INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 16, No. 13, pp. 2725-2730 DECEMBER 2015 / 2725 © KSPE and Springer 2015 Measurement of Lower Extremity Kinematics and Kinetics during Valley-Shaped Slope Walking Jiyoung Jeong 1 , Youkeun K. Oh 2 , and Choongsoo S. Shin 1,# 1 Department of Mechanical Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul, 04107, South Korea 2 Department of Mechanical & System Design Engineering, Hongik University, 94 Wausan-ro, Mapo-gu, Seoul, 04066, South Korea # Corresponding Author / E-mail: cshin@sogang.ac.kr, TEL: +82-2-705-8825, FAX: +82-2-712-0799 KEYWORDS: Valley-shaped slope walking, Lower extremity, Kinematics, Kinetics, Military boots Military personnel suffer from musculoskeletal injuries during military operations and training. Military training is often performed with military boots in challenging outdoor environments where the ground surface is not leveled. Thus, this study aimed to determine the hip, knee, and ankle joint kinematics and kinetics during valley-shaped slope walking (VSW). Eighteen Reserve Officer Training Corps cadets walked on a valley-shaped slope wearing military boots. Three-dimensional kinematic and kinetic data of the lower extremity were obtained using a force plate and motion capture system. Kinematics changed to control the lowered and raised body during VSW. Anterior–posterior ground reaction forces (GRF) and vertical GRF were significantly increased during VSW compared with that during level walking. Furthermore, compared with level walking, both the knee extension moment and ankle plantarflexion moment were significantly increased during VSW. Joint kinematics and kinetics changed in response to the shape of the ground surface. During VSW, the changes in the pattern and magnitude of the joint kinematics and kinetics demonstrated that different movement strategies are required to provide soldiers the necessary stability and mobility. Manuscript received: August 31, 2015 / Revised: October 5, 2015 / Accepted: October 13, 2015 1. Introduction Military personnel suffer from musculoskeletal injuries associated with military operations or training. Musculoskeletal injury rates for military recruits and infantry soldiers are reported to be higher than those for endurance athletes. 1 Additionally, the majority of those musculoskeletal injuries are related to the lower extremity 1 . High injury rates in the military population decreases military readiness and time for training, thereby resulting in unnecessary social and economic costs. However, there is a lack of biomechanical studies to identify risk factors for the musculoskeletal injuries that may aid in injury prevention. Military training is often performed in challenging outdoor environments where the ground surface is uphill, downhill, or a combination of both. Although movement on either uphill or downhill roads has been studied, the biomechanics of movements on a tilted surface, where uphill and downhill road conditions are combined, has not been reported. Previous studies have reported on joint kinematics and kinetics, which include ground reaction forces (GRF); hip, knee, and ankle joint moments; and traction coefficients, during uphill or downhill walking. 2-7 Although these studies provide biomechanical information during slope walking, no kinematic and kinetic data for a valley-shape slope have been published. Actual outdoor ground surfaces often consist of different shapes of slope such as a valley, which is a combination of declination and inclination. Therefore, the purpose of this study is to determine the three-dimensional hip, knee, and ankle joint kinematics and kinetics during valley-shaped slope walking (VSW). 2. Method Eighteen Reserve Officer Training Corps cadets were recruited (age: 22.8±2.5 years, height: 173.8±3.4 cm, mass: 66.5±5.3 kg, BMI: 22.0± 1.9 kg/m 2 ). All subjects were healthy without any current pain or history of lower extremity musculoskeletal injuries requiring surgery. Prior to participation, all subjects were asked to sign an informed consent form approved by the institutional review board. A three dimensional (3-D) motion capture system equipped with eight infrared cameras (Motion Analysis Corp., Santa Rosa, CA, USA) was used to record the motion of hip, knee, and ankle joints at a sampling rate of 200 Hz during VSW. The high frequency capturing increases the accuracy of the joint kinematics and kinetics. 8 However walking is not DOI: 10.1007/s12541-015-0348-y ISSN 2234-7593 (Print) / ISSN 2005-4602 (Online)