Abstract
The purpose of the present study was to investigate the effects of psychological pressure on corticospinal excitability, the spinal reflex, lower limb muscular activity, and reaction times during a task involving dominant leg movements. Ten healthy participants performed a simple reaction time task by raising the heel of their dominant foot from a switch. After 20 practice trials, participants performed 20 non-pressure and 20 pressure trials in a counterbalanced order. A combination of pressure manipulations, including reward and penalty by monetary incentives, was used in the pressure trials. Stress responses were successfully induced, as indexed by significant increases in state anxiety, mental effort, and heart rates under pressure. Significant increases in motor evoked potential (MEP) amplitude of the tibialis anterior muscle (TA) occurred under pressure. In terms of task-related electromyography (EMG) amplitude, the co-contraction rate between the soleus (SOL) and TA muscles significantly increased along with SOL and TA EMG amplitudes under pressure. Hoffmann reflexes for SOL and reaction times did not change under pressure. These results indicate that corticospinal excitability and leg muscle-related EMG activity increase homogeneously during lower limb movements that are performed under psychological pressure.
Highlights
Psychological pressure is defined as “any factor or combination of factors that increases the importance of performing well on a particular occasion [1]”, and pressure can have both facilitative (“clutch”) and detrimental (“choking”) effects on motor performance
In addition to such EEG studies, motor evoked potential (MEP) recordings can be used to examine motor neuron excitability in the efferent pathways extending from the primary motor area to the innervated muscles, which are elicited by monophasic transcranial magnetic stimulation (TMS) of the primary motor area
Wilcoxon signed-rank test results indicated that Tthaebrleew1 eshreowsigsnthifiecmanetainnscarenadsesstainndsatardteearnroxriestfyor(Wtaislkco-rxeolanteZd=su−b2j.e1c9t,ivpe=st0a.t0e1a4n, rxi=et0y.7a3n0d),mmeennttaall eeffffoorrtt a(Ws wilceollxaosnHZR=d−u2ri.6n7g, tph=e m0.0o0t4o,rrp=re0p.8a9r0a)t,ioanndphHaRse(.WWiliclcooxxoonnZs=ig−ne2d.2-r9a, npk=t0e.s0t1r1e,sru=lts0.i7n2d4i)cafrtoemd tthhaetnthoenr-eprwesesruerseigtonitfhiceapnrteisnscurreeasceosnidnitsitoant.e anxiety (Wilcoxon Z = −2.19, p = 0.014, r = 0.730), mental effort (Wilcoxon Z = −2.67, p = 0.004, r = 0.890), and Heart rate (HR) (Wilcoxon Z = −2.29, p = 0.011, r = 0.724) from the noTnab-plere1s. sMureeantos athnde pstraensdsaurrde ecrornordsitfioorns.ubjective state anxiety, mental effort, and heart rate in the non-pressure and pressure conditions
Summary
Psychological pressure is defined as “any factor or combination of factors that increases the importance of performing well on a particular occasion [1]”, and pressure can have both facilitative (“clutch”) and detrimental (“choking”) effects on motor performance. Decreased event-related potential (ERP) P3 amplitude was found when performing a dual task that involved responding to visual cues during a simulated driving task [2], suggesting a reduction in processing efficiency when performing motor skills under pressure. In addition to such EEG studies, motor evoked potential (MEP) recordings can be used to examine motor neuron excitability in the efferent pathways extending from the primary motor area to the innervated muscles, which are elicited by monophasic transcranial magnetic stimulation (TMS) of the primary motor area. In these studies, increased MEP amplitude (i.e., higher corticospinal excitability) is observed before (motor preparation phase) [6], during [7] and after [8] participants perform voluntary hand movements, under pressure evoked using monetary incentives or competition
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