Goode Caleigh, Cole David M, Bolton David A E
Department of Kinesiology and Health Science, Utah State University, 7000 Old Main Hill, Logan, UT, 84322-7000, USA.
Department of Kinesiology and Health Science, Utah State University, 7000 Old Main Hill, Logan, UT, 84322-7000, USA; Interdisciplinary Program in Neuroscience, Utah State University, 2810 Old Main Hill, Logan, UT, 84322-2810, USA.
Gait Posture. 2019 May;70:260-263. doi: 10.1016/j.gaitpost.2019.03.018. Epub 2019 Mar 20.
When automatic, yet unwanted action is quickly inhibited, short-lived suppression throughout the motor system ensues. This effect is referred to as global suppression. Although response inhibition is essential for behavioral flexibility, widespread motor suppression may delay action reprogramming. In reactive balance control, even fleeting suppression of the motor system could interfere with our ability to adapt compensatory reactions quickly enough to avoid a fall.
Is muscle activity in the hand suppressed when a prepotent compensatory step becomes suddenly blocked in a balance recovery task?
Nineteen young adults were tested using a lean and release apparatus. Participants were occasionally released from a support cable resulting in forward body displacement. At the start of each trial, vision was occluded and a leg block was either placed in front of the legs or removed to allow a forward step. After goggles opened, the cable was released to cause a postural perturbation and participants had to either quickly step forward (STEP) or use a feet-in-place reaction to regain stability (NO-STEP). Step trials were much more frequent to promote stepping. Transcranial magnetic stimulation (TMS) was delivered shortly after receving vision (but before postural perturbation) to assess corticospinal excitability in an intrinsic hand muscle that was irrelevant to the balance recovery task.
Repeated measures ANOVA compared motor-evoked potentials across two step conditions (STEP, NO-STEP) and two TMS latencies (100 ms, 200 ms). The resultant interaction provided evidence of motor suppression in the hand when a forward step was blocked.
Inhibition of a hand muscle uninvolved in a compensatory leg response provided evidence of global suppression in a whole-body, reactive balance context. Such widespread suppression of the motor system has implications for maintaining postural equilibrium, where even a momentary shutdown across body regions could interfere with the ability to adapt corrective balance reactions.
当自动但不必要的动作被迅速抑制时，整个运动系统会随之出现短暂的抑制。这种效应被称为全局抑制。尽管反应抑制对于行为灵活性至关重要，但广泛的运动抑制可能会延迟动作重新编程。在反应性平衡控制中，即使是对运动系统的短暂抑制也可能干扰我们足够快地调整补偿反应以避免摔倒的能力。
在平衡恢复任务中，当一个优势补偿步突然受阻时，手部肌肉活动是否会受到抑制？
使用一个倾斜和释放装置对19名年轻成年人进行测试。参与者偶尔会被从支撑缆绳上释放，导致身体向前位移。在每次试验开始时，遮住视觉，在腿部前方放置一个腿部阻挡物或移除该阻挡物以允许向前迈步。护目镜打开后，释放缆绳以引起姿势扰动，参与者必须要么迅速向前迈步（迈步），要么原地反应以重新获得稳定性（不迈步）。迈步试验更为频繁以促进迈步。在恢复视觉后不久（但在姿势扰动之前）进行经颅磁刺激（TMS），以评估与平衡恢复任务无关的手部固有肌肉中的皮质脊髓兴奋性。
重复测量方差分析比较了两种迈步条件（迈步、不迈步）和两个TMS潜伏期（100毫秒、200毫秒）下的运动诱发电位。由此产生的交互作用提供了证据，表明当向前迈步受阻时手部存在运动抑制。
对与补偿性腿部反应无关的手部肌肉的抑制提供了在全身反应性平衡背景下全局抑制的证据。运动系统的这种广泛抑制对维持姿势平衡具有影响，因为即使身体各部位的瞬间关闭也可能干扰调整平衡反应的能力。
