Unlocking the power of motor imagery: a comprehensive review on its application in alleviating foot pain

Motor imagery, the cognitive process of mentally simulating movements without physical execution, has emerged as a promising intervention for pain management in various conditions. In particular, its application in alleviating foot pain has garnered increasing attention [1]. Foot pain can significantly impact an individual's mobility and quality of life, and traditional pain management approaches may not always provide satisfactory results [2‐4]. Motor imagery offers a non-invasive and potentially effective alternative for addressing foot pain. The concept behind motor imagery is rooted in the understanding that the brain processes imagined movements in a similar manner to actual physical movements. By engaging in mental rehearsal of specific foot movements, individuals can activate and stimulate neural pathways associated with motor control, potentially influencing pain perception and promoting functional recovery [5, 6]. Motor imagery is believed to modulate cortical excitability, influence sensorimotor integration, and enhance body representation, leading to pain reduction and improved motor performance. This review aims to explore the current body of literature on motor imagery and its application in the context of foot pain [7‐10]. By examining studies conducted in this field, we seek to investigate the effectiveness, underlying mechanisms, and potential benefits of motor imagery interventions for individuals experiencing foot pain. We will explore various aspects, including the selection of motor imagery tasks, the duration and frequency of practice sessions, and the integration of motor imagery with other therapeutic approaches [11‐16]. Additionally, this review will delve into the neurophysiological mechanisms underlying the effects of motor imagery on foot pain. Understanding how motor imagery influences pain processing pathways and the neuroplastic changes it may induce can provide valuable insights into its therapeutic potential and guide the development of targeted interventions. By consolidating and analyzing the existing evidence, this review aims to provide clinicians and researchers with a comprehensive overview of the current state of knowledge regarding motor imagery in the context of foot pain [17]. The findings may contribute to the refinement and optimization of motor imagery interventions, ultimately leading to improved pain management strategies and enhanced functional outcomes for individuals suffering from foot pain. Furthermore, the utilization of motor imagery in foot pain management holds promise for individuals who may have limitations or contraindications for traditional physical interventions [18]. This non-invasive technique can be easily incorporated into rehabilitation programs, making it accessible to a wide range of individuals, including those with restricted mobility or sensitivity to touch. Moreover, motor imagery offers a patient-centered approach, empowering individuals to actively participate in their own pain management. By engaging in mental practice, individuals can gain a sense of control [19‐21] over their pain experience and actively contribute to their own recovery [22]. This self-directed approach can enhance motivation, self-efficacy, and overall engagement in the rehabilitation process. The potential benefits of motor imagery extend beyond pain reduction [23]. Studies have suggested that it may also improve motor function, proprioception, and movement accuracy in individuals with foot pain. By rehearsing specific movements in their mind, individuals can enhance their neuromuscular coordination, leading to improved balance, gait, and functional performance. While motor imagery shows promise in the context of foot pain, it is important to acknowledge the need for further research and refinement of protocols. Standardization of motor imagery techniques, optimization of training parameters, and identification of patient-specific factors that influence its effectiveness are crucial areas of investigation. Additionally, exploring the long-term effects and durability of motor imagery interventions in foot pain management is essential for establishing its role in clinical practice.

The present scoping review was conducted following the JBI methodology [24] for scoping reviews. The Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) [25] Checklist for reporting was used.

As presented in the PRISMA 2020-flow diagram (Fig. 1), from 39 records identified by the initial literature searches, 33 were excluded and 6 articles were included.

