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Head and pelvic movements during a dynamic reaching task in sitting: Implications for physical therapists
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Head and Pelvic Movements During a Dynamic Reaching Task in Sitting: Implications for Physical Therapists Fiona M. Campbell, MSc, MCSP, Ann M. Ashburn, PhD, MCSP, Ruth M. Pickering, PhD, Malcolm Burnett, BSc ABSTRACT. Campbell FM, Ashburn AM, Pickering RM, Burnett M. Head and pelvic movements during a dynamic reaching task in sitting: implications for physical therapists. Arch Phys Med Rehabil 2001;82:1655-60. Objectives: To describe the distance reached, speed, and movement of the head and pelvis of healthy volunteers; to describe any influence of age on these variables; and to compare healthy volunteers and subjects with hemiplegia while performing a seated reaching task. Design: Age-matched, case-control study. Setting: Gait laboratory in a general hospital. Participants: A convenience sample of 53 healthy volunteers (30 women; 23 men; mean age, 57yr; range, 30 –79yr) and 5 subjects with hemiplegia (2 women, 3 men; mean age, 65yr; range, 60 –78yr) were recruited within 6 weeks poststroke. Interventions: Participants sat on a bench with feet supported and reached laterally as far as they could without falling. Main Outcome Measures: The speed, distance reached, and angular movements of the head and pelvis were recorded by using the 3-dimensional movement analysis system. Results: A significant age-related reduction in the distance reached ( p ⬍ .001), velocity of the movement ( p ⫽ .000), and pelvic tilt used ( p ⬍ .01) was found among healthy volunteers. Comparison of data from healthy volunteers and subjects with hemiplegia showed a significant reduction in the angular movements of the heads of subjects with hemiplegia. Conclusions: The findings suggest conservation of movement with increasing age and stroke. This movement reduction could have negative effects on a subject’s ability to make postural changes in response to disturbance and activity. Such information may assist therapists to gain insight into the nature of balance deficits and the adaptive behavior that could result. Key Words: Aging; Balance; Hemiplegia; Posture; Range of motion, articular; Rehabilitation. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation ALANCE DISORDERS AMONG the elderly population and subjects with stroke are common and multifactorial in B nature. Changes in the ability to balance, particularly in complex, fast-moving situations, can occur as a result of disease or
From the Rehabilitation Research Unit (Campbell, Ashburn, Burnett) and Medical Statistics and Computing (Pickering), University of Southampton, Southampton, England. Accepted in revised form January 9, 2001. Supported by the Stroke Association and Hospital Savings Association. 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. Reprint requests to Ann M. Ashburn, PhD, MCSP, Health and Rehabilitation Research Unit, Level E, Centre Block, Mail Point 886, Southampton General Hospital, Tremona Rd, Southampton S016 6YD UK, e-mail: [email protected]. 0003-9993/01/8212-6406$35.00/0 doi:10.1053/apmr.2001.26818
aging.1,2 Patients with abnormal balance are often referred to physiotherapy, and therapists widely assume that correcting and controlling postural alignment will improve a subject’s balance.3,4 Movement strategies used to maintain balance have been extensively investigated during unexpected movements of the supporting surface.5 Movement strategies involved in balance during voluntary movements have been under less research scrutiny and, though the body of knowledge is growing, there are gaps and insufficient information to allow physiotherapists to diagnose abnormalities of balance responses in elderly subjects or those with pathology such as stroke. Current treatments are often based on experience or assumed knowledge about “normal” postural responses. This suggests a need to investigate normal balance in healthy subjects. BALANCE AND POSTURE The human body is not a rigid structure; it can adopt many postures. These postures are defined by the relative positions of the head to the trunk and by the positions of the upper and lower limbs, all of which affect the position of the center of gravity (COG).6 During a voluntary task, these body segments are offset in a coordinated manner to ensure the stabilization of the whole body and maintenance of balance.7 The head has been identified in research as playing a major role in eliciting and modifying postural responses.8-10 The head contains the visual, labyrinthine, and otolith organs critical to the achievement of postural control. It is thought that a “head stabilizing in space” strategy should be used10 to optimize sensory information during varying balance tasks. This strategy ensures the head is held in a reasonably constant position relative to the environment. There are minimal references in the physiotherapy literature to the role of head position in the facilitation of movement and balance control during the rehabilitation of subjects with impaired stability. Until recently, little attention has been paid to how elderly persons coordinate the head, pelvis, and trunk during movement. Age- and condition-related changes in the timing and coordination of body segments during functional movement11 have been identified. Patients who have had a stroke commonly adopt abnormal postural control strategies when performing tasks.12 More information about the changes in movement patterns and balance with age and stroke is needed. Our study sought (1) to describe the distance reached, speed of movement, and the balance responses of the head and pelvis in a population of healthy volunteers performing a seated reaching task; (2) to describe any influence of age on these variables in this population; and (3) to compare age-matched healthy volunteers and a small sample of individuals with hemiplegia performing the same seated reaching task. METHODS Study approval was gained from the Southampton and South West Hants Local Research Ethics Committee, England. A convenience sample of healthy subjects was recruited from staff at a general hospital. Subjects with a history of blindness, Arch Phys Med Rehabil Vol 82, December 2001
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vertigo, or previous neurologic or musculoskeletal abnormalities were excluded. Subjects with hemiplegia were recruited in the first 6 weeks poststroke while undergoing rehabilitation in an acute stroke unit. They were excluded if they had previous neurologic disorders, musculoskeletal abnormalities, confusion, or unilateral neglect. Unilateral neglect was tested by using the Star Cancellation Test of visuospatial neglect.13,14 Those scoring less than 47 were excluded from the study. The Middlesex Elderly Assessment of Mental State (MEAMS)15 was used to screen for people with confusion; those achieving less than 8 of 12 were not recruited to the study. The functional status of subjects with hemiplegia was measured by using the gross subsection of the Rivermead Motor Assessment (RMA; max score, 13).16 Sensation and proprioception were measured by using the shortened version of the Nottingham Sensory Assessment (max score, 18).17 Development of the Task A lateral dynamic reach task was chosen as the activity that allowed for observation and measurement of postural responses at 2 key body segments, the head and pelvis. The task allows safe transference of the body’s COG and is similar to techniques used in the rehabilitation of adults with balance and movement impairment.3,18 Subjects sat on a bench of standard height with their feet supported and eyes fixed on a red cross placed on the wall in front of them. With their dominant arm stretched out laterally at shoulder height, they were asked to reach out to the side as far as possible. The average of 3 performances was used in the analysis. Data was collected by using a 3-dimensional movement analysis system (CODA MPX30).a Ten noninvasive, small, infrared light-emitting diode (LED) markers were attached to the subject (fig 1) on the lateral orbital wall, forehead, chin, sternum, both acromioclavicular joints, both superior iliac
Fig 1. The reaching task.
