Relation between physical exertion and postural stability in hemiparetic participants secondary to stroke.

INTRODUCTION: Chronic hemiparetic stroke individuals are at a higher risk of falling. This may be due to balance impairments, cardiovascular deconditioning, and muscle weakness associated with stroke effects. Postural instability associated with fatigue would likely be attained more rapidly for stroke individuals than for healthy individuals. OBJECTIVE: To determine the effects of physical exertion induced by walking on postural stability in hemiparetic stroke participants. METHODS: Twelve hemiparetic participants and 12 control participants walked over-ground for a duration of 6 min and 18 min at their comfortable speed. Postural stability was assessed using centre of pressure related parameters during double-legged stance and tasks before the walk, immediately after the walk, 15 min post-walk, and 30 min post-walk. Measures of physical exertion during walking were also obtained from cardiorespiratory parameters, time-distance parameters, and subjective scales. Variables on postural stability and on physical exertion were analyzed using two-way repeated measures ANOVA and Generalized Estimating Equations. RESULTS: Physical exertion measures significantly increased when the duration of walk was increased from 6 min to 18 min in both control and hemiparetic participants. For postural stability measures, increasing the duration of walking led to a significant increase of postural sway in double-legged stance and sit-to-stand for the hemiparetic participants only. This effect on balance of hemiparetic participants was observed immediately after the end of the walk. CONCLUSION: This study demonstrated that physical exertion can increase postural sway in hemiparetic participants which could possibly lead to an increased risk of falling in these individuals.

Comparison of walking parameters and cardiorespiratory changes during the 6-minute walk test in healthy sexagenarians and septuagenarians.

BACKGROUND: The 6-minute walk test (6-MWT) is commonly used in research, with a focus on walking distance parameters rather than the physiological parameters. Even though it has been reported that the distance walked during the 6-MWT decreases with age, the adaptation of cardiorespiratory functions in healthy older adults remains to be studied. OBJECTIVES: The primary objective of this study was to compare the changes in walking distance and cardiorespiratory parameters during the 6-MWT in healthy sexagenarians and septuagenarians. A secondary objective was to determine the cardiorespiratory parameters and functional performance variables that best predict the distance covered during the 6-MWT. METHODS: Ten healthy sexagenarians (G60, mean age 63.6 +/- 3.3 years) and 10 septuagenarians (G70, mean age 76.0 +/- 3.3 years) performed the 6-MWT while the distance, heart rate and oxygen uptake (VO(2)) were recorded. The subjects also completed the Timed-Up-and-Go, the Berg Balance Scale and the Human Activity Profile to establish their functional level. RESULTS: Results showed that G60 reached significantly greater (p < 0.05) distance and VO(2) values during the 6-MWT than G70. In contrast, the energy cost of walking (O(2) cost) and heart rate did not differ between the 2 groups. Correlational analyses of the combined groups revealed that VO(2) was the variable that showed the strongest correlation with walking distance during the 6-MWT. CONCLUSION: Results revealed that, while G60 achieved a greater level of walking performance than G70, the 2 groups maintained the same level of walking efficiency (O(2) cost) during the walk. Both groups adjusted their walking speed to have an oxygen consumption rate at a level sufficient to meet the energy demands of the task and prevent early exhaustion. Therefore, the 6-MWT appears to be a simple tool that can be used to assess cardiorespiratory parameters in older adults and be sensitive enough to detect differences between sexagenarians and septuagenarians.

Effect of a community-based Argentine tango dance program on functional balance and confidence in older adults.

Tango-dancing and walking programs are compared in nondemented seniors at risk for falls. Fallers (N = 30) age 62-91 were randomly assigned to a 10-wk (40 hr, 2 hr 2x/wk) tango class or walk group. The Activities-specific Balance Confidence (ABC) scale, sit-to-stand scores, and normal and fast walk were measured pre-, post-, and 1 month postintervention. Two-way repeated-measures ANOVAs indicated a significant main effect (p < .01) for time on all measures. Group and interaction effects for ABC led to improvement only in tango because of high baseline mean for the walk group. Clinical improvements measured using Established Populations for Epidemiologic Studies of the Elderly scoring were greater for the tango group. From these preliminary results it is suggested that although both interventions are effective activities for increasing strength and walk speed, tango might result in greater improvements than walking in balance skills and in walking speed in the 10-wk intervention. The study needs to be repeated with a greater sample size to determine the effectiveness of walking on fear of falling.

Task-oriented intervention in chronic stroke: changes in clinical and laboratory measures of balance and mobility.

