This is a summary of the newly released eBook "Signal Processing Unlocked - Fitness Tracker Algorithms". Learn how to develop you own fitness-tracker app for smart phones and watches and help people monitor their daily energy expenditure.

1. Signal-Processing Unlocked
How to develop your own fitness tracker app
Fredrik Östman

2. Background
• The fitness tracker market is booming with
products varying from smartphones to
wearables that calculates the daily energy
expenditure (calories)
• To support app developers for smart phones
and watches, a concrete and to-the-point
eBook regarding fitness tracker algorithms
has been released on Amazon
• This slide show will summarize the main
points of the book.
Check it out on www.amazon.com!

3. Contents
• Introduction
– Limitations
• Basic digital signal-processing concepts
– Acceleration measurements
– The Nyquist-Shannon Theorem
– Aliasing
• Energy Expenditure
– Pre-processing
– Activity counter
– Energy expenditure calculation
– Post processing
• Conclusions
• Discussion
• References
• Appendix A – Filter parametersCheck it out on www.amazon.com!

4. Main points of the book
• The main points of the eBook “Signal-
processing Unlocked – Fitness
tracker algorithms” are
1. How to properly treat the sensor readings to
secure the quality of the data
2. Calculation of activity counts
3. Relating activity counts to energy expenditure
Check it out on www.amazon.com!

5. Reading sensor data
• The main movement of the body is within a frequency
spectre of 0.1 – 10 Hz
• 2 Hz has been reported to be sufficient for calculation of
activity counts
• To avoid alias effects and secure good signal
reconstruction, a sample frequency of 20 Hz is selected
with a down-sampling scheme to 2 Hz, including the
proper filtering

6. Activity counts
• Raw acceleration data is seldom used for direct
modelling of the daily energy expenditure
• Instead the accelerations in x, y and z directions are
used for calculating the activity counts for respective
direction
• For this application, an “Integration and threshold”
method was selected to calculate the activity counts

7. Energy expenditure
• To calculate the energy expenditure
rate (kJ/min), a linear model
presented by (Chen and Sun, 1997)
is used
• By integrating the energy expenditure
rate, the total daily energy
expenditure can be determined.
K. Y. Chen and M. Sun, “Improving Energy Expenditure Estimation by using a
Triaxial Acceleromterer”. Journal of Applied Physiology, vol. 83, no. 6, 1997.

8. Signal Processing Unlocked
For all the details, check out the new eBook on
www.amazon.com:
Signal-Processing Unlocked - Fitness Tracker Algorithms
Visit also and register on the web site to get a more
detailed presentation on activity count, including
measurement results
http://signalprocessingunlocked.weebly.com