Fitzpatrick, J., E. S. Chambers, J. R. C. Parkinson, G. Frost, J. D. Bell, and D. E. L. Thomas. “Psoas Major Cross‑sectional Area: A Potential Marker of Cardiorespiratory Fitness”. International Journal of Clinical and Experimental Physiology, Vol. 4, no. 1, Mar. 2015, pp. 15-20, https://ijcep.org/index.php/ijcep/article/view/148.