Postural organization and inter-limb coordination are altered after stroke when an isometric maximum bilateral pushing effort of the upper limbs is performed

Seated postural organization during bilateral upper limb symmetric and asymmetric pushing tasks in individuals after stroke compared to healthy controls

BACKGROUND

Asymmetric weight distribution in sitting has been reported in people after stroke. However, postural strategies used during bilateral symmetric and asymmetric movements performed while seated require more evidence to inform rehabilitation strategies.

RESEARCH QUESTIONS

How do symmetric and asymmetric effort levels exerted during upper limb (UL) pushing movements affect seated postural organization parameters (weight bearing (WB) between hands and hemibody sides, and forward trunk displacement) of stroke compared to healthy individuals? How are these parameters associated?

METHODS

Using an instrumented exerciser, 19 post-stroke individuals were compared to 17 healthy individuals when executing four bilateral UL pushing movements in a seated position: symmetrical pushing at 30 % and 15 % of their maximal force (MF) and asymmetrical pushing with 15 % of their MF for one UL vs. 30 % of the MF for the other UL and vice versa. Anterior and vertical forces of the push, as well as vertical forces under each foot and thigh were compared between groups, sides and conditions. Forward trunk displacement was compared between groups and conditions. Correlations were used to determine the association between trunk displacement, hands and hemibody vertical forces.

RESULTS

Increasing pushing effort caused increased WB on thighs and decreased on WB on feet during the 30 % MF symmetric condition compared to the 15 % MF and asymmetric conditions (p < 0.05). Individuals post-stroke showed WB asymmetry and greater forward trunk displacement when compared to healthy persons (p < 0.05). For both groups, hemibody WB and trunk displacement showed moderate association (r > - 0.5) in the asymmetric condition executed with more resistance on the paretic or non-dominant hand.

SIGNIFICANCE

Individuals post-stroke presented a similar WB pattern to that of healthy persons during symmetric and asymmetric bilateral UL movements with greater forward trunk displacement and asymmetry. Increased effort and asymmetric force between both UL had effects on seated postural organization strategy.

Validity and reliability of center of pressure measures to quantify trunk control ability in individuals after stroke in subacute phase during unstable sitting test

Objective

The objective of this study was to assess, for individuals with hemiparesis after a stroke in subacute phase, the validity and reliability of center of pressure (CoP) parameters measured during sitting balance on an unstable support.

Materials and methods

Thirty-two individuals after stroke were included in this observational study for validity and reliability (mean age: 64.34 ± 9.30y, 23 men, mean post-stroke duration: 55.64 ± 27days). Intra-Class Correlation (ICC) and Bland Altman plot assessed intra-rater reliability and inter-rater reliability of CoP parameters during unstable sitting balance test (anteroposterior or mediolateral imbalance). Validity was established by correlating CoP parameters with the Modified Functional Reach Test, trunk strength, Balance Assessment in Sitting and Standing and Timed Up and Go tests.

Results

The findings highlighted significant correlations between CoP parameters and trunk strength for anteroposterior seated destabilization. Good to excellent intra and inter-rater reliability (0.87 ≤ ICC ≤ 0.95) was observed for all CoP length parameters and CoP mean velocity in both mediolateral and anteroposterior imbalance conditions. CoP parameters for mediolateral unstable sitting condition were more reliable than for anteroposterior instability.

Conclusion

Trunk control assessment during unstable sitting position on a seesaw is a reliable test for assessing trunk control ability in individuals after a stroke. CoP length and mean velocity are found to be the best parameters.

•

Center of pressure values during anteroposterior perturbation is related to trunk strength.

•

Center of pressure length parameters have excellent intra-rater and inter-rater reliability in individuals after a stroke in subacute phase.

•

The reliability is better when the sitting instability is in mediolateral direction.

Bilateral motor coordination during upper limb symmetric pushing movements at two levels of force resistance in healthy and post-stroke individuals

BACKGROUND

Impairments of the upper limb (UL) are common after a stroke and may affect bilateral coordination. A better understanding of UL bilateral coordination is required for designing innovative rehabilitation strategies.

OBJECTIVE

To assess bilateral coordination after stroke using time-distance, velocity and force parameters during an UL bilateral task performed by simultaneously pushing handles on a bilateral exerciser at two levels of force.

METHODS

Two groups were included to assess bilateral coordination on a newly designed bimanual exerciser- One group of individuals at least 3 months post-stroke (n = 19) with moderate impairment and one group of healthy individuals (n = 20). Participants performed linear movements by pushing simultaneously with both hands on instrumented handles. The task consisted of two one-minute trials performed in sitting at two levels of participants' maximum force (MF): 30% and 15%, with visual feedback. Time-distance parameters, spatial, velocity and force profiles were compared between groups, between levels of resistance and the first part (0-50%) and entire duration of the pushing cycles (0-100%).

RESULTS

The mean pushing time was longer at 30% MF compared to 15% MF in the stroke group. Spatial profiles, represented by hand positions on the rail, revealed that the paretic hand lagged slightly behind throughout the cycle. For velocity, both groups displayed good coordination. It was less coupled at 30% than 15% MF and a trend was observed toward more lag occurrence in the stroke group. Except for lower forces on the paretic side in the stroke group, the shape of the force profiles was similar between groups, sides and levels of resistance. For all parameters, the coordination was good up to 75% of the pushing cycle and decreased toward the end of the cycle.

CONCLUSIONS

Individuals after stroke presented with overall spatial and temporal coupling of the UL during bilateral pushing movements. The relay of information at different levels of the nervous system might explain the coordinated pushing movements and might be interesting for training UL coordination.