Introduction:The positive aspects of performing yoga for

Introduction:The word yoga comes from the Sanskrit root yuj meaning union. Yoga comprises of mental and physical exercises helpful to attain  samadhi or the union of the individual self with the infinite1.The regular practice of yoga helps, establish natural harmony between various organs of the body. This in turn helps maintain well-being of the individual. The origin of yoga though a highly debated topic, could be traced back since the evolution of the Indus Valley civilization, as a typical Indian cultural phenomenon, firmly rooted in the society2,3. Since then yoga has undergone several variations in the style of practise pertaining to four generations- Pre-Vedic, Vedic, Pre-Classical, Classical and Postclassical periods, each adding its own essence to yoga4,5. Yoga is a broad concept involving various physical, mental and spiritual practises. The most popular amongst all yoga asanas is the Hatha Yoga. Some historians claim the emergence of hatha yoga practise predates even before the 11th century and sheds its persistence over following proper exercise routine, while maintaining specific body postures(asanas)6. During the late 20th century, the practise of hatha yoga was highly popularised in the western world by B.K.S Iyengar.A. TrikonasanaTrikonasana, an asana in Hatha Yoga, largely focuses on the lateral bend-stretching, resulting from the wider spacing of the feet. The movement is stabilized by the relationship between the pelvis and thighs which is directly related to the lateral bending of the spinal column7. Performing trikonasana, while maintaining the perfect posture elongates the leg muscles, removes stiffness in the legs and hips, thereby correcting any minor deformity in the legs further allowing them to develop uniformly8. Performing any yogasana, (especially Trikonasana) is governed by step-wise body posture maintenance and stability which, are the significant factors. The yoga asanas are usually taught by the teachers who learnt them from their predecessors who at no point have tried to step outside of this tradition of learning to look at yoga from a research point of view. The start of 21st century saw more of elaborate scientific research focused towards the positive aspects of performing yoga for various diseases and body pain and results delivered show yoga as a relatively safer form of exercise, capable of increasing strength, ?exibility, balance and functional endurance of people in good health conditions and also those with musculoskeletal affliction9-11. MengNi et al. analysed 11 yoga postures from Vinyasa yoga for trunk and hip muscles19.Heather S.Longpré et. al primarily compared the muscle activation of the thigh muscles in various standing poses, one of which being Trikonasana12. In one study, the authors have used EMG to analyse and compare abdominal muscles activity while doing breathing yoga exercise versus traditional curls13. Salem et al. proposed one of the first biomechanical analysis methods while performing hatha yoga using motion capture system integrated with surface electromyography(sEMG) to quantify the physical demands of performing the asanas and evaluating joint angles, muscle activation levels, etc, for various hatha yoga postures14.Although the surface-electromyography (sEMG) sensors have been used to study the muscle activation patterns, it has significant amount of demerits to its account. The surface electromyography(sEMG) can give the insights of the superficial muscles only. Human body is prone to the phenomenon of perspiration under high temperature or humid conditions, which can lead to sliding of the sEMG sensors and eventually falling-off the skin. Excessive fat deposition in the body can aggravate the application of the sEMG sensors15. Moreover they are prone to noise and often mixed up with other muscle signals16. The solution for this is to use inverse dynamics algorithms developed in robotics to obtain the joint torques of the skeleton and then run numerical optimization to compute the muscle tensions17.Here the joint torques are computed from the motion data and the geometric and inertial parameters of the skeleton model, and the mathematical optimization with physiologically appropriate criteria, e.g. minimizing the signal dependent noise, distributes them to the muscle tensions18.The motion data can be captured by various methods one of which is optical motion capture. The notion of motion capture system was primarily intended for research applications in the field of computer vision, computer-generated imagery(CGI), motion planning in robotics, etc. But recent developments in the field of biomechanical research has witnessed marker-based Optical Motion capture system as a non-invasive and highly valued tool for recording and analysis of the human motion tracking, particularly pertaining to sports & rehabilitation studies19,20.One of the reasons for using  the optical motion capture system in biomechanical studies is the ease of interfacing the acquired human motion  data with different musculoskeletal modelling algorithms (like OpenSim, Adams LifeMod, etc) for analyzing human gait patterns, kinematics, dynamics and determination of various associated parameters like muscle activation, joint torques and angles, etc21.In the field of sports-rehabilitation sciences optical motion capture has been extensively used as a medium of recording and analysing the motion patterns of the subjects22.Though, previously there have been experimental studies conducted on various yogasana based on surface Electromyography (sEMG) which involves integrating Inertial Measurement Unit (IMUs), accelerometer(ACC)23 or gyroscope based sensors, very few have taken the approach of the utilization of optical motion capture system as a means of data acquisition. Moreover, since body posture is very critical in yoga, optical motion capture system can be very useful to capture full body to check proper alignment.