Animal studies have shown that there are cell populations only discharging phasically before a motor task and others only active tonically during holding phase of the task. How muscle @entity1295 influences these two types of cell populations, however, is unknown. Because the phasic neurons are only active briefly before the task but the tonic ones are active continuously throughout the task, we hypothesized that @entity1295 would have a less effect on cortical signals during the preparation phase (representing phasic discharge) than that during the sustained phase (representing tonic discharge). Eight @entity1 performed 200 handgrip maximal @entity2472 (MVCs) with simultaneous recordings of scalp electroencephalographic (EEG), handgrip force, and finger flexor surface electromyographic (EMG) signals. Power spectrograms of the EEG during the preparation and sustained phases were analyzed in each of the five 40-trial blocks, with data from the first block representing a condition of moderate @entity1295 and the last, severe @entity1295 . Movement-related cortical potential (MRCP) was derived by trigger-averaging 40 EEG epochs in each block. The power of all EEG frequencies did not alter significantly during the preparation phase but decreased significantly during the sustained phase of the contraction. The MRCP negative potential (NP) related to motor task preparation only showed minimal changes. These results suggest that MVC-induced @entity1295 has differential effects on cortical signals during motor task preparation compared to its execution and maintenance. The signals of the two phases may represent activities of the two cortical cell populations previously found by animal studies.

Fatigue induces greater brain signal reduction during sustained than preparation phase of maximal XXXX .

@entity1 :: ('9606', 'Species') :: ['participants'] @entity1295 :: ('MESH:D005221', 'Disease') :: ['fatigue'] @entity2472 :: ('MESH:C536214', 'Disease') :: ['voluntary contractions']
@entity2472 :: (MESH:C536214,Disease) :: ['voluntary contraction']
