Results PWS was slower in cLBP [1.17 (SD = 0.13) m s −1 ] than in CTR group [1.33 (SD = 0.11) m s −1 ; P = 0.002]. No significant d ifference w as o bserved between groups in mechanical work (P ≥ 0.44), spa-tiotemporal parameters (P ≥ 0.16) and energy cost of walking (P ≥ 0.36). At the end of the treadmill protocol , perceived exertion was significantly h igher i n c LBP [11.7 (SD = 2.4)] than in CTR group [9.9 (SD = 1.1); P = 0.01]. Pain intensity did not significantly i ncrease over time (P = 0.21). Conclusions These results do not support the hypothesis of a less efficient walking pattern in patients with cLBP and imply that high walking speeds are well tolerated by patients with moderately disabling cLBP. Abbreviations BMI Body mass index cLBP Chronic low back pain COM Centre of body mass CTR Control Cw Energy cost of walking IPAQ International physical activity questionnaire ODI Oswestry disability index OWS Optimal walking speed PWS Preferred walking speed TSK Tampa scale for kinesiophobia VAS Visual analogue scale ˙ V CO 2 Carbon dioxide output ˙ V O 2 Oxygen uptake Wext External mechanical work Wint Internal mechanical work Wtot Total mechanical work Abstract Purpose Walking in patients with chronic low back pain (cLBP) is characterized by motor control adaptations as a protective strategy against further injury or pain. The purpose of this study was to compare the preferred walking speed, the biomechanical and the energetic parameters of walking at different speeds between patients with cLBP and healthy men individually matched for age, body mass and height. Methods Energy cost of walking was assessed with a breath-by-breath gas analyser; mechanical and spatiotem-poral parameters of walking were computed using two inertial sensors equipped with a triaxial accelerometer and gyroscope and compared in 13 men with cLBP and 13 control men (CTR) during treadmill walking at standard (0.83, 1.11, 1.38, 1.67 m s −1) and preferred (PWS) speeds. Low back pain intensity (visual analogue scale, cLBP only) and perceived exertion (Borg scale) were assessed at each walking speed.