ECSS Paris 2023: OP-BM01
INTRODUCTION: Motor imagery (MI) is the mental representation of movement without concurrent execution. The fact that MI can lead to similar brain cortical areas activation than actual movement makes it a valuable training for patients with motor impairments. The effectiveness of MI training is influenced by the quality of mental representation (i.e. MI vividness), that is further correlated to corticospinal excitability measurements [1]. MI can be enhanced by simultaneous movement [2], but when movement is impossible, tendon vibration (TV) may be an alternative to provide movement-like proprioceptive feedbacks. This study investigated whether combining MI with TV is likely to enhance MI vividness. METHODS: Ten healthy participants (8 males and 2 females, 24.9 ± 6.3 years) completed one test session. Transcranial magnetic stimulation (TMS) was used to elicit motor-evoked potentials in the right hand’s flexor carpi radialis muscle at increasing stimulating intensity during four conditions: at rest (REST), during the mental representation of a maximal right wrist flexion (MI), during the application of tendon vibration on the right wrist (TV) and during the combination of MI and TV (MI+TV). At each of the 6 tested TMS intensities, MI, and TV and MI+TV trials were applied for 10 repetitions lasting 6s with 6s of rest in-between. The area under the input-output curve was computed to quantify corticospinal excitability during each condition. RESULTS: The MI and VT conditions exhibited increases in corticospinal excitability with magnitude of 139.83% ± 124.30% (p<0.05) and 142.42% ± 75.20% (p<0.01) when compared to REST, respectively, and with no difference between MI and TV conditions (p=0.99). Moreover, the MI+TV condition showed a 295.23% ± 153.30% increase in corticospinal excitability when compared to REST (p<0.01), with values reached being greater than those observed for MI (p<0.01) and TV (p<0.01). CONCLUSION: The key finding of this study is that combining TV and MI allowed to increase corticospinal excitability compared to MI alone, suggesting that the application of TV improved MI vividness. Overall, these results suggest that TV could therefore strengthen MI effects in individuals unable to perform voluntary movements, likely through TV-related proprioceptive feedbacks, offering a promising non-invasive approach for motor rehabilitation. REFERENCES: [1] Guillot et al., International Review of Sport and Exercise Psychology, 2024 [2] Williams et al., Behavioural brain research, 2012
Read CV Vincent MALEJACECSS Paris 2023: OP-BM01
INTRODUCTION: In everyday life, motor and cognitive demands are intricately related. Effort is the intentional mobilization of resources towards a task, and its perception is the awareness of this mobilization. Current experimental paradigms investigating effort and its perception isolate motor and cognitive demands (1). As integrative views of effort considering the mobilization of motor and cognitive resources are emerging (2), experimental paradigms manipulating both types of demands are needed to better understand how each domain impact effort and its perception. This study aimed to develop an experimental paradigm to manipulate both motor and cognitive demands during psychomotor tasks. We hypothesized that effort perception would increase with both types of demands. METHODS: Two experiments were done (n=20 each), during which participants completed bimanual psychomotor tasks with computer mice (exp 1) or handgrip dynamometers (exp 2). The task consisted of identifying arrow directions displayed on a computer screen. In both experiments, there were three levels of cognitive demand; easy: identify arrow directions displayed in the center of the monitor (congruent responses), moderate: identify the opposite arrow direction (50% incongruent responses), difficult: identify opposite arrow direction (50% incongruent responses) displayed on the left and right sides of the screen (~50% of arrows pointing away from their spatial location). In exp 2, participants performed the same task and responded by squeezing either hands on handgrip dynamometers at one of two levels of motor demands: 5% and 30% of maximal voluntary force. Performance was measured with accuracy (correct vs incorrect responses) and response time (time taken for response validation). Effort perception was measured with visual analogue scales after each 30-s block. RESULTS: In exp 1, participants reported greater perceived effort with higher cognitive demand (main effect of cognitive demand, p<.001). In exp 2, participants reported greater perceived effort with higher motor and cognitive demands (main effects of motor and cognitive demands, p’s<.001). In both experiments, accuracy decreased (main effects of motor and cognitive demands, p’s<.001) while response time increased (main effects of motor and cognitive demands, p’s<.048) with both types of demands. CONCLUSION: Increasing both motor and cognitive demands lead to greater perceived effort This experimental paradigm can be used in future studies to explore effort and its perception by manipulating the motor and cognitive demands of the task. From a fundamental perspective, this will be useful to explore the neural correlates of effort and its perception. From a clinical perspective, this paradigm can be adapted into rehabilitation programs of clinical populations with cognitive and motor deficits, such as stroke patients. (1) Chong et al (2017). PLoS Biology, 15(2), e1002598 (2) Halperin & Vigotsky (2024). Sports Medicine, 54(8), 2019-2032
Read CV Maxime BergevinECSS Paris 2023: OP-BM01
INTRODUCTION: Perturbation-based gait training effectively improves fall resisting skills, which are retainable over years (1) and can be partly transferred to real world scenarios (2). An essential component to recover balance following trip-like perturbations is the ability to increase the base of support (BoS) via modulation of leg-extensor muscular output. We aimed to develop a mechatronic system which unpredictably perturbs knee-extensor muscular output during gait and prove its effectiveness to enhance trip-resisting skills via repeated perturbations in healthy young adults. METHODS: 20 young adults performed a functional gait training session on a treadmill using an electromagnetic resistive knee brace perturbing neuromuscular control during the swing phase of the gait cycle. Gait perturbations were conducted via a combination of unpredictable and sustained perturbations within a period of 20 min walking. Transfer to recovery actions in trip-like perturbation was assessed using pulling forces at subjects’ ankle either in early swing (elevating strategy: ELE; n=10) or mid swing phase (lowering strategy: LOW; n=10). Twenty matched controls experienced the transfer task either with elevating or lowering strategies. 3D motion capture was used to analyse joint kinematics and centre of mass (CoM) trajectories, allowing for the calculations of margin of stability (MoS) and BoS. Leg-extensor muscular activity was determined during walking using EMG and normalised to MVC. RESULTS: Knee muscular perturbations during walking led to a reduction in MoS and BoS (more instable body configuration) in relation to normal walking and caused a change in neuromuscular control by increasing EMG activity in the monoarticular knee extensors during swing phase and in the plantar flexors during push-off (p<.05). In the transfer tripping-task, the LOW group showed a higher MoS and BoS at touchdown of the perturbed leg in relation to the control group (p<.05) and required less recovery steps to reach positive MoS values following perturbation. Statistical parametric mapping identified differences in lower limb joint kinematics following a trip-like perturbation, with greater knee extension angles for LOW compared to control (p<.05). There were no differences between ELE and controls in the analysed parameters during tripping. CONCLUSION: Unpredictable and sustained perturbations at the knee during walking lead to adaptive changes in balance recovery responses which were transferred to trip-like perturbations, hence highlighting the relevance of knee extensor neuromuscular function for fall resilience. However, due to differences in neuromuscular control between elevating and lowering strategies, the effectiveness of knee extensor perturbation-based exercises in transferring locomotor adaptive changes to various trip scenarios seems to be limited. REFERENCES: 1) Epro et al., J Neurophysiol, 2018 2) Werth et al., Sci Rep, 2022
Read CV Mateus Albuquerque PlacidoECSS Paris 2023: OP-BM01