A Pilot Study to Measure Upper Extremity H-reflexes Following Neuromuscular Electrical Stimulation Therapy after Stroke

Upper extremity (UE) hemiparesis persists after stroke, limiting hand function. Neuromuscular electrical stimulation (NMES) is an effective intervention to improve UE recovery, although the underlying mechanisms are not fully understood. Our objective was to establish a reliable protocol to measure UE agonist–antagonist forearm monosynaptic reflexes in a pilot study to determine if NMES improves wrist function after stroke. We established the between-day reliability of the H-reflex in the extensor carpi radialis longus (ECRL) and flexor carpi radialis (FCR) musculature for individuals with prior stroke (n = 18). The same-day generation of ECRL/FCR H-reflex recruitment curves was well tolerated, regardless of age or UE spasticity. The between-day reliability of the ECRL H-reflex was enhanced above FCR, similar to healthy subjects [20], with the Hmax the most reliable parameter quantified in both muscles. H-reflex and functional measures following NMES show the potential for NMES-induced increases in ECRL Hmax, but confirmation requires a larger clinical study. Our initial results support the safe, easy, and efficacious use of in-home NMES, and establish a potential method to measure UE monosynaptic reflexes after stroke

Biomechanical measures of short-term maximal cycling on an ergometer: a test-retest study.

An understanding of test-retest reliability is important for biomechanists, such as when assessing the longitudinal effect of training or equipment interventions. Our aim was to quantify the test-retest reliability of biomechanical variables measured during short-term maximal cycling. Fourteen track sprint cyclists performed 3 × 4 s seated sprints at 135 rpm on an isokinetic ergometer, repeating the session 7.6 ± 2.5 days later. Joint moments were calculated via inverse dynamics, using pedal forces and limb kinematics. EMG activity was measured for 9 lower limb muscles. Reliability was explored by quantifying systematic and random differences within- and between-session. Within-session reliability was better than between-sessions reliability. The test-retest reliability level was typically moderate to excellent for the biomechanical variables that describe maximal cycling. However, some variables, such as peak knee flexion moment and maximum hip joint power, demonstrated lower reliability, indicating that care needs to be taken when using these variables to evaluate biomechanical changes. Although measurement error (instrumentation error, anatomical marker misplacement, soft tissue artefacts) can explain some of our reliability observations, we speculate that biological variability may also be a contributor to the lower repeatability observed in several variables including ineffective crank force, ankle kinematics and hamstring muscles' activation patterns

Effects of Lateral Shoe Wedges and Toe-in Foot Progression Angles on the Biomechanics of Knee Osteoarthritis during Stationary Cycling

Exercise is important for individuals with knee osteoarthritis (OA) but certain activities can be painful and discourage participation. Cycling is commonly prescribed for OA but practically no previous literature exists. Due to their altered knee kinematics, OA patients may be at greater risk of OA progression or other knee injuries during cycling. The purpose of Study One was to investigate the effects of lateral wedges on knee joint biomechanics and pain in patients with medial compartment knee OA. The purpose of Study Two was to investigate the effects of toe-in foot progression angles on the same variables. Thirteen OA subjects and 11 healthy subjects participated. A motion analysis system and custom instrumented pedal was used to collect 5 pedal cycles of kinematics and kinetics during 2 minutes of cycling in one neutral and two lateral wedge conditions (5° and 10°) for Study One and 2 toe-in conditions (5° and 10°) for Study Two. Subjects pedaled at 60 RPM and 80 watts and rated their knee pain on a visual analog scale. Study One: There was a 22% decrease in the knee abduction moment with the 10° wedge. This finding was not accompanied by a decrease in knee adduction angle or pain. Additionally, there was an increase in vertical and horizontal PRF which may negate the advantages of the decreased KAM. Study Two: For the OA subjects, there was a 61% (2.7°) and a 73% (3.2°) decrease in peak knee adduction angle compared to neutral. This finding was not accompanied by a decrease in pain or KAM because of high inter-subject variability. A simple linear regression showed a positive correlation between Kelgren-Lawrence (K/L) score and both peak knee adduction angle and KAM. For OA patients, cycling with a 10° lateral wedge or a decreased foot progression angle may be beneficial in slowing the progression of OA or minimizing other knee injuries. Patients with a higher K/L score may have greater risk of injury. More research is needed to investigate the joint contact forces as well as long term effects of riding with wedges or toe-in foot angles

