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PocketLab on a Skier's Edge Machine

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Submitted by Rich on Wed, 06/28/2017 - 04:00

The PocketLab is an ideal device for measuring user performance for a variety of exercise equipment.  One example of such equipment is the Skier's Edge, whose company was founded in 1987.  This machine was designed for non-impact lateral conditioning that simulates the experience of downhill skiing.  The photo below shows the skiing machine.  The skier stands on the two black platforms, holding poles and moves the carriage back-and-forth on the curved white tracks.

Skier's Edge


A close-up view of the carriage in the photo below shows that a Pocket Lab has been mounted to the carriage with tabs provide in the PocketLab Maker Kit.  The carriage moves back-and-forth on the curved track in the XZ plane.  Therefore, the Y angular velocity would be a variable of interest to measure.  In addition, the X acceleration would be of interest as it is the major component of the back-and-forth motion provided by the skier's legs.



An iPhone snapshot of the data and video combined is shown below.  The acceleration graph (red) shows that the maximum acceleration is about 4g.  This is a true measure of the skier's power.  The angular velocity graph (blue) shows that the maximum angular velocity is about 75 degrees/sec.  From study of the time axis, both graphs show that the  back-and-forth movements of the skier has a frequency of about 75 per minute.  Increasing this rate while keeping the amplitude of the swings the same would suggest that the maximum g "force" could be increased for a more powerful skier.

Screen Capture


The action movie shown below includes an overlay of both the acceleration and angular velocity graphs, with maximum acceleration occurring at the ends of the back-and-forth motion, and maximum angular velocity occurring at the center of each swing.

Closeup of Skier's Edge
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