Volume 90, Issue 6 , Pages 919-926, June 2009
Light Touch Cue Through a Cane Improves Pelvic Stability During Walking in Stroke
Article Outline
Abstract
Boonsinsukh R, Panichareon L, Phansuwan-Pujito P. Light touch cue through a cane improves pelvic stability during walking in stroke.
Objective
To examine the effect of a light touch cue provided through a cane on mediolateral (ML) pelvic stability during walking in subjects poststroke.
Design
Crossover trial examining ML pelvic stability during walking using a cane with the force contact and touch contact methods.
Setting
Physical therapy clinic, tertiary care center.
Participants
Subacute patients (N=40) with stroke with a mean age of 59.6 years and mean stroke duration of 46.8 days. The average gait speed with a cane was .13m/s (.05–.29m/s).
Intervention
Using a cane with the force contact and touch contact methods during walking.
Main Outcome Measures
ML pelvic stability as measured by averaged peak-to-peak pelvic acceleration, muscle activation of bilateral tensor fascia latae (TFL), semitendinosus (ST), and vastus medialis (VM) using an electromyography system, and vertical cane force.
Results
The average amount of cane force during touch contact and force contact cane use conditions was 2.3N and 49.3N, respectively. A light touch cue through a cane was required only when the paretic leg accepted the body weight, and this cue can provide ML pelvic stability (.16g of average pelvic acceleration) during walking to the same degree as the force contact method of cane use. However, significant increases in single-limb support duration with higher activations of TFL, VM, and ST muscles on the paretic leg were found during the paretic stance phase when using a cane in the touch contact fashion (P<.05).
Conclusions
A light touch cue can be provided during walking through the use of a cane. This augmented somatosensory information provides lateral stability during walking for subjects with stroke by facilitating the activations of weight-bearing muscles on the paretic leg during the stance phase.
Key Words: Gait, Rehabilitation
List of Abbreviations: EMG, electromyography, ML, mediolateral, RMS, root-mean-square, ST, semitendinosus, TFL, tensor fascia latae, VM, vastus medialis
SOMATOSENSORY INFORMATION from the fingertip that is obtained by lightly touching an object, known as a light touch cue, is a sensory input that could potentially help in the control of posture. Several studies have demonstrated that, when touching a rigid immobile object, a light touch cue reduces postural sway during quiet tandem stance1, 2 and single limb standing3 with eyes closed. A light touch cue also decreases postural sway caused by predictive and reactive postural perturbations.4 These fingertip cues are so prominent that they attenuate body sway even when persons are able to see their surroundings.1, 2
With a minimal amount of contact force, a light touch cue does not provide mechanical support to the body.1 A recent study suggested that light touch cue not only provides augmented sensory feedback regarding body movement but also may act as a constraint to the postural control system when preparing postural adjustments.4 Two types of sensory feedback have been implicated: one is related to the provision of a fixed reference point in space,5 and the other is involved in the information provided by transient forces developed between the body part and the contact surface.6, 7 The force changes encode the combined information of position and velocity of the body sway in relation to the reference point.8, 9 This finding was similar to that observed in the visual system, suggesting that the postural control system may use the fingertip cue in the same way that it does visual information.10
The benefit of a light touch cue is also demonstrated in subjects with postural control dysfunctions, such as individuals with vestibular loss11 and peripheral sensory neuropathy.12, 13 However, those studies have been conducted only in quiet standing. Postural control impairment is also commonly found in subjects with stroke, and regaining the ability to walk is a major goal in stroke rehabilitation.14 Our previous study examined the effect of a light touch cue on balance during standing and walking and found that light touch of the finger along a fixed handrail improved postural stability during walking under surface perturbation.15 Postural stability in subjects with stroke, as quantified by the RMS of the center of body mass and the center of pressure, showed a significant reduction in both anterior and ML directions, leading to a reduction in hyperactivity of the nonparetic lower-limb muscle.