Neuromuscular Fatigue and Biomechanical Alterations during High-Intensity, Constant-Load Cycling

Neuromuscular fatigue is an inevitable process at play during prolonged exercise, and may be caused by multiple alterations within the central nervous system and peripheral musculature. As fatigue develops, the neuromuscular system must adapt to these changes by making compensatory movement pattern adjustments so as to use motor pathways that are less fatigued in an effort to maintain task performance; motor variability is thus increased. The primary purpose of the four studies contained within this doctoral thesis was to detail the progression of exercise-induced neuromuscular fatigue, and to improve our understanding of the muscle activation and joint kinematic alterations that occur as fatigue accumulates. Within this context, cycling was used as the exercise model, and the relationship between physiological and biomechanical aspects of high-intensity, moderate duration (\u3c10 \u3emin) cycling were specifically examined. The first two studies of this thesis were aimed at understanding the progression of neuromuscular fatigue as well as the associated motor control and biomechanical (i.e. muscle activation and kinematic) changes that occur during exhaustive cycling. Specifically, the time course and relative contributions of central and peripheral fatigue mechanisms, and the associated changes in muscle activation and both lower (i.e. hip, knee and ankle joint) and upper (i.e. trunk) limb kinematics were examined during a high-intensity cycling time to exhaustion (TTE) test. This was performed at 90% maximal aerobic power (Pmax) with nine well-trained cyclists. Temporal relationships between joint kinematics and changes in markers of central and peripheral fatigue were also examined. Peripheral fatigue (i.e. impaired contractile function: reduced peak twitch torque, −39.9%; twitch contraction time, −10.7%; and the average rates of twitch torque development −34.7% and relaxation −36.7% at task failure i.e., T100) developed early in the exercise bout from 60% of the time to task failure (p \u3c 0.05). However, a central facilitation, measured as an increase in peak vastus medialis (38.9%) and gluteus maximus electromyogram (87.2%) amplitudes at T100, rather than central fatigue, occurred towards the end of the exercise task (p \u3c 0.05). Thus, neuromuscular fatigue development was associated with an increase in the magnitude of lower limb muscle activity, which may have represented an attempt to increase muscle force to maintain the required power output of the cycling task. Increases in trunk flexion were observed from 60% of the time to task failure (p \u3c 0.05), and were therefore notable at or after the point of significant peripheral fatigue. Conversely, increases in trunk medio-lateral sway (lateral flexion), hip abduction/adduction and knee valgus/varus were observed only from 80% of the time to task failure (p \u3c 0.05), which paralleled the increase in central motor drive. The results of this study therefore indicate that significant trunk kinematic changes in the sagittal plane occurred at or after the point of significant peripheral fatigue development, whereas, significant changes at the trunk, hip and knee joints in the coronal plane occurred later in the exercise task and paralleled the facilitation of central motor drive during the cycling task. In the third study, the effects of real-time, kinematic feedback provision for trunk flexion (TTETflex), trunk medio-lateral sway (TTETsway) and hip abduction/adduction (TTEHabd/add) during a high-intensity TTE cycling test (90% Pmax) in nine well-trained cyclists were examined. The times taken to reach task failure were compared to a TTE test completed with no feedback. The times taken to reach task failure were not significantly different when provided with trunk flexion (TTETflex) and hip abduction/adduction (TTEHabd/add) feedback compared to the non-feedback condition (p \u3e 0.05). There was, however, a significant decrease in the time to task failure during the TTETsway test (p \u3c 0.05). Not all participants could maintain trunk and/or hip movement within a set movement pattern criteria; and three participants were therefore excluded from the kinematic analyses for both the TTETflex and TTETsway tests (n = 6) as were two participants from the TTEHabd/add test (n = 7). For participants who