AUTHOR=Boullosa Daniel A. , Hautala Arto J. , Leicht Anthony S. TITLE=Introduction to the research topic: the role of physical fitness on cardiovascular responses to stress JOURNAL=Frontiers in Physiology VOLUME=5 YEAR=2014 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2014.00450 DOI=10.3389/fphys.2014.00450 ISSN=1664-042X