The Relationship Between Lower Limb Biomechanics and Muscle Strength With Non-Specific Low Back Pain

Background. The rising incidence of low back pain (LBP) poses a challenge in terms of pain-related healthcare costs and reduced work capacity. The main researched causes of LBP are such sociocultural and demographic aspects as sedentary work and age. Changes in body and step biomechanics have been found to be involved in the onset of LBP as well. However, analysis of lower limb biomechanics and muscle strength in relation to non-specific low back pain (NSLBP) is insufficient, thus the present study aims to explore this topic from a biomechanical and muscle strength perspective. Aim. To determine the relationships between lower limb biomechanics, gluteal and thigh muscle strength, and NSLBP. Methods. The study involved 34 participants (19 men and 15 women) divided into two groups. The first group con­sisted of individuals who experienced NSLBP (n = 17), while the second group included those who reported only minimal discomfort or no pain at all (n = 17). Pain intensity was assessed using the Visual Analogue Scale. The range of motion of the calf and thigh was measured with a goniometer, dynamic balance was evaluated using the Y Balance Test, lower limb biomechanics were assessed with a Step-Down Test, and the strength of the gluteal and thigh muscles was measured using the DIERS Myoline Professional system. Results. NSLBP had no effect on thigh and calf range of motion or on dynamic balance results. Participants without NSLBP had significantly greater hip adductor strength compared to control group (p = 0.01). Calf flexor strength was significantly lower compared to extensor strength (p < 0.05), and hip abductor strength was significantly lower than adductor strength, regardless of NSLBP presence (p < 0.05). Functional knee instability during the Drop Jump Test was observed in participants experiencing NSLBP (p < 0.01). Conclusions. The subjects’ thigh and calf range of motion and dynamic balance indicators were independent of perceived NSLBP. However, functional instability of the knee joint was observed in individuals with NSLBP. The strength of the thigh adductor muscles was greater in those without back pain. The strength of the calf flexors and thigh abductors was lower than that of their antagonists, regardless of the presence of low back pain. Keywords: low back pain; dynamic balance; functional knee joint stability; dynamometry