Towards efficient motor imagery interventions after lower-limb amputation.

BACKGROUND: The therapeutic benefits of motor imagery (MI) are now well-established in different populations of persons suffering from central nervous system impairments. However, research on similar efficacy of MI interventions after amputation remains scarce, and experimental studies were primarily designed to explore the effects of MI after upper-limb amputations. OBJECTIVES: The present comparative study therefore aimed to assess the effects of MI on locomotion recovery following unilateral lower-limb amputation. METHODS: Nineteen participants were assigned either to a MI group (n = 9) or a control group (n = 10). In addition to the course of physical therapy, they respectively performed 10 min per day of locomotor MI training or neutral cognitive exercises, five days per week. Participants' locomotion functions were assessed through two functional tasks: 10 m walking and the Timed Up and Go Test. Force of the amputated limb and functional level score reflecting the required assistance for walking were also measured. Evaluations were scheduled at the arrival at the rehabilitation center (right after amputation), after prosthesis fitting (three weeks later), and at the end of the rehabilitation program. A retention test was also programed after 6 weeks. RESULTS: While there was no additional effect of MI on pain management, data revealed an early positive impact of MI for the 10 m walking task during the pre-prosthetic phase, and greater performance during the Timed Up and Go Test during the prosthetic phase. Also, a lower proportion of participants still needed a walking aid after MI training. Finally, the force of the amputated limb was greater at the end of rehabilitation for the MI group. CONCLUSION: Taken together, these data support the integration of MI within the course of physical therapy in persons suffering from lower-limb amputations.

Implicit and explicit motor imagery ability after SCI: Moving the elbow makes the difference.

Cervical spinal cord injury (SCI) causes dramatic sensorimotor deficits that restrict both activity and participation. Restoring activity and participation requires extensive upper limb rehabilitation focusing elbow and wrist movements, which can include motor imagery. Yet, it remains unclear whether MI ability is impaired or spared after SCI. We investigated implicit and explicit MI ability in individuals with C6 or C7 SCI (SCIC6 and SCIC7 groups), as well as in age- and gender-matched controls without SCI. Inspired by previous studies, implicit MI evaluations involved hand laterality judgments, hand orientation judgments (HOJT) and hand-object interaction judgments. Explicit MI evaluations involved mental chronometry assessments of physically possible or impossible movements due to the paralysis of upper limb muscles in both groups of participants with SCI. HOJT was the paradigm in which implicit MI ability profiles differed the most between groups, particularly in the SCIC6 group who had impaired elbow movements in the horizontal plane. MI ability profiles were similar between groups for explicit MI evaluations, but reflected task familiarity with higher durations in the case of unfamiliar movements in controls or attempt to perform movements which were no longer possible in persons with SCI. Present results, obtained from a homogeneous population of individuals with SCI, suggest that people with long-term SCI rely on embodied cognitive motor strategies, similar to controls. Differences found in behavioral response pattern during implicit MI mirrored the actual motor deficit, particularly during tasks that involved internal representations of affected body parts.

Human local field potentials in motor and non-motor brain areas encode upcoming movement direction.

Limb movement direction can be inferred from local field potentials in motor cortex during movement execution. Yet, it remains unclear to what extent intended hand movements can be predicted from brain activity recorded during movement planning. Here, we set out to probe the directional-tuning of oscillatory features during motor planning and execution, using a machine learning framework on multi-site local field potentials (LFPs) in humans. We recorded intracranial EEG data from implanted epilepsy patients as they performed a four-direction delayed center-out motor task. Fronto-parietal LFP low-frequency power predicted hand-movement direction during planning while execution was largely mediated by higher frequency power and low-frequency phase in motor areas. By contrast, Phase-Amplitude Coupling showed uniform modulations across directions. Finally, multivariate classification led to an increase in overall decoding accuracy (>80%). The novel insights revealed here extend our understanding of the role of neural oscillations in encoding motor plans.

