Acute effects of bi-hemispheric transcranial direct current stimulation on the neuromuscular function of patients with chronic stroke: A randomized controlled study.

BACKGROUND: Muscle weakness in patients with chronic stroke is due to neuromuscular disorders such as muscle atrophy, loss of voluntary activation or weak muscle contractile properties which are majored by the imbalance of interhemispheric inhibition following stroke. In patients with chronic stroke, unilateral transcranial direct current stimulation improved the maximal isometric strength of paretic knee extensors, but bilateral transcranial direct current stimulation failed to improve concentric strength. This study aimed to assess if a bilateral current stimulation improves isometric maximal strength, voluntary activation and contractile properties of knee extensors in patients with chronic stroke. METHODS: Thirteen patients with chronic stroke and eight young healthy individuals participated in this randomized, simple-blinded, crossover study that included two experimental sessions: one with sham bilateral transcranial direct current stimulation and another with effective bilateral transcranial direct current stimulation (20 min, 2 mA). In the stroke patients, the anode was placed over the primary motor cortex of the affected hemisphere and the cathode over the contralateral primary motor cortex. In healthy participants, the brain side targeted by the anode and the cathode was randomly assigned. In each session, participants performed three assessments of strength, voluntary activation and contractile properties: before, during and after effective/sham bilateral transcranial direct current stimulation. FINDINGS: Bilateral transcranial direct current stimulation had no effect on any neuromuscular assessments in both groups (All P values > 0.05, partial eta-squares varied from 0.02 to 0.06). INTERPRETATION: A single session of bilateral transcranial direct current stimulation did not compensate muscular weakness of knee extensors in patients with chronic stroke.

Minimal detectable change of kinematic and spatiotemporal parameters in patients with chronic stroke across three sessions of gait analysis.

Three-dimensional gait analysis is the gold standard for gait-assessment in patients with stroke. This technique is commonly used to assess the effect of treatment on gait parameters. In clinical practice, three gait analyses are usually carried out (baseline, after treatment and follow-up), the objectives were to define the reproducibility and the Minimum Detectable Change (MDC) for gait parameters in stance and swing measured using 3D-gait analysis, and to assess changes in MDC across three repeated 3D-gait analyses. Three gait analyses (V1, V2 and V3) were performed at 7-day intervals in twenty-six patients with chronic stroke. Kinematic data (in the sagittal plane, during swing and stance) and spatiotemporal data were evaluated for the paretic limb. Reliability was tested using repeated measures ANOVA with a Tukey post hoc test, and the MDC values were calculated for each parameter. Only the range of hip motion during swing changed significantly between V1 and V2, but no other kinematic parameters changed. No significant differences were observed for the spatiotemporal parameters. MDC values were always higher during the V1vsV2 comparison for both kinematic and spatiotemporal parameters. This is the first study to evaluate the MDC for kinematic and spatiotemporal parameters during stance and swing. Reliability of kinematic and spatiotemporal data across sessions was very good over the three sessions. MDC values were the lowest between V2 and V3 for most parameters. Use of the MDC will allow clinicians to more accurately determine the effect of treatments.

The effect of transcranial direct current stimulation (tDCS) on locomotion and balance in patients with chronic stroke: study protocol for a randomised controlled trial.

BACKGROUND: Following stroke, patients are often left with hemiparesis that reduces balance and gait capacity. A recent, non-invasive technique, transcranial direct current stimulation, can be used to modify cortical excitability when used in an anodal configuration. It also increases the excitability of spinal neuronal circuits involved in movement in healthy subjects. Many studies in patients with stroke have shown that this technique can improve motor, sensory and cognitive function. For example, anodal tDCS has been shown to improve motor performance of the lower limbs in patients with stroke, such as voluntary quadriceps strength, toe-pinch force and reaction time. Nevertheless, studies of motor function have been limited to simple tasks. Surprisingly, the effects of tDCS on the locomotion and balance of patients with chronic stroke have never been evaluated. In this study, we hypothesise that anodal tDCS will improve balance and gait parameters in patients with chronic stroke-related hemiparesis through its effects at cortical and spinal level. METHODS/DESIGN: This is a prospective, randomised, placebo-controlled, double-blinded, single-centre, cross-over study over 36 months. Forty patients with chronic stroke will be included. Each patient will participate in three visits: an inclusion visit, and two visits during which they will all undergo either one 30-min session of transcranial direct current stimulation or one 30-min session of placebo stimulation in a randomised order. Evaluations will be carried out before, during and twice after stimulation. The primary outcome is the variability of the displacement of the centre of mass during gait and a static-balance task. Secondary outcomes include clinical and functional measures before and after stimulation. A three-dimensional gait analysis, and evaluation of static balance on a force platform will be also conducted before, during and after stimulation. DISCUSSION: These results should constitute a useful database to determine the aspects of complex motor function that are the most improved by transcranial direct current stimulation in patients with hemiparesis. It is the first essential step towards validating this technique as a treatment, coupled with task-oriented training. TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT02134158 . First received on 18 December 2013; last updated on 14 September 2016. Other study ID numbers: P120135 / AOM12126, 2013-A00952-43.

