Tania Lam

Background: The pelvic floor muscles (PFM) play a critical role in maintaining urogenital function. Pelvic floor muscle training (PFMT) is a commonly prescribed, non-invasive, exercise intervention to manage urinary incontinence. It involves the practice of voluntary contractions of the muscles to different intensities and durations, as well as in combination with different functional tasks. As a non-invasive intervention with few to no side effects, PFMT is an attractive intervention for the management of urinary incontinence in different clinical populations. Despite its known clinical benefits, we still do not have a full understanding of the underlying neurophysiological effects of the intervention.Objective: The objective of this study was to investigate the acute neurophysiological changes in sensorimotor pathways following a single session of PFMT, compared to a control intervention (biceps brachii contractions).Methods: We randomly assigned participants to either the experimental (PFMT) or control (biceps training) group. Participants completed a training program consisting of 55 contractions to different intensities and durations of either their PFM or biceps brachii. To examine changes in somatosensory excitability associated with the PFM, we used electroencephalography to record somatosensory evoked potentials in response to pudendal nerve stimulation. To examine changes in corticospinal excitability, we used surface electromyography to record motor evoked potentials from the PFM elicited by transcranial magnetic stimulation over the primary motor cortex. All measures were recorded before and after a single session of training and compared between groups.Results: Our data show no significant modulation in P40 amplitude of pudendal somatosensory evoked potential and PFM motor evoked potential amplitude. However, exploratory analysis suggests a possible relationship between intervention responder type (whether there was improvement in PFM contraction) and participant age, as well as somatosensory and corticospinal excitability.Conclusion: We found no acute modulation of somatosensory and corticospinal excitability of the PFM following a single session of PFMT. However, further exploration of the data revealed possible effect of age on the response to PFMT, as well as between responder type and changes in somatosensory and corticospinal excitability, which needs to be investigated further.

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Background: The pelvic floor muscles (PFM) are important for maintaining continence and a potential therapeutic target for bladder management after spinal cord injury (SCI). Locomotor training could be beneficial for bladder outcomes in people with motor-complete SCI (mcSCI), but it remains unclear if reported improvements are related to the PFM. The PFM are co-activated with abdominal and gluteal muscles, and active during regular walking in able-bodied controls; however, we do not fully understand if exoskeletons used for gait rehabilitation that require more active engagement of the trunk muscles (e.g., the Ekso), could elicit more PFM activity compared to the Lokomat, which restricts trunk movement. Further, considering the invasiveness of the necessary procedures to record PFM activity, establishing the feasibility of the surface PFM electromyography (EMG) self-setup for dynamic tasks in controls will facilitate work in this area.Objectives: To (1) determine the feasibility of PFM EMG self-setup in controls; (2) characterize PFM activation patterns with respect to exoskeleton device (Lokomat vs. Ekso) in controls; and (3) explore the presence of PFM activity during exoskeleton-assisted walking in people with mcSCI.Methods: Eleven able-bodied adults and 3 SCI participants enrolled in this within-subject, cross-sectional study. We recorded EMG from the PFM and lower back, abdominal, gluteal, and leg muscles, as well as pelvis acceleration, during walking in the Lokomat and Ekso at different speeds. Control participants completed a survey on their experiences related to the PFM EMG self-setup. Results: In controls, all except one had a left-right difference in signal quality during walking with the PFM EMG self-setup. PFM activity was 53% and 63% higher during walking in the Ekso than Lokomat at the slow and fast speeds, respectively. Visual inspection revealed higher PFM EMG amplitude with greater pelvis acceleration and trunk and gluteal muscle activation. Both the Lokomat and Ekso elicited PFM activity in SCI participants.Conclusion: PFM EMG setup by a trained professional might be necessary to ensure signal quality during dynamic tasks. The Ekso is more effective in eliciting PFM activity in controls, and further investigation is needed to better understand this phenomenon in people with mcSCI.

