Rectus Abdominis and Rectus Femoris muscles remained active during the posture phase (isometric contraction) while sternocleidomastoideus muscle was relatively silent.
Comparisons (paired t-tests) of the RMS values of the rest phase with those of the movement or the posture phase were applied for each participant.
The first one (Fig. 1A) consisted of elevating the trunk to the vertical position (movement phase) and remaining in that position (posture phase, hip angle ∼90°) for 5 s.
The second task (Fig. 1B) consisted of elevating both legs to the vertical position (movement phase) and remaining in that position (posture phase, hip and knee angles ∼90°) for 5 s.
These variables revealed a normal distribution (Kolmogorov-Smirnov & Lilliefors test and Shapiro-Wilk tests were not significant; p>.05) and therefore we compared, by means of paired t-tests, the RMS values of the rest phase with those of the movement or the posture phase.
Interestingly, during motor imagery, these muscles remained silent during both the movement and the posture phases.
For each participant, we calculated the average RMS values of the rest, movement and posture phases.
Furthermore, in the trunk condition, AP significantly decreased between the rest and the movement phases (−19.7%; p<.001) or between the rest and the posture phases (−16.8%; p<.001), while it remained similar between the movement and the posture phases (p>.05).
Specifically, HR increased between the rest and the movement phases (3.1%; p<.001) and between the rest and the posture phases (2.7%; p<.001), but remained similar between the movement and the posture phases (p>.05).
Furthermore, for the trunk condition, HR significantly increased between the rest and the movement phase (20.3%; p<.001), between the rest and the posture phases (24.4%; p<.001) and between the movement and the posture phases (4.1%; p<.001).
