Daniel Bourbonnais

Plantarflexor weakness as a limiting factor of gait speed in stroke subjects and the compensating role of hip flexors

OBJECTIVE To determine, using the Muscular Utilization Ratio (MUR) method, whether plantarflexor weakness is among the factors preventing stroke subjects from walking at faster speeds. Potential compensations by the hip flexors were also examined. DESIGN A convenience sample of 17 chronic stroke subjects in a context of a descriptive study. BACKGROUND Gait speed is correlated with the residual strength of the muscles involved in gait in stroke subjects. However, it has not been established if this residual strength limits gait speed. METHODS Kinetic and kinematic data for comfortable and maximal gait speeds were collected on the paretic side, and were used to determine the moments in plantarflexion (mechanical demand: MUR numerator) during the push-off phase. The maximal potential moment (MUR denominator) of the plantarflexors during gait was predicted using an equation derived from dynamometric data collected with a Biodex system. The MURs of the plantarflexors were then calculated at every 1% interval of the push-off phase. The pull-off phase of gait and the hip flexor strength were also examined. RESULTS Ten subjects of the sample had a MUR value between 80 and 150% at maximal gait speed. These subjects produced the lowest peak torques in plantarflexion. Each of the four fastest subjects of this group had a large hip flexion moment during the pull-off phase of gait and produced high hip flexion torque values on the dynamometer. Each of the seven remaining subjects had a MUR value under 70% when they walked at maximal speed. CONCLUSIONS Weakness of the plantarflexors should be considered as one factor limiting gait speed in 10 hemiparetic subjects. Some subjects with weak plantarflexors could walk rapidly because they compensated with the hip flexors. For the remaining stroke subjects, factors other than weakness of the plantarflexors have to be considered in order to explain the reduction in their gait speed.

Maximal grip force in chronic stroke subjects and its relationship to global upper extremity function

Objectives: Previous studies have shown that recovery of recordable grip strength in acute stroke subjects is one of the most sensitive assessments of initial upper limb recovery and a good prognostic factor for latter recovery. The objectives of this study were to test the reliability of maximal voluntary grip force (MVGF) measures and evaluate the relationship between paretic grip strength deficit and paretic upper extremity function in chronic stroke subjects. Design: Over a three-week period, bilateral MVGF was assessed three times with a modified strain gauge dynamometer in 15 chronic stroke subjects and 10 control subjects. The paretic MVGF deficit was expressed in relation to the MVGF of the nonaffected hand. Outcome measures: Upper extremity function in stroke subjects was measured using the Fugl-Meyer, the upper extremity performance test for the elderly (TEMPA), Box and Block and finger-to-nose tests. Results: MVGF measures in both groups of subjects demonstrated good reliability (intraclass correlation, ICC >0.86) and low standard error measurements (SEM). The paretic MVGF of the stroke subjects was greatly impaired in comparison to the control subjects. Results of linear and quadratic regressions analyses show that this impairment was significantly correlated (p <0.01) with the performance of the stroke subjects on the four upper extremity function tests. The percentages of variances explained by the MVGF deficit on all four upper extremity tests varied from 62% to 78% for the linear regressions and from 72% to 93% for the quadratic regressions. Conclusions: These results suggest that the paretic maximal grip strength, normalized with the maximal grip strength on the nonaffected side, appears to be a valuable outcome measure of upper extremity function in chronic stroke subjects.

Analysis of the clinical factors determining natural and maximal gait speeds in adults with a stroke.

The objective of this study was to identify the most important clinical variables determining gait speed in persons with stroke. Sixteen chronic stroke subjects (mean age, 47.9 (+/-15.6) yr; mean time post-stroke, 43.9 (+/-36.5) mo) able to walk independently without a brace participated in the study. The impairments in motor function, sensation of the paretic lower limb, and balance were evaluated with the Fugl-Meyer Assessment. A spasticity index was used to assess the muscle tone of the plantarflexors. The maximal strengths in plantarflexion and hip flexion were measured with a Biodex dynamometric system. Cinematography and foot-contact data collected on the paretic side were used to determine the comfortable and maximal gait speeds. The level of association between gait speeds and the clinical variables were first examined with Pearsons correlation coefficients and, then, with multiple linear regression analyses using the stepwise method. Results revealed that the motor function of the lower limb, balance, and hip flexion strength were significantly related to comfortable and maximal gait speeds (0.5 < r < 0.88; P < 0.05). For the comfortable gait speed, the regression analysis selected only the hip flexor strength as a significant variable (R2 = 0.69). For maximal gait speed, the variables retained were hip flexor strength, sensation at the lower limb, and plantarflexor strength (R2 = 0.85). The present results suggest that strength and sensation at the lower limb are important factors to consider in determining the gait capacity of chronic stroke subjects.