Anodal transcranial direct current stimulation does not enhance the effects of motor imagery training of a sequential finger-tapping task in young adults.

When applied over the primary motor cortex (M1), anodal transcranial direct current stimulation (a-tDCS) could enhance the effects of a single motor imagery training (MIt) session on the learning of a sequential finger-tapping task (SFTT). This study aimed to investigate the effect of a-tDCS on the learning of an SFTT during multiple MIt sessions. Two groups of 16 healthy young adults participated in three consecutive MIt sessions over 3 days, followed by a retention test 1 week later. They received active or sham a-tDCS during a MIt session in which they mentally rehearsed an eight-item complex finger sequence with their left hand. Before and after each session, and during the retention test, they physically repeated the sequence as quickly and accurately as possible. Both groups (i) improved their performance during the first two sessions, showing online learning; (ii) stabilised the level they reached during all training sessions, reflecting offline consolidation; and (iii) maintained their performance level one week later, showing retention. However, no significant difference was found between the groups, regardless of the MSL stage. These results emphasise the importance of performing several MIt sessions to maximise performance gains, but they do not support the additional effects of a-tDCS.

Brain plasticity underlying sleep-dependent motor consolidation after motor imagery.

Motor imagery can, similarly to physical practice, improve motor performance through experience-based plasticity. Using magnetoencephalography, we investigated changes in brain activity associated with offline consolidation of motor sequence learning through physical practice or motor imagery. After an initial training session with either physical practice or motor imagery, participants underwent overnight consolidation. As control condition, participants underwent wake-related consolidation after training with motor imagery. Behavioral analyses revealed that overnight consolidation of motor learning through motor imagery outperformed wake-related consolidation (95% CI [0.02, 0.07], P < 0.001, RP2 = 0.05). As regions of interest, we selected the generators of event-related synchronization/desynchronization of alpha (8-12 Hz) and beta (15-30 Hz) oscillations, which predicted the level of performance on the motor sequence. This yielded a primary sensorimotor-premotor network for alpha oscillations and a cortico-cerebellar network for beta oscillations. The alpha network exhibited increased neural desynchronization after overnight consolidation compared to wake-related consolidation. By contrast, the beta network exhibited an increase in neural synchronization after wake-related consolidation compared to overnight consolidation. We provide the first evidence of parallel brain plasticity underlying behavioral changes associated with sleep-dependent consolidation of motor skill learning through motor imagery and physical practice.

Comparative Efficacy of Robotic and Manual Massage Interventions on Performance and Well-Being: A Randomized Crossover Trial.

BACKGROUND: Manual massage (MM) interventions can improve psychophysiological states of relaxation and well-being. In this context, robotic massage (RM) represents a promising, but currently understudied, solution. HYPOTHESIS: Both MM and RM would improve flexibility of the hamstrings and lumbopelvic muscles and promote a psychophysiological state of relaxation through decreased sympathetic activity. STUDY DESIGN: Single-blind randomized crossover trial. LEVEL OF EVIDENCE: Level 2. METHODS: A total of 21 participants experienced 2 massage interventions targeting back soft tissues. During a first condition, the intervention was performed by a physical therapist, whereas during a second condition the intervention was performed by a robot. We collected objective and subjective indexes of performances and well-being before and after each massage intervention. We also collected physical therapists' self-reports of perceived fatigue, tension, and ability to maintain the massage routine. RESULTS: Skin conductance decreased from the pretest to the posttest in both conditions (partial R2 = 0.44, 95% CI [0.30, 1.00], P < 0.01), although the decrease was more pronounced after MM. Whereas both interventions were associated with improved subjective sensations, eg, pain, warmth, well-being (partial R2 = 0.08, 95% CI [0.06, 1.00], P < 0.01), MM yielded additional benefits compared with RM. The physical therapist reported greater fatigue and tension and reduced perceived massage efficiency along with repeated massage interventions. MM outperformed RM to elicit a psychophysiological state of relaxation. CONCLUSION: RM exhibited a pattern of changes comparable with that of MM, for both objective and subjective indexes of relaxation and well-being. CLINICAL RELEVANCE: RM could represent a prophylactic option to prevent the onset of counterproductive fatigability in physical therapists.

