Neuroscience Research Australia, Randwick, New South Wales, Australia 2031.
J Appl Physiol (1985). 2011 Sep;111(3):743-50. doi: 10.1152/japplphysiol.00603.2011. Epub 2011 Jul 7.
Muscle pain has widespread effects on motor performance, but the effect of pain on voluntary activation, which is the level of neural drive to contracting muscle, is not known. To determine whether induced muscle pain reduces voluntary activation during maximal voluntary contractions, voluntary activation of elbow flexors was assessed with both motor-point stimulation and transcranial magnetic stimulation over the motor cortex. In addition, we performed a psychophysical experiment to investigate the effect of induced muscle pain across a wide range of submaximal efforts (5-75% maximum). In all studies, elbow flexion torque was recorded before, during, and after experimental muscle pain by injection of 1 ml of 5% hypertonic saline into biceps. Injection of hypertonic saline evoked deep pain in the muscle (pain rating ∼5 on a scale from 0 to 10). Experimental muscle pain caused a small (∼5%) but significant reduction of maximal voluntary torque in the motor-point and motor cortical studies (P < 0.001 and P = 0.045, respectively; n = 7). By contrast, experimental muscle pain had no significant effect on voluntary activation when assessed with motor-point and motor cortical stimulation although voluntary activation tested with motor-point stimulation was reduced by ∼2% in contractions after pain had resolved (P = 0.003). Furthermore, induced muscle pain had no significant effect on torque output during submaximal efforts (P > 0.05; n = 6), which suggests that muscle pain did not alter the relationship between the sense of effort and production of voluntary torque. Hence, the present study suggests that transient experimental muscle pain in biceps brachii has a limited effect on central motor pathways.
肌肉疼痛对运动表现有广泛的影响，但疼痛对自愿激活的影响，即收缩肌肉的神经驱动水平，尚不清楚。为了确定诱导性肌肉疼痛是否会降低最大自主收缩期间的自愿激活，使用运动点刺激和经颅磁刺激对肱二头肌进行评估，以评估肘屈肌的自愿激活。此外，我们进行了一项心理物理学实验，以研究在广泛的次最大努力范围内（5-75%最大）诱导性肌肉疼痛的影响。在所有研究中，通过向二头肌注射 1 毫升 5%高渗盐水来诱发肌肉疼痛，在实验前、实验中和实验后记录肘部弯曲扭矩。高渗盐水注射会引起肌肉深部疼痛（疼痛评分在 0 到 10 的范围内约为 5）。在运动点和运动皮质研究中，实验性肌肉疼痛导致最大自主扭矩的小（约 5%）但显著降低（P <0.001 和 P = 0.045，分别;n = 7）。相比之下，尽管在疼痛缓解后收缩时运动点刺激测试的自愿激活降低了约 2%（P = 0.003），但使用运动点和运动皮质刺激评估时，实验性肌肉疼痛对自愿激活没有显著影响。此外，在次最大努力期间（P > 0.05;n = 6），诱导性肌肉疼痛对扭矩输出没有显著影响，这表明肌肉疼痛不会改变用力感和自愿扭矩产生之间的关系。因此，本研究表明，短暂的肱二头肌实验性肌肉疼痛对中枢运动通路的影响有限。