The limitation of touching the finger along a handrail, as in our previous study, is that the stable surface must be within reach. This is not always possible in daily life and can be temporarily solved by touching an accompanying person when there is no surface available.16 For instance, subjects with postural control problems often touch a family member during walking in order to orient themselves in the environment. We suggest another solution for this surface problem: using a walking aid to provide a light touch cue. A light touch cue through a cane has been found to reduce postural sway when standing with eyes closed.17 However, the fixed reference point in space alters continuously when walking. Therefore, it is unknown whether the nervous system could use the cane to determine the relative relationship of the fixed floor to the moving body in a way that is similar to touching a fixed surface with a finger. Moreover, the method of providing the light touch information through the use of a cane for improving postural control in subjects with stroke has not been identified.
During walking, one challenge for the postural control system is the regulation of the heavy mass of the trunk over the 2 supporting limbs. Because most body mass is located in the trunk and head, high above the ground, an unstable system is created in which trunk control is critical for maintaining balance.18 Trunk acceleration variability has been suggested as an indicator for balance control during gait,19 and the analysis of lateral displacement and lateral acceleration of the shoulder and pelvis during walking can provide information regarding asymmetric impairments and balance disorders for patients with stroke.20 It has been shown that adults with stroke had larger lateral displacement and lateral acceleration of the shoulder and pelvis than a healthy control group.20 Therefore, the reduction in lateral acceleration of the shoulder or pelvis can be used to indicate improvement in postural control during walking. In this study, we questioned whether postural control during walking, as represented by the lateral pelvic acceleration, in subjects with stroke can be improved with a light touch cue provided through a cane during walking. To answer this question, we first attempted to identify the practical method of using a cane for obtaining a light touch cue. Then, we examined lateral pelvic acceleration and lower-limb muscle activations during walking when a light touch cue was provided through a cane, compared with those during the traditional method of using a cane.
Methods
Subjects
Forty subjects with a cerebrovascular accident participated in this study. All participants were recruited from the inpatient and outpatient Physical Therapy Neurology program at the Prasart Neurological Institute (Bangkok, Thailand). All subjects with stroke showed evidence of lower-limb muscle deficits on the paretic side (Chedoke-McMaster impairment inventory,21 median leg and foot scores=5/7 and 3/7, respectively), but they were able to stand longer than 5 seconds without external support (Chedoke-McMaster, median postural control score=5/7). All participants were unable to walk without assistance, but if assistance in the form of manual support from the physical therapist or the cane was provided, they could walk at least 5m without rest (Functional Ambulation Classification22 class 1). Characteristics of subjects are summarized in table 1. However, 1 subject with stroke used the cane for obtaining a light touch cue in a different manner (see Results). Therefore, this subject was not included in the subsequent analysis, and the data from 39 subjects are reported.
Table 1. Characteristics of Subjects
| Characteristics | Values |
|---|---|
| Number (n) | 40 |
| Sex (male/female) | 21/19 |
| Age (y) | 59.6±10.9 (41–80) |
| Type of lesion (n) | Ischemia=28 Hemorrhage=12 |
| Stroke duration (d) | 46.8±52.2(2–180) |
| Paresis side (n) | Right=20 Left=20 |
| CM leg | 5(3–6) |
| CM foot | 3(2–6) |
| CM postural control | 5(4–6) |
| FAC score | 1(1–2) |
| Gait speed with cane (m/s) | 0.13±0.07(0.05–0.29) |
Subjects were excluded from the study if they (1) had used a cane during walking before participating in this study, (2) had cognitive or language impairment, (3) had severe hemineglect, (4) had cerebral aneurysm, (5) had bilateral cerebral impairment, (6) had brainstem and cerebellar lesions, or (7) had impaired touch and pressure sensation on the nonparetic hand. All subjects who had hemianopia, dizziness, or other symptoms indicating vestibular impairment; had taken medications that affect balance; had impaired sensation in the lower extremity; or had lower extremity deficits such as pain or contracture were also excluded from the study. Informed consent was received from all subjects, and the study was approved by the Prasart Neurological Institutional Ethics Review Committee.