In Marconi B et al., (2007), eight amputee subjects and nine healthy subjects were examined to investigate the functional reorganization in upper limb motor cortical maps following the loss of a leg. The amputees had undergone leg amputation above the knee several years prior, and all were using prostheses. The study aimed to understand the inhibitory relationship between foot and hand motor cortical representations and explore changes in cortical excitability during motor imagery tasks. The findings revealed that in healthy subjects, motor imagery of ankle movements resulted in a reduction of hand cortical map size and inhibition of hand muscle representations. However, in amputees, imagined ankle movements enhanced the excitability of the hand motor region instead of reducing its map size. Both amputees and healthy subjects exhibited a similar inhibition/facilitation pattern in forearm muscle cortical maps during motor imagery tasks. These results suggest that there is a breakdown in the inhibitory effects between foot and hand cortical representations following leg amputation. The study also highlighted the interlimb coordination mechanisms and the potential hardwired nature of isodirectional coupling between ipsilateral limbs. The findings contribute to our understanding of the neural mechanisms underlying interlimb coordination and provide insights for neurorehabilitation strategies. In summary, the study demonstrates that the loss of a leg induces functional reorganization in upper limb motor cortical maps and disrupts the inhibitory relationship between foot and hand representations. These findings have implications for rehabilitation approaches targeting interlimb coordination.

Coslett HB et al. (2010) study involved five groups of participants: bilateral leg pain (BLP), unilateral left leg pain (LLP), unilateral right leg pain (RLP), pain control (PC), and normal control (NC). Subjects with chronic leg pain and other types of pain were recruited, along with normal controls without chronic pain. The task required participants to indicate whether presented line drawings depicted a right or left foot. Stimuli included various angles of rotation. The results showed that subjects with leg pain were slower and less accurate compared to normal controls, and there was a group by rotation interaction, indicating that leg pain subjects were more affected by maximal rotation stimuli. Pain control subjects also showed slower and less accurate performance, but without a rotation by group interaction. There were rotation by group interactions between RLP and BLP groups and the PC group in the reaction time data. The findings suggested that the impaired performance of leg pain subjects was not solely due to the nonspecific effects of chronic pain. The foot laterality task was found to be a potentially useful adjunct for assessing leg pain. It was a brief task that did not require specialized equipment, and it provided an implicit measure of pain without explicit pain ratings. The task's implicit nature may minimize the influence of psychological factors on pain evaluation. Future evaluations should consider factors like depression, anxiety, and catastrophizing, and further explore the task's potential for assessing malingering or factitious pain disorders. The study also discussed the distinction between implicit and explicit movement representations and the relationship between pain and the sense of agency in action. The experience of chronic pain was suggested to alter the unconscious representation of the body involved in movement planning. The task's findings supported the hypothesis that the representation of imagined movements is mediated by a forward model that anticipates the sensory consequences, including pain. In summary, the foot laterality task showed differences in performance between subjects with leg pain and normal controls, providing a potential measure of pain associated with movement. The task's characteristics and implicit nature make it a promising tool for assessing leg pain in clinical settings.

King R et al. (2015) involved a 35-year-old female with Complex Regional Pain Syndrome (CRPS) who completed a Foot Laterality Recognition Task (LRT). Initially, she used a "3rd person" strategy, imagining another person's feet, and achieved good accuracy and comparable response times for left and right feet. However, when asked to imagine her own feet using a "1st person" strategy, her accuracy remained good but response times were significantly slower for right feet. The patient reported increased pain while using the "1st person" strategy. She then practiced LRTs at home and showed improvement in response times but maintained the same pattern of slower responses for right feet with the "1st person" strategy. Typically, LRTs are used to implicitly facilitate motor imagery, but this patient's alternative strategies challenged the therapeutic rationale. Biomechanical analysis confirmed that the patient's "1st person" strategy resulted in slower response times for awkward postures, especially for right feet, while her preferred "3rd person" strategy showed no such effects. These findings suggested distinct mechanisms for the two strategies. The case highlights that individuals can perform well on LRTs without engaging in motor imagery, which has implications for the use of LRTs in clinical settings. Practitioners should establish processes to carefully select images and analyze for the presence of biomechanical constraints to determine if patients are using a motor strategy or not. Current tools for LRTs may not provide sufficient control or analysis capabilities, and further research on alternative strategies in LRT performance is needed.

