Effect of facilitation on side-to-side H reflex amplitude ratio

Although voluntary facilitation is sometimes necessary to evoke the H reflex, relevant data is lacking on side-to-side amplitude ratios in facilitated condition. To determine the normal limits of H reflex amplitude ratio in facilitation and to assess it's clinical applicability, we performed FCR H reflex study in fifty asymptomatic subjects. The lower limit of the amplitude ratio that encompasses 97.5% of subjects in facilitation was 0.48. These data suggest H reflex amplitude ratio measured in facilitation without averaging is useful for the diagnosis of unilateral radiculopathy.