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spines, and the metacarpal joints of the lower half of the tibia; and a scanner unit tracked the movement of the markers in all 3-dimensional coordinates. CODA has been reported as accurate as .05mm in the x and y axes, respectively, and 0.6mm in the z axis.19 The LED marker placement was checked for reliability. It was estimated that replacing or repeating marker placement by the investigator was accurate to within less than 5mm of the true value 95% of the time. Each subject was seated on a standard height bench (height, 51cm; seat depth, 31cm) and given a standardized instruction as follows: Keep your eyes on the cross in front of you, when I say “go” reach out as far as you can. When you are ready, go (fig 1). Each subject had 6 practice attempts before completing the 3 trial performances. Measurements Taken During the Reaching Task The following 4 measurements were taken during the reaching task. The key parameters recorded by CODA were: (1) the distance reached (mm) and the speed (m/s) to complete the task; (2) range of angular head movements (deg), defined as the maximum minus the minimum angle recorded as an individual reached to the farthest point; (3) the direction of movement of the head, described in relation to the direction of the reach; and (4) the lateral tilt of the pelvis (deg), described in the direction of the reach. The task performance was repeated 3 times in succession. The average of the 3 readings for each of the measurements was used in data analysis. Statistical Analysis We present the rotation, flexion, and extension movements of the head and pelvic tilt in a lateral direction in the study. Total time to complete the task and the speed of the task is also reported. Scatter plots of the average distance reached, speed to complete the task, and angular movements of the head and pelvis against age were produced along with Lowess smoothed lines (with 60% of points in the fit). All analysis was performed by using the SPSS statistical package, version 7.5.b We examined the change in movement parameters by using linear regression.20 The mean pelvic tilt was compared between age groups by using Scheffe´’s multiple comparison procedure. We compared each movement parameter between hemiplegic subjects and healthy volunteers (controls) in the relevant age bands (60 – 69yr, 70 –79yr) by using 2 sample t tests and produced 95% confidence intervals (CIs) for mean differences. Separate variance t tests and CIs were produced for head rotation and pelvic tilt because standard deviations (SD) were larger in the control group than amongs hemiplegic subjects.20 Nonparametric two sample tests were also performed, but they made no material difference to the conclusions and are not reported here. RESULTS Fifty-three healthy individuals (30 women, 23 men) were recruited to the study; their characteristics are presented in table 1. Correlations between age and weight, spine length, and arm length were examined, but indicated little or no trend in the able-bodied subjects over age (none achieved significance). Five subjects with hemiplegia (2 women, 3 men) were recruited to the study within 6 weeks of a stroke; their characteristics are shown in table 2. Scores on the gross subsection of the RMA shows that the 5 patients could sit unsupported for a minimum of 10 seconds, but required help for all other functional tasks. Subjects C and D showed moderate to severe sensory impairments in both lower and upper limbs. These are
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MOVEMENTS DURING DYNAMIC REACHING, Campbell Table 1: Anthropometric Measures of Healthy Volunteers and Subjects With Hemiplegia Age Categories (yr)
Men n
Women n
Weight (kg)*
Spine Length (T1–L5) (cm)*
Arm Length (cm)*
30–39 40–49 50–59 60–69 70–79
5 4 6 4 4 23
7 5 8 5 5 30
68 ⫾ 8 72 ⫾ 11 73 ⫾ 10 72 ⫾ 17 64 ⫾ 8
57 ⫾ 9 57 ⫾ 7 57 ⫾ 8 57 ⫾ 6 56 ⫾ 8
61 ⫾ 5 63 ⫾ 2 61 ⫾ 4 58 ⫾ 5 56 ⫾ 6
3
2
72 ⫾ 7
58 ⫾ 1
59 ⫾ 2
Total Individuals with stroke
* Values are mean ⫾ SD.
low scores, which may be expected in the acute stages of stroke or secondary to stroke severity. All subjects scored 8 or better on the MEAMS test for cognitive function. Results from this group were compared with the 18 age-matched controls in the 60 – 69 and 70 –79 age categories. All subjects were able to complete the task. Stand-by help of 1 therapist was available, but no subjects required support. Distance Reached and the Speed of the Movement The values of the distance reached (mm) by age in the healthy group (n ⫽ 53) are plotted in figure 2A. The Lowess smoothed line in the figure shows the line of best fit between sequential points on the x and y axes. This is near linear and a true representation of the data. This line indicates a trend of diminished reach by age, which, from a linear regression model, was estimated to reduce by 4mm (95% CI, 2.4 –5.6mm) for each increasing year ( p ⫽ .001). Figure 3A shows the spread of distances reached by subjects in the age-matched control and hemiplegic groups. The mean value for those in the control group (205mm) was higher than for those in the hemiplegic group (134mm), but the difference was not significant (control ⫺ hemiplegic difference ⫽ 71mm; 95% CI, ⫺32.2 to 136.6mm; p ⫽ .262). The plot of the speed of the movement against age was similar to that for distance reached (fig 2A) and is not presented in this article. The linear regression indicated a reduction in velocity of .02m/s on average for each increasing year (95% CI, .43– .47m/s; p ⫽ .000). The difference in speed of executing the movement between the age-matched control group and the hemiplegic group was not significant ( p ⫽ .15). Rotation of the Head Most healthy volunteers (n ⫽ 41) rotated their heads in a direction counter to the direction of reach. Only 11 subjects rotated their heads in the direction of the reach and 1 subject kept his head in midline. The range of motion (ROM) was small
Fig 2. Scatter plots of (A) distance reached and (B) pelvic tilt against age in healthy volunteers.
(mean ⫾ SD, 12° ⫾ 10°) and no relationship was found between the rotational movements of the head and age ( p ⫽ .091). A difference between age-matched controls and hemiplegic subjects was found for head rotation. All subjects with hemiplegia (n ⫽ 5) rotated their heads (mean, 12°) in the direction of the reach in contrast to the control subjects (n ⫽ 41), who tended to move their heads (mean, ⫺10°) in the counter direc-
Table 2: Characteristics of Subjects With Hemiplegia Subject
Age (yr)
Time Since CVA (d)
Side of Hemiplegia
Kinesthetic Score (max ⫽ 24)
Sensory Score (max ⫽ 18)
RMA Gross Function (max ⫽ 13)
Star Cancellation Test (max ⫽ 54)
A B C D E
62 78 60 72 66
19 14 20 40 17
Right Right Left Left Right
24 21 12 3 24
18 8 9 7 18
1 1 1 1 1
54 54 48 47 48
Abbreviation: CVA, cerebrovascular accident; max, maximum.