Comparison of methodologies to assess muscle co-contraction during gait.

The aim of this study was to compare co-contraction index (CCI) computed from muscle moments to different co-activation indexes (Co-Act) derived from EMG data at the ankle and the knee joint during gait. An EMG-driven model was used to estimate muscle moments during over-ground walking gait at a self-selected velocity from twelve healthy subjects. The CCI calculated from muscle moments was compared with three Co-Acts estimated from the normalized EMG data. The co-activation methods produced lower values than the CCI during the first double-support and the swing phase at the ankle joint and during the stance phase at the knee joint. The co-activation methods trend is to underestimate the simultaneous action of agonist and antagonist contraction. Because the EMG-driven model included the muscle mechanical properties (e.g. force-length-velocity relationship) and muscle moment-arm, the co-contraction based on major agonist and antagonist muscle moment may provide a more confident description of muscle action compared to co-activation indexes.

Effects of a dynamic-ankle-foot orthosis (Liberté®) on kinematics and electromyographic activity during gait in hemiplegic patients with spastic foot equinus.

BACKGROUND: A dynamic-ankle-foot orthosis has recently emerged and consists of an elastic band allowing the variation of stiffness degree and adjusts dorsiflexion assistance in swing. The aim of this study was to quantify the biomechanical adaptations induced by this orthosis during gait in hemiplegic patients. METHODS: Twelve hemiplegic patients performed two gait analyses (without and with the ankle-foot orthosis). Spatiotemporal, kinematic, kinetic and electromyographic gait parameters were quantified using an instrumented gait analysis system during the stance and swing phases. RESULTS: During swing, peak ankle dorsiflexion was greater with the orthosis and associated with a decrease of pelvic obliquity angle. In stance, peak ankle plantarflexion and dorsiflexion were greater with the orthosis and associated with an increase of ankle angle at heel strike and toe-off. Electromyographic activities of both the tibialis anterior and the medial gastrocnemius were greater with the orthosis. CONCLUSIONS: This dynamic-ankle-foot orthosis improved gait in hemiplegic patients with spastic foot equinus. The spatiotemporal adaptations seem to be caused mainly by the increase of ankle dorsiflexion during stance and swing phases. The changes in electromyographic activity were related to an active dorsiflexion in stance and swing phases and an active plantarflexion in stance phase.

Isokinetic assessment of the effects of botulinum toxin injection on spasticity and voluntary strength in patients with spastic hemiparesis.

BACKGROUND: Peak knee flexion during swing phase is frequently reduced following stroke. The main treatment is botulinum toxin injection (BoNT-A) of the Rectus Femoris (RF) muscle. BoNT-A injections have been shown to decrease spasticity (assessed using the modified Ashworth scale) and to improve peak knee flexion during swing phase. Although the effect of BoNT-A has been clearly demonstrated on kinematic parameters during gait, the direct effects on spasticity and strength have been little studied using objective and sensitive outcome measures. AIM: The aim of this study was to use an isokinetic dynamometer to assess the effects of BoNT-A injection in the RF on stretch reflex-related torque at the knee joint and peak voluntary knee flexor and extensor torque and to evaluate the effect on functional capacity. DESIGN: Before-after trial: Assessments were carried out pre and post (four weeks) RF BoNT-A injection. Clinical and isokinetic evaluations were carried out. SETTING: Ambulatory care in a hospital setting. Participants. Population-based sample of fourteen chronic spastic hemiparetic patients with stiff knee gait. METHODS: Primary outcome measurements were stretch reflex-related torque at the knee joint and peak voluntary knee flexor and extensor torque. Secondary outcomes were knee angle at peak torque, the slope of the torque velocity curve, stiffness and functional outcomes. RESULTS: Peak knee extensor torque was significantly decreased and peak knee flexor torque was significantly increased during maximal voluntary concentric and isometric contractions following BoNT-A injection of the RF. Stretch reflex-related torque evaluated during passive stretching movements was reduced and the angle of occurrence of the peak was greater. Functional outcomes did not change. CONCLUSIONS AND CLINICAL REHABILITATION IMPACT: The results of this study indicate that BoNT-A injection reduced RF spasticity but also reduced quadriceps strength. In contrast, knee flexor strength increased. These changes did not, however, lead to functional gait changes.