correctly used the kinematic feedback, no differences in the times taken to reach failure were observed in between the feedback (TTETflex, TTETsway and TTEHabd/add) and nonfeedback test conditions (p \u3e 0.05). Despite being given feedback, changes in joint kinematics were similar across all test conditions; significant alterations were observed at the trunk and knee joints in the sagittal plane and at the hip and knee joints in the coronal plane (p \u3c 0.05). Given trunk flexion feedback (TTETflex), significant increases in left hip flexion and trunk medio-lateral sway ROM were observed (p \u3c 0.05), whereas given trunk medio-lateral sway feedback (TTETsway), increases in right hip flexion ROM also occurred (p \u3c 0.05). These results indicate that, regardless of whether or not well-trained cyclists are able to control the level of kinematic variability when fatigued, acute exposure to real-time kinematic feedback to limit trunk or hip movement during high-intensity cycling may influence cycling kinematics (i.e. technique) and, in some cases (e.g. trunk medio-lateral sway), may reduce performance. The final study examined the relationship between joint kinematics, measured in non-fatigued and fatigued high-intensity cycling, and the cyclists’ physiological profiles (i.e., physiological attributes indicative of successful cycling ability, including both maximal oxygen consumption and peak power output relative to body mass, maximal heart rate, both power output and heart rate at the first and second ventilatory thresholds and cycling economy at 100 W) and the time taken to reach task failure. Submaximal physiological attributes were correlated with hip (abduction/adduction angle and ROM), knee (flexion angle) and ankle (flexion ROM) kinematics measured in a non-fatigued state at the start of the trial (r \u3e 0.40; p \u3c 0.05). However, both physiological attributes associated with maximal exercise capacity and cycling economy were correlated with trunk (flexion angle) and ankle (flexion angle and ROM) kinematics measured in a fatigued state at the end of the test (r \u3e 0.40; p \u3c 0.05). Trunk flexion and medio-lateral sway ROM in a non-fatigued state, and trunk flexion angle in a fatigued state, were associated with the time to task failure (r \u3e 0.50; p \u3c 0.05). Thus, the degree of trunk flexion and medio-lateral sway may be important kinematic variables that are indicative of cycling performance. These findings reveal an interdependence between cycling kinematics and both the physiological attributes indicative of successful cycling performance and the time taken to reach task failure during high-intensity, constant-load cycling. In conclusion, the findings presented in this thesis indicate that the temporal patterns of central and peripheral neuromuscular fatigue differ (Study 1; Chapter 3). Task failure during high intensity cycling appears to be associated with the development of peripheral fatigue despite the presence of an increase in central motor drive. Subsequent to the development of neuromuscular fatigue, muscle activation and joint kinematic alterations can be observed, which may represent compensatory mechanisms employed by the neuromuscular system to continue task performance (Studies 1 and 2; Chapters 3 and 4). Joint kinematic alterations in the sagittal plane were associated with the development of peripheral fatigue whereas coronal plane adjustments occurred in parallel with central facilitation, and/or when a more substantial level of peripheral fatigue accumulated. Such compensatory kinematic strategies are also associated with an athlete’s physiological attributes and their cycling performance (i.e., time to task failure) (Study 4; Chapter 6). Importantly, imposing specific joint kinematic restrictions (trunk flexion, trunk medio-lateral sway and hip abduction/adduction) during exhaustive cycling, influenced cycling kinematics (i.e. technique) and, in some cases (e.g. trunk medio-lateral sway), reduced the time taken to reach task failure for well-trained cyclists (Study 3; Chapter 5). Such findings enhance our understanding of how the neuromuscular system copes with fatigue development, and should assist coaches and/or occupational health practitioners to better understand the fatigue process and neuromuscular strategies utilised during exercise tasks with similar characteristics to that used in the current studies

