290 Journal of Applied Biomechanics, 2010, 26, 290-294 © 2010 Human Kinetics, Inc. Richard W. Bohannon (Corresponding Author) is with the Department of Physical Therapy, Neag School of Education, University of Connecticut, Storrs, Connecticut. Jason Smut- nick is with Physical Therapy and Sports Medicine Centers, Watertown, Connecticut. Pelvifemoral Kinematics While Ascending Single Steps of Different Heights Richard W. Bohannon and Jason Smutnick Motion of the femur and pelvis during hip fexion has been examined previously, but principally in the sagittal plane and during nonfunctional activities. In this study we examined femoral elevation in the sagittal plane and pelvic rotation in the sagittal and frontal planes while subjects fexed their hips to ascend single steps. Fourteen subjects ascended single steps of 4 different heights leading with each lower limb. Motion of the lead femur and pelvis during the fexion phase of step ascent was tracked using an infrared motion capture system. Depending on step height and lead limb, step ascent involved elevation of the femur (mean 47.2° to 89.6°) and rotation of the pelvis in both the sagittal plane (tilting: mean 2.6° to 9.7°) and frontal plane (listing: mean 4.2° to 11.9°). Along with maximum femoral elevation, maximum pelvic rotation increased signifcantly (p < .001) with step height. Femoral elevation and pelvic rotation during the fexion phase of step ascent were synergistic (r = .852–.999). Practitioners should consider pelvic rotation in addition to femoral motion when observing individuals’ ascent of steps. Keywords: biomechanics, gait, pelvis Numerous studies have established that shoulder abduction and fexion are accomplished by a combina- tion of elevation of the humerus and upward rotation of the scapula (Crosbie et al., 2008; Price et al., 2000). Research over the past 25 years has demonstrated that hip fexion (angular approximation of the thigh and anterior trunk) is likewise dependent on a combined elevation of the femur and rotation (posterior tilting) of the pelvis. The research shows that 13.1–37.1% of the hip fexion of individuals who are supine, standing, or suspended from a bar can be attributed to sagittal plane tilting of the pelvis (Bohannon 1982; Bohannon et al., 1985a, 1985b; Congdon et al., 2005; Dewberry et al., 2003; Murray et al., 2002). The aforementioned research, though diverse, does not address pelvifemoral rhythm during a common functional activity. Other research has described the kinematics of the femur and pelvis during level-ground gait (Bejek et al., 2006; Crosbie & Vachalathiti, 1997; Taylor et al., 1999), a functional activity requiring only minimal hip fexion. That research demonstrates that the pelvis rotates in both the sagittal plane (tilts) and frontal plane (lists) during the walking cycle and that the list in the frontal plane is phase-locked with hip fexion (Crosbie & Vachalathiti, 1997). If hip fexion is accompanied by sagittal and frontal plane tilting of the pelvis, then both may be relevant to the manner in which individuals perform functional activities such as ascent of a step which require such fexion. This possibility led to the present investigation, the purpose of which was to describe pelvifemoral kinematics while the hip was fexed to ascend single steps of different heights. We hypothesized that hip fexion would involve femoral elevation and pelvic rotation (both sagittal and frontal) and that the femoral and pelvic motions would be related to one another over the course of hip fexion. We also hypothesized that ascent of progressively higher steps would be associated with increases in maximum femoral elevation and pelvic rotation. Methods Subjects A convenience sample of 8 men and 6 women (26.2 ± 9.2 years old) participated. None reported current orthopedic or neurologic problems affecting function. To allow for accurate and unobscured placement of markers, no sub- jects were obese (body mass index = 23.5 ± 2.2 kg/m 2 ). Before participation, all signed a consent form approved by the Institutional Review Board of the University of Connecticut. Instrumentation and Procedures Three-dimensional movement kinematics were captured at 240 Hz using a seven-camera infrared Qualisys Motion Capture System. Before initiating motion capture, the system was calibrated to establish the location of the