OBJECTIVE: The objective of this study was to evaluate whether, after a task-oriented exercise program, the changes in clinical measures of balance and mobility were paralleled by changes in biomechanical parameters in subjects with chronic stroke. DESIGN: Ten stroke subjects took part in an 8-wk exercise program aimed at improving balance and mobility through various functional tasks. Subjects were evaluated before and after the exercise intervention. Clinical measures included the Berg Balance Scale and the Timed-Up-and-Go and laboratory measures included ground reaction forces and center of pressure displacement during four functional tasks. RESULTS: Stroke subjects showed significant improvements (P < 0.05) in the clinical measures after completing the exercise program. Significant improvements (P < 0.05) were also found in postural steadiness during tandem stance and stool touch and in force production through the paretic lower limb during sit-to-stand. This last result was strongly correlated (r = -0.93) with the improvements on the Timed-Up-and-Go after exercise intervention. In contrast, the increase in postural steadiness was poorly correlated with the improvements on the Berg Balance Scale. CONCLUSIONS: A task-oriented exercise program might improve both clinical and laboratory measures of balance and mobility in stroke subjects. However, several correlations between the changes in clinical and laboratory measures after exercise intervention were generally weak, indicating that these outcome measures assessed different components of improvements.

Postural adaptation to walking on inclined surfaces: II. Strategies following spinal cord injury.

OBJECTIVE: To investigate the postural adaptations to inclined walking in spinal cord injured (SCI) subjects. METHODS: Eight subjects with an incomplete spinal cord injury and eight age- and sex-matched healthy control subjects walked on a treadmill at five different grades (from -10 to 10%) without any assistance. The movements of the trunk and pelvis were recorded with four high-resolution cameras. RESULTS: The SCI subjects walked with greater forward tilt of both trunk and pelvic segments during level or inclined walking and could not adapt their body orientation to the inclination of the support surface as observed in healthy control subjects. Trunk and pelvic rotations as well as lateral excursions were maintained constant during inclined walking in both groups of subjects but total excursions were always greater in the SCI subjects. CONCLUSIONS: We argue that the forward bending posture observed in SCI subjects at any treadmill grade is adopted to compensate for a certain degree of instability due to lower-limb deficits and is a postural adaptation to the daily use of ambulatory assistive devices. SIGNIFICANCE: The bent posture adopted by SCI subjects is not adequate when performing level or downhill walking and can lead to a loss of balance or a fall in these subjects.

Vastus medialis: anatomical and functional considerations and implications based upon human and cadaveric studies.

OBJECTIVE: To provide an electrophysiological and functional description of the vastus medialis (VM) and contrast it to an anatomical description. METHODS: Motor points of all superficial portions of the quadriceps were identified on the dominant side of 8 human subjects and electrically stimulated to achieve a light contraction to trace and measure the orientation of the fibers. Electromyography of the VM was then recorded over 2 motor points during isometric and isokinetic maximum knee extensions. An independent laboratory dissected 39 cadaveric specimens focusing on fiber orientations and distal insertions of the VM. RESULTS: Results revealed 5 motor points for the quadriceps: 1 point for the vastus lateralis, 1 point for the rectus femoris (RF), and 3 points for the VM. The 3 VM motor points suggest 3 separate groups of fibers: proximal (pf), median (mf), distal (df). Fiber orientations ranged from 45 degrees for VMpfs to 55 degrees for VMdfs. Motor point stimulation and anatomical dissection clearly showed that the VMpfs and VMmfs were inserted on a tendon common to the RF, whereas VMdfs were attached directly to the medial aspect of the patella. Furthermore, the VMpfs were more active (P < .05) than VMdfs during maximum knee extensions. CONCLUSION: The anatomy, motor points, and electromyography clearly support an important distinction between the VMpfs and VMdfs. The role of the VMpfs would be one of assisting the RF in knee extension, whereas the VMdfs would track the patella medially without participating in knee extension. Because of these anatomical and functional differences, the VMpfs and VMdfs should be addressed very differently during quadriceps rehabilitation in patellofemoral dysfunctions.

Balance training following stroke: effects of task-oriented exercises with and without altered sensory input.

