The controversy over the influence of static tilt on soleus motoneuron excitability in man.

The influence of static fore-aft body tilts on the excitability of the human soleus motoneuronal pool had been studied by mapping the H reflex amplitude as a function of head positions by two groups of investigators with different results. In 11 of 13 subjects studied, we (C.W.Y. Chan and R.E. Kearney, 1982, Neurosci. Lett. 33: 333-338) found that the H reflex was a minimum when the head was near the vertical position, and often increased as a sinusoidal function of tilt to a maximum of 60 degrees forward or backward. In contrast, I.G. Aiello, G. Rosati, G. Serra, V. Jugnoli, and M. Manca (1983, Exp. Neurol. 79: 18-26) reported a linear decrease in the H reflex amplitude in all their subjects when the body was tilted from the vertical to the horizontal supine position. The differences in these findings were discussed from the point of view of methodology and in light of recent animal and human studies.