Testing Protocols
All subjects were instructed to walk at a comfortable pace across a 7-m walkway while holding a cane in the nonparetic hand. Two methods of cane use, light touch contact and force contact, were tested in this study. A special, adjustable-height cane, outfitted with a force sensor, was used to measure the amount of vertical force with which a subject pushed on the cane. These force data were captured at the sampling rate of 100Hz and continuously transferred, through a cable, to a computer that recorded the force patterns. The auditory biofeedback from the computer was used to help patients use the cane if only the light touch cue was allowed. The height of the cane was adjusted at the level of each subject's radial styloid process of the nonparetic hand with the arm hanging straight down.23 In the touch contact condition, the subject's goal was to use the cane while walking without the auditory buzzer being activated. A buzzer was activated whenever the subjects pressed on the cane with more than 400g (4N) of vertical force. Although this touch contact force is higher than reported in other studies, this amount of force is considered a light contact force24 that provides insufficient mechanical support to the body.3 As soon as the beeping sound was heard, the trial was rejected. In the force contact condition, the subject's goal was to walk and push on the cane at the desired level. A certified physical therapist was walking near the subjects as a safety precaution.
Prior to data collection, the subjects practiced both conditions of cane use, force contact, and touch contact, until they became familiarized with each condition. The force contact method was the conventional cane use method that is taught regularly by therapists. In the force contact condition, the patients were instructed to push intermittently on the cane when the paretic leg supported the body weight to help the nonparetic leg lift off the ground. For the touch contact condition, the patients were not given instructions on how to use the cane except to push on the cane lightly and not to trigger the auditory buzzer. During data collection, each subject performed force contact and touch contact cane use 6 times, each in a random order, resulting in 12 repetitions of walking. The subjects were given a rest of 5 to 10 minutes (sitting) between each trial to prevent fatigue.
Data Collection and Analysis
Time spent walking to the 5-m mark of a 7-m walkway was used to calculate the average gait speed. EMG activity was recorded using the Telemyo systema at 1500Hz. Bipolar silver-silver chloride disposable surface electrodes were placed over the muscle bellies of 3 bilateral lower-limb muscles, right and left TFL, VM, and ST. Voluntary contractions from each muscle were performed and monitored on the Telemyo software at the beginning of each trial to ensure that the correct muscle was recorded and no crosstalk existed between muscles. EMG recordings were band-pass–filtered between 16 and 500Hz. The EMG signals were then full-wave–rectified and smoothed using an RMS smoothing algorithm at the window interval of 100ms.
A uniaxial accelerometera with a resolution of 400mV/g was attached to the posterior superior iliac crest of the paretic pelvis to measure the ML acceleration of the pelvis at a sampling rate of 1500Hz. A 1-camera Peak Motus system 3.2b with a sampling rate of 50Hz was used to capture 2 reflective markers placed at the lateral side of the heel and fifth metatarsophalangeal joint of the nonparetic leg to identify the temporal component of the gait cycle. The displacements of the heel and fifth digit markers were digitized and calculated using the Peak Motus software program. The inline foot switcha consisting of 4 sensors positioned at the big toe, first metatarsal, fifth metatarsal, and heel of the paretic foot was used to determine the paretic stance and swing phases of the gait cycle. The force setting of the foot switch was 0.15 to 1.2kg/cm2, and its sampling frequency was 1500Hz. Stance and swing phases were then calculated as the percentage of each gait cycle. An average of approximately 60 gait cycles from each subject was used as the representative percentage of gait cycle. The data from foot switch and cane were also synchronized to characterize the temporal component of cane use.
The Matlab software programc was used to perform subsequent data analysis. The amount of peak force exerted on the cane during each gait cycle was subtracted by the weight of the cane, and then averaged and compared between the touch contact and force contact conditions. The onset of cane force was manually identified by 2 researchers who were blind to the condition of cane use, and calculated as the percentage of gait cycle. Displacements of the heel and fifth digit markers were used to calculate the duration of the paretic single limb support phase of walking. The beginning of paretic single limb support was identified as the lowest position of the fifth digit marker, and the end of this phase was selected when the heel marker was lowest in position.
