Archives of Physical Medicine and Rehabilitation
Volume 87, Issue 11 , Pages 1463-1470, November 2006

Kinematic Analysis of Upper Limbs and Trunk Movement During Bilateral Movement After Stroke

  • Sylvie Messier, PhD, OT

      Affiliations

    • School of Rehabilitation, Université de Montréal, Montreal, QC, Canada
    • Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, Rehabilitation Institute of Montreal, Montreal, QC, Canada
    • Corresponding Author InformationReprint requests to Sylvie Messier, PhD, OT, Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, Rehabilitation Institute of Montreal, 6300 Darlington, Montreal, QC H3S 2J4, Canada
    • ,
  • Daniel Bourbonnais, PhD, OT

      Affiliations

    • School of Rehabilitation, Université de Montréal, Montreal, QC, Canada
    • Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, Rehabilitation Institute of Montreal, Montreal, QC, Canada
    • ,
  • Johanne Desrosiers, PhD, OT

      Affiliations

    • Department of Family Medicine, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
    • Research Centre on Aging, University Institute of Geriatrics of Sherbrooke, Sherbrooke, QC, Canada
    • ,
  • Yves Roy, MSc

      Affiliations

    • Faculty of Physical and Sports Education, Université de Sherbrooke, Sherbrooke, QC, Canada.

Article Outline

Abstract 

Messier S, Bourbonnais D, Desrosiers J, Roy Y. Kinematic analysis of upper limbs and trunk movement during bilateral movement after stroke.

Objective

To compare the kinematics of the upper limbs and trunk during unilateral and parallel bilateral tasks in subjects with hemiparesis and control subjects.

Design

Comparative study.

Setting

Geriatric center offering rehabilitation services.

Participants

Convenience sample of 15 persons (age, 69.4±12.0y; ≥3mo poststroke) recruited in a geriatric center with rehabilitation services, and 13 control persons (67.8±7.5y) participated in the study.

Interventions

Not applicable.

Main Outcome Measures

Unilateral and bilateral movements toward 1 or 2 targets located beyond arm’s length and positioned in 3 directions. Angular changes of both upper limbs and trunk were characterized in the sagittal, frontal, and horizontal planes.

Results

During the bilateral task, the deficits of the kinematic joints of the paretic upper limb persisted in subjects with hemiparesis as compared with the corresponding upper limb in the control subjects (abduction shoulder: subjects with hemiparesis, 5.7°±5.3°; control subjects, 0.7°±4.8°; extension elbow: subjects with hemiparesis, 38.2°±14.2°; control subjects, 52.8°±12.5°) with a marked flexion of the trunk (subjects with hemiparesis, 33.7°±8.7°; control subjects, 26.8°±5.8°). The elbow extension of the nonparetic upper limb was reduced (subjects with hemiparesis, 41.0°±13.6°; control subjects, 52.8°±12.5°).

Conclusions

The use of parallel bilateral reaching tasks and placing movements of the upper extremities in the subjects with hemiparesis contributed an increase in the trunk flexion rather than improve the motor performance of the paretic upper limb, especially with regard to increasing elbow extension.

Key Words: Movement, Paresis, Range of motion, articular, Rehabilitation, Stroke, Upper limbs

 

STROKE IS AMONG THE LEADING causes of motor impairments in the elderly in Canada1 and the United States.2 One of the most common outcomes of stroke is hemiparesis contralateral to the brain lesion. In general, the paretic upper limb presents a greater motor function deficit than the lower limb.3 Bilateral use of the upper limbs is therefore badly affected in a person with hemiparesis. Application of simultaneous bilateral exercises for the upper limbs in patients is consequently encouraged from the time they start rehabilitation.

Traditional approaches, such as the Bobath neurodevelopmental approach, have proposed symmetrical exercises that allow the nonparetic limb to mobilize the paretic upper limb to improve trunk control and provide guidance to the paretic upper limb.4 Recent approaches have proposed simultaneous and mirror activities of the upper limbs with the rationale of improving motor performance of the paretic upper limb by sharpening or facilitating the movement of the paretic upper limb by the nonparetic limb. Recent studies have observed an improvement in the paretic upper limb after a treatment program based specifically on bilateral training of the upper limbs, mainly in hemiparetic subjects.5, 6, 7, 8, 9 However, a recent study10 found only limited improvements in paretic upper-limb motor performance in adults poststroke after symmetric bilateral training, and another11 did not find any benefits compared with usual therapy. Other studies12, 13, 14 have examined disturbances in the bilateral motor control of the upper limbs within a single session. Although improvement in the performance of the paretic upper limb was observed,12, 13 deterioration of the nonparetic upper limb was also noticed in all these studies.12, 13, 14

