in the lift.
The second setup is ok too. But as you can see there is a change in angle being presented to the unit. If this angle is moderate (less than 20 degrees) then the errors due to change in angle will be insignificant.
The third setup should be avoided. While still far more accurate than an LPT not measuring angle, this setup makes the (less accurate) angle measurement a greater component of the final result, and therefore less accurate.
Note that change in angle is the condition to be avoided as a large change in angle contributes a larger error to the overall measurement signal.
A large but constant angle, like in a leg press or hack squat is fine. The Power Tool will measure the angle and the result will be very accurate.
In this case the angle is constant at the incline of the leg press and so adds no error to the signal. GymAware will report the lift distance shown and will use the lift height in all calculations.
When you attach the unit to a leg press or hack squat, do a test while observing the tether to make sure any change in angle during the movement is minimised.
How to Use the Angle Measurement Feature
There are two simple steps required to take advantage of angle measurement.
- Turn on angle measurement in settings
- Zero angle when prompted