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Background: Urinary incontinence negatively impacts quality of life for over 420 million people worldwide. The pelvic floor muscles (PFM) are crucial for maintaining urinary continence in humans. Transcutaneous tibial nerve stimulation (TcTNS) is a promising therapeutic technique used to manage urinary incontinence. There is compelling evidence from upper and lower limb studies that peripheral nerve stimulation alone can trigger neuroplastic changes in the primary motor cortex in the absence of motor training. Since the tibial nerve (L4-S3) shares segmental innervation with the pudendal nerve (S2-S4), which supplies the PFM, TcTNS may lead to neuromodulation of the corticospinal projections to the PFM as well as abductor hallucis (AH) muscle, which is innervated by the tibial nerve.Purpose: To evaluate the effects of two distinct patterns of TcTNS (intermittent vs. continuous) on corticomotor excitability of the PFM and AH. We hypothesized that intermittent TcTNS would increase, while continuous TcTNS would suppress, the excitability of both muscles.Methods: Twelve able-bodied adults (20-33 years of age) enrolled in this study. TcTNS was delivered either intermittently (1-ms pulses delivered at 30Hz with an on:off duty cycle of 600:400 ms, for 60 min), or continuously (1-ms pulses delivered at 30Hz for 36 min). The order of the TcTNS patterns was randomized and tested on separate days. Surface electromyography (EMG) was used to record motor evoked potentials (MEPs) from PFM and AH by transcranial magnetic stimulation (TMS) over the motor cortical areas controlling these muscles before and after TcTNS. Results: Our results suggest that intermittent, but not continuous stimulation of the tibial nerve might have increased the excitability of corticospinal projections to AH without altering the excitability of those controlling the PFM.Conclusion: Based on our observations, to induce corticomotor excitability of the lower limb muscles, intermittent stimulation should be used. Moreover, it is possible that there are differences in the mechanisms underlying TcTNS-induced modulation of the corticospinal projections to AH and PFM, which require further investigation.

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Background: The pelvic floor muscles (PFM) are crucial in maintaining urinary continence. Damage and denervation to this muscle group is associated with urine leakage. In able-bodied individuals, exercise programs intended to strengthen the core and PFM are considered the first line of treatment against urinary incontinence. However, limited research has explored applying these exercises to people with spinal cord injury (SCI), where more than 80% of individuals experience bladder dysfunction. PFM training programs may not have been attempted in people with SCI because of assumptions about remaining PFM function post-injury. Further, for those with high-thoracic motor-complete SCI (mc-SCI), it is often incorrectly assumed that they are unable to engage muscles of the core based on standard neurological assessment. Evidence from previous work has already shown that sparing in abdominal function can be detected using manual palpation, surface electromyography, and transcranial magnetic stimulation. It remains unknown to what extent the PFM may be similarly spared in this population.Objectives: To a) characterize and compare activation patterns of pelvic floor, abdominal, and gluteal muscles during validated PFM training exercises in able-bodied individuals and those with mc-SCI and b) evaluate corticospinal excitability to the PFM via transcranial magnetic stimulation. Methods: This study will use a two-part cross-sectional design. In both parts, EMG recordings will be taken bilaterally from rectus abdominis, external oblique, erector spinae, levator ani, and gluteus maximus muscles. In Part 1, participants will attempt a variety of validated maneuvers to attempt to elicit PFM activity. In Part 2, participants will receive transcranial magnetic stimulation targeting the pelvic floor. Results: Our results show that voluntary activation is possible for all AB and the majority of SCI participants. For AB participants, Kegels and gluteal contractions elicited the largest responses, but for SCI participants, abdominal exercises elicited the largest responses. MEPs were elicited in the PFM for all AB subjects and all but two SCI participants. Conclusion: Our results suggest that those with mc-SCI retain functional sparing to the PFM after injury. This supports the application of PFM training programs to this population.

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Introduction: Proprioception gives us the ability to know the location of our limbs in space. It plays a critical role in movement control, including walking. After a spinal cord injury (SCI), individuals experience not only weakness or paralysis, but also proprioceptive deficits, which further compound difficulties with movement control. In this study, we tested the effects of a new robotic-based protocol to train proprioceptive sense in the lower limbs and assessed whether improvements in proprioceptive sense could also improve performance of a skilled walking task in people with SCI. Methods: Skilled walking performance was assessed by participants’ accuracy in matching their heel position during the swing phase of walking to a virtual target presented on a monitor. Proprioceptive sense was assessed by knee joint position sense with a validated protocol using the Lokomat robotic exoskeleton. Subjects then underwent proprioceptive training. The training protocol required subjects to detect whether their heel position was higher or lower compared to an initial position. After each trial, visual feedback about their accuracy was provided. The assessments of skilled walking and knee joint position sense were assessed post-training as well as 24-hours later.Results and Conclusion: Our results showed that the training protocol was effective, with a significant improvement in knee joint position sense post-training that was also evident 24-hours later. A slight trend in improvement was also observed in skilled walking performance post-training. These findings indicate that it is possible to improve lower limb proprioceptive acuity following sensory training and that such improvements could further influence skilled walking performance.

