title: Predicting timing of foot strike during running, independent of striking technique, using principal component analysis of joint angles.
abstract: As 3-dimensional (3D) motion-capture for clinical gait analysis continues to evolve, new methods must be developed to improve the detection of gait cycle events based on kinematic data. Recently, the application of principal component analysis (PCA) to gait data has shown promise in detecting important biomechanical features. Therefore, the purpose of this study was to define a new foot strike detection method for a continuum of striking techniques, by applying PCA to joint angle waveforms. In accordance with Newtonian mechanics, it was hypothesized that transient features in the sagittal-plane accelerations of the lower extremity would be linked with the impulsive application of force to the foot at foot strike. Kinematic and kinetic data from treadmill running were selected for 154 subjects, from a database of gait biomechanics. Ankle, knee and hip sagittal plane angular acceleration kinematic curves were chained together to form a row input to a PCA matrix. A linear polynomial was calculated based on PCA scores, and a 10-fold cross-validation was performed to evaluate prediction accuracy against gold-standard foot strike as determined by a 10 N rise in the vertical ground reaction force. Results show 89-94% of all predicted foot strikes were within 4 frames (20 ms) of the gold standard with the largest error being 28 ms. It is concluded that this new foot strike detection is an improvement on existing methods and can be applied regardless of whether the runner exhibits a rearfoot, midfoot, or forefoot strike pattern.
authors.affiliation: Running Injury Clinic, Faculty of Kinesiology, University of Calgary, Calgary AB, Canada T2N 1N4. Electronic address: stosis@ucalgary.ca.
authors.forename: Sean T
authors.initials: ST
authors.lastname: Osis
authors.affiliation: Running Injury Clinic, Faculty of Kinesiology, University of Calgary, Calgary AB, Canada T2N 1N4.
authors.forename: Blayne A
authors.initials: BA
authors.lastname: Hettinga
authors.affiliation: Run3D Inc. Oxford, UK, OX4 1EQ and Oxford University, Oxford, OX1 2JD, UK.
authors.forename: Jessica
authors.initials: J
authors.lastname: Leitch
authors.affiliation: Running Injury Clinic, Faculty of Kinesiology, University of Calgary, Calgary AB, Canada T2N 1N4; Faculty of Nursing, University of Calgary, Calgary AB Canada T2N 1N4.
authors.forename: Reed
authors.initials: R
authors.lastname: Ferber
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005528:Foot / Q000502:physiology*; D005545:Forefoot, Human / Q000502:physiology*; D005684:Gait; D006801:Humans; D021621:Imaging, Three-Dimensional; D007700:Kinetics; D016014:Linear Models; D008297:Male; D025341:Principal Component Analysis; D015203:Reproducibility of Results; D012420:Running; D013314:Stress, Mechanical
keywords: Biomechanics; Foot strike; Gait; Kinematics; Treadmill running