Considering the growing interest in simultaneous bilateral movement as an intervention strategy in rehabilitation, it seems important to reach a better understanding of the performance of the upper limbs during this type of movement to clarify its rehabilitation potential. In view of the trunk’s contribution to the movement of the upper limb15 and the relatively few studies dedicated to exploring this component in a bilateral task, it would be important to take a look at this factor.

The objective of this study was to describe the parallel bilateral movement of the paretic and nonparetic upper limbs compared with the unilateral movement of the upper limb, including the trunk. The first hypothesis underlying this objective is that the deficits of the paretic upper limb observed during a unilateral task are similar to those in a bilateral task so that the bilateral performance of the paretic upper limb should be different from that of the corresponding upper limb of the control subjects. The second hypothesis is that, in view of the persistent deficits of the paretic upper limb during bilateral movement, the performance of the nonparetic upper limb will deteriorate in this type of movement.

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Methods 

Participants 

Fifteen subjects with poststroke hemiparesis (7 men, 8 women; average age, 69.4±12.0y) participated in the study. Regarding the inclusion criteria, subjects had had a cerebrovascular accident (CVA) 3 or more months before the study and had to be able to remain in a sitting position without support, maintain a palmar grasp, and have a good understanding of simple verbal instructions. The characteristics of the sample have been previously described in a recently published article.16 All subjects had had a unilateral CVA, and most of them presented with a left hemiparesis (n=11). Generally speaking, the motor function (43 to 63/66) and sensation (14 to 20/20) of the paretic upper limb were relatively well preserved, according to the Fugl-Meyer Assessment (FMA),17, 18 which showed good mobility of the paretic upper limb, thus reducing the possibility of contractures. In fact a study by Levin19 has revealed a negative correlation between the level of spasticity and the motor function measured with the FMA. Thirteen control subjects (6 men, 7 women; average age, 67.8±7.5y), all but 1 right-handed, constituted the comparison group. A consent form approved by the Research Ethics Committee of the University Institute of Geriatrics of Sherbrooke was signed by all.

The experimental setup used for this study was described in an earlier article20 and is shown in figure 1. Subjects were seated on a chair fixed to the floor facing targets (pressure switches) placed in a standard position on a table of standard height (fig 1A). The subject put his/her clenched fists on the target(s) placed nearby with the upper arms at around 25° of abduction. A cone weighing 150g (height, 14cm; base, 5cm) was placed on the starting target(s). After the instruction “Get ready … go,” subjects had to move 1 or 2 cones toward 1 or 2 distal targets at a comfortable speed. After a 3-second time delay, they were then instructed to return to their initial position. During the unilateral task, the inactive upper limb remained positioned against the trunk to prevent it from interfering with the execution of the task. The switches indicated when the subject left the proximal target and reached the distal target. The time taken for the movement was defined as the time interval between lift-off of the cone from the first target(s) and touchdown on the end target(s). The task was performed successively in three directions: in front of the subject and at a 45° angle on either side (fig 1B). The subjects did 3 tests for each direction. No particular consideration was given to the reaction time or the time taken to complete the task.

  • View full-size image.
  • Fig 1. 

    Experimental setup. (A) Subject’s initial position and (B) the 3 directions of the task. For the 45° directions, the plastic strips were turned until the stopper marking the 45° position was reached. Abbreviations: −45NP/D, 45° nonparetic direction (for the subjects with hemiparesis) and 45° dominant direction (for the control subjects); +45P/ND, 45° paretic direction (for the subjects with hemiparesis) and 45° nondominant direction (for the control subjects). Adapted from Messier et al.20 Reprinted with permission.

Fourteen infrared markers were applied on each upper limb and each side of the trunk of subjects on the following anatomic points: dorsal surface (1) of the head of the second metacarpal; (2) of the head of the fifth metacarpal; (3) of the joint center of the wrist, aligned with the base of the third metacarpal; (4) the joint center of the elbows, epicondyle; (5) the center of the glenohumeral joints, acromion; (6) the ear lobes, aligned with the styloid process; and (7) the center of the hip joints, greater trochanter.21, 22 Kinematic data were collected from an Optotrak/3020a motion analysis system at a frequency of 50Hz. Three optoelectric units were placed in front, 90° to the subject’s right, and 90° to the subject’s left. The calibration of the 3-dimensional space was performed before each experimental session.