Performance of the ‘Unaffected’ Upper Extremity of Elderly Stroke Patients

BACKGROUND AND PURPOSE The main objective of this study was to compare the sensorimotor performance of the unaffected upper extremity (UE) of elderly stroke patients with that of healthy elderly people. METHODS The group of stroke patients was composed of 43 hemiplegic/paretic subjects who had had a cerebrovascular accident at least 6 months earlier. They were > or = 60 years old, were right-handed before the stroke, had visual perception within normal limits, and showed no major cognitive impairments. A group of 43 healthy subjects matched for dominance, age, and sex was used for comparison. The main parameters of the performance of the unaffected UE of the stroke subjects and of the same side of the healthy subjects were measured with valid, reliable instruments. Some variables potentially related to the unaffected UE were also measured: affected UE motor function, functional independence, length of time since the stroke, self-perceived health status, activity level, and hand anthropometry. RESULTS Statistical analyses showed significant deficits in the unaffected UE of hemiplegic/paretic subjects compared with normal subjects with regard to the following parameters: gross manual dexterity, fine manual dexterity, motor coordination, global performance, and kinesthesia (P < .01 to P < .0001). No significant clinical or statistical difference was found for grip strength (P < .81), static and moving two-point discrimination (P = .21 and P = .12), or touch/pressure threshold (P < .91). CONCLUSIONS Many factors (frequency of use of the unaffected hand, sensorimotor interaction tasks, severity of the deficits in corticifugal projections, and deficits in postural stabilization) could interact to provide the clinical picture obtained in the present study.

Predictors of long-term participation after stroke.

Purpose: (1) To explore factors that predict long-term participation after stroke (2 – 4 years after discharge from rehabilitation), and (2) to determine factors that predict both short- and long-term participation. Methods: Biopsychosocial data of people who had had a stroke were measured at discharge from an intensive rehabilitation unit using valid instruments. Six months later (n = 102) as well as 2 – 4 years later (n = 66), social participation of the survivors was measured in their living environments. Participation was estimated with the Assessment of Life Habits (LIFE-H), which includes 12 categories of daily activities and social roles. Results: From mutivariate regression analyses, the best predictors of long-term participation after stroke appear to be age, comorbidity, motor coordination, upper extremity ability and affect. Age, comorbidity, affect and lower extremity coordination are the best predictors of participation after stroke at both measurement times. Conclusions: With the exception of age, these factors may be positively modified and thus warrant special attention in rehabilitation interventions.

Cerebellar cortical activity during antagonist cocontraction and reciprocal inhibition of forearm muscles

Monkeys were trained to perform a maintained isometric grip of the thumb and forefinger that elicited a simultaneous cocontraction of the antagonist muscles of the forearm. The same monkeys were also trained to flex and extend the wrist against a stop with the fingers extended and to maintain an isometric wrist position for 1.0-1.5 s. During wrist movement, some of the synergist forearm muscles contracted during both flexion and extension. However, during the maintained isometric wrist position, the prime mover and synergist muscles were reciprocally active or silent. In the culmen-simplex region of the cerebellar cortex bordering on the primary fissure, 62% of the Purkinje cells that were identified by the climbing fiber discharge and that changed firing frequency decreased activity during maintained prehension. Almost all of these same Purkinje cells were reciprocally active during isometric wrist flexion and extension, although three neurons had similar discharge patterns during movements in both directions. In contrast, 79% of the unidentified neurons recorded from the same region of the cerebellar cortex increased discharge frequency during prehension. In general, most of these same neurons had reciprocal patterns of discharge during wrist movement even though a few cells were active during the dynamic phase in both directions. Together, the Purkinje cells and the unidentified neurons with bidirectional response patterns were thought to be related to muscles active during both flexion and extension wrist movements. No cells were found that increased discharge with the static isometric wrist torque exerted in both directions. The discharge frequency of some Purkinje and some unidentified neurons could be shown to be related to prehensile force as well as wrist movement velocity and isometric wrist torque. These data suggest that the discharge of about two-thirds of the Purkinje cells related to forearm muscles located along the borders of the primary fissure may depend on whether antagonist muscles are activated reciprocally or coactively. As a consequence, these cells may play a role in the selection or alternation between either of these two modes of muscular contraction. The increased discharge of the remaining one-third of the Purkinje cells excited during antagonist coactivation may provide inhibition of nuclear cells to stabilize the posture at joints other than the wrist and fingers or, alternatively, they may act to reduce nuclear cell discharge in proportion to the intensity of cutaneous stimulation.

