Fig 1.
(a) Participants stood upright on a restraining device with pelvis and knees securely fixed to minimise movement of pelvis and lower limbs. Electrodes were attached over erector spinae at the 4th lumbar vertebral level (panel in top right), rectus abdominis and left deltoid. An accelerometer was positioned on the dorsum of the hand contralateral to the stimulation. (b) Representative data from a single subject showing left erector spinae EMG, left deltoid EMG and accelerometer data during dynamic shoulder flexion task. TMS was delivered 25 ms after the onset of deltoid EMG (dotted vertical line).
Fig 2.
Averaged data (10 stimuli) from a representative subject showing the motor evoked potentials (MEP) in erector spinae during the different tasks.
Arrows indicate the time of transcranial magnetic stimulation (TMS) over the motor cortex. There is a clear increase in EMG prior to the TMS in the bilateral dynamic shoulder flexion (DSF). Tonic EMG activity is present in the two static tasks; bilateral static shoulder flexion (SSF) and static trunk extension (STE).
Fig 3.
Group mean (SEM) data of motor evoked potentials (MEPs) and EMG recorded from erector spinae (ES).
(a) Amplitudes of MEPs obtained during the bilateral dynamic shoulder flexion (DSF), bilateral static shoulder flexion (SSF) and static trunk extension (STE) tasks. (b) MEP latencies in ES in the three tasks. (c) Pre-stimulus ES rmsEMG amplitude during the three tasks. *—significant difference, p<0.017.
Fig 4.
Group mean (SEM) data of motor evoked potentials (MEPs) and EMG recorded from rectus abdominis (RA).
(a) Amplitudes of MEPs obtained during the bilateral dynamic shoulder flexion (DSF), bilateral static shoulder flexion (SSF) and static trunk extension (STE) tasks. (b) Pre-stimulus RA rmsEMG amplitude during the three tasks.