The comparison of wavelet- and Fourier-based electromyographic indices of back muscle fatigue during dynamic contractions: validity and reliability results.

The purpose of this study was to compare the electromyographic (EMG) fatigue indices computed from short-time Fourier transform (STFT) and wavelet transform (WAV), by analyzing their criterion validity and test-retest reliability. The effect of averaging spectral estimates within and between repeated contractions (cycles) on EMG fatigue indices was also demonstrated. Thirty-one healthy subjects performed trunk flexion-extension cycles until exhaustion on a Biodex dynamometer. The load was determined theoretically as twice the L5-S1 moment produced by the trunk mass. To assess reliability, 10 subjects performed the same experimental protocol after a two-week interval. EMG signals were recorded bilaterally with 12 pairs of electrodes placed on the back muscles (at L4, L3, L1 and T10 levels), as well as on the gluteus maximus and biceps femoris. The endurance time and perceived muscle fatigue (Borg CR-10 scale) were used as fatigue criteria. EMG signals were processed using STFT and WAV to extract global (e.g, median frequency and instantaneous median frequency, respectively) or local (e.g., intensity contained in 8 frequency bands) information from the power spectrum. The slope values of these variables over time, obtained from regression analyses, were retained as EMG fatigue indices. EMG fatigue indices (STFT vs. WAV) were not significantly different within each muscle, had a variable association (Pearson's r range.: 0.06 to 0.68) with our fatigue criteria, and showed comparable reliability (Intra-class correlation range: 0.00 to 0.88), although they varied between muscles. The effect of averaging, within and between cycles, contributed to the strong association between EMG fatigue indices computed from STFT and WAV. As for EMG spectral indices of muscle fatigue, the conclusion is that both transforms carry essentially the same information.

Topographical effects of transcutaneous electrical nerve stimulation on the H-reflex of the triceps surae muscles.

The present study was conducted on eight normal subjects in order to evaluate the effects of transcutaneous electrical nerve stimulation (TENS); 99 Hz, 250 µs pulse duration, applied over either the common peroneal (CPN) or sural nerve, on the H-reflex of the soleus (SO), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) muscles. Within each session, SO, GL and GM H-reflexes were recorded before (for 5 min), during (for 30 min) and after (for 10 min) TENS was applied at twice the sensory threshold for perception. It was found that, on average, while the stimulation was administered on the CPN: (a) the GL H-reflex amplitude increased by 40% (Friedman test: χ(2) = 11.71, P < 0.05); (b) the SO H-reflex decreased (≥ 10% H(ctrl)), although not in a statistically significant manner, in five of eight subjects; and (c) the GM H-reflex remained, overall, relatively stable. No significant effects of TENS over the sural nerve were found on any of the investigated muscles. The finding of increased H-reflex amplitudes in GL during TENS made it less likely that CPN stimulation had reciprocal inhibitory effects. However, such an increase could be attributed to a selective effect (such as a decrease in the recruitment threshold) on type II motoneurons of the GL. Furthermore, the topographical effects observed on the GL during TENS may reflect selective local effects due to stimulation of a sensory branch of the CPN, the lateral sural nerve, which mainly innervates the skin overlying the GL. The absence of effects noted on the GM during TENS further supports this hypothesis as the cutaneous afferents overlying that muscle were not stimulated. The repetitive cutaneous stimulation over the sural nerve, at the lateral malleolus, may have been too distal to stimulate the cutaneous receptors overlying the SO.

A method for quantification of directional patterns of muscle activation at the lower limb.

Several studies have examined muscle activation patterns during movements or static torques exerted in different directions in human subjects as well as in trained monkeys. However, no statistical approach has ever been proposed to characterize directional patterns of muscle activation in a given population. This report describes a method for the quantification and statistical analysis of directional patterns of muscle activation at the lower limb. This method was used with a group of 18 healthy subjects. Using a multidirectional dynamometer for the lower limb, subjects were asked to exert static torques (at approximately 5 and 15% of the maximal voluntary contraction) in eight directions covering a 360 degrees range at the hip. These were hip abduction, adduction, flexion, extension, and the intermediate directions (e.g., hip flexion and abduction). Electromyographic (EMG) activities of eight lower limb muscles were recorded during these efforts using surface electrodes. For each muscle, the mean rectified EMG activity obtained in each direction was considered a vector. Then, the overall directional pattern of activation for a given muscle was quantified for each subject by a vectorial summation of these vectors. The angle of the resultant vector was used along with the other subjects' angular values to calculate a mean vector representing the muscle's directional pattern of activation for the complete sample. This mean vector was used to perform the statistical analysis of the data. More specifically, the Rayleigh test for circular data was performed at both torque levels to determine, through the length of the mean vector, if a muscle showed a directional specificity in its activity, i.e., a tendency to be preferentially recruited toward a specific direction. In general, hip muscle activity demonstrated significant directional specificity during hip efforts in contrast to knee and ankle muscle activity. Moreover, the angle of the mean vector calculated for each hip muscle across the sample remained relatively stable at both torque levels. These results indicate that directional patterns of muscle activation are unaffected by the level of torque produced. It is concluded that the method used in the present study is effective in characterizing directional patterns of muscle activation in a given population. Also, this method provides new perspectives for further quantification of muscle activation patterns disturbances in populations presenting various neuromuscular disorders.

