A re-evaluation of the pattern of group I fibre projections in the human lower limb on using randomly alternated stimulations.

Changes in amplitude of soleus, quadriceps and biceps femoris monosynaptic reflexes were studied when preceded by conditioning stimulations applied to group I fibres from different muscles of the human lower limb. Control test reflexes and conditioned reflexes were alternated either regularly or randomly. For the most part, the same qualitative pattern of group I fibre projections was found with both modes of alternation, but the amount of facilitation or inhibition induced by group I fibre stimulation was significantly smaller with the random mode. This may be due to an underestimation of randomly-induced effects and/or an overestimation of regularly-induced effects. Because this overestimation can lead to artefactual results, regular mode of alternation should be avoided.