Forman Davis A, Monks Michael, Power Kevin E
Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada; Faculty of Science, University of Ontario Institute of Technology, Oshawa, Ontario, Canada.
Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.
Neurosci Lett. 2019 Jan 23;692:100-106. doi: 10.1016/j.neulet.2018.11.003. Epub 2018 Nov 3.
The purpose of the present study was to examine corticospinal excitability to the biceps and triceps brachii during arm cycling and an intensity-matched tonic contraction using stimulus response curves (SRCs) elicited via transcranial magnetic stimulation (TMS). Corticospinal excitability was assessed using TMS elicited motor-evoked potentials (MEPs) at eight different stimulation intensities (85-190% of MEP threshold). MEPs were recorded during arm cycling at two different positions, mid-elbow flexion (6 o'clock relative to a clock face) and mid-elbow extension (12 o'clock relative to a clock face), in addition to an intensity-matched (12 o'clock) tonic contraction. At the 12 o'clock position, the slope of the SRC was significantly lower during arm cycling than the tonic contraction for the biceps brachii (Cycling: 0.64 ± 0.47, Tonic: 1.02 ± 0.38, P < 0.05) but was not different for the triceps brachii (Cycling: 1.33 ± 0.49, Tonic: 1.48 ± 0.43, P = 0.42). Within arm cycling, the SRC slope was significantly greater at the 6 o'clock position than 12 o'clock position for the biceps brachii (6 o'clock: 1.37 ± 0.24, 12 o'clock: 0.64 ± 0.47, P < 0.05) but was not different for the triceps brachii (6 o'clock: 1.11 ± 0.28, 12 o'clock: 1.33 ± 0.49, P = 0.34). These findings demonstrate that corticospinal excitability to the biceps brachii is task-dependent during the extension phase of arm cycling. Neither position nor task influenced corticospinal excitability to the triceps brachii, providing further support that the motor control of locomotor outputs is muscle-specific.
本研究的目的是通过经颅磁刺激（TMS）诱发的刺激反应曲线（SRC），研究在手臂骑行和强度匹配的强直收缩过程中，皮质脊髓对肱二头肌和肱三头肌的兴奋性。使用TMS在八种不同刺激强度（运动诱发电位（MEP）阈值的85-190%）下诱发运动诱发电位（MEP）来评估皮质脊髓兴奋性。除了强度匹配（12点）的强直收缩外，在手臂骑行的两个不同位置，即肘部中间屈曲（相对于钟面的6点）和肘部中间伸展（相对于钟面的12点）记录MEP。在12点位置，肱二头肌在手臂骑行过程中SRC的斜率显著低于强直收缩（骑行：0.64±0.47，强直：1.02±0.38，P<0.05），但肱三头肌无差异（骑行：1.33±0.49，强直：1.48±0.43，P = 0.42）。在手臂骑行过程中，肱二头肌在6点位置的SRC斜率显著大于12点位置（6点：1.37±0.24，12点：0.64±0.47，P<0.05），但肱三头肌无差异（6点：1.11±0.28，12点：1.33±0.49，P = 0.34）。这些发现表明，在手臂骑行的伸展阶段，皮质脊髓对肱二头肌的兴奋性是任务依赖性的。位置和任务均未影响皮质脊髓对肱三头肌的兴奋性，这进一步支持了运动输出的运动控制是肌肉特异性的。