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Fig 3. Comparison of healthy age-matched controls and subjects with hemiplegia. (A) Distance reached, (B) head rotation, (C) head flexion and extension, and (D) pelvic tilt. p values indicate the results of comparing the movement parameters by using 2-sample t tests between age-matched controls and subjects with hemiplegia.
tion (control ⫺ hemiplegic difference ⫽ ⫺22°; 95% CI, ⫺31° to ⫺11°; p ⫽ .000; fig 3B). It is tempting to suggest that, as all the subjects with hemiplegia rotated their head in the direction of the reach, they lacked a counter-balancing response; but clearly it is not possible to draw conclusions or to generalize findings from this study because of the small sample size. Head Flexion and Extension A variety of movement patterns of the head were observed in the healthy volunteers, with some flexing and some extending their heads throughout the movement. The ROM was ⫺14° to 14° (negative angles depict flexion). Thirty-three controls (62%) moved their head in a forward (flexion) direction whereas 18 (34%) moved their head in a backward (extension) direction, and 2 (4%) maintained their head in the middle. Therefore, a variety of movement patterns within this sample was shown. No clear relationship was observed from the scatter plots (not shown) for each of these movements. Thirteen volunteers (72%) from the age-matched control group flexed their head forward whereas 5 (28%) extended their head. All 5 (100%) subjects with hemiplegia used a pattern of head extension during the reach task. Comparison of the control group with the hemiplegic group shows a significant difference in head flexion and extension: hemiplegic subjects extended by on average 7.5°, whereas controls flexed on average ⫺3.5° (conArch Phys Med Rehabil Vol 82, December 2001
trols ⫺ hemiplegic difference ⫽ ⫺10.9°; 95% CI, ⫺18° to ⫺3.9°; p ⫽ .004; fig 3C). Lateral Pelvic Tilt Lateral pelvic tilt was defined in this study as the movement resulting from side flexion of the trunk on the opposite side to the direction of movement. The relationship between age and pelvic tilt is shown in figure 2B. Here the Lowess smoothed line suggests that there is a gradual reduction in pelvic tilt until the age of 50 years, when it levels off. We compared mean pelvic tilt in each of the 5 age bands because of this nonlinear pattern (table 3).
Table 3: Summary of Lateral Pelvic Tilt Measured for Each Age Group in the 53 Healthy Volunteers Age Group (yr)
n
Mean ⫾ SD (deg)
Min–Max Range (deg)
30–39 40–49 50–59 60–69 70–79
12 9 14 9 9
34 ⫾ 10 20 ⫾ 12 20 ⫾ 8 16 ⫾ 10 16 ⫾ 8
20–49 6–46 10–33 4–38 4–49
Abbreviation: Min, minimum.
MOVEMENTS DURING DYNAMIC REACHING, Campbell
The analysis of variance test revealed that the mean pelvic tilt was not the same in each age band. A Scheffe´’s test for multiple comparisons was used to identify where differences lay. The only significant differences were those between the younger age group (30 –39yr) and all other groups. When the pelvic tilt of subjects with hemiplegia (mean, 11°) was compared with that of the age-matched control subjects (mean, 16.4°), a difference was identified but that difference did not reach significance (control ⫺ hemiplegic difference ⫽ 5.6°; 95% CI, ⫺3.3 to 14.6; p ⫽ .072; fig 3D). DISCUSSION The ability of younger healthy subjects to reach a greater distance, to move faster, and therefore to displace the COG further in a lateral direction may reflect more efficiency or greater confidence in their balance control system than in older subjects.21 Our study was designed to investigate some of the head and pelvis postural strategies used when subjects required balance control during a seated task. No studies could be found describing the normal ROM of the head or the pelvis during a seated reaching task. The ROM found for the head during this study was small, meaning the head shows good angular stabilization relative to the trunk during the task. This is similar to other findings studying head movements during standing tasks.7 In our study, angular movements of the head did not vary greatly across age in the sample of healthy subjects, but were significantly different when compared between controls and hemiplegic subjects. The patterns of head movement used by hemiplegic subjects were also dissimilar to those used by age-matched controls. To date, little attention has been given to this role of the head during voluntary activities in sitting. Pozzo et al9 measured the degree of pitch and rotation in 10 subjects. They suggested that “normal” subjects stabilize their heads when compared with those with bilateral vestibular deficits, who were unable to do so under the same conditions. Interestingly, systematic flexion of the head was recorded during specific walking and running activities in healthy adults. But they found an extension pattern in 7 subjects with bilateral vestibular deficits during the same task. Only 10 “normal” subjects were included in that study, therefore, it is difficult to generalize the results.9 In our larger group of healthy adults, we found a trend among the healthy volunteers to use a pattern of head flexion during the reaching task, whereas all subjects with hemiplegia extended their heads for the same task. It is possible that head extension may have been a method used to control or limit excursion of the COG. DiFabio and Emasithi10 examined the head position of 24 subjects when standing on a moveable platform. They found that older subjects have less movement than younger subjects under the same condition. Assiante and Amblard22 and Allum et al23 describe the technique of head stabilization on the trunk. It is postulated that this may regulate and monitor trunk motion and stability during balance activities. Our study used a seated reaching task, whereas previous research looked at tasks while standing. However, head extension observed in the hemiplegic subjects may reflect a similar movement strategy used secondary to the subjects’ poor balance control. None of the 5 subjects with hemiplegia recruited to our study were able to stand independently or walk. Their trunk control, other than the ability to sit independently, was not objectively assessed. Therefore, it would be difficult to know if head extension was associated with poor trunk control. However, it was noted that 4 of the 5 hemiplegic subjects were unable or not confident to move the head outside of the pelvis in a lateral
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direction. This shows a limited excursion of the COG outside the supporting surface, which is the pelvis while sitting. We found no relationship between the range of head rotation and age in the healthy volunteers; there was, however, a significant reduction in the range of head movements found in the sample of people with hemiplegia. The patterns or direction of movement adopted by this group of subjects differed from those in the control group. The 5 people with hemiplegia used significantly less range of head rotation than the healthy controls, but caution must prevail in the interpretation of these findings because of the small sample size in this study. All subjects with hemiplegia rotated their heads in the direction of the reach, whereas the control group tended to use a counter-rotation. It is possible that the loss of this counterbalancing rotatory movement of the head in the hemiplegic sample reflects impairments in postural control. Only 2 subjects in the hemiplegic sample scored a maximum on the kinesthetic and sensory scores, with 2 of the subjects scoring particularly low (table 2). The same 2 subjects also had the poorest scores on the Star Cancellation Test. A loss of visuospatial awareness may result in poor awareness of the body in reference to its environment and affect the “normal” movement patterns of the head. The preliminary findings of (1) reduced ROM in the head with stroke and (2) loss of counter-balancing patterns of movement in part support the theory of head stabilization. Subjects with impaired sensory information may stabilize their heads to enable greater orientation to a vertical frame of reference and to reduce potential ambiguities in the interpretation of sensory inputs.9 Studies using greater numbers of subjects would be required to justify this observation. Movement of the pelvis is often encouraged during physiotherapy treatment of adults with balance and movement disorders.3 Pelvic movement is believed to assist retraining of balance responses and to encourage greater functional movement. No literature could be found describing the ranges or the patterns of movement, which are normal in an adult population. Lateral pelvic tilt reduces with increasing age and was significantly higher in the younger age category of the 30 to 39 years versus the