Variables and Measures 

The relative angles (fig 2) of the amplitudes of the upper limbs (shoulder flexion and abduction and adduction, elbow extension) were measured in relation to the orientation of the proximal segment. Shoulder flexion and abduction and adduction were determined as a function of the trunk segment, which was defined by the shoulder and greater trochanter markers. The upper arm was defined by the shoulder and elbow markers. Positive values indicate abduction. Elbow extension was determined from the orientations of the upper arm and forearm. The forearm was defined by the elbow and wrist markers. Shoulder flexion and abduction and adduction and elbow extension were obtained from the difference in the relative angles of the final position minus the initial position.

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  • Fig 2. 

    The shoulder abduction and flexion provide an example of the measurement calculated as a function of the orientation of the proximal segment. The projection (a) of the arm on the frontal plane of the trunk gives the abduction angle and that on the sagittal plane (b) gives the flexion.

The trunk segment was defined as the bisector of the lines between markers located at the center of both shoulders and both trochanters. The absolute angles of anterior and lateral flexion of the initial and final positions were calculated with regard to the anteroposterior and mediolateral (ML) axes of the global frame of reference. The anterior and lateral flexion values were obtained from the difference in the absolute angles (final position minus initial position) expressed in relation to the initial position of the trunk and as a function of trunk longitudinal rotation. The latter was calculated by considering the orientation of an axis joining the 2 shoulder markers with regard to the ML axis. Positive values for the trunk indicate lateral flexion to the right side and rotation to the left side.

Data and Statistical Analysis 

When required, missing markers were interpolated by using either a linear method (1 or 2 missing frames) or cubic splines (>2 missing frames). Thereafter, the angular position data of the segments were determined. These signals were then filtered by using a fourth-order Butterworth filter. The cutoff frequencies were defined from residual analyses.22 The filter cutoff frequency is usually below 5Hz. The analysis programs were developed with the Matlab programming software.b For the analyses, the measures in the subjects with right hemiparesis were reversed so that the paretic side was the left side for all the hemiparetic subjects. Similarly, the measures of the only control left-handed subject were inverted because the rest of the control subjects were right-handed. Because of the small sample size and nonnormal distribution of the data, we used nonparametric statistics; the Wilcoxon signed-rank test to verify the differences between the unilateral and bilateral tasks for each group of subjects and the Kruskal-Wallis test to examine the differences between the 2 groups for the same task condition. We used the SPSS statistical packagec to analyze the data. Because most of our subjects with hemiparesis had left hemiparesis, the left (nondominant) side of the control subjects was used in the analyses. These analyses were performed for the 3 directions, in front of the subject and at a 45° angle on either side.

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Results 

Between-Group Comparisons for Unilateral Movement of the Paretic Upper Limb 

The data from the unilateral task (table 1, fig 3) shows that, for all directions, the paretic upper limb presents less extension of the elbow than the nondominant upper limb of the control subjects (anterior direction, P=.02; 45° in the nonparetic [45NP] direction, P=.001; 45° in the paretic [45P] direction, P=.03). No difference was found at the shoulder. For the trunk, although the results are not significant for the anterior direction, the data show higher values for the anterior flexion in the subjects with hemiparesis than in the control subjects (subjects with hemiparesis, 25.8°±10.3°; control subjects, 20.0°±5.7°). For the 45NP and 45P directions, trunk flexion is significantly greater in the subjects with hemiparesis (45NP, P=.003; 45P, P=.02), and trunk rotation (not shown in the table 1) is significantly less for the 45P direction (subjects with hemiparesis, 2.8°±5.3°; control subjects, 7.1°±2.1°; P=.03).

