Energy Cost Expression for a Youth Compendium of Physical Activities: Rationale for Using Age Groups. - Pfeiffer, Karin A.; Watson, Kathleen B.; McMurray, Robert G.; Bassett, David R.; Butte, Nancy F.; Crouter, Scott E.; Herrmann, Stephen D.; Trost, Stewart G.; Ainsworth, Barbara E.; Fulton, Janet E.; Berrigan, David (Pediatric Exercise Science, 2018)