Shamsi F et al. (2020) study aimed to investigate whether motor imagery tasks can be distinguished in EEG data under pain-free and pain conditions. Four healthy, right-handed volunteers participated in the study. Painful stimuli were delivered to the dorsum of the left hand using a thermode, and temperatures associated with pain threshold and tolerance were determined for each subject. The main experiment consisted of 12 blocks, alternating between pain-free and under-pain conditions. During under-pain blocks, the thermode was heated to a random temperature within a specific range, while it was set to baseline temperature for pain-free blocks. Subjects performed motor imagery tasks based on visual cues indicating the type of task (right hand, left hand, foot, or tongue). EEG data were recorded using a 32-channel EEG system. The study utilized a functional connectivity-based method to extract functional connectivity graphs from EEG data and classify motor imagery tasks under pain-free and pain conditions. An LSTM artificial neural network was employed for classification. The results showed that the proposed method accurately differentiated pain-free motor imagery tasks from those performed under pain conditions. The classification accuracy was highest in the gamma frequency band. The findings suggest that the method can reliably determine whether motor imagery tasks are performed in pain-free or under pain conditions. Further research could explore the generalizability of the method to other tasks and investigate how the brain processes motor imagery tasks in the presence of pain. The results could contribute to the development of motor imagery-based brain–computer interfaces that adapt to pain conditions without affecting classification performance.

Shepherd M et al. (2020) case report describes the treatment of a 57-year-old female with Complex Regional Pain Syndrome (CRPS) following an ankle injury. The patient experienced progressive sensitivity, pain, and other symptoms in her right foot and ankle. She underwent a nine-month course of physical therapy (PT) that incorporated Graded Motor Imagery (GMI), Pain Neuroscience Education (PNE), and graded exposure. The patient's treatment progression included PNE to provide knowledge and understanding of pain, GMI to address the central nervous system and promote motor imagery, and graded exposure to gradually expose the patient to functional activities. Manual therapy was also integrated to facilitate her transition to weight-bearing and gait activities. The outcomes showed improvements in functional outcomes, pain levels, and psychosocial factors. The patient's functional milestone achievements were sustained at a 2-year follow-up, with no functional deficits related to her foot or ankle. The integration of PNE within GMI and graded exposure created an effective treatment approach, leading to significant improvements in the patient's condition. It is important to note that while GMI has shown promise in the treatment of CRPS, the evidence base is still limited, and more high-quality research is needed. The translation of GMI into clinical practice can also be challenging, requiring careful implementation and adaptation to individual patients. Overall, this case report highlights the potential benefits of combining PNE, GMI, and graded exposure in the treatment of CRPS, emphasizing the importance of addressing both physical and psychosocial factors in managing this complex condition.

Rio EK et al. (2021) study aimed to evaluate implicit motor imagery performance in individuals with Achilles tendinopathy (AT) compared to healthy controls. Participants with symptomatic mid-portion or insertional AT were recruited, and three different study sites implemented slightly different diagnostic criteria. The participants underwent a left–right judgment (LRJ) task using Recognise^©, a program that presents pictures of hands and feet in various positions, and participants had to determine whether the image belonged to the left or right side of the body. The findings showed that there were no significant differences in LRJ performance between unilateral AT cases and healthy controls. The accuracy and reaction time for hand images were similar between the two groups. Regarding foot images, the primary analysis showed worse performance for unilateral AT cases compared to controls, suggesting impaired function of the working body schema for the foot. However, this impairment was not consistent across sensitivity analyses. The unaffected side of AT cases did not differ from the affected side. Exploratory analyses also found no differences between healthy controls and unilateral or bilateral AT cases. These findings suggest that motor imagery performance is not impaired in individuals with AT, at least in terms of LRJ tasks. However, the study had limitations, including not measuring other key outcomes such as proprioception, strength, sensorimotor processing, or cognitive ability. Further research is needed to explore the potential impairments in these areas and their relationship to motor imagery, movement, and disease progression in AT. The study also highlighted the importance of considering factors such as symptom duration, cognitive processes, and sensorimotor integration in understanding motor imagery performance in AT. It is unclear whether the size of implicit motor imagery impairment is relevant to movement dysfunction, pain levels, or response to treatment. The findings do not support the need to measure LRJ performance or target implicit motor imagery in the assessment or treatment of AT. The study's limitations include the combination of data from different study sites and the variability in data collection methods. Future studies should focus on standardizing protocols, including detailed demographic information, and investigating the role of factors such as activity level and chronicity in motor imagery performance in AT.