Directional patterns of muscle activation at the lower limb in subjects with hemiparesis and in healthy subjects: A comparative study.

This article reports the results of a comparative study on directional patterns of muscle activation at the lower limb in 15 subjects with hemiparesis and 18 healthy subjects. Subjects were required to exert static hip and knee torques using multidirectional and biarticular dynamometers designed for the lower limbs. Hip torques were performed in abduction, adduction, flexion, extension, and in combined directions (e.g., hip flexion and abduction) and knee torques were exerted in flexion and extension. The required torque levels corresponded to approximately 5% of the maximal voluntary contraction of healthy subjects. Electromyographic (EMG) activities of the rectus femoris, biceps femoris, gracilis, gluteus medius, gluteus maximus, vastus lateralis, tibialis anterior, and soleus were recorded during these torques. The descriptive analysis involved comparison between either the polar plots (for hip tasks) or the histograms (for knee tasks) representing the mean muscle activity obtained across subjects during torques exerted in each direction for the three groups of muscles analyzed (normal, paretic, and nonparetic muscles). Ciucular statistics were also used to characterize directional patterns of activation in each muscle during hip tasks while linear statistics permitted one to analyze these patterns during knee tasks. In general, the results of both the descriptive and inferential statistical analyses indicated that directional patterns of muscle activation during hip and knee torques are not altered in subjects with hemiparesis. These results are in contrast to the disturbances observed previously in a study of directional patterns of muscle activation at the upper extremity in this population. It is suggested that the contrast between the present results and those obtained at the upper limb in subjects with hemiparesis may reflect the difference in the motor recovery of upper and lower paretic limbs or in the severity of spasticity in the muscles involved at the studied joints. Results of this study also showed that the paretic muscles often demonstrate larger EMG signals than normal and nonparetic muscles, especially during knee flexion torques. These last observations, in addition to the fact that some subjects with hemiparesis could not complete all of the tasks with their paretic limb, under-score the muscle weakness inherent to this population.

Influence of gender on the EMG power spectrum during an increasing force level.

The aim of the present study was to contrast, between men and women, the behavior of EMG power spectrum statistics (median frequency (MF) and mean power frequency (MPF) obtained across increasing force levels. Thirteen men and sixteen women produced ramp (single contractions with the force increasing linearly) elbow flexions and extensions from 0 to 100% of the maximum voluntary contraction (MVC). Each ramp was produced in a 5-s period. Surface EMG signals from triceps brachii (TB), anconeus (AN), and biceps brachii (BB) were recorded with miniature surface electrodes placed 6 mm apart. These signals were sampled at 2,000 Hz. The MPF and MF of power spectra, obtained from single 256-ms windows, were computed for each muscle at 10, 20, 40, 60, and 80% MVC. Significant differences (two-way analyses of variance (ANOVAs); p < 0.05) in the behaviors of the MPF and MF across force levels were found between men and women. In general, the MPF and MF showed more pronounced increases across increasing force levels for men than for women. It is proposed that this gender effect could be explained by differences in skinfold thickness and fiber type characteristics between the two groups of subjects.

Median frequency of the electromyographic signal: effect of time-window location on brief step contractions.