Intrinsic factors, performance and dynamic kinematics in optimisation of cycling biomechanics

Kinematic measurements conducted during bike set-ups utilise either static or dynamic measures. There is currently limited data on reliability of static and dynamic measures nor consensus on which is the optimal method. The aim of the study was to assess the difference between static and dynamic measures of the ankle, knee, hip, shoulder and elbow. Nineteen subjects performed three separate trials of a 10min duration at a fixed workload (70% of peak power output). Static measures were taken with a standard goniometer (GM), an inclinometer (IM) and dynamic three dimensional motion capture (3DMC) using an eight camera motion capture system. Static and dynamic joint angles were compared over the three trials to assess repeatability of the measurements and differences between static and dynamic values. There was a positive correlation between GM and IM measures for all joints. Only the knee, shoulder and elbow were positively correlated between GM and 3DMC, and IM and 3DMC. Although all three instruments were reliable, 3D motion analysis utilised different landmarks for most joints and produced different means. Changes in knee flexion angle from static to dynamic are attributable to changes in the positioning of the foot. Controlling for this factor, the differences are negated. It was demonstrated that 3DMC is not interchangeable with GM and IM, and it is recommended that 3DMC develop independent reference values for bicycle configuration

Efficacy of a Cycling Intervention with Pedal Reaction Force Augmented Feedback on Reducing Inter-Limb Asymmetries in Patients with Unilateral Total Knee Arthroplasty

Fifteen patients with unilateral total knee arthroplasty (TKA) performed cycling at two workates (80 W and 100 W) and two walking conditions (preferred and fast speeds). Ten of these patients of TKA also participated in a short-term cycling intervention paired with visual augmented feedback of vertical pedal reaction forces for six sessions over two-three weeks. These ten patients of TKA participated in a 2nd post-training testing session. Study One compared the knee joint biomechanics for all fifteen participants during stationary cycling to ascertain if any biomechanical asymmetries may be present. The replaced limbs displayed significantly lower peak knee extension moment (KEM) and vertical pedal reaction (PRF) compared to non-replaced limbs during stationary cycling. Study Two examined the effect of the short-term cycling intervention on the knee joint biomechanics and biomechanical asymmetries during stationary cycling for the selected ten patients of TKA. The short-term cycling intervention had no significant effect for peak KEM or vertical PRF asymmetries during stationary cycling. Peak KEM asymmetries did decrease by 10% and 9.9% at 80 W and 100 W, respectively. Study Three examined the effect of the short-term cycling intervention on the knee joint biomechanics and biomechanical asymmetries during gait. Similarly, the short-term cycling intervention had no effect on peak KEM asymmetries and vertical ground reaction force (GRF) asymmetries during both walking condition. Study Four compared the estimated tibiofemoral joint forces during stationary cycling between the replaced and non-replaced limbs of the fifteen patients of TKA. The replaced limbs also had lower medical tibiofemoral contact force (MCF) compared to the non-replaced limbs during stationary cycling at 80 W. The non-replaced limb had greater peak MCF compared to the lateral tibiofemoral contact force (LCF). Unilateral TKA patients cycling with similar reductions of KEM in their replaced limbs. During cycling, there was no difference between MCF and LCF for the replaced limbs, potentially indicating a successful operation to restore knee joint alignment. In summary, the use of a short-term cycling intervention with augmented feedback for six sessions were not significantly beneficial for addressing KEM asymmetries in both cycling and gait. However, the 10% reductions of peak KEM asymmetries may indicate some clinical benefits of this intervention. Future studies should examine similar interventions with an increased number of training sessions

Afferent information modulates spinal network activity in vitro and in preclinical animal models