remaining age categories. The increased segmental motion of the pelvis found in younger subjects, who reached greater distances, compares favorably with that found by other researchers24 who found greater segmental motion of the trunk and upper arm as reach distance increased. In our study, there was very little difference in the range of lateral pelvic tilt in subjects older than 40 years of age. Older subjects seemed reluctant to move their pelvis away from the supporting surface during the reach task. The reduced ROM observed in the older subjects may be secondary to reduced muscle strength, soft-tissue shortening, or increasing degenerative changes of the vertebral bodies consistent with aging.25 Stiffening of the larger muscles surrounding the hip, for example, the hip abductors, adductors, and quadratus lumborum, as the subject reached to the side will achieve a stabilization of the pelvis thus reducing the lateral pelvic tilt.4 It in effect restricts the COG from moving too far. Changes in muscle strength and joint range may be the result of deteriorating balance control or deteriorating balance control may be secondary to muscular changes or a combination of both. In the hemiplegic sample, the reduced lateral pelvic tilt may be a compensatory or protective strategy used to avoid the threat to balance by reducing the amount of potential movement of the COG outside of the supporting surface.4 The findings from this study are not unexpected, and have been observed in clinical practice, but, to date, have not been accurately measured. Arch Phys Med Rehabil Vol 82, December 2001
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Study Limitations The study sample was small, and one of convenience. Healthy adults were recruited from a volunteer organization helping hospitals in the United Kingdom, so it is possible that the healthy volunteer sample was fitter and more active and motivated than the general population. For those reasons, the data collected from the healthy volunteers may be better than that which could be expected from the general population. In addition, it would be misleading to assume that the data from 5 people with hemiplegia could be generalized to the wider community. Findings from this small group of people with acute stroke need further exploration with a larger sample of people consecutively hospitalized with stroke. Relevance to Clinical Practice Many investigators3,17,26 have described normal movement as a basis for treatment of patients with poor balance, particularly the neurologically damaged patient. The findings from this study begin to define normal and abnormal movements used when performing a dynamic reaching task. The findings also highlight a considerable variation in the movements of healthy subjects. Balance control is often disrupted after a stroke. Although this study has described normal or common movement patterns within a small adult population, it is not a simple picture because wide variations in some movement patterns were observed. Analyses of the reach task in healthy adults also showed a change in patterns of movement used according to age and stroke. Such findings may have clinical relevance in the treatment of both young and old patients by increasing awareness of expected movement patterns and ROM. The head has been identified and suggested as playing a key role in balance and movement. The head moved through only a small range during the reach task and deviated minimally from the vertical position. There was, however, less head movement measured with stroke. Patterns of movement adopted also differed. The reduced ROM in the pelvis occurring with age may also have an effect on balance response. CONCLUSIONS Findings from this study confirm some clinical observations made by physiotherapists who describe rigid movement strategies or lack of ability of patients with balance disorders to dissociate segmental movements of the head, pelvis, and trunk; rather, patients move the head, pelvis, and trunk as a system. All these changes would mean the stroke subjects and the elderly are less able to make postural changes during voluntary movements. Therapists often use techniques in rehabilitation to encourage the isolation of movement at a segmental level (ie, trunk or pelvis). This approach seems appropriate but should perhaps include assessment of head control. It is hoped that the effectiveness of rehabilitation strategies used in clinical practice could be examined in more detail and techniques developed that control or enhance an individual’s ability to achieve sitting balance after stroke. This raises the question as to whether it is possible to retrain common patterns of movement with patients? In addition, would this approach be more effective in achieving improved motor and balance control than other methods? Currently missing are similar descriptive studies, which provide normative data for clinical therapists to develop the accuracy of their techniques and to apply them to the retraining of voluntary activities. References 1. Overstall PW, Exton-Smith AN, Imms FJ, Johnson AL. Falls in the elderly related to postural imbalance. Br Med J 1977;1:262-4.
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2. Konrad HR, Girardi M, Helfert R. Balance and aging. Laryngoscope 1999;109:1454-60. 3. Bobath B. Adult hemiplegia: evaluation and treatment. 3rd ed. Oxford: Butterworth-Heinemann; 1997. 4. Carr JH, Shepherd RM. Neurological rehabilitation. London: Butterworth-Heinemann; 1998. 5. Horak FB, Nashner LM. Central programming of postural movements: adaptation to altered support-surface configurations. J Neurophysiol 1986;55:1369-70. 6. Wing AM, Allison S, Jenner JR. Retaining and retraining balance after stroke. Baillieres Clin Neurol 1993;1:87-120. 7. Pozzo T, Levik Y, Berthoz A. Head and trunk movements in the frontal plane during complex dynamic equilibrium tasks in humans. Exp Brain Res 1995;106:327-38. 8. Pozzo T, Berthoz A, Lefort L. Head stabilization during various locomotor tasks in humans I. Normal subjects. Exp Brain Res 1990;82:97-106. 9. Pozzo T, Berthoz A, Lefort L, Vitte E. Head stabilization during various locomotor tasks in humans II. Patients with bilateral peripheral vestibular deficits. Exp Brain Res 1991;85:208-17. 10. DiFabio RP, Emasithi A. Ageing and the mechanisms underlying head and postural control during voluntary motion. Phys Ther 1997;77:458-74. 11. Mourey F, Pozzo T, Routhier-Marcier I, Didier JP. A kinematic comparison between elderly and young subjects standing up from and sitting down in a chair. Age Ageing 1998;27:137-46. 12. Perennou DA, Amblard B, Leblond C, Pelissier J. Biased postural vertical in humans with hemispheric cerebral lesions. Neurosci Lett 1998;252:75-8. 13. Wilson B, Cockburn J, Halligan P. Development of a behavioral test of visuospatial neglect. Arch Phys Med Rehabil 1987;68:98102. 14. Halligan PW, Marshall JC, Wade DT. Visuospatial neglect: underlying factors and test sensitivity. Lancet 1989;14:908-11. 15. Shiel A, Wilson B. Performance of stroke patients on the Middlesex Elderly Assessment of Mental State. Clin Rehabil 1992; 6:283-9. 16. Lincoln NB, Leadbetter D. Assessment of motor function in stroke patients. Physiotherapy 1979;65:48-51. 17. Lincoln NB, Jackson JM, Adams SA. Reliability and revision of the Nottingham Sensory Assessment for stroke patients. Physiotherapy 1998;84:358-65. 18. Carr JH, Shepherd RM, Gordon J, Gentile AM, Held JM. Movement science foundations for physical therapy in rehabilitation. London: Heinemann Physiotherapy; 1987. 19. Charnwood Dynamics Ltd, CODAmpx30. Available: http://www. charndyn.com/technology/coda-mpx30.htm. Accessed April 19, 2001. 20. Bland M. An introduction to medical statistics. 2nd ed. Oxford: Oxford Medical Publications; 1997. 21. Robinovitch SN, Cronin T, Wolf SL. Perception of postural limits in elderly nursing home and day care participants. J Gerontol A Biol Sci Med Sci 1999;54:B124-31. 22. Assiante C, Amblard B. Ontogenesis of head stabilization in space during locomotion in children: influence of visual cues. Exp Brain Res 1993;93:499-515. 23. Allum JH, Gretsy M, Keshner E, Shuperts C. The control of head movements during human balance corrections. J Vestib Res 1997; 7:189-218. 24. Dean C, Shepherd R, Adams R. Sitting balance I: trunk-arm coordination of the lower limbs during self-paced reaching in sitting. Gait Posture 1999;10:135-46. 25. Hubbard B, Squier M. The physical ageing of the neuromuscular system. In: Tallis R, editor. Clinical neurology of old age. New York: John Wiley; 1989. p 15-22. 26. Davies PM. Steps to follow: a guide to the treatment of adult hemiplegia. Berlin: Springer-Verlag; 1985. Suppliers a. Charnwood Dynamics Ltd, 17 South St, Barrow-on-Soar, Leicester, LE12 8LY, England. b. SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.