The purpose of this study was to compare the effects of a task-oriented exercise program with and without altered sensory input on postural stability in subjects with stroke. Sixteen hemiparetic subjects, at least 6 months post-stroke, were randomly assigned to the experimental or control group, and participated in an 8-week task-oriented exercise program focusing on balance and mobility exercises. Exercises were performed under normal conditions by the control group, and under conditions of vision and surface manipulation by the experimental group. Pre- and post-test assessments involved the measurement of the center of pressure (COP) displacement during double-legged stance and sit-to-stand under four sensory conditions: (1) eyes open, normal surface; (2) eyes open, soft surface; (3) eyes closed, normal surface; and (4) eyes closed, soft surface, as well as the 10-m walking test. Results showed significant improvements (P<0.05) in COP displacement under sensory conditions (1) and (2) for the experimental group only, and limited changes for the sit-to-stand in both groups after training. Significant improvements (P<0.05) were also found in both groups for the walking test. It is concluded that a task-oriented exercise program, assisted by sensory manipulation, is more effective at improving the standing balance of stroke subjects than a conventional task-oriented program.

Exercise training to improve motor performance in chronic stroke: effects of a community-based exercise program.

The purpose of this study was to investigate the feasibility and efficacy of an exercise program offered by a community organization on motor performance in individuals with chronic stroke. Twenty hemiparetic individuals at least 6 months after a stroke and discharged from all rehabilitation services enrolled in the study. They took part in an 8-week group program (two times per week) aimed at improving balance, mobility, coordination, walking endurance and strength on the hemiparetic side through various functional exercises. Pre- and post-exercise assessments included the stroke impairment assessment set, the Berg balance scale, the step test, the timed-up-and-go and the 6 min walk. Results showed significant improvements (P<0.008) in all of the above tests, excluding the 6 min walk, after completion of the exercise training. Correlation analyses revealed that the individuals' age and time since injury were poorly related to the improvement in performance. It is concluded that an exercise program offered by a community organization can lead to improvement in motor performance of individuals with chronic stroke. To prevent decline in motor performance, community-based exercise programs should thus be made available for stroke patients discharged from rehabilitation services.

The effect of Trager therapy on the level of evoked stretch responses in patients with Parkinson's disease and rigidity.

OBJECTIVE: To quantify changes of evoked stretch responses (ESR) in the most rigid arm of patients with Parkinson's disease (PD) after Trager therapy. METHODS: Gentle rocking motion associated with this type of manual therapy was imparted to the upper limbs and body of 30 patients for 20 minutes. A pretest and 2 posttests (at 1 and 11 minutes after the treatment, respectively) were performed, consisting of electromyographic (EMG) recordings of the flexor carpi radialis and extensor digitorum communis while the patient's wrist was passively flexed and extended with an amplitude of 60 degrees and a frequency of 1 Hz. Patients received the treatment on the most rigid side of their bodies (ipsi-group) or on the contralateral side (contra-group). Half of patients in each group received the treatment while lying supine on a massage table (ipsi- and contra-supine) or sitting in a chair (ipsi- and contra-sitting). RESULTS: In general, the level of ESR were reduced by 36% immediately after treatment and remained 32% lower than pretest values 11 minutes after treatment (F = 41.45, P <.05). Patients who received the treatment lying supine benefited from a 42% reduction of ESR (F = 4.07, P <.05). The side on which the treatment was performed did not significantly influence the outcome of the treatment (F = 0.50, P >.05). However, post hoc analysis of the triple interaction (test x side x position) indicated that the sitting position was much less efficient for sustained contralateral effect (P >.05). CONCLUSIONS: Results from the present study strongly suggest that it is possible to modify the level of ESR by using Trager therapy. This stretch reflex inhibition may induce a reduction of the muscle rigidity seen in these patients. The present results may eventually lead to the development of a specific complementary therapy for patients with Parkinson's disease and rigidity.

Postural adaptation to walking on inclined surfaces: I. Normal strategies.

This study investigated the postural strategies to adapt to uphill and downhill treadmill inclination (0, 5 and 10%) during walking and standing in eight healthy subjects. Increasing the treadmill grade from 0 to 10% induced an increasingly flexed posture of the hip, knee and ankle at initial foot contact as well as a progressive forward tilt of pelvis and trunk. These postural changes were accompanied by a progressive decrease in pelvic lateral drop toward the swinging limb and a gradual increase in stride length as the uphill slope became steeper. Decreasing the treadmill grade from 0 to -10% lead to a decreasingly flexed posture of the hip at initial foot contact as well as an increase in knee flexion during weight acceptance and late stance. These changes were accompanied by a gradual decrease in stride length, a progressive backward tilt of trunk and pelvis and an increase in pelvic lateral drop toward the swinging limb as downhill slope became steeper. Changes in trunk and pelvic postural alignment in the sagittal plane might be used to facilitate power generation or absorption in adapting to slope changes during walking. During quiet standing, however, the trunk and pelvis remained aligned with respect to earth's vertical at any surface inclination. These results showed that postural adaptations are task-specific and the control requirements are different between standing and walking on an inclined surface.