Classification of Changes in Speed and Inclination during Running Bjoern Eskofier

1. Classification of Changes in Speed and
Inclination during Running
Bjoern Eskofier, Dr. Benno Nigg
Human Performances Lab (HPL)
University of Calgary, Canada
Martin Wagner
Chair of Pattern Recognition
University of Erlangen, Germany
Mark Oleson, Ian Munson
adidas innovation team, adidas AG
A Digital Sports Embedded Classification Task
September 24, 2009

2. Digital Revolution – Even In Sports
The adidas_1: “the world‘s
first intelligent shoe”
Direct processing of sport-
specific information
Microprocessor adapts the
shoe to the run situation
Intelligence modeled by
Pattern Recognition
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

3. Overview of the Talk
Introduction
Data collection
Methods
Results
Discussion
Acknowledgments
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

4. Introduction
Runners need different cushioning
Inclination, speed, …: changing demands
adidas_1 developed for that
Ideal cushioning: pattern recognition
Embedded task: cheap computations
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

5. Introduction – adidas_1
3 adidas_1 main parts
Cushioning element (01)
with compression
measurement
Microcontroller (02)
Motor for cushioning
adaptation (03)
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

6. Introduction – Pattern Recognition
Sensors Preprocessing Features Classification
Online analysis
Offline analysis
Data Sample Learning
Challenges: - Hardware environment
- Real-time classification
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

7. Data Collection
84 runners (30 ♀, 54 ♂) - 56 usable
Measurement device 1: Polar RS 800
Measurement device 2: Cell phone
Eskofier et el., 2008
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

8. Data Collection – adidas_1
Measurement device 3:
adidas_1
Magnet at bottom,
Hall sensor at top of
cushioning element
Measures compression
of the heel
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

9. Methods – Features
Eskofier et al., 2009
Step detection:
linear filter
11 features
+ Mean {4,8,16}
+ SD {4,8,16}
+ Gradients {16}
88 features
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

10. Methods – Labels
Definition of 3 inclination classes
α < -3°
-3° ≤ α ≤ 3°
3° < α
Definition of 3 speed classes [m/s]
0 ≤ v < 2.5
2.5 ≤ v < 3.6
3.6 ≤ v
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

11. Methods – Classifiers
Bayes Classifier (BC)
Polynomial Classifier (PC)
Linear Discriminant Analysis (LDA)
Support Vector Machine (SVM)
Multilayer Perceptron (MLP)
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

12. Methods – Classification
5 fold Cross-Validation
105 random vectors from each class
Feature selection: dynamic programming
with Mahalanobis distance G
T
Gk ,l = (µk − µ l ) Σ −1 (µk − µ l )
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

13. Results – Inclination Classification
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

14. Results – Speed Classification
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

15. Discussion
Inclination classifier not implemented
Speed classifier implemented
accuracy rise for 2 features (all methods)
further accuracy rise: 4 features (BC, SVM, MLP)
two feature approach (µ16(F1), µ16(F3))
SVM as classifier
Microcontroller implementation successful
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

16. Acknowledgments
Running study participants
Colleagues and reviewers
Pascal Kuehner (University of Landau)
adidas innovation team ait.
B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia

17. B. Eskofier Running Speed and Inclination Classification
September 24, 2009 IACSS09, Canberra, Australia