Head and Pelvic Movements During a Dynamic Reaching Task in Sitting: Implications for Physical Therapists Fiona M. Campbell, MSc, MCSP, Ann M. Ashburn, PhD, MCSP, Ruth M. Pickering, PhD, Malcolm Burnett, BSc ABSTRACT. Campbell FM, Ashburn AM, Pickering RM, Burnett M. Head and pelvic movements during a dynamic reaching task in sitting: implications for physical therapists. Arch Phys Med Rehabil 2001;82:1655-60. Objectives: To describe the distance reached, speed, and movement of the head and pelvis of healthy volunteers; to describe any influence of age on these variables; and to compare healthy volunteers and subjects with hemiplegia while performing a seated reaching task. Design: Age-matched, case-control study. Setting: Gait laboratory in a general hospital. Participants: A convenience sample of 53 healthy volunteers (30 women; 23 men; mean age, 57yr; range, 30 –79yr) and 5 subjects with hemiplegia (2 women, 3 men; mean age, 65yr; range, 60 –78yr) were recruited within 6 weeks poststroke. Interventions: Participants sat on a bench with feet supported and reached laterally as far as they could without falling. Main Outcome Measures: The speed, distance reached, and angular movements of the head and pelvis were recorded by using the 3-dimensional movement analysis system. Results: A significant age-related reduction in the distance reached ( p ⬍ .001), velocity of the movement ( p ⫽ .000), and pelvic tilt used ( p ⬍ .01) was found among healthy volunteers. Comparison of data from healthy volunteers and subjects with hemiplegia showed a significant reduction in the angular movements of the heads of subjects with hemiplegia. Conclusions: The findings suggest conservation of movement with increasing age and stroke. This movement reduction could have negative effects on a subject’s ability to make postural changes in response to disturbance and activity. Such information may assist therapists to gain insight into the nature of balance deficits and the adaptive behavior that could result. Key Words: Aging; Balance; Hemiplegia; Posture; Range of motion, articular; Rehabilitation. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation ALANCE DISORDERS AMONG the elderly population and subjects with stroke are common and multifactorial in B nature. Changes in the ability to balance, particularly in complex, fast-moving situations, can occur as a result of disease or
From the Rehabilitation Research Unit (Campbell, Ashburn, Burnett) and Medical Statistics and Computing (Pickering), University of Southampton, Southampton, England. Accepted in revised form January 9, 2001. Supported by the Stroke Association and Hospital Savings Association. 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. Reprint requests to Ann M. Ashburn, PhD, MCSP, Health and Rehabilitation Research Unit, Level E, Centre Block, Mail Point 886, Southampton General Hospital, Tremona Rd, Southampton S016 6YD UK, e-mail: [email protected]. 0003-9993/01/8212-6406$35.00/0 doi:10.1053/apmr.2001.26818
aging.1,2 Patients with abnormal balance are often referred to physiotherapy, and therapists widely assume that correcting and controlling postural alignment will improve a subject’s balance.3,4 Movement strategies used to maintain balance have been extensively investigated during unexpected movements of the supporting surface.5 Movement strategies involved in balance during voluntary movements have been under less research scrutiny and, though the body of knowledge is growing, there are gaps and insufficient information to allow physiotherapists to diagnose abnormalities of balance responses in elderly subjects or those with pathology such as stroke. Current treatments are often based on experience or assumed knowledge about “normal” postural responses. This suggests a need to investigate normal balance in healthy subjects. BALANCE AND POSTURE The human body is not a rigid structure; it can adopt many postures. These postures are defined by the relative positions of the head to the trunk and by the positions of the upper and lower limbs, all of which affect the position of the center of gravity (COG).6 During a voluntary task, these body segments are offset in a coordinated manner to ensure the stabilization of the whole body and maintenance of balance.7 The head has been identified in research as playing a major role in eliciting and modifying postural responses.8-10 The head contains the visual, labyrinthine, and otolith organs critical to the achievement of postural control. It is thought that a “head stabilizing in space” strategy should be used10 to optimize sensory information during varying balance tasks. This strategy ensures the head is held in a reasonably constant position relative to the environment. There are minimal references in the physiotherapy literature to the role of head position in the facilitation of movement and balance control during the rehabilitation of subjects with impaired stability. Until recently, little attention has been paid to how elderly persons coordinate the head, pelvis, and trunk during movement. Age- and condition-related changes in the timing and coordination of body segments during functional movement11 have been identified. Patients who have had a stroke commonly adopt abnormal postural control strategies when performing tasks.12 More information about the changes in movement patterns and balance with age and stroke is needed. Our study sought (1) to describe the distance reached, speed of movement, and the balance responses of the head and pelvis in a population of healthy volunteers performing a seated reaching task; (2) to describe any influence of age on these variables in this population; and (3) to compare age-matched healthy volunteers and a small sample of individuals with hemiplegia performing the same seated reaching task. METHODS Study approval was gained from the Southampton and South West Hants Local Research Ethics Committee, England. A convenience sample of healthy subjects was recruited from staff at a general hospital. Subjects with a history of blindness, Arch Phys Med Rehabil Vol 82, December 2001
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vertigo, or previous neurologic or musculoskeletal abnormalities were excluded. Subjects with hemiplegia were recruited in the first 6 weeks poststroke while undergoing rehabilitation in an acute stroke unit. They were excluded if they had previous neurologic disorders, musculoskeletal abnormalities, confusion, or unilateral neglect. Unilateral neglect was tested by using the Star Cancellation Test of visuospatial neglect.13,14 Those scoring less than 47 were excluded from the study. The Middlesex Elderly Assessment of Mental State (MEAMS)15 was used to screen for people with confusion; those achieving less than 8 of 12 were not recruited to the study. The functional status of subjects with hemiplegia was measured by using the gross subsection of the Rivermead Motor Assessment (RMA; max score, 13).16 Sensation and proprioception were measured by using the shortened version of the Nottingham Sensory Assessment (max score, 18).17 Development of the Task A lateral dynamic reach task was chosen as the activity that allowed for observation and measurement of postural responses at 2 key body segments, the head and pelvis. The task allows safe transference of the body’s COG and is similar to techniques used in the rehabilitation of adults with balance and movement impairment.3,18 Subjects sat on a bench of standard height with their feet supported and eyes fixed on a red cross placed on the wall in front of them. With their dominant arm stretched out laterally at shoulder height, they were asked to reach out to the side as far as possible. The average of 3 performances was used in the analysis. Data was collected by using a 3-dimensional movement analysis system (CODA MPX30).a Ten noninvasive, small, infrared light-emitting diode (LED) markers were attached to the subject (fig 1) on the lateral orbital wall, forehead, chin, sternum, both acromioclavicular joints, both superior iliac
Fig 1. The reaching task.