Primary afferents are responsible for the transmission of peripheral sensory information to the spinal cord. Spinal circuits involved in sensory processing and in motor activity are directly modulated by incoming input conveyed by afferent fibres. Current neurorehabilitation exploits primary afferent information to induce plastic changes within lesioned spinal circuitries. Plasticity and neuromodulation promoted by activity-based interventions are suggested to support both the functional recovery of locomotion and pain relief in subjects with sensorimotor disorders. The present study was aimed at assessing spinal modifications mediated by afferent information. At the beginning of my PhD project, I adopted a simplified in vitro model of isolated spinal cord from the newborn rat. In this preparation, dorsal root (DR) fibres were repetitively activated by delivering trains of electrical stimuli. Responses of dorsal sensory-related and ventral motor-related circuits were assessed by extracellular recordings. I demonstrated that electrostimulation protocols able to activate the spinal CPG for locomotion, induced primary afferent hyperexcitability, as well. Thus, evidence of incoming signals in modulating spinal circuits was provided. Furthermore, a robust sensorimotor interplay was reported to take place within the spinal cord. I further investigated hyperexcitability conditions in a new in vivo model of peripheral neuropathic pain. Adult rats underwent a surgical procedure where the common peroneal nerve was crushed using a calibrated nerve clamp (modified spared nerve injury, mSNI). Thus, primary afferents of the common peroneal nerve were activated through the application of a noxious compression, which presumably elicited ectopic activity constitutively generated in the periphery. One week after surgery, animals were classified into two groups, with (mSNI+) and without (mSNI-) tactile hypersensitivity, based on behavioral tests assessing paw withdrawal threshold. Interestingly, the efficiency of the mSNI in inducing tactile hypersensitivity was halved with respect to the classical SNI model. Moreover, mSNI animals with tactile hypersensitivity (mSNI+) showed an extensive neuroinflammation within the dorsal horn, with activated microglia and astrocytes being significantly increased with respect to mSNI animals without tactile hypersensitivity (mSNI-) and to sham-operated animals. Lastly, RGS4 (regulator of G protein signaling 4) was reported to be enhanced in lumbar dorsal root ganglia (DRGs) and dorsal horn ipsilaterally to the lesion in mSNI+ animals. Thus, a new molecular marker was demonstrated to be involved in tactile hypersensitivity in our preclinical model of mSNI. Lastly, we developed a novel in vitro model of newborn rat, where hindlimbs were functionally connected to a partially dissected spinal cord and passively-driven by a robotic device (Bipedal Induced Kinetic Exercise, BIKE). I aimed at studying whether spinal activity was influenced by afferent signals evoked during passive cycling. I first demonstrated that BIKE could actually evoke an afferent feedback from the periphery. Then, I determined that spinal circuitries were differentially affected by training sessions of different duration. On one side, a short exercise session could not directly activate the locomotor CPG, but was able to transiently facilitate an electrically-induced locomotor-like activity. Moreover, no changes in reflex or spontaneous activity of dorsal and ventral networks were promoted by a short training. On the other side, a long BIKE session caused a loss in facilitation of spinal locomotor networks and a depression in the area of motor reflexes. Furthermore, activity in dorsal circuits was long-term enhanced, with a significant increase in both electrically-evoked and spontaneous antidromic discharges. Thus, the persistence of training-mediated effects was different, with spinal locomotor circuits being only transiently modulated, whereas dorsal activity being strongly and stably enhanced. Motoneurons were also affected by a prolonged training, showing a reduction in membrane resistance and an increase in the frequency of post-synaptic currents (PSCs), with both fast- and slow-decaying synaptic inputs being augmented. Changes in synaptic transmission onto the motoneuron were suggested to be responsible for network effects mediated by passive training. In conclusion, I demonstrated that afferent information might induce changes within the spinal cord, involving both neuronal and glial cells. In particular, spinal networks are affected by incoming peripheral signals, which mediate synaptic, cellular and molecular modifications. Moreover, a strong interplay between dorsal and ventral spinal circuits was also reported. A full comprehension of basic mechanisms underlying sensory-mediated spinal plasticity and bidirectional interactions between functionally different spinal networks might lead to the development of neurorehabilitation strategies which simultaneously promote locomotor recovery and pain relief