Inter-task transfer of force gains is facilitated by motor imagery.

Introduction: There is compelling evidence that motor imagery (MI) contributes to improve muscle strength. While strong effects have been observed for finger muscles, only few experiments with moderate benefits were conducted within applied settings targeting large upper or lower limb muscles. The aim of the present study was therefore to extend the investigation of embedded MI practice designed to improve maximal voluntary strength on a multi-joint dynamic exercise involving the lower limbs. Additionally, we tested whether targeting the content of MI on another movement than that physically performed and involving the same body parts might promote inter-task transfer of strength gains. Methods: A total of 75 participants were randomly assigned into three groups who underwent a physical training on back squat. During inter-trial recovery periods, a first MI group (n = 25) mentally rehearsed the back squat, while a second MI group (n = 25) performed MI of a different movement involving the lower limbs (deadlift). Participants from the control group (n = 25) completed a neutral cognitive task during equivalent time. Strength and power gains were assessed ecologically using a velocity transducer device at 4 different time periods. Results: Data first revealed that participants who engaged in MI of the back squat improved their back squat performance (p < 0.03 and p < 0.01, respectively), more than the control group (p < 0.05), hence supporting the positive effects of MI on strength. Data further supported the inter-task transfer of strength gains when MI targeted a movement that was not physically trained (p = 0.05). Discussion: These findings provide experimental support for the use of MI during physical training sessions to improve and transfer force development.

A Quantitative Investigation of Mental Fatigue Elicited during Motor Imagery Practice: Selective Effects on Maximal Force Performance and Imagery Ability.

In the present study, we examined the development of mental fatigue during the kinesthetic motor imagery (MI) of isometric force contractions performed with the dominant upper limb. Participants (n = 24) underwent four blocks of 20 MI trials of isometric contractions at 20% of the maximal voluntary contraction threshold (20% MVCMI) and 20 MI trials of maximal isometric contractions (100% MVCMI). Mental fatigue was assessed after each block using a visual analogue scale (VAS). We assessed maximal isometric force before, during and after MI sessions. We also assessed MI ability from self-report ratings and skin conductance recordings. Results showed a logarithmic pattern of increase in mental fatigue over the course of MI, which was superior during 100% MVCMI. Unexpectedly, maximal force improved during 100% MVCMI between the 1st and 2nd evaluations but remained unchanged during 20% MVCMI. MI ease and vividness improved during 100% MVCMI, with a positive association between phasic skin conductance and VAS mental fatigue scores. Conversely, subjective measures revealed decreased MI ability during 20% MVCMI. Mental fatigue did not hamper the priming effects of MI on maximal force performance, nor MI's ability for tasks involving high physical demands. By contrast, mental fatigue impaired MI vividness and elicited boredom effects in the case of motor tasks with low physical demands.

Revisiting Motor Imagery Guidelines in a Tropical Climate: The Time-of-Day Effect.

(1) Background: Motor imagery (MI) is relevantly used to improve motor performance and promote rehabilitation. As MI ability and vividness can be affected by circadian modulation, it has been proposed that MI should ideally be performed between 2 p.m. and 8 p.m. Whether such a recommendation remains effective in a hot and humid environment, such as a tropical climate, remains unknown. (2) Methods: A total of 35 acclimatized participants completed a MI questionnaire and a mental chronometry test at 7 a.m., 11 a.m., 2 p.m., and 6 p.m. Visual (VI) and kinesthetic imagery (KI) abilities, as well as temporal congruence between actual walking and MI, were collected. Ambient temperature, chronotypes, thermal comfort, affect, and fatigue were also measured. (3) Results: VI scores were higher at 6 p.m. than at 7 a.m., 11 a.m., and 2 p.m., and temporal congruence was higher at 6 p.m. than at 7 a.m. Comfort, thermal sensation, and positive affect scores were higher at 7 a.m. and 6 p.m. (4) Conclusion: Data support greater imagery ability and accuracy when participants perceive the environment as more pleasant and comfortable. MI guidelines typically provided in neutral climates should therefore be adapted to tropical climates, with MI training sessions ideally scheduled in the late afternoon.