Table 1. Unilateral Task: Comparison of the Angular Changes of the Paretic Upper Limb and Trunk in the Subjects With Hemiparesis and of the Nondominant Upper Limb and Trunk in the Control Subjects for Each Direction
SubjectsAnterior Direction45° Nonparetic Direction45° Paretic Direction
Abduction ShoulderExtension ElbowAnterior Flexion TrunkAdduction ShoulderExtension ElbowAnterior Flexion TrunkAbduction ShoulderExtension ElbowAnterior Flexion Trunk
Subjects with hemiparesis
Paretic upper limb15.0±5.8(15.7)47.0±15.9(48.2)25.8±10.3(24.6)−5.8±7.9(−6.0)33.7±13.1(31.6)23.8±7.8(22.8)26.9±6.2(26.4)46.1±16.2(44.0)22.7±8.3(19.6)
Control subjects
Nondominant upper limb15.4±4.0(14.8)61.0±12.7(61.1)20.0±5.7(20.6)−9.3±5.6(−9.8)52.0±10.8(51.5)16.0±4.0(17.0)28.6±3.7(28.6)60.1±13.9(60.0)15.7±4.4(15.1)
P⁎.63.02.22.11.001.003.42.03.02

NOTE. Values are mean degrees ± SD (median). For the shoulder, the sign “—” indicates adduction.

⁎Kruskal-Wallis test.

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  • Fig 3. 

    Illustrations of between-groups results for the unilateral task in the (A) anterior direction, (B) 45° nonparetic direction, and (C) 45° paretic direction. Legend: —, paretic side for the subjects with hemiparesis and nondominant side for the control subjects.

Within-Group Comparison of the Unilateral and Bilateral Movements of the Paretic Upper Limb and of the Nondominant Upper Limb 

Because, in general, the changes in joint angular amplitudes were similar for both groups of subjects between the unilateral and bilateral movements for all 3 directions, only the results for the anterior direction are shown in table 2. For both groups of subjects, the bilateral task produced a decrease in shoulder abduction and elbow extension compared with the unilateral task (subjects with hemiparesis: shoulder abduction, P=.002; elbow extension, P=.001; control subjects: shoulder abduction, P=.002; elbow extension, P=.005). Also during the bilateral movement, the trunk showed greater anterior flexion and less lateral flexion and rotation than the unilateral movement in both groups of participants (subjects with hemiparesis: anterior flexion, P=.001; lateral flexion, P=.001; rotation, P=.001; control subjects: anterior flexion, P=.002; lateral flexion, P=.01; rotation, P=.002). No difference was found for shoulder flexion for both groups.

Table 2. Unilateral and Bilateral Tasks: Comparison of the Angular Changes of the Paretic Upper Limb and Trunk in the Subjects With Hemiparesis and of the Nondominant Upper Limb and Trunk in the Control Subjects in the Anterior Direction
Subjects With HemiparesisParetic Upper LimbTrunk
Shoulder FlexionShoulder AbductionElbow ExtensionAnterior FlexionLateral FlexionRotation
Unilateral task62.6±7.0(64.4)15.0±5.8(15.7)47.0±15.9(48.2)25.8±10.3(24.6)−4.4±4.1(−4.3)−14.4±4.5(−14.7)
Bilateral task62.4±5.5(61.2)5.7±5.3(3.8)38.2±14.2(33.5)33.7±8.7(31.2)0.1±2.1(0.2)1.0±2.7(1.0)
P⁎.82.002.001.001.001.001
Control SubjectsNondominant Upper LimbTrunk
Shoulder FlexionShoulder AbductionElbow ExtensionAnterior FlexionLateral FlexionRotation
Unilateral task65.8±8.0(65.0)15.4±4.0(14.8)61.0±12.7(61.1)20.0±5.7(20.6)−3.6±1.5(−3.6)−16.0±2.8(−15.4)
Bilateral task64.0±4.8(63.0)0.7±4.8(0.5)52.9±13.1(55.3)26.8±5.8(27.0)0.5±1.6(0.3)1.2±1.3(0.9)
P⁎.10.002.005.002.01.002

NOTE. Values are mean degrees ± SD (median). For the trunk, the “—” sign indicates lateral flexion toward the left and rotation toward the right.

⁎Wilcoxon signed-rank test.

There were only 2 exceptions for the 45° toward the paretic direction (not shown). Shoulder flexion remained the same in the bilateral movement as in the unilateral movement in the subjects with hemiparesis but was reduced in the control subjects (shoulder flexion for subjects with hemiparesis: unilateral movement, 42.6°±6.0°; bilateral movement, 39.8°±11.4°; P=0.31; shoulder flexion for control subjects: unilateral movement, 47.7°±7.2°; bilateral movement, 41.6°±6.0°; P=.02). Also, trunk rotation was greater in the bilateral movement in the subjects with hemiparesis but was similar in the control subjects (rotation in subjects with hemiparesis: unilateral movement, 2.8°±5.3°; bilateral movement, 9.4°±3.3°; P=.01; rotation in control subjects: unilateral movement, 7.1°±2.1°; bilateral movement, 6.6°±2.1°; P=.60).

