Reliability and validity of the international physical activity questionnaire compared to calibrated accelerometer cut-off points in the quantification of sedentary behaviour and physical activity in older adults.

Author(s)	Ryan D J, Wullems J A, Stebbings G K, Morse C I, Stewart CE. and Onambele-Pearson G L.
Journal / Source	http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0195712&type=printable
Date	May 2018