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Background: A spinal cord injury (SCI), results in a myriad of serious secondary health complications including cardiovascular disease, obesity, and pressure sores due to immobility. These health conditions could be reduced by improving fitness and mobility by participation in physical activity (PA) and exercise. However the SCI population has been found to have the lowest levels of PA when compared to the general population. The reasons for this have been attributed to the many extrinsic barriers that those living with an SCI face daily, including cost, transportation, and lack of adapted equipment or facilities. In May 2013, the Physical Activity Research Centre (PARC) at ICORD opened its doors in an effort to reduce the extrinsic barriers, however, this did not address the many intrinsic barriers to exercise participation, including lack of motivation, time, and knowledge about where or how to exercise. Previous studies have indicated that the preferred messenger for the delivery of PA knowledge includes peers, and health service providers. Here, our goal was to investigate whether peers can change PA behavior and bring this knowledge to action. Methods: In this pilot randomized controlled trial, ten individuals with a SCI were randomly assigned to meet with a peer or student trainer (control) to discuss the PA guidelines for SCI. After the initial intervention, we investigated the effectiveness of peer trainers, compared to student trainers, to translate the PA guidelines to a SCI participant. We then instructed participants to meet with their peer/student trainer as desired for the remainder of the 3-month study. Exercise self-efficacy and overall PA levels were compared between baseline, week 1 and week 12. During an exit interview we explored the effect on intrinsic barriers to exercise along with participant satisfaction with the study. Results: Overall no statistically significant findings were detected between groups, however nearly all participants scored well on knowledge acquisition and are now meeting the recommended PA guidelines. Conclusion: Our findings suggest that student trainers could be as effective as peer trainers as it relates to overcoming intrinsic barriers and increasing overall PA within the SCI population.

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Background: Maintaining postural stability during sitting or standing depends critically on motor function in the trunk muscles. Trunk muscle function is typically assumed to be poor or absent in people with a complete spinal cord injury (SCI) at or above the thoracic level. However, recent studies have revealed sparing of trunk muscle function in people with high-thoracic motor-complete SCI, opening up the possibility for training techniques to improve their function. The Lokomat and Ekso are used in gait rehabilitation for people with SCI, but it remains unknown how much they engage those trunk muscles that are normally activated during walking. These devices provide gait training in different methods. In Lokomat, the trunk is rigidly and passively supported by a body weight support harness, which could imply lesser recruitment of postural muscles. In contrast, the Ekso requires continuous weight shifting from one limb to the other to trigger steps, which could lead to better postural muscle activation. Objective: To compare trunk muscle activation patterns during Ekso- vs Lokomat-assisted walking in people with high-thoracic motor-complete SCI. Methods: 8 individual with C7-T4 chronic motor-complete SCI were recruited. Subjects performed 3 walking conditions (at matched speeds): Lokomat-assisted walking (Loko-TM), Ekso-assisted walking on treadmill (Ekso-TM), and Ekso-assisted walking overground (Ekso-OG). Surface electromyography (EMG) signals were recorded bilaterally from rectus abdominis (RA), external oblique (EO), and erector spinae (ES) and normalized to (attempted) maximum voluntary contraction (MVC). EMG amplitudes were compared during baseline (lying supine) (BAS) and across the 3 walking conditions. EMG onset and total activity times were compared across the 3 walking conditions.Results: Trunk EMG amplitudes were significantly higher in Ekso-TM compared to both Loko-TM and BAS. RA and ES amplitudes were not different during Loko-TM walking compared to BAS. When Ekso-OG was compared to Ekso-TM, only ES amplitude was significantly different. Onset and total activity times were not significantly different across the walking conditionsConclusion: Ekso-assisted walking was better in activating trunk muscles than the Lokomat-assisted walking. These results suggest that Ekso could possibly be used to train trunk strength and improve sitting postural control in people with high-thoracic motor-complete SCI.

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Background: The simultaneous performance of a postural and suprapostural task has been shown to result in the deterioration of the performance of one or both tasks. For people with spinal cord injury (SCI), whose standing balance is challenged, it is unknown the extent to which they rely on attentional resources to maintain quiet stance. The overall aim of this study was to use a dual task paradigm to investigate the attentional requirements for maintaining standing balance in people with SCI. Methods: We recruited 9 adults with incomplete SCI and 8 matched able-bodied controls. Subjects were asked to perform two suprapostural tasks: a mathematical task (counting backwards by 3s) and an auditory reaction time (RT) task with eyes open/closed. Three single task (ST) trials were recorded: i) standing on force plates; ii) math task while seated; iii) RT task while seated. Two dual-task (DT) trials were recorded: i) standing + math task; ii) standing + RT task. The primary outcome measures were the change in performance between ST and DT between SCI and controls for: i) RT, ii) maximum standing time, iii) error ratio and total number of words uttered, and iv) movement reinvestment. Secondary outcomes such as center of pressure (CoP) measures from force plates as well as perceptual measures such as fear, confidence and perceived mental workload were also recorded. Results: SCI subjects stood for shorter duration during DT (stand and count) than ST (stand) compared to controls during eyes closed. Main effects between groups were observed for movement reinvestment, CoP performance, perceived mental effort, fear and confidence. No significant effects were observed for RT task or math task performance. Conclusion: Total standing time during eyes closed is adversely affected with the addition of a math task for SCI subjects. Perceptual measures such as increased fear and perceived mental workload and decreased confidence correspond to increases in postural sway and conscious control of standing in subjects with SCI. Individuals who can stand for >60 seconds eyes closed do not appear to be significantly affected by the addition of a concurrent secondary task of minimal mental workload. 