The purpose of this study was to determine, for different back muscles, if the median frequency (MF) of the electromyographic (EMG) power spectrum changes according to the position of the time window during a 5 s step contraction. Twenty males with no known back problems were standing upright in a dynamometer allowing lower limb and pelvis stabilization. Trunk extension efforts were performed by pushing on a force platform positioned at the T4 level while the extension moment at L5/S1 was displayed as visual feedback. The EMG signals from four homologous back muscles (multifidus at L5, ilicostalis lumborum at L3, and longissimus at L1 and T10) were collected using active surface electrodes during two 5 s static step contractions performed at five force levels (10, 20, 40, 60 and 80% of the maximal voluntary contraction). The root mean square (RMS) and MF values of the EMG signals corresponding to three 250 ms time windows (beginning, middle and end of each step contraction) were computed. The RMS values of several back muscles increased from the first to the third time window for contractions performed at high force levels only. However, a concomitant decrease in the MF values was observed only for the left multifidus muscle. It was concluded that muscle fatigue does not generally manifest itself during 5 s step contractions through the EMG signal. However, it is recommended to use step contractions lasting less than 5 s and to choose a time window located in the first 1-3 s to completely eliminate the possible effects of fatigue.

Normality and stationarity of EMG signals of elbow flexor muscles during ramp and step isometric contractions.

The purpose of this study was to test the stationarity and normality of electromyographic (EMG) signals obtained while exerting isometric contractions: (a) where a steady force level is maintained (step contractions); and (b) where the force level is increased linearly over time (ramp contractions). Ramp elbow flexions were performed from 0 to 100% of the maximum voluntary contraction (MVC) in a 5-s period. For the step contractions, four force levels (20, 40, 60 and 80% MVC) were maintained for a period of 3 s each. EMG signals of the biceps brachii (BB) and brachioradialis (BR) muscles of 16 subjects were recorded with surface electrodes and digitized at a sampling frequency of 2000 Hz. Tests of normality (Shapiro-Wilk test) and stationarity (reverse arrangement test) were performed locally on short finite time records (512-ms windows). Results show that, in general, EMG signals present a non-Gaussian amplitude distribution and are stationary. Furthermore, the amplitude distribution characteristics and the stationarity of the signal were not dependent on the muscle investigated, nor on the type of contraction or force level tested. The finding of local stationarity for both tasks is important, because it suggests that performing standard spectral analysis is applicable for both step and ramp contractions. It also allows a direct comparison between results obtained under both conditions.

Evaluation of measurement strategies to increase the reliability of EMG indices to assess back muscle fatigue and recovery.

The purpose of this study was to assess different measurement strategies to increase the reliability of different electromyographic (EMG) indices developed for the assessment of back muscle impairments. Forty male volunteers (20 controls and 20 chronic low back pain patients) were assessed on three sessions at least 2 days apart within 2 weeks. Surface EMG signals were recorded from four pairs (bilaterally) of back muscles (multifidus at the L5 level, iliocostalis lumborum at L3, and longissimus at L1 and T10) while the subjects performed, in a static dynamometer, two static trunk extension tasks at 75% of the maximal voluntary contraction separated by a 60 s rest period: (1) a 30 s fatigue task and (2) a 5 s recovery task. Different EMG indices (based on individual muscles or averaged across bilateral homologous muscles or across all muscles) were computed to evaluate muscular fatigue and recovery. Intra-class correlation coefficient (ICC) and standard error of measurement (SEM) in percentage of the grand mean were calculated for each EMG variable. Reliable EMG indices are achieved for both healthy and chronic low back pain subjects when (1) electrodes are positioned on medial back muscles (multifidus at the L5 level and longissimus at L1) and (2) measures are averaged across bilateral muscles and/or across two fatigue tests performed within a session. The most reliable EMG indices were the bilateral average of medial back muscles (ICC range: 0.68-0.91; SEM range: 5-35%) and the average of all back muscles (ICC range: 0.77-0.91; SEM range: 5-30%). The averaging of measures across two fatigue tests is predicted to increase the reliability by about 13%. With regards to EMG indices of fatigue, the identification of the most fatigable muscle also lead to satisfactory results (ICC range: 0.74-0.79; SEM range: 21-26%). The assessment of back muscle impairments through EMG analysis necessitates the use of multiple electrodes to achieve reliable results.

Effect of pronation and supination tasks on elbow flexor muscles.