The influence of an increase in the level of force on the EMG power spectrum of elbow extensors

SummaryIt has been proposed that the mean power frequency (MPF) of the electromyogram (EMG) power spectrum increases gradually with force of contraction and that this increase is a function of the fiber-type content of the muscle investigated and the inter-electrode distance (IED) used when recording the EMG signals. In order to test these hypotheses, the values of the MPF of two elbow extensor muscles, triceps brachii (TB, 65% fast twitch fibers) and anconeus (AN, 65% slow twitch fibers), were compared at different levels of contraction. Subjects (n =13) produced ten static ramp elbow extensions [0–100% maximum voluntary contraction (MVC)]. EMG signals of each muscle were recorded with two pairs of surface miniature electrodes having IEDs of 6 mm and 30 mm respectively. MPFs were obtained at each of the following levels: 10, 20, 40, 60, 80 and 100% MVC. Statistical analyses indicated that the MPF of AN increased significantly (P<0.05) up to 60% MVC. In contrast, the MPF values for TB showed no significant change across different levels of contraction (P>0.05). Since skinfold was on average 3.2 times thicker over TB than over AN it is suggested that the low-pass filtering effect of the skin could have prevented the observation of an increase of the MPF for TB. It thus appears that changes of the MPF with the level of force, as disclosed by surface electrode recordings, is specific to each muscle. Consequently one has to account for factors such as thickness of the skinfold when it comes to the determination of the fiber-type content of different muscles within a subject.

Relative shoulder flexor and handgrip strength is related to upper limb function after stroke

Objective: To compare the relative strength of different muscle groups of the paretic upper limb and assess the relationship with motor performance. Design: Descriptive study. Setting: Secondary care rehabilitation centre. Subjects: A convenience sample of 13 chronic hemiparetic stroke subjects. Main outcome measures: The maximal active torques of fivemuscle groups were measured in both upper limbs (UL) and converted into relative strength (paretic/nonparetic). The UL function was assessed using the Box and Block Test, the Finger-to-Nose Test, the Fugl-Meyer Test and the TEMPA (Test Evaluant les Membres supérieurs des Personnes Agées). Results: The Friedman two-way analysis of variance shows a significant difference across the relative strength of the different muscle groups (p = 0.017), but subsequent multiple comparisons indicate a significant difference between handgrip and elbow extension only (relative strength of 0.52 ± 0.27 and 0.73 ± 0.23 respectively). However, data show the presence of large intra-subject imbalances between muscle groups. The relative forces for shoulder flexion and handgrip are the best predictors of the UL function, the higher Spearmans rho correlation coefficients for each clinical test ranging from 0.70 to 0.81. Conclusions: These results do not confirm classical clinical teaching regarding the distribution of weakness following stroke (e.g., proximal to distal gradient; extensors more affected than flexors) but support the hypothesis that strength is related to the function of the paretic upper limb.

Physiotherapy for persistent postnatal stress urinary incontinence: a randomized controlled trial.

OBJECTIVE: The aim of this study was to compare the effectiveness of multimodal supervised physiotherapy programs with the absence of treatment among women with persistent postnatal stress urinary incontinence. METHODS: This was a single-blind randomized controlled trial. Sixty-four women with stress urinary incontinence were randomly assigned to 8 weeks of either multimodal pelvic floor rehabilitation (n = 21), multimodal pelvic floor rehabilitation with abdominal muscle training (n = 23), or control non–pelvic floor rehabilitation (n = 20). The primary outcome measure consisted of a modified 20-minute pad test. The secondary outcome measures included a Visual Analog Scale describing the perceived burden of incontinence, the Urogenital Distress Inventory, the Incontinence Impact Questionnaire, and pelvic floor muscle function measurements. RESULTS: Two patients dropped out, leaving 62 for analysis. At follow-up, more than 70% of the women in the treatment groups (14/20 in the pelvic floor and 17/23 in the pelvic floor plus abdominal group) were continent on pad testing compared with 0% of women in the control group. Scores on the pad test, Visual Analog Scale, Urogenital Distress Inventory, and Incontinence Impact Questionnaire improved significantly in both treatment groups (all P < .002), whereas no changes were observed in the control group. Pelvic floor muscle function, however, did not improve significantly in either active group. CONCLUSION: Multimodal supervised pelvic floor physiotherapy is an effective treatment for persistent postnatal stress urinary incontinence. LEVEL OF EVIDENCE: I

EMG power spectra of elbow extensors during ramp and step isometric contractions

SummaryThe goal of the present study was to compare electromyogram (EMG) power spectra obtained from step (constant force level) and ramp (progressive increase in the force level) isometric contractions. Data windows of different durations were also analysed for the step contractions, in order to evaluate the stability of EMG power spectrum statistics. Fourteen normal subjects performed (1) five ramp elbow extensions ranging from 0 to 100% of the maximum voluntary contraction (MVC) and (2) three stepwise elbow extensions maintained at five different levels of MVC. Spectral analysis of surface EMG signals obtained from triceps brachii and anconeus was performed. The mean power frequency (MPF) and the median frequency (MF) of each power spectrum were obtained from 256-ms windows taken at 10, 20, 40, 60 and 80% MVC for each type of contraction and in addition on 512-, 1024-and 2048-ms windows for the step contractions. No significant differences (P>0.05) were found in the values of both spectral statistics between the different window lengths. Even though no significant differences (P>0.05) were found between the ramp and the step contractions, significant interactions (P<0.05) between these two types of contraction and the force level were found for both the MPF and the MF data. These interactions point out the existence of different behaviours for both the MPF and the MF across force levels between the two types of contraction.