Objectively measured physical activity and vitamin D status in older people from Germany
Jochen Klenk, Kilian Rapp, Michael Denkinger, Gabriele Nagel, Thorsten Nikolaus, Richard Peter, Bernhard O Boehm, Wolfgang Koenig, Dietrich Rothenbacher, and the ActiFE Study Group
J Epidemiol Community Health Apr 2015, 69 (4) 388-392; DOI: 10.1136/jech-2014-204632