The aim of this study was to verify the presence of modulatory effects of pronation (P) and supination (S) on biceps brachii (BB) and brachioradialis (BR) electromyographic (EMG) signals while performing isometric elbow flexions at different angles (50, 90, and 130°). The EMG activity of BB and BR was recorded for normal subjects (N = 6) with surface electrodes during an isometric ramp contraction of elbow flexion (F) that was combined with 20% of maximal voluntary contraction (MVC) in pronation or in supination. The results indicate that (a) the BB muscle presents an increased EMG activity in the combined task of S-F and a decreased EMG activity in the combined task of P-F (Friedman ANOVA, p < 0.01); (b) the EMG activity of the BR is not significantly influenced by the different tasks (Friedman's ANOVA, p > 0.05); and (c) the modulation of the BB occurs only at a midrange angle of flexion. This study partly supports results that were previously reported by other authors, suggesting that a combined task can modulate the EMG activity of elbow flexor muscles. However, this modulation, observed especially for the BB, appears to be limited to elbow flexion angles that are close to 90°.

The influence of the type of contraction on the masseter muscle EMG power spectrum.

Different behaviours of the EMG power spectrum across increasing force levels have been reported for the masseter muscle. A factor that could explain these different behaviours may be the type of contraction used, as was recently shown for certain upper limb muscles(5). The purpose of this study was to compare, between two types of isometric contractions, the behaviour of EMG power spectrum statistics (median frequency (MF) and mean power frequency (MPF)) obtained across increasing force levels. Ten women exerted, while biting in the intercuspal position, three 5 s ramp contractions that increased linearly from 0 to 100% of the maximal voluntary contraction (MVC). They also completed three step contractions (constant EMG amplitude) at each of the following levels: 20, 40, 60 and 80% MVC. EMG signals from the masseter muscle were recorded with miniature surface electrodes. The RMS, as well as the MPF and MF of the power spectrum were calculated at 20, 40, 60 and 80% MVC for each type of contraction. As expected, the RMS values showed similar increases with increasing levels of effort for both types of contractions. Different behaviours for both MPF (contraction(∗)force interaction, ANOVA, P<0.05) and MF (contraction(∗)force interaction, ANOVA, P>0.05) across increasing levels of effort were found between the two types of contraction. The use of step contractions gave rise to a decrease of both MPF and MF with increasing force, while the use of ramp contractions gave rise to an increase in both statistics up to at least 40% MVC followed by a decrease at higher force levels. These findings suggest that the type of contraction used does influence the behaviour of the spectral statistics across increasing force levels and that this could explain the differences obtained in previous studies for the masseter muscle.

EMG power spectrum as a measure of muscular fatigue at different levels of contraction.

The shift in the power spectrum resulting from a 5-7 min fatigue-inducing effort followed by a 1-2 min recovery period of two elbow flexors, the biceps brachii (BB) and the brachio-radialis (BR), was assessed using two variables, the mean frequency Fm and the median or central frequency Fmd. These two variables were calculated in pre- and post-fatigue conditions and following a brief recovery, at four levels, namely 20, 40, 60 and 80 per cent of maximum voluntary contraction (MVC). These were taken from a ramped isometric effort that is from 0 to 100 per cent MVC. The EMG activity of the two flexors was recorded with bipolar surface electrodes from a group of ten volunteers. Following muscle fatigue, induced with a maintained 60 per cent MVC isometric contraction, a statistically significant (p less than 0.05) shift towards the lower frequencies was observed for both Fm and Fmd for both muscles. Following a brief recovery, a shift towards the pre-fatigue higher frequencies was statistically significant (p less than 0.05). These two synergists responded to muscle fatigue and recovery similarly, as they both demonstrated parallel shifts in power spectrum. The power spectrum is consequently a reliable measure of muscular fatigue. It is also complementary to the net articular moment results.

Patellofemoral pain syndrome: the possible role of an inadequate neuromuscular mechanism.

The patellofemoral pain syndrome is described by a great number of papers as a pathology related mainly to the knee extensor mechanism. However, this knee problem may have an influence on the other joints of the lower extremity. To explain the interdependence between joints of the lower extremity, the support moment concept was used as a framework for the present study. Based on this concept we hypothesized that patellofemoral pain syndrome subjects reduce the stress on their painful patellofemoral joint by decreasing the use of the knee extensor muscles during functional activities. In order to achieve the same support moment, a smaller contraction of the knee extensors could be compensated by an overuse of the hip extensors and ankle plantarflexors. The aim of this study was to verify these compensations in a strenuous functional activity for the knee by comparing 11 subjects having a patellofemoral pain syndrome with 11 normal subjects. Three squat tests were performed:NATURAL, IMPOSED, and TIP TOES. The results obtained in the tip toes test indicated that patellofemoral pain subjects have: (a) a significantly greater knee extensor moment, and (b) a significantly lower hip extensor moment as compared to the normal. A greater straightening of the trunk was observed on patellofemoral pain syndrome patients during the tip toes test as compared to the other tests. Contrary to the expected hypothesis, the patellofemoral pain subjects did not show a strategy tending to decrease the knee extensor moments. In fact in the squat test on tip toes, the subjects affected by a patellofemoral pain syndrome overused the knee extensor muscles.

