Performance control in one consecutive motor task sequence – Approaching central neuronal motor behaviour preceding isometric contraction onsets and relaxation offsets at lower distinct torques

OBJECTIVE: Motor-related cortical potentials (MRCP) often compared separated muscle activations; however, MRCP preceding combined contraction onsets and relaxation offsets of one consecutive motor task sequence remain to be elucidated. METHODS: Twelve healthy males (27.92±4.33 years, 181.83±7.15 cm, 84.58±7.15 kg) performed 40 submaximal isometric right-limb wrist flexions (i.e. motor task sequences). Each motor task sequence combined timed contractions to and relaxations from distinct torque levels, i.e. 20% and 40% of maximum voluntary contractions (MVC). Synchronized continuous EEG (32 Ag/AgCl-electrodes mounted over motor-related areas) and EMG (i.e. flexor carpi radialis, FCR) recordings served to detect torque level-on/offsets for MRCP analyses. RESULTS: Motor task sequences were accurately maintained with participants' mean values of FCR muscle activity revealing no signs of fatigue (p⟩0.05). Main findings (i.e. readiness potential) were larger amplitudes over frontal electrode sites (p⟨0.05) preceding contractions compared to relaxations, whereas amplitudes were larger (i.e. peak) over centro-parietal electrode sites (p⟨0.05) preceding 40% compared to 20% MVC. CONCLUSION: When performed in one consecutive motor task sequence, controlling the production as well as the releasing of force may require similar proprioceptive and visuo-motor processing preceding the same force level (i.e. 20% or 40%); however, this is irrespective of the muscle activation type (i.e. contraction or relaxation).