Timing-specific patterns of cerebral activations during motor imagery: A case study of the expert brain signature.

Brain activations elicited during motor imagery (MI) in experts are typically reduced compared to novices, which is interpreted as a neurophysiological correlate of increased neural efficiency. However, the modulatory effects of MI speed on expertise-related differences in brain activation remains largely unknown. In the present pilot study, we compared the magnetoencephalographic (MEG) correlates of MI in an Olympic medallist and an amateur athlete under conditions of slow, real-time and fast MI. Data revealed event-related changes in the time course of alpha (8-12 Hz) power of MEG oscillations, for all timing conditions. We found that slow MI was associated with a corollary increase in neural synchronization, in both participants. Sensor-level and source-level analyses however disclosed differences between the two expertise levels. The Olympic medallist achieved greater activation of cortical sensorimotor networks than the amateur athlete, particularly during fast MI. Fast MI elicited the strongest event-related desynchronization of alpha oscillations, which was generated from cortical sensorimotor sources in the Olympic medallist, but not in the amateur athlete. Taken together, data suggest that fast MI is a particularly demanding form of motor cognition, putting a specific emphasis on cortical sensorimotor networks to achieve the formation of accurate motor representations under demanding timing constraints.

Anodal tDCS does not enhance the learning of the sequential finger-tapping task by motor imagery practice in healthy older adults.

Background: Motor imagery practice (MIP) and anodal transcranial direct current stimulation (a-tDCS) are innovative methods with independent positive influence on motor sequence learning (MSL) in older adults. Objective: The present study investigated the effect of MIP combined with a-tDCS over the primary motor cortex (M1) on the learning of a finger tapping sequence of the non-dominant hand in healthy older adults. Methods: Thirty participants participated in this double-blind sham-controlled study. They performed three MIP sessions, one session per day over three consecutive days and a retention test 1 week after the last training session. During training / MIP, participants had to mentally rehearse an 8-element finger tapping sequence with their left hand, concomitantly to either real (a-tDCS group) or sham stimulation (sham-tDCS group). Before and after MIP, as well as during the retention test, participants had to physically perform the same sequence as fast and accurately as possible. Results: Our main results showed that both groups (i) improved their performance during the first two training sessions, reflecting acquisition/on-line performance gains, (ii) stabilized their performance from one training day to another, reflecting off-line consolidation; as well as after 7 days without practice, reflecting retention, (iii) for all stages of MSL, there was no significant difference between the sham-tDCS and a-tDCS groups. Conclusion: This study highlights the usefulness of MIP in motor sequence learning for older adults. However, 1.5 mA a-tDCS did not enhance the beneficial effects of MIP, which adds to the inconsistency of results found in tDCS studies. Future work is needed to further explore the best conditions of use of tDCS to improve motor sequence learning with MIP.

Personality traits affect anticipatory stress vulnerability and coping effectiveness in occupational critical care situations.