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spines, and the metacarpal joints of the lower half of the tibia; and a scanner unit tracked the movement of the markers in all 3-dimensional coordinates. CODA has been reported as accurate as .05mm in the x and y axes, respectively, and 0.6mm in the z axis.19 The LED marker placement was checked for reliability. It was estimated that replacing or repeating marker placement by the investigator was accurate to within less than 5mm of the true value 95% of the time. Each subject was seated on a standard height bench (height, 51cm; seat depth, 31cm) and given a standardized instruction as follows: Keep your eyes on the cross in front of you, when I say “go” reach out as far as you can. When you are ready, go (fig 1). Each subject had 6 practice attempts before completing the 3 trial performances. Measurements Taken During the Reaching Task The following 4 measurements were taken during the reaching task. The key parameters recorded by CODA were: (1) the distance reached (mm) and the speed (m/s) to complete the task; (2) range of angular head movements (deg), defined as the maximum minus the minimum angle recorded as an individual reached to the farthest point; (3) the direction of movement of the head, described in relation to the direction of the reach; and (4) the lateral tilt of the pelvis (deg), described in the direction of the reach. The task performance was repeated 3 times in succession. The average of the 3 readings for each of the measurements was used in data analysis. Statistical Analysis We present the rotation, flexion, and extension movements of the head and pelvic tilt in a lateral direction in the study. Total time to complete the task and the speed of the task is also reported. Scatter plots of the average distance reached, speed to complete the task, and angular movements of the head and pelvis against age were produced along with Lowess smoothed lines (with 60% of points in the fit). All analysis was performed by using the SPSS statistical package, version 7.5.b We examined the change in movement parameters by using linear regression.20 The mean pelvic tilt was compared between age groups by using Scheffe´’s multiple comparison procedure. We compared each movement parameter between hemiplegic subjects and healthy volunteers (controls) in the relevant age bands (60 – 69yr, 70 –79yr) by using 2 sample t tests and produced 95% confidence intervals (CIs) for mean differences. Separate variance t tests and CIs were produced for head rotation and pelvic tilt because standard deviations (SD) were larger in the control group than amongs hemiplegic subjects.20 Nonparametric two sample tests were also performed, but they made no material difference to the conclusions and are not reported here. RESULTS Fifty-three healthy individuals (30 women, 23 men) were recruited to the study; their characteristics are presented in table 1. Correlations between age and weight, spine length, and arm length were examined, but indicated little or no trend in the able-bodied subjects over age (none achieved significance). Five subjects with hemiplegia (2 women, 3 men) were recruited to the study within 6 weeks of a stroke; their characteristics are shown in table 2. Scores on the gross subsection of the RMA shows that the 5 patients could sit unsupported for a minimum of 10 seconds, but required help for all other functional tasks. Subjects C and D showed moderate to severe sensory impairments in both lower and upper limbs. These are
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MOVEMENTS DURING DYNAMIC REACHING, Campbell Table 1: Anthropometric Measures of Healthy Volunteers and Subjects With Hemiplegia Age Categories (yr)
Men n
Women n
Weight (kg)*
Spine Length (T1–L5) (cm)*
Arm Length (cm)*
30–39 40–49 50–59 60–69 70–79
5 4 6 4 4 23
7 5 8 5 5 30
68 ⫾ 8 72 ⫾ 11 73 ⫾ 10 72 ⫾ 17 64 ⫾ 8
57 ⫾ 9 57 ⫾ 7 57 ⫾ 8 57 ⫾ 6 56 ⫾ 8
61 ⫾ 5 63 ⫾ 2 61 ⫾ 4 58 ⫾ 5 56 ⫾ 6
3
2
72 ⫾ 7
58 ⫾ 1
59 ⫾ 2
Total Individuals with stroke
* Values are mean ⫾ SD.
low scores, which may be expected in the acute stages of stroke or secondary to stroke severity. All subjects scored 8 or better on the MEAMS test for cognitive function. Results from this group were compared with the 18 age-matched controls in the 60 – 69 and 70 –79 age categories. All subjects were able to complete the task. Stand-by help of 1 therapist was available, but no subjects required support. Distance Reached and the Speed of the Movement The values of the distance reached (mm) by age in the healthy group (n ⫽ 53) are plotted in figure 2A. The Lowess smoothed line in the figure shows the line of best fit between sequential points on the x and y axes. This is near linear and a true representation of the data. This line indicates a trend of diminished reach by age, which, from a linear regression model, was estimated to reduce by 4mm (95% CI, 2.4 –5.6mm) for each increasing year ( p ⫽ .001). Figure 3A shows the spread of distances reached by subjects in the age-matched control and hemiplegic groups. The mean value for those in the control group (205mm) was higher than for those in the hemiplegic group (134mm), but the difference was not significant (control ⫺ hemiplegic difference ⫽ 71mm; 95% CI, ⫺32.2 to 136.6mm; p ⫽ .262). The plot of the speed of the movement against age was similar to that for distance reached (fig 2A) and is not presented in this article. The linear regression indicated a reduction in velocity of .02m/s on average for each increasing year (95% CI, .43– .47m/s; p ⫽ .000). The difference in speed of executing the movement between the age-matched control group and the hemiplegic group was not significant ( p ⫽ .15). Rotation of the Head Most healthy volunteers (n ⫽ 41) rotated their heads in a direction counter to the direction of reach. Only 11 subjects rotated their heads in the direction of the reach and 1 subject kept his head in midline. The range of motion (ROM) was small
Fig 2. Scatter plots of (A) distance reached and (B) pelvic tilt against age in healthy volunteers.
(mean ⫾ SD, 12° ⫾ 10°) and no relationship was found between the rotational movements of the head and age ( p ⫽ .091). A difference between age-matched controls and hemiplegic subjects was found for head rotation. All subjects with hemiplegia (n ⫽ 5) rotated their heads (mean, 12°) in the direction of the reach in contrast to the control subjects (n ⫽ 41), who tended to move their heads (mean, ⫺10°) in the counter direc-
Table 2: Characteristics of Subjects With Hemiplegia Subject
Age (yr)
Time Since CVA (d)
Side of Hemiplegia
Kinesthetic Score (max ⫽ 24)
Sensory Score (max ⫽ 18)
RMA Gross Function (max ⫽ 13)
Star Cancellation Test (max ⫽ 54)
A B C D E
62 78 60 72 66
19 14 20 40 17
Right Right Left Left Right
24 21 12 3 24
18 8 9 7 18
1 1 1 1 1
54 54 48 47 48
Abbreviation: CVA, cerebrovascular accident; max, maximum.
