Unger Janelle, Andrushko Justin W, Oates Alison R, Renshaw Doug W, Barss Trevor S, Zehr E Paul, Farthing Jonathan P
College of Kinesiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Rehabilitation Neuroscience Laboratory, Physical and Health Education, University of Victoria, Victoria, British Columbia, Canada.
Physiol Rep. 2019 Jul;7(14):e14179. doi: 10.14814/phy2.14179.
Hoffmann (H-) reflex amplitudes in plantar flexor soleus muscle are modulated by posture, yet dorsiflexor tibialis anterior (TA) H-reflex parameters have sparingly been studied. The purpose was to investigate modulation of the TA H-reflex when postural demands are increased from sitting to standing. In this study, data from 18 participants (Age: 25 ± 4 years, Height: 170.9 ± 9.5 cm, Weight: 75.9 ± 17.2 kg) allowed comparison of two experimental conditions involving different postures (i.e. sitting and standing). Maximal amplitude of the TA H-reflex (H ) as a percent of the maximal M-wave amplitude (M ) (H (% M )) during sitting and standing was compared using ANOVA. Modulation of TA H-reflex amplitude was found: Eleven participants showed facilitation and seven showed no change of reflex amplitudes. Only participants in the facilitation group showed modulation related to changes in posture (sitting: 8.7 ± 2.9%; standing: 14.8 ± 6.7%, P = 0.005). These data provide evidence of the sensitivity to posture of TA H-reflexes. As with task-dependent changes in soleus H-reflexes, presynaptic regulation of Ia afferent transmission is a possible mechanism. Further investigations into causes of modulation are warranted.
跖屈比目鱼肌的霍夫曼（H-）反射波幅受姿势调制，但背屈胫骨前肌（TA）的H反射参数鲜有研究。本研究目的是探究当姿势需求从坐姿增加到站姿时TA肌H反射的调制情况。本研究纳入18名参与者（年龄：25±4岁，身高：170.9±9.5厘米，体重：75.9±17.2千克）的数据，比较两种不同姿势（即坐姿和站姿）的实验条件。采用方差分析比较坐姿和站姿时TA肌H反射的最大波幅（H）占最大M波幅（M）的百分比（H（%M））。结果发现TA肌H反射波幅存在调制现象：11名参与者表现为易化，7名参与者反射波幅无变化。仅易化组参与者表现出与姿势变化相关的调制（坐姿：8.7±2.9%；站姿：14.8±6.7%，P=0.005）。这些数据证明了TA肌H反射对姿势的敏感性。与比目鱼肌H反射的任务依赖性变化一样，Ia传入神经传递的突触前调节是一种可能的机制。有必要进一步研究调制的原因。
