1. Gender Differences in Frontal Plane Gait Biomechanics During Declined Walking With a Heavy Load Becky Krupenevich, Jake Ridings, Rachel Tatarski, Patrick Rider, Zachary J Domire, Paul DeVita Department of Kinesiology, East Carolina University, Greenville, NC 27858 Introduction Frequent hill-walking may present an injury risk due to the increased stress imposed on the lower extremity. Decline walking, in particular, substantially increases knee joint loading, which can exacerbate knee joint injuries [1]. Individuals in the military carry heavy loads and often encounter hilly terrains when walking. Military load carriage is associated with high rates of injury, particularly in females. Previous investigations of gender differences during load carriage used a relative load normalized to body mass [2]. Due to anthropometric differences between genders, this methodology may mask gender differences in response to the load by under-loading females compared to the absolute loads all military personnel carry. An absolute, heavy load would stress females more than males relative to their mass. Therefore, we hypothesize an interaction effect between gender and load carriage such that females compared to males will respond differently to absolute, heavy loads during declined walking. The purpose of this study was to compare the effects of carrying an absolute load on frontal plane gait kinematics and kinetics in males and females during decline walking. Methods We recruited 8 males and 8 females to participate in this study. Subjects wore standard ROTC boots during testing and a MOLLE rucksack containing 22kg (U.S. Army fighting load) during loaded conditions. Subjects performed several walking trials on a ramp declined 10 degrees at a standard speed of 1.5m/s. Three load conditions (unloaded, mid-back position, and low-back position) were tested. Kinematic data were captured using an eight camera Qualisys motion tracking system. An AMTI forceplate fitted into the ramp was used to capture force data. Data were analyzed using Visual 3D. Frontal plane hip and knee internal, abducting joint moments were calculated with inverse dynamics. Peak moments were analyzed using a 2x3 (gender by load condition) repeated measures ANOVA, p<0.05. Post hoc tests were run on significant interactions. Figures: A) Peak hip abduction moment, B) Maximum hip adduction position, C) Peak knee abduction moment, D) Maximum knee adduction position (#gender by load interaction, *different from unloaded, †gender effect, p<0.05) Results & Conclusions We found significant gender by load interactions in peak hip and knee abduction joint moments (p 0.05). Increased knee abduction moment has been correlated with patellofemoral pain syndrome and degeneration at the knee joint [3]. It is therefore possible that the observed gender differences in hip and knee abduction moments in response to heavy loads may serve as an underlying mechanism for higher injury rates in female vs. male military personnel. References 1. Lay et al. J. Biomech. 39, 1621-1628 (2006). 2. Silder et al. J. Biomech. (2013). 3. Stefanyshyn et al. Am. J. Sports. Med. 34(11), 1844- 1851 (2006). A B C D # # Scan QR code to view videos of decline walking