Between-Group Comparisons for Bilateral Movement of the Paretic Upper Limb 

When we compared the bilateral movement between the 2 groups of subjects (table 3, fig 4), the results showed greater shoulder abduction of the paretic upper limb especially in the anterior and 45NP directions (indicated by less adduction of the shoulder for the 45NP direction in subjects with hemiparesis, −9.0°±7.0°; control subjects, −17.8°±6.2°; P=.003). For the 3 directions, the paretic upper limb presents less elbow extension (anterior direction: shoulder abduction, P=.005; elbow extension, P=.006; 45NP direction: shoulder adduction, P=.003; elbow extension, P=.004; 45P direction: shoulder abduction, P=.28; elbow extension, P=.02). The bilateral task shows more pronounced anterior flexion of the trunk in the subjects with hemiparesis and significantly greater trunk rotation (not shown in table 3) for the 45P direction (anterior direction: anterior flexion, P=.04; 45NP direction: anterior flexion, P=.03; 45P direction: anterior flexion, P=.02; rotation in subjects with hemiparesis, 9.4°±3.3°; control subjects, 6.6°±2.1°; P=.01).

Table 3. Bilateral Task: Comparison of the Angular Changes of the Paretic Upper Limb and Trunk in the Subjects With Hemiparesis and of the Nondominant Upper Limb and Trunk in the Control Subjects for Each Direction
SubjectsAnterior Direction45° Nonparetic Direction45° Paretic Direction
Abduction ShoulderExtension ElbowAnterior Flexion TrunkAdduction ShoulderExtension ElbowAnterior Flexion TrunkAbduction ShoulderExtension ElbowAnterior Flexion Trunk
Subjects with hemiparesis
Paretic upper limb5.7±5.3(3.8)38.2±14.2(33.5)33.7±8.7(31.2)−9.0±7.0(−9.1)25.1±11.7(25.3)29.6±8.0(25.9)20.0±5.8(20.0)38.8±17.5(38.3)29.0±7.0(26.3)
Control subjects
Nondominant upper limb0.7±4.8(0.5)52.8±12.5(52.5)26.8±5.8(27.0)−17.8±6.2(−17.5)40.0±11.5(40.2)23.4±4.4(24.0)17.7±4.6(18.9)52.5±13.5(54.3)23.1±5.8(24.0)
P⁎.005.006.04.003.004.03.28.02.02

NOTE. Values are mean degrees ± SD (median). For the shoulder, the sign “—” indicates adduction.

⁎Kruskal-Wallis test.

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  • Fig 4. 

    Illustrations of between-groups results for the bilateral task in the (A) anterior direction, (B) 45° nonparetic direction, and (C) 45° paretic direction. Legend: —, paretic side for the subjects with hemiparesis and nondominant side for the control subjects.

Between-Group Comparisons for Unilateral and Bilateral Movements of the Nonparetic Upper Limb 

The data from the unilateral task (fig 5A) show that the nonparetic elbow extension did not differ from that of the dominant upper limb of the control subjects. For the trunk, the anterior flexion was significantly greater for the 45NP (P=.02) and 45P (P=.02) directions. Trunk rotation was significantly greater for the 45P direction (P=.03).

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  • Fig 5. 

    (A) Unilateral and (B) bilateral tasks: angular changes of the nonparetic upper limb for the subjects with hemiparesis and of the dominant upper limb for the control subjects and angular changes of the trunk of both groups for each direction. Abbreviations: D, dominant side (for the control subjects); 45NP/D, 45° nonparetic direction/dominant direction; 45P/ND, 45° paretic direction/nondominant direction; NP, nonparetic side (for the subjects with hemiparesis). *P=.02, †P=.03, ‡P=.04, §P=.01 (Kruskal-Wallis test).

During the bilateral task (fig 5B), the nonparetic upper limb of the subjects with hemiparesis shows significantly less elbow extension than in the control subjects for the anterior direction (P=.03). For the 45NP and 45P directions, although the results are nonsignificant, the data show values smaller than the dominant upper limb of the control subjects (45NP direction: subjects with hemiparesis, 43.2°±14.3°; control subjects, 52.2°±12.2°; 45P direction: subjects with hemiparesis, 30.7°±12.7°; control subjects, 37.4°±10.1°). For all 3 directions, trunk flexion is greater in the subjects with hemiparesis (anterior direction, P=.04; 45NP direction, P=.03; 45P direction, P=.02). Trunk rotation is more pronounced in the 45P direction in the subjects with hemiparesis than in the control subjects (P=.01).

