THE BIOMECHANICAL EFFECTS OF CROSS-LEGGED SITTING ON THE LOWER LIMBS AND THEIR IMPLICATIONS FOR REHABILITATION

Abstract

Project Title: The biomechanical effects of cross-legged sitting on the lower limbs and their implications for rehabilitation. Background: Balanced coordination between several body parts could play a significant role in protecting these body parts from injury and the body posture from deformities, particularly during the sitting position, as sitting constitutes more than half of people’s daily activities. Although the cross-legged sitting posture is widely practiced as part of the daily routine in certain communities, limited research is focused on the effects of CLS on biomechanics. Therefore, the aim of this study was to analyze the biomechanical effects of cross-legged sitting on the lower limb joints and muscles and investigate the effect of CLS on body balance. Methods: Thirty healthy volunteers were invited to participate in this study: 15 males and 15 females. Cross-legged sitting (CLS) was analysed biomechanically by comparing the situation before and after 20 minutes of CLS, based on temporospatial measures, kinetic and kinematic parameters, muscular electrical activity, muscular strength, and a static and dynamic balance assessment. The instruments used were the Vicon motion capture system with a combination of the force platform, Electromyography, Force sensor, the single-leg stance test, and the four-square step test. The variables were analysed using SPSS® version 28. Results: CLS can affect the gait’s temporospatial parameters positively by increasing the cadence, increasing the walking speed, and decreasing the stride and step time. In addition, the kinematic ROM for all the lower limb joints increased post-CLS compared to pre-CLS in all planes except for the knee sagittal ROM, which decreased significantly following CLS. Considering the kinetic parameters, the medial and lateral forces increased significantly in terms of RoF during walking post-CLS compared to pre-CLS xviii in almost all of the lower limb joints, including the hip, knee, and ankle on both sides. Moreover, the left knee and right ankle joints were similar in terms of an increased anterior force post-CLS, while the posterior force was increased in both sides of the hip joints and decreased significantly in only the left ankle. Furthermore, the compression force increased significantly on both sides of almost all of the lower limb joints except for the right knee, while the tension force improved noticeably on only the right hip, left hip, and left knee joint. When comparing walking pre-CLS with post-CLS according to the moment values, it was observed that the flexion/extension moment rose significantly post-CLS in the hip and knee joints in terms of ROM, while only the plantar flexion moment increased in the right ankle during walking post-CLS compared to pre-CLS. However, it was noticed that only the left leg displayed a significant increase in the knee valgus moment, as well as the hip and ankle abduction moment. Regarding the rotation direction, the left knee displayed a significant decline in terms of the internal/external rotational moment. Regarding the power values of all of the lower extremity joints, it was found that all of the hip, knee, and ankle joints were similar in terms of displaying increased RoP during the gait after 20 min of CLS compared to before. Regarding muscular electrical activity and muscular strength, only the lateral gastrocnemius muscle was activated significantly post-CLS. In the case of muscle strength, the hip extensor and knee flexor muscles became significantly stronger (by approximately 14%) post-CLS compared to pre-CLS roughly and the ankle plantar flexor’s maximum force increased noticeably, by about 4%, post-CLS. Regarding balance, CLS had a positive impact on the dynamic balance, while the static balance was affected negatively post-CLS compared to pre-CLS. Conclusion: CLS has a positive impact on all of the lower limb joints and muscles apart from the knee Flexion/Extension angle and Internal/External rotational moments. Depending on the muscular results, CLS can be safely included in people’s daily routine xix and in any rehabilitation programmes to improve the muscular strength that is responsible for hip extension, knee flexion and ankle plantar flexion, and increase the range of motion accordingly. However, CLS should be avoided for any patients suffering from static balance disturbance.