Despite the accumulating evidence supporting an interaction between cognitive functions and postural control, little is known about the selective impact of the mental representation of an action, i.e., motor imagery (MI) on postural control. As postural oscillations are reduced during a cognitive task of backward silent counting, a greater stability is also expected during MI compared to a no-task condition (standing). Twenty participants took part in this experiment, which aimed at providing evidence that MI may improve postural stability. They were requested to mentally imagine a movement while standing on a force-plate. Results showed a decrease in both path length and postural sway variability on the anterior-posterior and lateral axes during all dual-task sessions, as compared to the motionless condition. These postural adjustments might result from both central and peripheral processes, and/or increased muscle stiffness. Conversely, postural oscillation amplitude increased on the vertical axis during MI of three vertical jumps, hence suggesting that postural regulations remain task-related during MI. Finally, our data showed that kinesthetic and visual imagery differentially impacted the postural regulation.

Study design: A case study. Objective: The aim was to investigate whether motor imagery (MI) could be successfully incorporated into conventional therapy among individuals with spinal cord injury (SCI) to improve upper limb (UL) function. Setting: The Physical Medicine and Rehabilitation Unit at the Henry Gabrielle Hospital in Lyon, France. Methods: The participant was an individual with a complete C6 SCI. MI content was focused on functional UL movements, to improve hand transport to reach out and grasp with tenodesis. The participant was tested before and after 15 MI training sessions (45 min each, three times a week during 5 consecutive weeks). MI ability and program compliance were used as indicators of feasibility. The Minnesota and Box and Blocks tests, as well as movement time and hand trajectory during targeted movements were the dependent variables, evaluating motor performance before and after MI training. Results: The participant's ability to generate MI was checked and compliance with the rehabilitation program was confirmed. The time needed to complete the Minnesota test decreased by 1 min 25 s. The Box and Blocks score was improved by three units after MI program. Decreased movement time and enhanced hand trajectory smoothness were still observed 3 months later, despite a slight decrease in performance. Conclusions: This study supports the feasibility for introducing MI in conventional therapy. Further studies should confirm the potential role of MI in motor recovery with a larger sample.

BackgroundSensorimotor impairments secondary to a spinal cord injury affect standing postural balance. While quasi-static postural balance impairments have been documented, little information is known about dynamic postural balance in this population. The aim of this study was to quantify and characterize dynamic postural balance while standing among individuals with a spinal cord injury using the comfortable multidirectional limits of stability test and to explore its association with the quasi-static standing postural balance test.MethodsSixteen individuals with an incomplete spinal cord injury and sixteen able-bodied individuals participated in this study. For the comfortable multidirectional limits of stability test, participants were instructed to lean as far as possible in 8 directions, separated by 45° while standing with each foot on a forceplate and real-time COP visual feedback provided. Measures computed using the center of pressure (COP), such as the absolute maximal distance reached (COPmax) and the total length travelled by the COP to reach the maximal distance (COPlength), were used to characterize performance in each direction. Quasi-static standing postural balance with eyes open was evaluated using time-domain measures of the COP. The difference between the groups and the association between the dynamic and quasi-static test were analyzed.ResultsThe COPlength of individuals with SCI was significantly greater (p ≤ 0.001) than that of able-bodied individuals in all tested directions except in the anterior and posterior directions (p ≤ 0.039), indicating an increased COP trajectory while progressing towards their maximal distance. The COPmax in the anterior direction was significantly smaller for individuals with SCI. Little association was found between the comfortable multidirectional limits of stability test and the quasi-static postural balance test (r ≥ −0.658).ConclusionStanding dynamic postural balance performance in individuals with an incomplete spinal cord injury can be differentiated from that of able-bodied individuals with the comfortable limits of stability test. Performance among individuals with an incomplete spinal cord injury is characterized by lack of precision when reaching. The comfortable limits of stability test provides supplementary information and could serve as an adjunct to the quasi-static test when evaluating postural balance in an incomplete spinal cord injury population.

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Multidirectional seated postural stability is reduced in individuals with SCI who have paralysis of the abdominal and lower back muscles in comparison to able-bodied individuals.

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