Lower Extremity Joint Kinematics and Muscle Activity During Cross-Legged Sitting Posture: A Preliminary Study Report

Cross-legged sitting, (lotus pose), is a commonly practiced posture for activities-of- daily-living(ADL) and meditation that demands multi-planar motion of lower-extremity joints. Negligible information on biomechanical demands of cross-legged sitting, motivated the present study. A 12-camera 3-D motion capture system was used to evaluate kinematics of cross-legged sitting in 10 healthy female adults. Muscle activity of abdominals, erector spinae and lower extremity antigravity muscles was studied using surface - electromyography(s-EMG). Data were processed using PlugIn-gait model and filtered at 10Hz. Spine, pelvis and lower-extremity joint angles were computed and validated with observational analysis of joint motion and data from previous studies. Kinematic analyses revealed tri-planar motion at lower extremity joints; namely: hip flexion [82<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>(11.2<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>)], hip abduction [28°(3.6°)] and hip external rotation [14<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>(8.4<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>)]; knee flexion [150°(6.6°)] with knee varus [36.8<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>(8.4°)], ankle plantarflexion of 17.4°(7.3°) with ankle inversion[16.4°(13.2°)] During descent, the abdominals(including oblique) and erector spinae demonstrated highest muscle activity. Sustaining of cross-legged sitting posture required minimal activity in rectus abdominis, external oblique, and erector spinae; whereas ascent from cross-legged sitting activated trunk muscles and lower extremity muscles. The preliminary findings unravel kinematic and muscular demands of the complex cross-legged sitting posture based on the plug-in-gait model. Further biomechanical exploration of this posture using a specific musculo-skeletal model will provide valuable insights about the postural control and kinetic demands during the posture. Biomechanical exploration will open doors to wider therapeutic applications of the posture; and enhanced prosthetic and orthotic design for maximization of functioning.