EMG data were normalized to the gait cycle, and the integrals of EMG data during the stance and swing phases were calculated. The EMG integrals were then normalized to the EMG integrals from peak activity of the same muscles in the nonparetic side. On average, each subject performed 60 gait cycles of each cane use condition; therefore, each subject's EMG integrals were the average of normalized EMG integrals from 60 gait cycles. The duration of VM activation in the stance phase was manually identified by 2 researchers who were blind to the condition of cane usage. Compared with the foot switch signal, the EMG “on” was selected based on the starting of VM activation above the average EMG in the baseline period. When the activation began before the beginning of the stance phase, the starting point was counted at the beginning of the stance phase. Similarly, the EMG “off” was selected based on the end of VM activation before it went below the average EMG in the baseline period. The VM durations recorded by both researchers were then averaged.
Variability of pelvic acceleration was calculated from averaged peak-to-peak ML acceleration of the pelvis during the paretic stance phase in each gait cycle. Averaged peak-to-peak lateral acceleration of the pelvis was used to quantify the postural stability in the ML direction during walking, particularly when the paretic limb was on the ground. Statisticad software was used to perform statistical analysis. All dependent variables were compared between touch contact and force contact conditions using a repeated (dependent) t test. Data from all subjects were further divided into 3 subgroups according to gait speed, and a 2-way analysis of variance was used to determine the effect of gait speed and cane handling conditions on the dependent variables. A P level of less than .05 was accepted as significant.
Results
Methods of Cane Usage
Table 2 shows the cane usage information in the force contact and touch contact conditions. From this table, it can be seen that all subjects with stroke except 1 chose to obtain the light touch cue through a cane in an intermittent fashion, whereas only 1 subject obtained a light touch cue during walking in a continuous fashion. Further analysis of the cane force patterns revealed that the subject who performed continuous touch contact kept the tip of a cane on the ground at all times and dragged the cane behind the body during walking. In contrast, those subjects who used the cane in the intermittent fashion during touch contact condition pushed on the cane only 1 time in each gait cycle. The intermittent method of cane use in the touch contact condition was similar to that in the force contact condition, in which the subjects with stroke used the cane during the stance phase of the paretic leg (fig 1). However, the amount of force exerted on the cane during the force contact condition was significantly higher than during the touch contact condition (P<.001) (see table 2). During the force contact condition, the subjects with stroke pushed on the cane earlier in the stance phase than during the touch contact condition (P<.001), as can be seen from the onset of force in table 2. Furthermore, subjects with stroke exerted force on the cane for a longer duration in the force contact condition than in the touch contact condition (P<.001).
Table 2. Cane Use Information
| FC | TC | |
|---|---|---|
| Method of cane use (n) | Intermittent=40 | Intermittent=39 |
| Continuous=1 | ||
| Cane force (N) | 49.3±17.7⁎ | 2.3±1.6 |
| Onset of force (%GC) | 10.3±7.2⁎ | 30.8±10.9 |
| Duration of force (%GC) | 47.0±16.8⁎ | 23.1±5.8 |
⁎Significance at P<.05 compared with TC condition. |
Fig 1.
The relationship of the cane force (N) during the force contact and touch contact conditions and the gait cycle normalized to 100%, from the initial contact of the paretic leg to another initial contact of the same paretic leg. The data are from a representative subject with stroke. The cane force is represented by the dark line, and the foot switch is represented by the dotted gray line. The foot switch lines above the x-axis and on the x-axis depict the stance and swing phase of the paretic leg, respectively. Abbreviations: FC, force contact; TC, touch contact.
Gait Speed and Pelvic Acceleration
Group averages of gait speed when using the cane and pelvic acceleration during walking are shown in table 3. As seen in this table, the condition of cane use has no effect on the speed of walking. Comparison of the average peak-to-peak pelvic acceleration in the ML direction showed no difference between the force contact and touch contact condition (see table 3 and fig 2), suggesting that the touch contact cane use can provide similar pelvic stability to force contact cane use.