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Discussion 

This study shows that the bilateral task did not improve the performance of the paretic upper limb compared with the nondominant upper limb of the control subjects. Overall, our results show that, for all 3 directions, changing from the unilateral task to the parallel bilateral task reduced shoulder abduction, which is often present to an exaggerated degree in persons with hemiparesis during a reaching movement of the paretic upper limb.23 Also, elbow extension was reduced in the paretic upper limb of the subjects with hemiparesis and in the corresponding upper limb (nondominant) of the control subjects. There was an increase in anterior flexion of the trunk in both groups. However, when we compared the bilateral task between the 2 groups of subjects, shoulder abduction was greater, elbow extension more limited, and trunk flexion more pronounced in the subjects with hemiparesis than in the control subjects.

It is possible that muscle weakness limits the mobility of the paretic upper limb and accounts for the deficits in its kinematics.24, 25 Mathiowetz and Bass Haugen26 suggest that to compensate for muscle weakness in the shoulder, persons with hemiparesis flex the elbow because this strategy shortens the lever arm, making it easier to raise. The limited extension of the paretic elbow could also be indicative of excessive cocontraction between the agonist and antagonist muscles that may be related to limitations in the range of regulation of the threshold of the tonic stretch reflex.27

Furthermore, there is evidence suggesting that the deficits in shoulder and elbow amplitude could be partly explained by the presence of an abnormal synergistic link between shoulder abduction and elbow flexion. In fact, some studies show an increase in elbow flexion torque in the paretic upper limb in subjects with hemiparesis accompanied by greater shoulder abduction than the control subjects.28, 29 This abnormal synergy between shoulder abductors and elbow flexors makes extension of the paretic elbow difficult.

This study also revealed that elbow extension in the nonparetic upper limb of subjects with hemiparesis does not differ from that of control subjects during the unilateral task; however, the anterior flexion of the trunk was greater, especially for the two 45° directions. During the bilateral task, the extension of the nonparetic upper limb was reduced, especially for the anterior direction, whereas trunk flexion was greater in subjects with hemiparesis in the 3 directions. The mutual adaptation between the upper limbs might explain the reduced extension of the nonparetic elbow. The studies by Kelso et al30, 31 on the relation between the upper limbs in control subjects showed a mutual adaptation toward bilateral symmetry meaning that one of the upper limbs adapts its movement to the other. Subsequent studies performed with people who had a stroke reported by Cunningham et al32 suggest that movements, which differ when executed individually, show a tendency toward bilateral similarity when executed together, with one of the limbs acting as the dominant pole of attraction. The results of our study suggest that this action operates in the direction of the nonparetic upper limb toward the paretic upper limb during a bilateral task performed the subjects with hemiparesis. Under this scenario, the limited extension of the paretic elbow would force the nonparetic upper limb to adapt to this constraint, resulting in limited extension of the elbow in this limb as well.

Thus, our results suggest that the reduced performance of the paretic upper limb in clients with poststroke hemiparesis controls the dynamics of the movement of both upper limbs during a parallel bilateral movement, as described in our study. Kelso30, 31 also found that during a bilateral movement of the upper limbs, the limb that had the most difficulty executing the task led the bilateral activity with the result that the duration of the movement of the 2 limbs was similar to that of the movement for the difficult task in the unilateral condition. Previous studies have reported that the nonparetic upper limb adjusts to the performance of the paretic upper limb during difficult bilateral tasks, such as rapid aiming movements at 2 targets13 and oscillatory movements against gravity.14

It is also possible that visuospatial or attentional demands of the bilateral task also encourage the nonparetic upper limb to adapt to the movement of the paretic upper limb. In fact, it has been suggested that the right hemisphere in particular is activated to control movement when there are substantial visuospatial33 or attentional34 demands. Cunningham et al32 also suggested that difficulty in dividing attention during tasks executed simultaneously is more pronounced in older adults.35, 36

It is also possible that the greater involvement of the trunk limits the use of the upper limbs in the performance of the bilateral task. From this perspective, it has been shown that constraining the trunk during a reaching task may increase elbow extension.37 Therefore, it is possible that the improvements in the paretic upper limb observed in some bilateral studies7, 12, 13 are caused in part by the combination of the bilateral movement with the stabilization of trunk movement. It has been suggested by Cirstea and Levin38 that greater trunk involvement during unilateral reaching tasks of the paretic upper limb helped to reduce movement errors in persons with moderate to severe hemiparesis. Our results show that this strategy is also present during a symmetrical bilateral task of the upper limbs, even in subjects with a relatively good motor function, as shown by their score on the FMA (43–63).

