The metric is available on most fitness trackers. Here’s what it means. By Talya Minsberg You just finished a long, hard bike ride. But how hard was it, exactly? That depends on what you measure: How ...

Correspondence to Professor Tim J Gabbett, Gabbett Performance Solutions, Brisbane, QLD, Australia and University of Southern Queensland, Institute for Resilient Regions, Ipswich, QLD, Australia; ...