Table 3. Speed and Acceleration During Walking
| FC | TC | |
|---|---|---|
| Gait speed with cane (m/s) | 0.13±0.07 | 0.14±0.08 |
| PPA (M/L) (g) | 0.16±0.08 | 0.15±0.06 |
Fig 2.
ML pelvic acceleration from a representative subject with stroke during 1 gait cycle of the paretic leg in the force contact and touch contact conditions. Peak-to-peak amplitude has been calculated to represent the ML pelvic stability during walking. Abbreviations: FC, force contact; g, gravity; p-p amplitude, peak-to-peak amplitude; TC, touch contact.
Temporal Gait Parameters
Analysis of stance duration and single limb support duration of the paretic leg is shown in figure 3A. From this figure, it can be seen that the paretic stance duration was similar during both cane use conditions. However, the duration of the single-limb support phase of the paretic leg in the touch contact cane condition was significantly longer than in the force contact condition (P<.001). The increase in single-limb support duration corresponded to the significantly longer muscle activation of paretic vastus medialis in the touch contact condition than the force contact condition (fig 3B).
Fig 3.
(A) Group average of paretic stance duration, paretic single-limb support duration and paretic VM activation duration, normalized to gait cycle, during FC and TC conditions. (B) Muscle activity (rectified and smooth) of paretic VM from a representative subject normalized to 100% of gait cycle, starting from the initial contact of the paretic leg to another initial contact of the same paretic leg, during the force contact and touch contact conditions. The dotted grey line represents the foot switch; the line above the x-axis and on the x-axis depicts the stance and swing phase of the paretic leg, respectively. Arrow represents the end of the muscle activation (off). *Significant difference in duration between FC and TC conditions of cane usage. Abbreviations: FC, force contact; TC, touch contact.
Muscle Activations
Figure 4 shows the group average of EMG integrals during the stance and swing phases of walking in the force contact and touch contact conditions. All 3 observed muscles (TFL, VM, ST) on the paretic side during stance phase were activated higher in the touch contact condition than in the force contact condition (P<.001). It can also be seen that the nonparetic VM increased its activation during the touch contact condition compared with the force contact condition (P<.001). Nevertheless, these increased muscle activations did not extend into the swing phase, because the muscle activations in the swing phase did not alter during either cane use condition (see fig 4B). The relationship between muscle recruitment and gait cycle from a representative subject is shown in figure 5. This figure demonstrates that muscle activation of the paretic VM was increased throughout the stance phase in the touch contact condition. The increased muscle activation of paretic TFL was more pronounced at the middle of the gait cycle, whereas the paretic ST was more highly activated at the beginning of the gait cycle.
Fig 4.
Group average of EMG integrals of bilateral TFL, ST, and VM during the stance phase (A) and the swing phase (B) of the paretic leg when using the cane in the force contact and touch contact conditions. These EMG integrals are normalized to integrals of peak activity of the same muscle on the nonparetic leg. *Significant difference in EMG integrals between FC and TC conditions of cane usage. Abbreviations: FC, force contact; TC, touch contact.
Fig 5.
Muscle activity (rectified and smooth) of paretic VM, ST, and TFL from a representative subject normalized to 100% of gait cycle, starting from the initial contact of the paretic leg to another initial contact of the same paretic leg, during the force contact and touch contact conditions. The dotted gray line represents the foot switch; the lines above the x-axis and on the x-axis depict the stance and swing phase of the paretic leg, respectively. Abbreviations: FC, force contact; TC, touch contact.
Subgroup Analysis
Subgroup analysis was performed to determine whether the speed of walking affected the influence of the light touch cue. All subjects with stroke were classified into 3 categories according to their gait speed: A (<.10m/s), B (.10–.19m/s), and C (>.19–.30m/s). Characteristics of subjects by subgroup are listed in table 4. There were no group differences in terms of age and stroke duration. However, the amount of force exertion on the cane during touch contact and force contact conditions was less in group C than the other groups. Table 5 shows temporal variables, pelvic acceleration, and lower-limb EMG integrals according to the gait speed. Gait speed did not alter the effect of a light touch cue through the use of a cane provided during walking for the subjects with stroke who had a gait speed of less than 0.3m/s. Similar to the whole group analysis, each subgroup had longer single-limb support duration and larger EMG integrals of paretic TFL, VM, and ST during the touch contact condition.