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Fig 3. Comparison of healthy age-matched controls and subjects with hemiplegia. (A) Distance reached, (B) head rotation, (C) head flexion and extension, and (D) pelvic tilt. p values indicate the results of comparing the movement parameters by using 2-sample t tests between age-matched controls and subjects with hemiplegia.
tion (control ⫺ hemiplegic difference ⫽ ⫺22°; 95% CI, ⫺31° to ⫺11°; p ⫽ .000; fig 3B). It is tempting to suggest that, as all the subjects with hemiplegia rotated their head in the direction of the reach, they lacked a counter-balancing response; but clearly it is not possible to draw conclusions or to generalize findings from this study because of the small sample size. Head Flexion and Extension A variety of movement patterns of the head were observed in the healthy volunteers, with some flexing and some extending their heads throughout the movement. The ROM was ⫺14° to 14° (negative angles depict flexion). Thirty-three controls (62%) moved their head in a forward (flexion) direction whereas 18 (34%) moved their head in a backward (extension) direction, and 2 (4%) maintained their head in the middle. Therefore, a variety of movement patterns within this sample was shown. No clear relationship was observed from the scatter plots (not shown) for each of these movements. Thirteen volunteers (72%) from the age-matched control group flexed their head forward whereas 5 (28%) extended their head. All 5 (100%) subjects with hemiplegia used a pattern of head extension during the reach task. Comparison of the control group with the hemiplegic group shows a significant difference in head flexion and extension: hemiplegic subjects extended by on average 7.5°, whereas controls flexed on average ⫺3.5° (conArch Phys Med Rehabil Vol 82, December 2001
trols ⫺ hemiplegic difference ⫽ ⫺10.9°; 95% CI, ⫺18° to ⫺3.9°; p ⫽ .004; fig 3C). Lateral Pelvic Tilt Lateral pelvic tilt was defined in this study as the movement resulting from side flexion of the trunk on the opposite side to the direction of movement. The relationship between age and pelvic tilt is shown in figure 2B. Here the Lowess smoothed line suggests that there is a gradual reduction in pelvic tilt until the age of 50 years, when it levels off. We compared mean pelvic tilt in each of the 5 age bands because of this nonlinear pattern (table 3).
Table 3: Summary of Lateral Pelvic Tilt Measured for Each Age Group in the 53 Healthy Volunteers Age Group (yr)
n
Mean ⫾ SD (deg)
Min–Max Range (deg)
30–39 40–49 50–59 60–69 70–79
12 9 14 9 9
34 ⫾ 10 20 ⫾ 12 20 ⫾ 8 16 ⫾ 10 16 ⫾ 8
20–49 6–46 10–33 4–38 4–49
Abbreviation: Min, minimum.
MOVEMENTS DURING DYNAMIC REACHING, Campbell
The analysis of variance test revealed that the mean pelvic tilt was not the same in each age band. A Scheffe´’s test for multiple comparisons was used to identify where differences lay. The only significant differences were those between the younger age group (30 –39yr) and all other groups. When the pelvic tilt of subjects with hemiplegia (mean, 11°) was compared with that of the age-matched control subjects (mean, 16.4°), a difference was identified but that difference did not reach significance (control ⫺ hemiplegic difference ⫽ 5.6°; 95% CI, ⫺3.3 to 14.6; p ⫽ .072; fig 3D). DISCUSSION The ability of younger healthy subjects to reach a greater distance, to move faster, and therefore to displace the COG further in a lateral direction may reflect more efficiency or greater confidence in their balance control system than in older subjects.21 Our study was designed to investigate some of the head and pelvis postural strategies used when subjects required balance control during a seated task. No studies could be found describing the normal ROM of the head or the pelvis during a seated reaching task. The ROM found for the head during this study was small, meaning the head shows good angular stabilization relative to the trunk during the task. This is similar to other findings studying head movements during standing tasks.7 In our study, angular movements of the head did not vary greatly across age in the sample of healthy subjects, but were significantly different when compared between controls and hemiplegic subjects. The patterns of head movement used by hemiplegic subjects were also dissimilar to those used by age-matched controls. To date, little attention has been given to this role of the head during voluntary activities in sitting. Pozzo et al9 measured the degree of pitch and rotation in 10 subjects. They suggested that “normal” subjects stabilize their heads when compared with those with bilateral vestibular deficits, who were unable to do so under the same conditions. Interestingly, systematic flexion of the head was recorded during specific walking and running activities in healthy adults. But they found an extension pattern in 7 subjects with bilateral vestibular deficits during the same task. Only 10 “normal” subjects were included in that study, therefore, it is difficult to generalize the results.9 In our larger group of healthy adults, we found a trend among the healthy volunteers to use a pattern of head flexion during the reaching task, whereas all subjects with hemiplegia extended their heads for the same task. It is possible that head extension may have been a method used to control or limit excursion of the COG. DiFabio and Emasithi10 examined the head position of 24 subjects when standing on a moveable platform. They found that older subjects have less movement than younger subjects under the same condition. Assiante and Amblard22 and Allum et al23 describe the technique of head stabilization on the trunk. It is postulated that this may regulate and monitor trunk motion and stability during balance activities. Our study used a seated reaching task, whereas previous research looked at tasks while standing. However, head extension observed in the hemiplegic subjects may reflect a similar movement strategy used secondary to the subjects’ poor balance control. None of the 5 subjects with hemiplegia recruited to our study were able to stand independently or walk. Their trunk control, other than the ability to sit independently, was not objectively assessed. Therefore, it would be difficult to know if head extension was associated with poor trunk control. However, it was noted that 4 of the 5 hemiplegic subjects were unable or not confident to move the head outside of the pelvis in a lateral
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direction. This shows a limited excursion of the COG outside the supporting surface, which is the pelvis while sitting. We found no relationship between the range of head rotation and age in the healthy volunteers; there was, however, a significant reduction in the range of head movements found in the sample of people with hemiplegia. The patterns or direction of movement adopted by this group of subjects differed from those in the control group. The 5 people with hemiplegia used significantly less range of head rotation than the healthy controls, but caution must prevail in the interpretation of these findings because of the small sample size in this study. All subjects with hemiplegia rotated their heads in the direction of the reach, whereas the control group tended to use a counter-rotation. It is possible that the loss of this counterbalancing rotatory movement of the head in the hemiplegic sample reflects impairments in postural control. Only 2 subjects in the hemiplegic sample scored a maximum on the kinesthetic and sensory scores, with 2 of the subjects scoring particularly low (table 2). The same 2 subjects also had the poorest scores on the Star Cancellation Test. A loss of visuospatial awareness may result in poor awareness of the body in reference to its environment and affect the “normal” movement patterns of the head. The preliminary findings of (1) reduced ROM in the head with stroke and (2) loss of counter-balancing patterns of movement in part support the theory of head stabilization. Subjects with impaired sensory information may stabilize their heads to enable greater orientation to a vertical frame of reference and to reduce potential ambiguities in the interpretation of sensory inputs.9 Studies using greater numbers of subjects would be required to justify this observation. Movement of the pelvis is often encouraged during physiotherapy treatment of adults with balance and movement disorders.3 Pelvic movement is believed to assist retraining of balance responses and to encourage greater functional movement. No literature could be found describing the ranges or the patterns of movement, which are normal in an adult population. Lateral pelvic tilt reduces with increasing age and was significantly higher in the younger age category of the 30 to 39 years versus the