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Background: In people with motor-incomplete spinal cord injury (m-iSCI), the ability to perform skilled walking tasks (e.g. obstacle crossing) is an essential component of functional mobility. Sensorimotor integration of visual and proprioceptive inputs, alongside indicators of functional ambulation (i.e. self-efficacy) is important for successful obstacle crossing. Thus, the overall objective was to understand how motor and sensory (specifically proprioception) deficits in people with m-iSCI affect obstacle-crossing strategies. Methods: Nine individuals with m-iSCI and 10 able-bodied controls were asked to step over an obstacle scaled to their motor abilities under full and obstructed vision conditions. An eye tracker was used to determine gaze behavior, motion capture analysis was used to determine toe kinematics relative to the obstacle, and electrogoniometers were used to determine peak ankle, hip and knee (dorsi)flexion angles during obstacle crossing. In subjects with m-iSCI, questionnaires were used to determine balance and ambulatory self-efficacy. Lower limb proprioceptive sense was assessed using a hip and knee joint position-matching task using the Lokomat and customized software controls.Results: Lower limb proprioceptive sense was impaired and varied across subjects with m-iSCI. m-iSCI subjects tended to glance at the obstacle more frequently as they approached it and with shorter gaze durations compared to controls. Decreased self-efficacy and impaired proprioceptive sense may have contributed to these differences in gaze behavior. Obstruction of the lower visual field led to appropriate modulation of lead and trail horizontal distance, however toe clearance height in m-iSCI subjects was increased to a greater extent than controls. An emerging relationship was observed between proprioceptive sense and toe clearance height, in particular for the trail limb. m-iSCI subjects increased peak knee flexion to a greater extent than controls when vision was obstructed. All other changes in joint kinematics were similar across groups. Conclusion: The results of this study indicate that people with m-iSCI rely more heavily on vision to cross obstacles and show impairments in the key gait parameters required for successful obstacle crossing. Our data suggest that proprioceptive deficits also need to be considered in rehabilitation programs aimed at improving functional mobility in individuals with m-iSCI.

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Generalization of these adaptations have been found to occur across task, workspace and between limbs. Interlimb adaptation transfer appears to depend on limb dominance. Transfer of adaptation from the non-dominant to the dominant limb involves faster rate of adaptation in movement trajectory patterns, while transfer from the dominant limb to the non-dominant limb involves a faster rate of adaptation positioning related parameters of movement. Although such observations are robust for upper limb adaptations, the extent of interlimb transfer during locomotor tasks is still unclear. The objective of this study was to determine whether locomotor adaptations to a velocity-dependent resistance transfers asymmetrically depending on dominance associated with the legs. It was expected that transfer of adaptation will occur according to dominance, with the dominant limb showing faster adaptation in terms of foot trajectory following non-dominant limb learning; and the non-dominant limb showing faster adaptation in terms of heel strike position following dominant limb learning. Twenty able-bodied adults who were right hand and right leg dominant walked unipedally in the Lokomat robotic gait orthosis, which applied a velocity-dependent resistance against leg movements. The resistance was scaled to 10% of the individual’s maximum voluntary contraction of the hip and knee flexors. Subjects performed a heel targeting task that was scaled to their individual step length. Subjects were then randomly assigned to either the RL training group, testing transfer to the non-dominant limb, or to the LR training group, testing transfer to the dominant limb. Muscle activity (surface electromyography) and joint kinematics were recorded from the lower limbs. The adaptation rate in the initial foot trajectory slope and end point error were compared between the groups and across trials using a 2 by 3 repeated measures ANOVA. There was no difference between the groups for either initial foot trajectory slope (p = 0.106) or end point error (p = 0.763). There was also no evidence for transfer of motor adaptations between the lower limbs in the other gait variables. These results suggest that interlimb transfer of locomotor adaptations is limited, but further studies are warranted to understand the neuromechanical mechanisms controlling locomotor adaptations.