Physiological and Mechanical Comparisons between Clipless and Flat Pedals

The purpose of this study was to investigate the physiological and mechanical comparisons between clipless and flat pedals. Participants (n=4) completed two at-home 20-minute FTP tests: using clipless and flat pedals using Zwift. The order of conditions were randomized for each participant. Participants used their personal Smart Trainers, clipless pedals, and cycling shoes while flat pedals were provided (Syun-LP, Road Bike Platform Pedals). Power, heart rate and cadence were recorded and used for analysis. All dependent variables were compared using paired t-tests. Power was significantly greater for clipless (226.7 ± 46.2 W) vs. flat (215.2 ± 41.8 W) pedals (p \u3c 0.05). Heart rate was significantly greater for flat (138.5 ± 17.4 bpm) vs. clipless (135.2 ± 18.1 bpm) pedals (p \u3c 0.05). However, cadence was not significantly different between clipless (70 ± 8.7 rpm) vs. flat (71.7 ± 13.3 rpm) pedals (p \u3e 0.05). The greater power when using clipless pedals combined with a lower heart rate is an indication that clipless pedals are preferable to flat pedals

Bicycle rider control: A balancing act

Cycling is increasing in popularity which is accompanied with a higher rate of injuries sustained due to collisions, crashes or falls. A high proportion of these events happen when the bicycle rider loses control of the bicycle. In order to improve bicycle rider control, the skill of riding a bicycle needs to be understood. Therefore, the overall aim of this PhD work was to explore bicycle rider control skills and to examine the effects of different constraints on the control of a bicycle. The first part of this thesis focuses on developing a valid and reliable methodology that can be further used for studying bicycle rider control skill. Firstly, a protocol to determine knee angle during cycling is being developed. Secondly, some technical approaches when studying muscle activity during cycling are being questioned. Lastly, a portable device based on a single angular rate sensor to record steering rate and bicycle roll rate was tested for reliability in an outdoor setup. Second part of the thesis examines the effects on bicycle rider control of three different constraints: 1) expertise, 2) body position and 3) cycle lane design. Results overall showed that all three constraints significantly affect steering and bicycle roll rate

Effects of auditory stimuli on electrical activity in the brain during cycle ergometry

© 2017 The Authors. The present study sought to further understanding of the brain mechanisms that underlie the effects of music on perceptual, affective, and visceral responses during whole-body modes of exercise. Eighteen participants were administered light-to-moderate intensity bouts of cycle ergometer exercise. Each exercise bout was of 12-min duration (warm-up [3 min], exercise [6 min], and warm-down [3 min]). Portable techniques were used to monitor the electrical activity in the brain, heart, and muscle during the administration of three conditions: music, audiobook, and control. Conditions were randomized and counterbalanced to prevent any influence of systematic order on the dependent variables. Oscillatory potentials at the Cz electrode site were used to further understanding of time–frequency changes influenced by voluntary control of movements. Spectral coherence analysis between Cz and frontal, frontal-central, central, central-parietal, and parietal electrode sites was also calculated. Perceptual and affective measures were taken at five timepoints during the exercise bout. Results indicated that music reallocated participants' attentional focus toward auditory pathways and reduced perceived exertion. The music also inhibited alpha resynchronization at the Cz electrode site and reduced the spectral coherence values at Cz–C4 and Cz–Fz. The reduced focal awareness induced by music led to a more autonomous control of cycle movements performed at light-to-moderate-intensities. Processing of interoceptive sensory cues appears to upmodulate fatigue-related sensations, increase the connectivity in the frontal and central regions of the brain, and is associated with neural resynchronization to sustain the imposed exercise intensity.Coordination for the Improvement of Higher Education Personnel (CAPES)