The present study aimed at investigating the influence of personality on both anticipatory stress vulnerability and the effectiveness of coping strategies in an occupational stressful context. Following assessment of individual personality traits (Big Five Inventory), 147 volunteers were exposed to the anticipation of a stressful event. Anxiety and cardiac reactivity were assessed as markers of vulnerability to anticipatory stress. Participants were then randomly assigned to three groups and subjected to a 5-min intervention: relaxation breathing, relaxation breathing combined with cardiac biofeedback, and control. The effectiveness of coping interventions was determined through the cardiac coherence score achieved during the intervention. Higher neuroticism was associated with higher anticipatory stress vulnerability, whereas higher conscientiousness and extraversion were related to lower anticipatory stress vulnerability. Relaxation breathing and biofeedback coping interventions contributed to improve the cardiac coherence in all participants, albeit with greater effectiveness in individuals presenting higher score of openness to experience. The present findings demonstrated that personality traits are related to both anticipatory stress vulnerability and effectiveness of coping interventions. These results bring new insights into practical guidelines for stress prevention by considering personality traits. Specific practical applications for health professionals, who are likely to manage stressful situations daily, are discussed.

Corticomotor Plasticity Underlying Priming Effects of Motor Imagery on Force Performance.

The neurophysiological processes underlying the priming effects of motor imagery (MI) on force performance remain poorly understood. Here, we tested whether the priming effects of embedded MI practice involved short-term changes in corticomotor connectivity. In a within-subjects counterbalanced experimental design, participants (n = 20) underwent a series of experimental sessions consisting of successive maximal isometric contractions of elbow flexor muscles. During inter-trial rest periods, we administered MI, action observation (AO), and a control passive recovery condition. We collected electromyograms (EMG) from both agonists and antagonists of the force task, in addition to electroencephalographic (EEG) brain potentials during force trials. Force output was higher during MI compared to AO and control conditions (both p < 0.01), although fatigability was similar across experimental conditions. We also found a weaker relationship between triceps brachii activation and force output during MI and AO compared to the control condition. Imaginary coherence topographies of alpha (8−12 Hz) oscillations revealed increased connectivity between EEG sensors from central scalp regions and EMG signals from agonists during MI, compared to AO and control. Present results suggest that the priming effects of MI on force performance are mediated by a more efficient cortical drive to motor units yielding reduced agonist/antagonist coactivation.

Effects of relaxing breathing paired with cardiac biofeedback on performance and relaxation during critical simulated situations: a prospective randomized controlled trial.

BACKGROUND: Active participation in high-fidelity simulation remains stressful for residents. Increased stress levels elicited during such simulation impacts performance. We tested whether relaxing breathing, paired or not with cardiac biofeedback, could lead to enhanced performance of residents during simulation. METHODS: This randomized pilot study involved the fifth-year anesthesiology and critical care residents who participated in high-fidelity at Lyon medical simulation center in 2019. Residents were randomized into three parallel interventions: relaxing breathing, relaxing breathing paired with cardiac biofeedback, and control. Each intervention was applied for five minutes immediately after the scenario briefing. The primary endpoint was the overall performance during the simulation rated by two blinded independent investigators. The secondary endpoints included component scores of overall performance and changes in psychological states. RESULTS: Thirty-four residents were included. Compared to the control group, residents in the relaxing breathing (+ 7%, 98.3% CI: 0.3 to 13.7, P = 0.013) and relaxing breathing paired with cardiac biofeedback (+ 8%, 98.3% CI: 0.82 to 14.81, P = 0.009) groups had a higher overall performance score. Following the interventions, compared to the control group, stress level was lower when participants had performed relaxing breathing alone (P = 0.029) or paired with biofeedback (P = 0.035). The internal relaxation level was higher in both the relaxing breathing alone (P = 0.016) and paired with biofeedback groups (P = 0.035). CONCLUSIONS: Performing five minutes of relaxing breathing before the scenario resulted in better overall simulation performance. These preliminary findings suggest that short breathing interventions are effective in improving performance during simulation. TRIAL REGISTRATION: The study protocol was retrospectively registered on clinicaltrials.gov ( NCT04141124 , 28/10/2019).

The Role of Motor Inhibition During Covert Speech Production.

