Background: McKenzie back extension exercises from prone position has been widely prescribed forpatients with lumbosacral radiculopathy (LSR). It has been reported to reduce radicular symptoms. Suchreduction might indicate that decompression effect of this exercise on the compromised nerve root. The aimof this study was to evaluate the effect of McKenzie back extension exercise from prone position on soleusH-reflex of patients with LSR.Patient and Method: Seventeen male and Thirteen female patients (46.27±10.13 years) with confirmedchronic unilateral LSR participated in the study. All patients had done thirty repetitions of McKenzieback exercise from prone position. The soleus H-reflex was measured before and after the exercise. TheHreflex was elicited by electrical stimulation of the tibial nerve on the popliteal fossa of each legs. Thenon-involved leg of the patient was used as a control. Subjective pain intensity and sit-to-stand performancewere additionally measured before and after back extension exercise using numerical pain analog scale anda stopwatch respectively.Results: The H-reflex latency within the affected leg showed significant difference after the exercise (p<0.05). The pain intensity and the sit-to-stand test had shown significant changes following exercise (p <0.05).Conclusion: This study could indicate that the McKenzie repeated back extension exercises the mannerperformed in this study had improved the H-reflex, pain intensity or functional level of the patients.