Table 4. Characteristics of Subjects in Each Subgroup
| Characteristics | A (<.10m/s) | B (.10–.19m/s) | C (>.19m/s) |
|---|---|---|---|
| Number (n) | 13 | 16 | 10 |
| Sex (male/female) | 4/9 | 9/7 | 7/3 |
| Age (y) | 61.9±11.7 | 58.7±9.3 | 57.9±12.5 |
| Stroke duration (d) | 49.4±51.2 | 44.4±56.2 | 47.4±52.3 |
| Paresis side (n) | R=6 L=7 | R=7 L=9 | R=6 L=4 |
| CM leg | 5 | 5 | 6 |
| CM foot | 2 | 3 | 3 |
| CM postural control | 5 | 5 | 5 and 6 |
| FAC score | 1 | 1 | 2 |
| Gait speed with cane (m/s) | 0.07±0.01 | 0.12±0.02 | 0.24±0.03 |
| FC cane force (N) | 55.8±21.3 | 52.1±14.1 | 36.3±11.3⁎ |
| TC cane force (N) | 2.7±1.3 | 2.4±1.6 | 1.3±1.3 |
⁎Significance at P<.05 compared with group A and B. |
Table 5. Observed Variables in 3 Subgroups
| A | B | C | ||||
|---|---|---|---|---|---|---|
| Characteristics | FC | TC | FC | TC | FC | TC |
| Temporal duration (%GC) | ||||||
| Stance | 76.2±11.4 | 78.6±9.6 | 68.3±18.9 | 68.6±18.0 | 68.6±11.5 | 65.9±14.7 |
| Single-limb support | 10.1±2.9 | 15.4±4.3⁎ | 12.3±5.2 | 15.3±5.1⁎ | 17.9±2.0 | 20.7±3.2⁎ |
| Acceleration (g) | ||||||
| PPA (ML) | 0.14±0.09 | 0.13±0.07 | 0.17±0.08 | 0.16±0.05 | 0.16±0.06 | 0.15±0.05 |
| EMG integrals (%NPA) | ||||||
| Paretic TFL | 4.8±4.4 | 7.8±6.4⁎ | 3.9±2.7 | 6.3±5.5⁎ | 15.7±11.4 | 19.3±13.4⁎ |
| Nonparetic TFL | 17.7±9.8 | 20.4±10.7 | 20.7±13.5 | 19.7±9.7 | 31.4±10.1 | 33.2±12.1 |
| Paretic VM | 13.6±6.8 | 20.6±9.4⁎ | 10.6±8.9 | 15.2±11.2⁎ | 20.7±5.9 | 26.8±8.2⁎ |
| Nonparetic VM | 23.9±8.1 | 32.8±11.9⁎ | 25.1±14.9 | 30.7±17.5⁎ | 29.3±9.0 | 35.0±8.1⁎ |
| Paretic ST | 9.0±8.6 | 11.4±11.1 | 8.2±7.9 | 10.8±8.8⁎ | 12.6±7.9 | 15.8±10.6 |
| Nonparetic ST | 19.0±12.1 | 19.7±11.5 | 24.4±14.4 | 25.6±16.6 | 27.7±12.8 | 31.5±17.6 |
⁎Significance at P<.05 compared with TC condition. |
Discussion
Stroke and Light Touch Through a Cane
In this study, we confirmed that the subjects with stroke were able to use a cane to obtain a light touch cue, because the average contact force through a cane during the touch contact condition was 2.3N. However, this amount of contact force was higher than that reported in earlier studies in which healthy persons exerted a contact force of less than 1N.1, 2 The increase in contact force seen in the participants with stroke could be a result of the severity of the stroke impact and the loss of tactile sensation caused by aging. From this study, the severity of stroke impact, as measured by the gait speed, seems to influence the amount of contact force (see table 4) such that the slower-walking group exerted higher contact force through a cane than the faster-walking group. Gait speed has been widely used as an indicator for functional capability after stroke, and subjects with stroke who have a slower gait speed tend to have more sensorimotor deficits than those who walk faster do.25 Therefore, those with more severe stroke-related deficits would require more augmented somatosensory inputs, resulting in increasing pressure on the cane to enhance the amount of somatosensory feedback required in the control of balance during walking.