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.

Principal components analysis of an evaluation of the hemiplegic subject based on the Bobath approach.

An evaluation based on the Bobath approach to treatment has previously been developed and partially validated. The purpose of the present study was to verify the content validity of this evaluation with the use of a statistical approach known as principal components analysis. Thirty-eight hemiplegic subjects participated in the study. Analysis of the scores on each of six parameters (sensorium, active movements, muscle tone, reflex activity, postural reactions, and pain) was evaluated on three occasions across a 2-month period. Each time this produced three factors that contained 70% of the variation in the data set. The first component mainly reflected variations in mobility, the second mainly variations in muscle tone, and the third mainly variations in sensorium and pain. The results of such exploratory analysis highlight the fact that some of the parameters are not only important but also interrelated. These results seem to partially support the conceptual framework substantiating the Bobath approach to treatment.

An evaluation of the hemiplegic patient based on the Bobath approach: a reliability study.

The intra- and inter-rater reliability of a motor function evaluation of stroke patients, based on the Bobath approach, was studied. The intraclass correlation coefficient (ICC) was used to determine the degree of agreement between repeated measurements on the same patient taken by the same rater and between measurements taken by three raters on the same patient. In the intra-rater study, each of 19 patients was evaluated in three different sessions by one of 19 raters. In the inter-rater study 18 patients were each evaluated by three different raters. The intra-rater data were highly reliable, with ICCs of 0.95 and 0.97 for the upper and lower limbs respectively. For the inter-rater study, the ICCs were 0.79 and 0.77 for the upper and lower limbs respectively. It can therefore be concluded that this instrument, previously demonstrated to quantify patient progress, is also reliable both in intra- and inter-rater dimensions.

Cocontraction of the elbow muscles during combined tasks of pronation-flexion and supination-flexion.

The aim of this study was to determine if the antagonist activity of the triceps brachii (TB) and anconeus (AN) muscles is modulated when the activity of the biceps brachii (BB) and brachioradialis (BR) is modulated by the performance of combined tasks and to verify if this behavior is similar at different elbow angles. Electromyographic (EMG) activity of BB, BR, AN and TB was recorded for normal subjects (N = 6) with surface electrodes during a ramp isometric contraction in elbow flexion (F) which was performed alone or combined with 20% of maximal voluntary contraction (MVC) in pronation (P) or in supination (S). Two cocontraction ratios, using the EMG root mean square (rms) values of each muscle and identified as BB/TB and BR/AN were calculated. The results indicate that for low flexion torque levels, the BB/TB ratio is higher for the S-F condition while the BR/AN ratio is higher during the pure flexion task. Variations of the EMG activity across tasks were significant only for BB (Friedman ANOVA, p less than .01) whereas there was no significant change in EMG activity (rms) for TB, BR and AN (Friedman ANOVA, p greater than .01). Furthermore, the behavior of both ratios across tasks was similar at 50 degrees, 90 degrees and 130 degrees of elbow flexion. Thus, for isometric conditions, there appears to be no evidence of modulation of EMG activity of elbow extensors while performing combined tasks of S-F and P-F. In addition, cocontraction activity during these tasks tends to be similar across elbow angles.

Changes in hip position modulate soleus H-reflex excitability in man.

The effects of hip flexion and extension on the ipsilateral soleus Hoffmann (H) reflex recruitment curve were studied in 11 healthy subjects. Hip flexion (50 degrees), but not hip extension (15-20 degrees), produced changes in the H-reflex. A maintained facilitation, peaking at intensities of stimulation producing a maximal H-reflex (Hmax), was observed in 6/18 sessions. Inhibition, peaking at intensities submaximal for Hmax, was seen in 7/18 sessions. In some of the latter experiments, there was also a facilitation at high intensities of stimulation (greater than Hmax). The remaining experiments were classified as showing no effect: 3 were unmodulated but 2 showed a facilitation at high intensities of stimulation (greater than Hmax). Since the knee was extended in the test position, a second series of experiments (n = 7) were carried out to determine the possible influence of stretch of the biarticular hamstrings muscle group on the soleus H-reflex by comparing the effects of hip flexion with the knee extended with those obtained when the knee was flexed, thereby relaxing the hamstrings. The results provided no evidence that the variability could be explained by differences in the relative degree of stretch on the hamstrings muscle group. There were, however, systematic variations in the shape of the corresponding control H-reflex recruitment curves between subjects: the mean slope of the rising limb of the recruitment curve was highest in those experiments showing an inhibition, intermediate in the ineffective experiments and lowest in those showing a maintained facilitation. These observations indicate that the reflex output studied was different in the three groups, possibly reflecting differences in the relative proportions of slow- and fast-twitch motor units contributing to the reflex response.