However, trunk control is frequently impaired in patients with stroke, even with good functional recovery. Indeed, we recently showed that simply flexing the trunk was impaired in this population compared with control subjects.16 It was suggested that the upper part of the trunk was more used in the movement than the lower trunk compared with control subjects. However, it should be pointed out that the trunk flexion measured in the present study does not provide valid information concerning the compensation of trunk movement; because only the angular value between the trochanter and shoulder is provided, one cannot infer where the flexion is taking place. It is therefore possible that the execution of trunk flexion is affected in this population and contributes to limits of the upper limbs in both tasks.

The use of the brain structures available in the intact hemisphere could also provide an explanation of our findings. In fact, a certain number of uncrossed pyramidal fibers, the ventral pyramidal tract, and the bilateral control exercised by the medial descending projections of the brainstem may provide a certain degree of motor control of the shoulder and trunk muscles.39, 40

It is also possible that better reorganization of the proximal cortical representation in the damaged hemisphere at the expense of the distal segments could also explain why the subjects favored a much more proximal movement. After small ischemic vascular lesions that occurred within the cortical distal forelimb movement representation in a group of adult monkeys, Nudo and Milliken41 observed that the distal representation spared was replaced by proximal representations of the upper limb contralateral to the hemispheric lesion. The researchers noted that the monkeys used this upper limb to climb but rarely to grasp objects. In view of the time since the stroke in these subjects and the use of the paretic upper limb to assist in tasks of daily living,23 the cortical reorganization probably favored the motor areas related to the overall movement of this limb at the expense of the distal areas. We may hypothesize that proximal cortical representation is better preserved in the damaged cortex.

Therefore, the task conditions would have allowed the subjects with hemiparesis to use the best-preserved resources in the central nervous system, including ipsilateral hemispheric control, the subcortical structures of the brainstem and medulla, and better cortical representation of the proximal segments. This preservation probably made it possible to successfully execute the bilateral task described in our study, which consisted of the synchronized holding and moving of the objects to the remote targets. Thus, the control of the best preserved cortical and subcortical structures appears to have had more influence than the interhemispheric transfers, not allowing the paretic upper limb to take advantage of the model offered by the nonparetic upper limb.

Last, we should point out some inherent limitations to our study. The reduced sample size prevents us from generalizing our results. In addition, certain visuospatial deficits associated with the presence of a left hemiparesis may affect the subject’s postural control42, 43 and impair the performance of a reaching task. Although these deficits were not measured, all the subjects managed to reach the target without falling. However, this factor needs to be controlled for research purposes to be able to generalize the results.

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Conclusions 

Our results show that, in a parallel bilateral task performed by using the upper limb, deficits persist in the paretic upper limb, the nonparetic upper limb adjusts, and there is a marked anterior flexion at the trunk. We suggest that impairments of the paretic upper limb as well as trunk control are factors that should be considered when parallel bilateral tasks are used to improve the joint kinematics of the paretic upper limb in subjects with hemiparesis.

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Acknowledgment 

We thank our colleagues for their comments.

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References 

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  • a Northern Digital Inc, 103 Randall Dr, Waterloo, ON N2V 1C5, Canada.
  • b Version 5.3; The MathWorks Inc, 3 Apple Hill Dr, Natick, MA 01760-2098.
  • c Version 8.0; SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.

 Supported by the Canadian Institutes of Health Research (grant no. 9810DRN-1241-58411), the Réseau provincial de recherche en adaptation-réadaptation (REPAR) (grant no. 1895), and the Fonds de la recherche en santé du Québec-REPAR (grant no. 22113-2078).No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated.

PII: S0003-9993(06)01267-6

doi:10.1016/j.apmr.2006.07.273

Archives of Physical Medicine and Rehabilitation
Volume 87, Issue 11 , Pages 1463-1470, November 2006

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