Stand Up to Excite the Spine: Neuromuscular, Autonomic, and Cardiometabolic Responses During Motor Imagery in Standing vs. Sitting Posture

Figures

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  FIGURE 1. Experimental design. An experimental motor imagery (MI) condition is depicted. The control condition had the same rationale with 15 min rest observed instead of the MI training session. H50: H-reflex recorded at 50% of maximal H-wave amplitude. MMAX: maximal muscle compound action potential.

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  FIGURE 2. Myoelectrical recordings of leg muscles in standing and sitting postures. The root mean square (RMS) of electromyographic (EMG) activities were calculated for soleus (SOL), Gastrocnemius Medialis (GM), Gastrocnemius Lateralis (GL), and Tibialis Anterior (TA) in MI conditions (right panels) and in CTRL conditions (left panel). For SOL, GM, and GL, RMS is normalized by the maximal M-wave recorded in corresponding condition at PRE (RMS/MMAX). The RMS of the EMG recorded continuously during the 15-min conditions was spitted in seven parts: during the four series of MI (S1, S2, S3, and S4) and during the three rest periods (R1, R2, and R3). In the CTRL conditions the same cutting was applied. (A) Kinetic of SOL RMS/MMAX. (B) SOL RMS/MMAX value of the entire session. (C) Kinetic of GM RMS/MMAX. (D) GM RMS/MMAX value of the entire session. (E) Kinetic of GL RMS/MMAX. (F) GL RMS/MMAX value of the entire session. (G) Kinetic of TA RMS. (H) TA RMS value of the entire session. T: time effect; C: condition effect; P: position effect; I: interaction effect between “time,” “condition,” and “posture”; ns: non-significant. ###: significantly different from sitting at p < 0.001. *, **, ***:…

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  FIGURE 3. Postural sway during motor imagery (MI) and control (CTRL) in standing condition. In panels (A–D), data are split according to the different phases of the motor imagery session (MI, black squares): S1, S2, S3, and S4 are for the four different successive series of MI (2.5 min), while R1, R2, and R3 represent the three rest periods between the series (1.5 min). The same cut has been performed in the CTRL session to provide valuable comparison with MI session. In panel (A), length of the Center of Pressure (CoP) is normalized by the duration of each period (in mm/sec). In panel (B), CoP area (ellipse) is expressed in mm2 in each phase. In panels (C,D), the mean amplitude of the CoP displacement over the different time periods on the antero-posterior (C) and mediolateral (D) axis. * and ***: main effect of the factor condition (MI vs. CTRL) at p < 0.05 and p < 0.001, respectively. #: significant differences between the indicated time points, at p < 0.05.

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  FIGURE 4. Spinal excitabilities of the triceps surae during the motor imagery (MI) and control (CTRL) conditions in the sitting and standing postures. In panels (A–C) are depicted responses for soleus, gastrocnemius medialis and gastrocnemius lateralis, respectively. PRE and POST responses are recorded during rest (white bars) and during MI (black bars) in sitting (left panel) and in standing condition (middle panel). In panels (A–C) upper panels depict data of the motor imagery session and lower panels depict data of the CTRL session. Spinal excitabilities are measured by the H-reflex recorded at 50% of its maximal value (H50). This response is normalized by the maximal muscle compound action potential (H50/MMAX) recorded in the same condition (MI or rest). The right panel represent the gain associated to motor imagery in the mental session {determined by the formula [(MI-REST)/REST] × 100} in each condition from PRE (white circles) to POST (black circles). This gain is calculated according to the results obtained in H-reflexes in MI and at rest, depicted in the left panels. *, **: significant differences at p < 0.05 and p < 0.01, respectively. #: significant pre–post differences at p <…