Blink reflex excitability and blood lactate levels

The aim of the present study was to assess, in healthy humans, the effects of high blood lactate levels, induced with a maximal cycling, on the excitability of brainstem motoneurons, tested by using the Blink Reflex (BR) recovery cycle. The study was carried out on 10 male athletes from the Track and Field Team of the University. The study previewed the assessment of BR excitability after an exhaustive exercise. Capillary blood lactate and glucose levels as well as BR excitability were measured before, at the end and 10 minutes after the conclusion of the exercise. The Blink Reflex (BR) was elicited by electric stimulation of supraorbital nerve. The recovery cycle of the R2 component of the reflex was obtained using the paired-stimulus paradigm (conditioning and test electric pulse of equal intensity), at ISI of 100, 600, 1000 and 1500 ms. In these experimental conditions, it was observed that an increase of blood lactate is associated with a significant decrement of R2 component (ipsi- as well as contralateral) at ISI 1000 and 1500 ms. Although a direct action of lactate at medullary level cannot be excluded, it could be reasonable to hypothesize that lactate influences BR by acting on motor cortex.