Decreased amplitude of surface electromyo- graphic recordings of muscle activation along the posterior myofascial kinematic chain in subjects with chronic nonspecific low back pain compared to healthy subjects

BACKGROUND: The concept of myofascial continuity suggests that muscles activate along kinematic chains with common fascial coverings. Yet, the literature lacks evidence in regards to the function of anatomical chains in populations suffering from low back pain (LBP). OBJECTIVE: To examine muscle activations along the superficial back line in LBP patients compared to healthy controls. METHODS: The sample study included 20 males with chronic LBP (mean age 28.7 (± 3.05) years, mean BMI 24.91 (± 2.76)) and 17 healthy controls (mean age 31.06 (± 7.76) years, mean BMI 23.46 (± 3.43)). Muscle activation (gastrocnemius, hamstrings, erector spine, and upper trapezius) along the superficial back line was measured using surface EMG. All subjects underwent five test conditions: Conditions 1-3 involved passive movement, active movement and active movement against maximum isometric resistance of the right gastrocnemius muscle. Conditions 4 and 5 involved neck extension without and with isometric resistance from the prone position. The main outcome was relative muscle activation amplitude between research and control subjects. RESULTS: Muscle activation along the posterior anatomical chain was observed during distal movement (plantar flexion or neck extension). LBP patients showed significant lower muscle activation in the erector spine of lower back region compared with the control group during active plantar flexion and active neck extension (p< 0.05). Lower muscle activation in other regions (gastrocnemius, hamstrings, erector spine level T6) was observed in the research group (although not significant). CONCLUSION: LBP may cause or result in a lower muscle activation of the posterior kinematic myofascial chain muscles.