Muscle Tone in Diabetic Polyneuropathy Evaluated by the Quantitative Pendulum Test

Lin C-CK, Ju M-S, Huang H-W. Muscle tone in diabetic polyneuropathy evaluated by the quantitative pendulum test. Objective: To quantify the muscle tone of upper limbs in patients with diabetic polyneuropathy (DPN). Design: Case-control study. Quantitative upper-limb pendulum tests were conducted, and model analysis was performed. Setting: Outpatient clinic of a medical center. Participants: The experimental group consisted of patients with type 2 diabetes suffering from symptomatic but not disabling polyneuropathy. The diagnosis of polyneuropathy was based on symptoms, signs, and nerve conduction velocity (NCV) study. The control group consisted of age- and sex-matched normative subjects. In total, 181 subjects were recruited, including 128 controls and 53 DPN patients. Interventions: Not applicable. Main Outcome Measures: Quantitative biomechanic parameters (number of swings, relaxation index, stiffness constant and damping coefficient) were formulated and the differences between groups were investigated. Results: The number of swings and stiffness constant showed no difference between groups. Relaxation index increased and damping coefficient decreased significantly in the DPN group. Conclusions: Muscle tone, defined as passive resistance in the tested range, in DPN patients was shown to be decreased. The decrease was mainly due to a decrease in the velocity-dependent component. The decrease did not correlate with the decrease in NCV and could not be detected by the conventional manual pendulum test performed at the bedside.