Guide to the assessment of physical activity: Clinical and research applications: a scientific statement from the American Heart Association.
Strath SJ, Kaminsky LA, Ainsworth BE, Ekelund U, Freedson PS, Gary RA, Richardson CR, Smith DT, Swartz AM. Guide to the assessment of physical activity: Clinical and research applications: a scientific statement from the American Heart Association. Circulation. 2013 Nov 12; 128(20):2259-79.