Muscle activation state does not alter paretic lower extremity motor threshold responses in individuals with chronic stroke

Abstract Repetitive transcranial magnetic stimulation (rTMS) is commonly dosed using resting motor threshold (rMT), i.e., the minimal stimulator power needed to elicit a response in musculature. Many stroke survivors do not present with rMT, necessitating rTMS dosing during active contractions, or an (aMT). However, relationship between rMT and aMT post-stroke unknown. We conducted cross-sectional comparison of MTs measured at four states muscle activation: resting, 5% maximal voluntary contraction (5%MVC), 10%MVC, standing (sMT). Paretic non-paretic were participants chronic phase (>6 months) (N=10, Age=60.9, SD 8.1, 7F/3M), dominant limb healthy controls (N=11; Age=39.9 9.4; 7F/4M) tibialis anterior. The criteria for MT determination across activation established averaged peak-to-peak background electromyography activity 10%MVC + 2 each participant, instead 50uV 100uV. state randomized order simple adaptive parameter estimation individualized criteria. Linear mixed models Bonferroni correction used compare estimates within (a=0.05). different (p=0.7962). Non-paretic was less than sMT (10%MVC=34 SE 3.8 mso; sMT=47 4.3 mso, p=0.0333; rMT=50 p=0.0082). Dominant (10%MVC=28 2.7 rMT=41 p=0.0018; sMT=37 p=0.0215), 5%MVC (5%MVC=30 p=0.0074). Using same criterion on paretic yielded no differences required recruit similar neuron pool amount. based versus could allow comparable neuromodulatory effects output. Research Category Technology Methods Clinical Research: 10. Transcranial Magnetic Stimulation (TMS) Keywords: Stroke, TMS,