“…Therefore, results can be influenced by several individual confounding factors such as motivation, pain tolerance, competitiveness (Mannion & Dolan, 1994); furthermore pain on exertion, anticipation or fear of pain and reflex inhibition of motor activation can be additional factors resulting in 152 inability or unwillingness to produce a truly maximal effort in patients with LBP (Menard et al, 1994;Vlaeyen et al, 1995;Crombez et al, 1996;Keller et al, 1999;Rashiq et al, 2003;Rainville et al, 2004;Al-Obaidi et al, 2005;Ropponen et al, 2005;Verbunt et al, 2005;Thomas et al, 2008;Huijnen et al, 2010). These individual factors might explain the absence or low correlations found in some studies between morphologic variables and performance (Parkkola et al, 1993;Gibbons et al, 1997a).…”