Covert speech is accompanied by a subjective multisensory experience with auditory and kinaesthetic components. An influential hypothesis states that these sensory percepts result from a simulation of the corresponding motor action that relies on the same internal models recruited for the control of overt speech. This simulationist view raises the question of how it is possible to imagine speech without executing it. In this perspective, we discuss the possible role(s) played by motor inhibition during covert speech production. We suggest that considering covert speech as an inhibited form of overt speech maps naturally to the purported progressive internalization of overt speech during childhood. We further argue that the role of motor inhibition may differ widely across different forms of covert speech (e.g., condensed vs. expanded covert speech) and that considering this variety helps reconciling seemingly contradictory findings from the neuroimaging literature.

Evaluating the Effect of the Combat Style Congruency on Performance and Fatigability in Brazilian Jiu-Jitsu: A Pilot Study.

PURPOSE: Brazilian jiu-jitsu is a martial art emphasizing ground combat with multiple ramifications to self-defense and military training. Some Brazilian jiu-jitsu athletes prefer fighting on their back (Guardadors), while others preferentially adopt a standing or kneeling position (Passadors). Whether the combat scenario leading to adopt a preferential or nonpreferential combat style influences the combat outcomes remains unexplored. METHODS: In a counterbalanced design, 13 athletes performed simulated combats from either a congruent or incongruent scenario with regard to their preferred combat style. We collected combat scores from the official ranking system and measured upper- and lower-limb explosive performance before and after the combats, as well as the rating of perceived exertion and blood lactate concentrations to index fatigability. RESULTS: Passadors had greater grip strength than Guardadors (Rp2 = .23, P = .03), whereas Guardadors showed higher lower-limb performance (Rp2 = .16, P = .05). When forced to combat as Passadors, Guardadors exhibited greater grip-strength impairment and a greater increase in perceived exertion (Rp2 = .12, P = .04; Rp2 = .15, P = .05, respectively). They also had higher blood lactate concentrations (Rp2 = .19, P = .02). CONCLUSION: Guardadors exhibited greater fatigability after fighting from an incongruent combat situation compared to Passadors, presumably due to greater difficulties to adjust to the loss of initiative when restricted to a primarily defensive role. Future studies should examine how combat style congruency might affect performance and influence recovery strategies during high-level competitive events.

Motor imagery and action observation following immobilization-induced hypoactivity: A narrative review.

BACKGROUND: In sports, the risk of pathology or event that leads to an injury, a cessation of practice or even to an immobilization is high. The subsequent reduction of physical activity, or hypoactivity, induces neural and muscular changes that adversely affect motor skills and functional motor rehabilitation. Because the implementation of physical practice is difficult, if not impossible, during and immediately following injury or immobilization, complementary techniques have been proposed to minimize the deleterious impact of hypoactivity on neuromuscular function. OBJECTIVE: The current narrative review aimed to discuss the contributions of motor imagery and action observation, which enhance motor (re)learning and induce neural adaptations in both healthy individuals and injured athletes. METHODS: Online literature research for studies of the effects of motor imagery, action observation and their combination on hypoactivity, extracting relevant publications within the last decade (2009-2020). RESULTS: From published studies and the authors' knowledge of both motor imagery and action observation, some elements are provided for developing applied protocols during and after the immobilization period. Such interventions consist of associating congruent action observation with kinesthetic motor imagery of different movements, organized in increasing difficulty. The aim is to maintain motor functions and promote motor relearning by activating sensorimotor cortical areas and corticomotor pathways of the injured effector. CONCLUSION: This narrative review supports the implementation of combined motor imagery and action observation protocols in the context of sports rehabilitation.

Translation and validation of the movement imagery questionnaire-3 second French version.