Changes in electromyographic activity after botulinum toxin injection of the rectus femoris in patients with hemiparesis walking with a stiff-knee gait.

PURPOSE: This study was designed to evaluate the effects of botulinum toxin type-A (BoNTA) injection of the rectus femoris (RF) muscle on the electromyographic activity of the knee flexor and extensor and on knee and hip kinematics during gait in patients with hemiparesis exhibiting a stiff-knee gait. METHOD: Two gait analyses were performed on fourteen patients: before and four weeks after BoNTA injection. Spatiotemporal, kinematic and electromyographic parameters were quantified for the paretic limb. RESULTS: BoNTA treatment improved gait velocity, stride length and cadence with an increase of knee angular velocity at toe-off and maximal knee flexion in the swing phase. Amplitude and activation time of the RF and co-activation duration between the RF and biceps femoris were significantly decreased. The instantaneous mean frequency of RF was predominantly lower in the pre-swing phase. CONCLUSIONS: The results clearly show that BoNTA modified the EMG amplitude and frequency of the injected muscle (RF) but not of the synergist and antagonist muscles. The reduction in RF activation frequency could be related to increased activity of slow fibers. The frequency analysis of EMG signals during gait appears to be a relevant method for the evaluation of the effects of BoNTA in the injected muscle.

Effects of a three-month combined training program on the cardiopulmonary and muscle strength capacities of type 2 diabetic subjects.

AIM: For many years, exercise has been regarded as one of the three primary interventions to treat type 2 diabetes along with diet and medication. Combined exercise programs consisting of both aerobic and resistance training have been demonstrated to have more benefits in a sedentary population than either type of training alone. This study was designed to evaluate the effects of combined exercise training on physiological parameters (cardiopulmonary, blood, muscle) of a type 2 diabetic population. METHODS: Twelve type 2 diabetic patients (6 males and 6 females) performed a three-month combined exercise program comprised of two sessions of exercise per week. Cardiopulmonary exercise testing, blood sampling, anthropometric measurements and strength tests were carried out on each subject before (PRE) and immediately after (POST) the training program. RESULTS: The VO2peak and the maximal aerobic power during exercise, the blood profile and the body mass were unchanged after the three-month training program. However, the oxygen uptake and the heart rate at submaximal exercise intensity were significantly lower after the three-month training and muscle strength for many muscle groups was significantly increased. CONCLUSION: These results highlighted the effectiveness of the combined training to improve submaximal cardiopulmonary efficiency and muscle strength capacity of type 2 diabetic patients.

Effects of a gait training session combined with a mass on the non-paretic lower limb on locomotion of hemiparetic patients: a randomized controlled clinical trial.

BACKGROUND: Results of recent studies have suggested that restraint of non-paretic lower limb movement could improve locomotion in hemiplegic patients. The aim of this study was therefore to determine if a mass applied to the non-paretic lower limb during a single gait training session (GTS) would specifically improve spatio-temporal, kinematic and kinetic gait parameters (GP) of the paretic lower limb. METHODS: Sixty chronic hemiplegic subjects were included in this randomized study. Each participated in one of four GTS conditions: overground or on a treadmill while wearing or not wearing an ankle mass. All subjects were assessed before, immediately after and 20 min after the end of the GTS using 3D gait analysis. RESULTS: The results showed that restraining the non-paretic lower limb during a GTS had no specific effect on GP of the paretic limb, whereas it increased braking force of the non-paretic limb. CONCLUSION: Restraining the non-paretic lower limb of hemiparetic patients with a mass applied to the ankle does not seem to be an effective approach to improve paretic lower limb parameters during a single GTS.

Effects of a knee-ankle-foot orthosis on gait biomechanical characteristics of paretic and non-paretic limbs in hemiplegic patients with genu recurvatum.

