There was little or no EMG activity without stimulation during sitting or standing. With increasing levels of epidural stimulation, EMG amplitudes were modulated in a tonic pattern while the subject remained sitting. During the transition from sitting to standing, amplitudes and patterns of EMG were modulated in all recorded muscles. Transition (white) from sitting (gray) to standing (yellow) with
(a) no stimulation,
(b) rostral (spinal segments L
1-L
2) stimulation (4–7.5V, 15Hz), and
(c) caudal (spinal segments L
4-S
1) stimulation (4–7.5V, 15Hz).
(d) Averaged mean EMG amplitude responses on the right side during sitting and standing with no stimulation (○), and rostral (
) and caudal (
) stimulation at 7.5V, 15Hz.
(e) Kinematic representation of sitting to standing transition with caudal stimulation (illustration at 10 frames per sec) (Supplementary Video 2). Array diagram illustrates the stimulation configuration; anode electrodes are black and cathode electrodes are gray. Right (R) side muscles: fine wire: iliopsoas (IL); surface EMG: vastus lateralis (VL), medial hamstrings (MH), tibialis anterior (TA), soleus (Sol), and medial gastrocnemius (MG). Stim indicates the stimulation intensity. Interpulse interval depicting stimulation frequency is shown at the bottom of graphs
b and
c.