Motor evoked potentials in the human upper and lower limb do not increase after single 30-minute sessions of acute intermittent hypoxia

J Appl Physiol (1985). 2024 May 9. doi: 10.1152/japplphysiol.00010.2024. Online ahead of print.ABSTRACTAcute Intermittent Hypoxia (AIH) can induce sustained facilitation of motor output in people with spinal cord injury (SCI). Most studies of corticospinal tract excitability in humans have used 9% FiO2 AIH (AIH-9%), with inconsistent outcomes. We investigated the effect of single sessions of 9% FiO2 and 12% FiO2 AIH (AIH-12%) on corticospinal excitability of a hand and leg muscle in able-bodied adults. Ten naïve participants without SCI completed three sessions comprising 15 cycles of one minute of AIH-9%, AIH-12% or sham (SHAM-21%) followed by one minute of room air (21% FiO2) in a randomised crossover design. Motor evoked potentials (MEPs, n=30, ~1mV) elicited at rest by transcranial magnetic stimulation and maximal M-waves (Mmax) evoked by peripheral nerve stimulation were measured from the first dorsal interosseous (FDI) and tibialis anterior (TA) muscles at baseline and at ~0, 20, 40, and 60 minutes post-intervention. AIH-9% induced the greatest reduction in SpO2 (to 85% vs 93% and 100% in AIH-12% and SHAM-21%, respectively; p < 0.001) and the greatest increase in ventilation (by 22% vs 12% and -3% in AIH-12% and SHAM-21%, respectively (p<0.001)). There was no difference in MEP amplitudes (%Mmax) after any of the three conditions (AIH-9%, AIH-12%, SHAM-21%) for both FDI (p=0.399) and TA (p=0.582). Despite greater cardiorespiratory changes during AIH-9%, there was ...
Source: Appl Human Sci - Category: Physiology Authors: Source Type: research