Effects of age and leg length upon central loop of the Gastrocnemius-soleus H-reflex latency

BACKGROUND: central loop of the gastrocnemius-soleus H-reflex latency (T(c)) that looks promising in the diagnosis of S1 radiculopathy; has been investigated in a few studies and only two of them have focused on the constitutional factors affecting it. Although leg length has been shown to contribute to the T(c), the role of age is controversial. More confusing, none of the previously performed studies have used strict criteria to rule out subclinical neuropathy, so the results could be misleading. This study has been performed to determine the influence of leg length and age on T(c )among a carefully selected group of healthy volunteers. METHODS: after screening forty six volunteers by taking history, physical examination and a brief electrophysiologic study; forty of them were selected to enroll into the study. T(c )was obtained in all the study subjects and leg length and age were recorded for correlational analyses. RESULTS: this group was consisted of 26 males (65%) and 14 females (35%) with the age range of 19–65 years (Mean ± SD: 37 ± 10.7) and leg length range of 29.5–43 centimeters (36.4 ± 3.4). Mean ± SD for T(c )was 6.78 ± 0.3. We found a significant correlation between T(c )and leg length (p value= 0.003, r = 0.49 and confidence interval 95% = 0.59–0.88), no significant correlation was found between age and T(c )(p value= 0.48, r = 0.11), also we obtained the regression equation as: T(c )= 0.04L + 5.28 CONCLUSIONS: in contrast to leg length, age was not correlated with T(c). Future studies are required to delineate other contributing factors to T(c)