INTRODUCTION: Motor imagery (MI) can be defined as the mental simulation of an action without performing it. Its effectiveness can be substantially influenced by imagery ability, and it is currently accepted that three main modalities are used in MI (kinaesthetic imagery, and internal or external visual imageries). In the context of rehabilitation, MI combined with physical therapy is further known to facilitate functional improvements, and promote cortical reorganization and long-term recovery. This study aimed to test the reproducibility and the validity of constructs (internal consistency and factorial structure) of the Movement Imagery Questionnaire-3 Second French version (MIQ-3Sf). METHOD: The internal consistency as well as the validity of constructs and the test-retest inter-rate reproducibility of the MIQ-3Sf was examined, in 553 participants, for the kinaesthetic and visual items. RESULTS: The composite reliability scores (≥0.92) and the intraclass correlation coefficients (>0.88) for the kinaesthetic, internal visual and external visual imagery subscales revealed satisfactory internal consistency and reproducibility. Moreover, Pearson correlations revealed a strong relationship between the MIQ-3Sf and the MIQ-3f. CONCLUSIONS: /Implications. The MIQ-3Sf can be considered as a valid, reliable and useful questionnaire for examining MI ability in the context of rehabilitation.

Combining proactive transcranial stimulation and cardiac biofeedback to substantially manage harmful stress effects.

BACKGROUND: Previous studies have identified the dorsolateral prefrontal cortex (dlPFC) as a core region in cognitive emotional regulation. Transcranial direct current stimulations of the dlPFC (tDCS) and heart-rate variability biofeedback (BFB) are known to regulate emotional processes. However, the effect of these interventions applied either alone or concomitantly during an anticipatory stress remains unexplored. OBJECTIVE: The study investigated the effect of anodal tDCS and BFB, alone or combined, on psychophysiological stress responses and cognitive functioning. METHODS: Following a stress anticipation induction, 80 participants were randomized into four groups and subjected to a 15-min intervention: neutral video viewing (ctrl), left dlPFC anodal tDCS (tdcs), heart-rate variability biofeedback (bfb), or a combined treatment (bfb + tdcs). Participants were then immediately confronted with the stressor, which was followed by an assessment of executive functions. Psychophysiological stress responses were assessed throughout the experiment (heart rate, heart-rate variability, salivary cortisol). RESULTS: The tdcs did not modulate stress responses. Compared with both ctrl and tdcs interventions, bfb reduced physiological stress and improved executive functions after the stressor. The main finding revealed that bfb + tdcs was the most effective intervention, yielding greater reduction in psychological and physiological stress responses than bfb. CONCLUSIONS: Combining preventive tDCS with BFB is a relevant interventional approach to reduce psychophysiological stress responses, hence offering a new and non-invasive treatment of stress-related disorders. Biofeedback may be particularly useful for preparing for an important stressful event when performance is decisive.

Revisiting the acute effects of resistance exercise on motor imagery ability.

Motor imagery (MI) shares psychological and physiological similarities with the physical practice of the same action. Yet, it remains unclear whether fatigue elicited by exercise impairs MI ability. Fourteen participants performed MI of a self-paced walking sequence of 22 m before and after a resistance exercise eliciting muscle fatigue from upper and lower limbs, selectively. We indexed MI ability using psychometric and behavioral methods. Electromyography of the quadriceps was also recorded during physical practice trials of the walking sequence. For both experimental conditions, we recorded improved temporal congruence between MI and physical practice of the walking sequence (9.89 %, 95 % CI [7.03, 12.75], p < 0.01). Vividness decreased immediately after the fatiguing exercise (6.35 %, 95 % CI [5.18, 7.51], p < 0.05), before rapidly returning to pre-fatigue values during recovery trials. The results challenge the hypothesis of an effect of acute fatigue elicited by a resistance exercise on MI ability, i.e. restricted to MI tasks focusing fatigued effectors. The beneficial effects of fatigue conditions on the psychometric and behavioral indexes of MI ability are discussed in the broader context of psychobiological fatigue models linking perceived exertion with the reallocation of attentional resources. The general perception of fatigue, rather than local muscle fatigue, appeared linked to the acute effects of resistance exercise on MI ability.