EMG power spectrum of elbow extensors: a reliability study.

In order to be considered a potential tool for the characterization of muscle activity, the reliability of EMG power spectral analysis should be demonstrated. In this study, the reliability of the mean power frequency (MPF) and of the median frequency (MF) of power spectra (triceps brachii (TB), anconeus (AN)) obtained at different force levels from both ramp and stepwise isometric contractions was tested across three similar sessions performed on three different days (N = 9). Two-way ANOVAs for repeated measures did not disclose any significant differences (p > 0.05) in the value of either the MF or the MPF across the different sessions for either type of contraction. In contrast, significant changes (p < 0.05) in both the MF and the MPF were found across force levels. No significant interactions (p > 0.05) were found between the session and the force factors, for any of the analyses performed. The present results indicate that the MPF and the MF of the EMG power spectrum, taken at a specific force level, are reliable measures across sessions performed on different days. Consequently, this supports the possible use of power spectral analysis of EMG signals as an evaluation technique that could monitor changes in the neuromuscular system that can occur over a given period.

Effects of transcutaneous electrical nerve stimulation on the H-reflex of muscles of different fibre type composition.

Differential effects of repetitive stimulation of low threshold afferents on both the recruitment threshold and motoneuronal excitability of type I and type II motor units have been demonstrated. The present study was aimed at further investigating the differential effects of 30 minutes of transcutaneous electrical nerve stimulation (TENS) on the H-reflex amplitude (Hmax/2) of the Soleus (SO), gastrocnemius lateralis (GL) and medialis (GM) muscles. Eleven healthy subjects were tested in order to evaluate the effects of TENS on either the common peroneal (CPN), saphenous or sural nerve. The experimental session consisted of three consecutive 45 min periods. Within each of these periods, H-reflexes were recorded before, during and after the TENS was applied. It was hypothesized that repetitive low threshold afferent stimulation would either have inhibitory or facilitatory effects on the H-reflex amplitude of the SO or gastrocnemii muscles respectively. Non-parametric Friedman ANOVAs revealed a significant tendency (p < 0.05) toward inhibition of the H-reflex amplitude of the SO and GL muscle during TENS applied over either the CPN or sural nerve, as well as that of the GM during repetitive stimulation of the saphenous nerve. Although the present study failed to reveal any differential effects of TENS on the H-reflex amplitude of muscle on different fibre type content, the significant decrease in H-reflex observed on the triceps surae muscles during TENS applied over the CPN might have promising clinical outcomes for hyperreflexive subjects.

Motor function and activities of daily living assessments: a study of three tests for persons with hemiplegia.

The relationship between upper extremity motor function and independence in basic activities of daily living in subjects with hemiplegia was explored. The Barthel Index (Mahoney & Barthel, 1965) and the Fugl-Meyer Test (Fugl-Meyer, Jääskö, Leyman, Olsson, & Steglind, 1975) were selected as the standard instruments for the evaluation of activities of daily living and upper extremity motor function, respectively, because their validity and reliability have been demonstrated many times. The Functional Test for the Hemiplegic/Paretic Upper Extremity (Wilson, Baker, & Craddock, 1984a, 1984b) was also used for the evaluation of upper extremity motor function. The results obtained in 18 subjects with hemiplegia indicate that the scores on the Barthel Index are poorly correlated with both the Fugl-Meyer Test and the Functional Test for the Hemiplegic/Paretic Upper Extremity scores. It is suggested that variables other than motor function, such as the learning of compensatory techniques and perceptual-cognitive status, are responsible for this discrepancy because they can influence activities of daily living performance in persons with hemiplegia. The high correlation between the scores on the Fugl-Meyer Test and the Functional Test for the Hemiplegic/Paretic Upper Extremity indicates that either test may be used for the assessment of upper extremity motor function.