BACKGROUND: A knee-ankle-foot orthosis may be prescribed for the prevention of genu recurvatum during the stance phase of gait. It allows also to limit abnormal plantarflexion during swing phase. The aim is to improve gait in hemiplegic patients and to prevent articular degeneration of the knee. However, the effects of knee-ankle-foot orthosis on both the paretic and non-paretic limbs during gait have not been evaluated. The aim of this study was to quantify biomechanical adaptations induced by wearing a knee-ankle-foot orthosis, on the paretic and non-paretic limbs of hemiplegic patients during gait. METHODS: Eleven hemiplegic patients with genu recurvatum performed two gait analyses (without and with the knee-ankle-foot orthosis). Spatio-temporal, kinematic and kinetic gait parameters of both lower limbs were quantified using an instrumented gait analysis system during the stance and swing phases of the gait cycle. FINDINGS: The knee-ankle-foot orthosis improved spatio-temporal gait parameters. During stance phase on the paretic side, knee hyperextension was reduced and ankle plantarflexion and hip flexion were increased. During swing phase, ankle dorsiflexion increased in the paretic limb and knee extension increased in the non-paretic limb. The paretic limb knee flexion moment also decreased. INTERPRETATION: Wearing a knee-ankle-foot orthosis improved gait parameters in hemiplegic patients with genu recurvatum. It increased gait velocity, by improving cadence, stride length and non-paretic step length. These spatiotemporal adaptations seem mainly due to the decrease in knee hyperextension during stance phase and to the increase in paretic limb ankle dorsiflexion during both phases of the gait cycle.

Muscle fatigue during cross country sprint assessed by activation patterns and electromyographic signals time-frequency analysis.

The aims of this study were as follows: (i) analysis of activation patterns during the spurt of two heats of a cross country skiing sprint with the double poling technique and (ii) quantification of muscle fatigue of the investigated muscles. Eight elite skiers were tested and surface electromyographic signals (EMG) were recorded from seven muscles of the upper and lower limbs. For each subject and each muscle, the activation intervals were calculated for relying on a double-threshold statistical detector and the average rectified value was calculated on each activation interval. The detected activations were processed by a time-frequency algorithm in order to assess the progression of muscle fatigue. The EMG activation patterns and EMG amplitude highlighted no significant difference between the two spurts, despite a generally lower speed in the second spurt. The frequency analysis showed that upper body muscles are the first to be affected by fatigue and that clear signs of muscle fatigue appear right from the first spurt of the sprint simulation (i.e., biceps and triceps brachii) with a decrease in the instantaneous mean frequency. Biceps brachii activations and fatigue demonstrated the involvement of this muscle in propulsion.

Thigh muscles' responses caused by a single combined aerobic and resistance training session in healthy young men.

The aim of this study was to understand the amplitude and localization of neuromuscular response induced by a training session combining an aerobic and a resistance component. Ten healthy men completed a single session of combined (aerobic and resistance) and aerobic only training, in a randomized order. Surface electromyographic activity and torque obtained during maximal voluntary and electrically evoked contractions of the knee extensor muscles were analyzed to distinguish peripheral from central adaptations. The isometric torque developed by the knee extensor muscles during maximal voluntary contraction decreased significantly following a single session of both combined (-9.2%, p=0.043) and aerobic (-9.6%, p=0.005) training. This was accompanied by a decrease in central activation of the knee extensor muscles after each training session (respectively 2.9, p=0.005 and 1.8% p=0.040) as indicated by twitch interpolation technique. After the combined training protocol, the peak torque of the twitch significantly increased by 6.8% (p=0.046), whereas it decreased by 17.3% (p=0.016) after the aerobic training protocol. The present study demonstrates that the decrease in torque production is similar after a single combined training session or after an aerobic training session of the same duration. Both central and peripheral mechanisms could explain the decrease of torque.

Central and peripheral fatigue of the knee extensor muscles induced by electromyostimulation.

The main purpose of this study was to characterise neuromuscular fatigue induced by 30 contractions of the knee extensor muscles evoked by electromyostimulation (EMS). Twelve healthy subjects were tested before and after a typical EMS session (frequency: 75 Hz, on-off ratio: 6.25 s on-20 s off) used for quadriceps femoris muscle strengthening. Surface electromyographic (EMG) activity and torque obtained during maximal voluntary and electrically evoked contractions were analysed to distinguish peripheral from central fatigue. Maximal voluntary torque of the knee extensor muscles decreased approximately 20 % (p < 0.001) following EMS. In the same way, peak torque associated to single (p < 0.05) and paired (p < 0.001) stimuli as well as M-wave amplitude (p < 0.05) significantly decreased as a result of EMS. The raw EMG activity of both vastus lateralis and rectus femoris muscle recorded during maximal voluntary isometric contraction significantly decreased after the session (-17.3 and -14.5 %, respectively) whereas no changes were observed when EMG signals were normalised to respective M-wave amplitudes. Similarly, voluntary activation estimated by using the twitch interpolation technique was unchanged following EMS. In conclusion, a typical session of EMS of the knee extensor muscles mainly induced neuromuscular propagation failure while excitation-contraction coupling and neural mechanisms were not significantly affected. It is recommended to interpret surface EMG data together with the corresponding M wave, at least for the knee extensor muscles, in order to distinguish peripheral from central causes of fatigue.