Computer Vision in Fitness: Exercise Recognition and Repetition Counting

Sammanfattning: Motion classification and action localization have rapidly become essential tasks in computer vision and video analytics. In particular, Human Action Recognition (HAR), which has important applications in clinical assessments, activity monitoring, and sports performance evaluation, has drawn a lot of attention in research communities. Nevertheless, the high-dimensional and time-continuous nature of motion data creates non-trivial challenges in action detection and action recognition. In this degree project, on a set of recorded unannotated mixed workouts, we test and evaluate unsupervised and semi-supervised machine learning models to identify the correct location, i.e., a timestamp, of various exercises in videos and to study different approaches in clustering detected actions. This is done by modelling the data via the two-step clustering pipeline using the Bag-of-Visual-Words (BoVW) approach. Moreover, the concept of repetition counting is under consideration as a parallel task. We find that clustering alone tends to produce cluster solutions with a mixture of exercises and is not sufficient to solve the exercise recognition problem. Instead, we use clustering as an initial step to aggregate similar exercises. This allows us to effectively find many repetitions of similar exercises for their further annotation. When combined with a subsequent Support Vector Machine (SVM) classifier, the BoVW concept proved itself, achieving an accuracy score of 95.5% on the labelled subset. Much attention has also been paid to various methods of dimensionality reduction and benchmarking their ability to encode the original data into a lower-dimensional latent space.