In terms of age-related loss in tactile sensation, previous studies have shown that elderly subjects deployed higher fingertip contact force for postural stabilization in standing, and that the increase in this contact force was correlated with a decrease in sensitivity of spatial acuity in the hand.24, 26 The decrease in spatial acuity implied the reduction in density of sensory innervations in the hand as a result of age-related changes. Thus, the increase in fingertip contact force in the older adults was suggested as a compensatory strategy to help achieve postural stabilization in the presence of reduced tactile inputs from contact with the touched surface.26
The practical method of using a cane for light touch in subjects with stroke has been identified in this study. The intermittent use of a cane suggested that, in daily circumstances, the person with stroke did not need continuous augmented somatosensory information during walking. In our study, subjects with stroke required a light touch cue during the stance phase of the paretic leg, specifically during the single limb support phase of walking (as identified from the onset of the cane force). During the single-limb support phase of walking, the nonparetic leg was lifted off the ground and the paretic leg remained on the ground to support the body weight. Balancing on the paretic leg has been reported as one of the difficulties found in subjects with stroke, which resulted in shorter paretic stance duration compared with the nonparetic leg.27 Therefore, it seems that a light touch cue provided during walking was purposely required when balance was threatened.
Gait Stability With Light Touch Cue Through a Cane
Stroke disrupts the ability to maintain posture and equilibrium during walking. Instability of the body, especially in the lateral direction, is compromised in individuals with stroke.28 A cane is clinically acceptable to be prescribed to patients with stroke during. It has been shown that stability during walking in subjects with stroke has been improved with the use of a cane.29 With the conventional method of cane use (force contact), the body weight shifts toward the cane (nonparetic) side during walking, which is beneficial for the paretic limb to lift off the ground.30, 31 However, a person with stroke who walked with the assistance of a cane primarily relied on the sound limb for propulsion.29 It was also found that muscles on the paretic leg decreased activation during walking when using a cane in the conventional fashion.32 This finding corresponds to a previous study of force contact on standing balance that found that as muscle activations of upper extremities increased to assist in the control of posture, muscle activations of the leg used to maintain upright stance decreased.2 Therefore, improvement of body lateral stability during walking with the use of a cane in the force contact fashion is not the result of an increased activity of the paretic leg, but of the mechanical support provided by the cane and the increased function of the upper extremities.
In the present study, we showed that the use of a cane in the touch contact fashion (touch contact) provides lateral stability during walking for participants with stroke similar to that obtained when using the cane in the force contact method. With the amount of touch force between 1 to 4N, only 20% of body stability during single-legged stance was a result of mechanical support.3 This amount of mechanical support may be sufficient for healthy persons, but it is insufficient for subjects with stroke. An earlier study showed that subjects poststroke typically applied 7% to 25% body weight of peak vertical force on the cane,29, 33 which is between approximately 4.1kg and 14.8kg in a 60-kg person. Thus, one may imply that the subjects with stroke required more than 4kg of force applied on the cane to provide mechanical support to the body during walking. The average force exerted on the cane in our study was .23kg, which can be considered insufficient to provide mechanical support to the body.