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Adaptations in kinematic and kinetic measurements have been demonstrated to occur in response to dynamic perturbations in the environment via feedback (e.g., reflexes) and feedforward (anticipatory) mediated mechanisms. Generalization of motor adaptations has been found to occur between the limbs, a process called interlimb transfer. Few studies have explored this phenomenon in the lower limbs and none have yet to elucidate whether the response to manipulation of the dynamic properties of one limb during a walking task will transfer to the other limb. This study aimed to determine whether locomotor adaptations to a velocity-dependent force field in one (trained) leg will transfer to the contralateral (test) leg during unipedal walking. It is expected that neuromuscular adaptations to force perturbations in the trained leg during walking will transfer to the contralateral test leg via generalization of anticipatory adaptive strategies. Twenty able-bodied, right leg dominant, adults walked unipedally in the Lokomat robotic gait orthosis, which applied velocity-dependent resistance to the legs. The amount of resistance was scaled to 10% percent of each individual’s maximum voluntary contraction of the hip flexors. Electromyography and kinematics of the lower limb were recorded. All subjects were tested for transfer of motor adaptations from the right leg to the left leg. Catch trials, consisting of the unexpected removal of resistance, were presented after the first step with resistance and after a period of adaptation to determine if there were any after-effects. The time course of adaptation in hip kinematics showed no significant differences between the legs. Catch trials of the lower limb kinematics were compared within and between the legs using a 2 by 2 repeated measures ANOVA. There was a main effect for time (p
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Adding resistance to the legs during walking increases swing phase muscle activity, presumably through load-sensitive flexor muscle feedback pathways. However, increased muscle activity could also be due to the changes in lower limb kinematics that accompany resistance. Thus, the purpose of this study is to evaluate the contribution of resistance and knee pattern manipulations to muscle responses during force perturbations. The natural kinematic pattern associated with resistance was determined as subjects walked with the Lokomat applying resistances of 0%, 5% and 10% of their maximum voluntary contraction (MVC) to the hip and knee joints of both legs. Walking with increased resistance causes decreased knee flexion during the swing phase and decreased stride frequency. Knee joint data and stride frequencies at these resistance levels were used to create three biofeedback traces, representing three different knee pattern conditions, to be used in the experimental block. Subjects then walked at 9 different combinations of resistance (0%, 5% and 10% MVC) and knee pattern (fast, medium and slow). Leg muscle activity and joint kinematics were recorded and analyzed. Results indicate that both resistance and knee pattern perturbations independently contribute to ongoing swing phase activity in the quadriceps. Analysis of effect sizes indicate that resistance contributes more than the knee pattern manipulation to quadriceps muscle activity. Information arising from both load sensitive and length sensitive afferents could be involved in mediating these responses.

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There are many health complications resulting from manual wheelchair use after spinal cord injury (SCI). Biomechanical and neural control components are critical in teaching wheelchair skills and developing efficient wheeling strategies. Thus, the overall goal of this thesis was to gain a comprehensive understanding of the biomechanics and neural control underlying upper limb movements during manual wheeling.A) Many studies examining the biomechanical and physiological characteristics of manual wheeling have examined able-bodied subjects, however, it is unknown if this data can be applied to manual wheelchair users (MWUs) with SCIs. Thirteen able-bodied subjects and 9 MWUs participated in this study. Kinetic, kinematic, and electromyography (EMG) data were collected while subjects wheeled for several minutes at a self-selected cadence. The MWUs demonstrated different wheeling strategies, significantly larger wrist range of motion, larger average forces, larger percentage of the wheeling strategy spent in propulsion and larger push angles. These differences may be key in developing effective wheeling strategies.B) The neural modulation of upper limb movements during manual wheeling was investigated by examining reflex responses to cutaneous nerve stimulation. Cutaneous reflexes from the superficial radial nerve were elicited while subjects wheeled for several minutes at a self-selected cadence. Subjects also performed a symmetrical arm cycling task at the same cadence while receiving nerve stimulation. EMG was recorded from 6 upper limb muscles. The data were divided into cycles and then all cycles were divided into 8 chronological bins. All reflexes occurring from stimuli in a specific bin were averaged together for each individual and then reflex averages were determined for the able-bodied and MWU groups. No significant differences were found in the amount of reflex modulation between the groups, but there were significant differences between tasks in the early latency response of the triceps brachii and the middle latency response of the posterior deltoid. There was also a significant correlation in the amplitude of the early latency reflex of the triceps brachii between amount of modulation and years of manual wheeling experience. Manual wheeling, like arm cycling and walking, demonstrates examples of both phase dependent and task dependent reflex modulation.

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