An X3D Neural Network Analysis for Runner's Performance Assessment in a
  Wild Sporting Environment
David Freire-Obregón Javier Lorenzo-Navarro Oliverio J. Santana Daniel Hernández-Sosa Modesto Castrillón-Santana
We present a transfer learning analysis on a sporting environment of the
expanded 3D (X3D) neural networks. Inspired by action quality assessment
methods in the literature, our method uses an action recognition network to
estimate athletes' cumulative race time (CRT) during an ultra-distance
competition. We evaluate the performance considering the X3D, a family of
action recognition networks that expand a small 2D image classification
architecture along multiple network axes, including space, time, width, and
depth. We demonstrate that the resulting neural network can provide remarkable
performance for short input footage, with a mean absolute error of 12 minutes
and a half when estimating the CRT for runners who have been active from 8 to
20 hours. Our most significant discovery is that X3D achieves state-of-the-art
performance while requiring almost seven times less memory to achieve better
precision than previous work.