A previous study suggested that when lightly touching a surface with a cane, cutaneous receptors from the fingers and palm of the hand and proprioceptive receptors from the finger, wrist, and shoulder joints are activated in a feed-forward mechanism.1 These somatosensory receptors function together to confer the combined information of position and velocity of the body sway.8, 9 The information is then sent to the cortical areas that control posture, leading to the activation of postural muscles to attenuate sway.1 In accordance with previous findings, we showed that the paretic TFL, VM, and ST muscles increased activation in the touch contact condition, and that this increase was only apparent during the paretic stance phase. TFL and ST muscles play the role at the pelvis and hip segments.34 The activity of TFL occurs during the stance phase of the gait cycle. This muscle functions at the first half of the stance phase to stabilize the pelvis by preventing excessive vertical translation (pelvic drop). During the later stage of the stance phase, the muscle acts as a medial rotator of the pelvis. It also helps to initiate forward rotation of the pelvis to assist in the advancement of the swing limb during the terminal stance phase. The activity of ST begins at the terminal swing phase, where it acts as a knee flexor to help in decelerating the leg and foot, through the midstance phase, where it works as a hip extensor to prepare the limb for weight acceptance and pelvic stabilization. VM also acts during the stance phase of walking, but its role is in the control of the knee joint into extension.34 These muscle groups, therefore, are the postural muscles that are important in maintaining the upright body posture during weight-bearing. Increased activation of paretic weight-bearing muscles could explain the longer duration of the paretic single-limb support phase found in our study.
Despite the increased muscle activations on the paretic leg, we did not see a significant increase in muscle activations on the nonparetic leg, except in the nonparetic VM muscle. The increase in nonparetic VM muscle activation was found during the double support period of walking; however, the amount of increase was not beyond the normal activation of healthy subjects during natural walking without using a cane.35 Therefore, such an increase was not considered the overcompensation of the nonparetic side. It could be otherwise suggested that during conventional cane handling, the nonparetic VM muscle may not be required to work as much as when walking without a cane because the cane and the shoulder and arm muscles provide support to the body during walking.
Study Limitations
The success in modifying the method of obtaining a light touch cue through the use of a cane suggests an alternative approach for rehabilitative training of subjects poststroke with gait impairments. The increased muscle activation on the paretic leg during weight acceptance suggests that light touch cue through a cane could facilitate the function of the paretic leg during walking. Therefore, the light touch method of cane handling could reduce the adverse effect of conventional cane use that subjects reduce the function of the paretic side during walking, because they are more dependent on the nonparetic side.
Results from this study, however, were obtained from a group of subjects with moderate functional impairments. The participants were able to perform hip-knee extension and flexion independently when lying and were able to raise a thigh off the bed when sitting. They were also able to perform dynamic righting from side to side in sitting and to stand up with equal weight-bearing on each foot. However, they were unable to stand on the paretic leg or walk independently without using an aid. With the cane, our participants could walk independently at the walking speed of less than 0.3m/s with supervision. The limitation of our study is that we could not extend our findings to the subjects with stroke who can walk faster than 0.3m/s because different levels of severity from stroke, measured by the speed of walking, may show different degrees of stability deficits and, hence, demonstrate different responses to the light touch cue. For example, data from a previous study36 showed that subjects with stroke who had a gait speed of 0.66m/s tended to walk better without a walking aid. Using the cane had no detrimental or beneficial effect if a patient could walk at 0.58m/s, whereas those who walked at the speed of 0.28m/s showed a better spatiotemporal walking pattern with a walking aid than without one. Therefore, further study must be performed to identify the extent of stroke severity or postural control deficits on the effect of light touch cuing through a cane during walking.
Conclusions
A light touch cue can be provided during walking through the use of a cane. This augmented sensory information provides lateral stability during walking for subjects with stroke by facilitating the activations of weight-bearing muscles on the paretic leg during the stance phase, resulting in better stability when the paretic leg supports the body weight.
Suppliers
Acknowledgments
We thank the Prasart Neurological Institute, Department of Medical Services, Ministry of Public Health, Thailand, for offering their facilities and space. We express our sincere gratitude to Joyce Fung, PhD, School of Physical and Occupational Therapy, McGill University, Montreal, Canada, for her scientific advice.
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Supported by the Thailand Research Fund, the Pharmaceutical Research and Manufacturers Association, and the Office of the Higher Education Commission (grant no. TRG4880003).
No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.
PII: S0003-9993(09)00188-9
doi:10.1016/j.apmr.2008.12.022
© 2009 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
Volume 90, Issue 6 , Pages 919-926, June 2009
