Central alterations of neuromuscular function and 1 feedback from group III - IV muscle afferents following 2 exhaustive high intensity one leg dynamic exercise

23 The aims of this investigation were to describe the central alterations of neuromuscular 24 function induced by exhaustive high intensity one leg dynamic exercise (OLDE, study 1), and 25 to indirectly quantify feedback from group III-IV muscle afferents via muscle occlusion 26 (MO, study 2) in healthy adult male humans. We hypothesized that these central alterations 27 and their recovery are associated with changes in afferent feedback. Both studies consisted of 28 two time to exhaustion tests at 85% peak power output. In study 1, voluntary activation level 29 (VAL), M-wave (M), cervicomedullary motor evoked potential (CMEP), motor evoked 30 potential (MEP) and MEP cortical silent period (CSP) of the knee extensor muscles were 31 measured. In study 2, mean arterial pressure (MAP) and leg muscle pain were measured 32 during MO. Measurements were performed pre-exercise, at exhaustion and after three 33 minutes recovery. Compared to pre-exercise values, VAL was lower at exhaustion (-13±13%, 34 P<0.05) and after three minutes recovery (-6±6%, P=0.05). CMEParea/Marea was lower at 35 exhaustion (-38±13%, P<0.01) and recovered after three minutes. MEParea/Marea was higher at 36 exhaustion (+25±27%, P<0.01) and after three minutes recovery (+17±20%, P<0.01). CSP 37 was higher (+19±9%, P<0.01) only at exhaustion and recovered after three minutes. Markers 38 of afferent feedback (MAP and leg muscle pain during MO) were significantly higher only at 39 exhaustion. These findings suggest that the alterations in spinal excitability and CSP induced 40 by high intensity OLDE are associated with an increase in afferent feedback at exhaustion, 41 whilst central fatigue does not fully recover even when significant afferent feedback is no 42 longer present. 43 250 words 44