remaining age categories. The increased segmental motion of the pelvis found in younger subjects, who reached greater distances, compares favorably with that found by other researchers24 who found greater segmental motion of the trunk and upper arm as reach distance increased. In our study, there was very little difference in the range of lateral pelvic tilt in subjects older than 40 years of age. Older subjects seemed reluctant to move their pelvis away from the supporting surface during the reach task. The reduced ROM observed in the older subjects may be secondary to reduced muscle strength, soft-tissue shortening, or increasing degenerative changes of the vertebral bodies consistent with aging.25 Stiffening of the larger muscles surrounding the hip, for example, the hip abductors, adductors, and quadratus lumborum, as the subject reached to the side will achieve a stabilization of the pelvis thus reducing the lateral pelvic tilt.4 It in effect restricts the COG from moving too far. Changes in muscle strength and joint range may be the result of deteriorating balance control or deteriorating balance control may be secondary to muscular changes or a combination of both. In the hemiplegic sample, the reduced lateral pelvic tilt may be a compensatory or protective strategy used to avoid the threat to balance by reducing the amount of potential movement of the COG outside of the supporting surface.4 The findings from this study are not unexpected, and have been observed in clinical practice, but, to date, have not been accurately measured. Arch Phys Med Rehabil Vol 82, December 2001
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Study Limitations The study sample was small, and one of convenience. Healthy adults were recruited from a volunteer organization helping hospitals in the United Kingdom, so it is possible that the healthy volunteer sample was fitter and more active and motivated than the general population. For those reasons, the data collected from the healthy volunteers may be better than that which could be expected from the general population. In addition, it would be misleading to assume that the data from 5 people with hemiplegia could be generalized to the wider community. Findings from this small group of people with acute stroke need further exploration with a larger sample of people consecutively hospitalized with stroke. Relevance to Clinical Practice Many investigators3,17,26 have described normal movement as a basis for treatment of patients with poor balance, particularly the neurologically damaged patient. The findings from this study begin to define normal and abnormal movements used when performing a dynamic reaching task. The findings also highlight a considerable variation in the movements of healthy subjects. Balance control is often disrupted after a stroke. Although this study has described normal or common movement patterns within a small adult population, it is not a simple picture because wide variations in some movement patterns were observed. Analyses of the reach task in healthy adults also showed a change in patterns of movement used according to age and stroke. Such findings may have clinical relevance in the treatment of both young and old patients by increasing awareness of expected movement patterns and ROM. The head has been identified and suggested as playing a key role in balance and movement. The head moved through only a small range during the reach task and deviated minimally from the vertical position. There was, however, less head movement measured with stroke. Patterns of movement adopted also differed. The reduced ROM in the pelvis occurring with age may also have an effect on balance response. CONCLUSIONS Findings from this study confirm some clinical observations made by physiotherapists who describe rigid movement strategies or lack of ability of patients with balance disorders to dissociate segmental movements of the head, pelvis, and trunk; rather, patients move the head, pelvis, and trunk as a system. All these changes would mean the stroke subjects and the elderly are less able to make postural changes during voluntary movements. Therapists often use techniques in rehabilitation to encourage the isolation of movement at a segmental level (ie, trunk or pelvis). This approach seems appropriate but should perhaps include assessment of head control. It is hoped that the effectiveness of rehabilitation strategies used in clinical practice could be examined in more detail and techniques developed that control or enhance an individual’s ability to achieve sitting balance after stroke. This raises the question as to whether it is possible to retrain common patterns of movement with patients? In addition, would this approach be more effective in achieving improved motor and balance control than other methods? Currently missing are similar descriptive studies, which provide normative data for clinical therapists to develop the accuracy of their techniques and to apply them to the retraining of voluntary activities. References 1. Overstall PW, Exton-Smith AN, Imms FJ, Johnson AL. Falls in the elderly related to postural imbalance. Br Med J 1977;1:262-4.
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2. Konrad HR, Girardi M, Helfert R. Balance and aging. Laryngoscope 1999;109:1454-60. 3. Bobath B. Adult hemiplegia: evaluation and treatment. 3rd ed. Oxford: Butterworth-Heinemann; 1997. 4. Carr JH, Shepherd RM. Neurological rehabilitation. London: Butterworth-Heinemann; 1998. 5. Horak FB, Nashner LM. Central programming of postural movements: adaptation to altered support-surface configurations. J Neurophysiol 1986;55:1369-70. 6. Wing AM, Allison S, Jenner JR. Retaining and retraining balance after stroke. Baillieres Clin Neurol 1993;1:87-120. 7. Pozzo T, Levik Y, Berthoz A. Head and trunk movements in the frontal plane during complex dynamic equilibrium tasks in humans. Exp Brain Res 1995;106:327-38. 8. Pozzo T, Berthoz A, Lefort L. Head stabilization during various locomotor tasks in humans I. Normal subjects. Exp Brain Res 1990;82:97-106. 9. Pozzo T, Berthoz A, Lefort L, Vitte E. Head stabilization during various locomotor tasks in humans II. Patients with bilateral peripheral vestibular deficits. Exp Brain Res 1991;85:208-17. 10. DiFabio RP, Emasithi A. Ageing and the mechanisms underlying head and postural control during voluntary motion. Phys Ther 1997;77:458-74. 11. Mourey F, Pozzo T, Routhier-Marcier I, Didier JP. A kinematic comparison between elderly and young subjects standing up from and sitting down in a chair. Age Ageing 1998;27:137-46. 12. Perennou DA, Amblard B, Leblond C, Pelissier J. Biased postural vertical in humans with hemispheric cerebral lesions. Neurosci Lett 1998;252:75-8. 13. Wilson B, Cockburn J, Halligan P. Development of a behavioral test of visuospatial neglect. Arch Phys Med Rehabil 1987;68:98102. 14. Halligan PW, Marshall JC, Wade DT. Visuospatial neglect: underlying factors and test sensitivity. Lancet 1989;14:908-11. 15. Shiel A, Wilson B. Performance of stroke patients on the Middlesex Elderly Assessment of Mental State. Clin Rehabil 1992; 6:283-9. 16. Lincoln NB, Leadbetter D. Assessment of motor function in stroke patients. Physiotherapy 1979;65:48-51. 17. Lincoln NB, Jackson JM, Adams SA. Reliability and revision of the Nottingham Sensory Assessment for stroke patients. Physiotherapy 1998;84:358-65. 18. Carr JH, Shepherd RM, Gordon J, Gentile AM, Held JM. Movement science foundations for physical therapy in rehabilitation. London: Heinemann Physiotherapy; 1987. 19. Charnwood Dynamics Ltd, CODAmpx30. Available: http://www. charndyn.com/technology/coda-mpx30.htm. Accessed April 19, 2001. 20. Bland M. An introduction to medical statistics. 2nd ed. Oxford: Oxford Medical Publications; 1997. 21. Robinovitch SN, Cronin T, Wolf SL. Perception of postural limits in elderly nursing home and day care participants. J Gerontol A Biol Sci Med Sci 1999;54:B124-31. 22. Assiante C, Amblard B. Ontogenesis of head stabilization in space during locomotion in children: influence of visual cues. Exp Brain Res 1993;93:499-515. 23. Allum JH, Gretsy M, Keshner E, Shuperts C. The control of head movements during human balance corrections. J Vestib Res 1997; 7:189-218. 24. Dean C, Shepherd R, Adams R. Sitting balance I: trunk-arm coordination of the lower limbs during self-paced reaching in sitting. Gait Posture 1999;10:135-46. 25. Hubbard B, Squier M. The physical ageing of the neuromuscular system. In: Tallis R, editor. Clinical neurology of old age. New York: John Wiley; 1989. p 15-22. 26. Davies PM. Steps to follow: a guide to the treatment of adult hemiplegia. Berlin: Springer-Verlag; 1985. Suppliers a. Charnwood Dynamics Ltd, 17 South St, Barrow-on-Soar, Leicester, LE12 8LY, England. b. SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.