Motor imagery plays a crucial role in pain perception and rehabilitation, particularly in the context of foot pain. The reviewed articles provide valuable insights into the effects of motor imagery on foot pain and its underlying neural mechanisms. Marconi et al. (2007) explored the functional reorganization of upper limb motor cortical maps in amputees. They found that following leg amputation, there was a breakdown in the inhibitory relationship between foot and hand cortical representations. This suggests that the loss of a leg induces changes in motor cortical maps, potentially impacting interlimb coordination. These findings have implications for neurorehabilitation strategies targeting interlimb coordination in amputees. Coslett et al. [12] investigated the performance of individuals with leg pain in a foot laterality task. The results revealed that individuals with leg pain exhibited slower and less accurate performance compared to healthy controls. This task showed promise as an adjunct measure of pain associated with movement and may have clinical utility in assessing leg pain. The findings also shed light on the relationship between pain, implicit movement representations, and the sense of agency in action. King et al. [13] presented a case study of a patient with Complex Regional Pain Syndrome (CRPS). The patient exhibited distinct motor imagery strategies during a foot laterality task. The case highlighted the importance of analyzing biomechanical constraints and determining whether patients are using motor strategies or alternative approaches. This study emphasized the need for further research on alternative strategies in motor imagery tasks and their implications for clinical applications. Shamsi et al. [14] investigated the feasibility of distinguishing motor imagery tasks performed under pain-free and pain conditions using EEG data. The study employed a functional connectivity-based method and an artificial neural network for classification. The results demonstrated the potential of this approach to accurately differentiate between pain-free and pain-related motor imagery tasks. This research contributes to the development of motor imagery-based brain-computer interfaces that adapt to pain conditions. Shepherd et al. [15] presented a case report on the treatment of a patient with CRPS. The integration of Graded Motor Imagery (GMI), Pain Neuroscience Education (PNE), and graded exposure in the patient's physical therapy resulted in significant improvements in functional outcomes, pain levels, and psychosocial factors. This case report underscores the potential benefits of a multimodal approach in the management of CRPS and highlights the importance of addressing both physical and psychosocial factors in treatment. Collectively, these articles highlight the potential of motor imagery in foot pain management and neurorehabilitation. Motor imagery techniques can induce changes in cortical maps, facilitate interlimb coordination, and provide a measure of pain associated with movement. Furthermore, advances in EEG-based classification methods offer the potential for real-time assessment and adaptation of motor imagery tasks based on pain conditions. Integrating motor imagery approaches, such as GMI and PNE, into comprehensive treatment programs may enhance outcomes for individuals with foot pain conditions. While the reviewed articles provide valuable insights, further research is needed to explore the optimal protocols, individualized approaches, and long-term effects of motor imagery interventions in foot pain management. Future studies should also investigate the impact of factors such as psychological variables, cognitive processes, and sensorimotor integration on motor imagery performance and its clinical implications. Overall, motor imagery holds promise as a non-invasive, adjunctive approach for foot pain management, with potential applications in both clinical and rehabilitation settings.

This review emphasizes the potential of motor imagery in foot pain management. Motor imagery holds promise as a non-invasive approach in clinical and rehabilitation settings.

In conclusion, the reviewed articles provide evidence on the role of motor imagery in foot pain. The findings suggest that individuals with foot pain may experience impairments in motor imagery abilities, such as reduced accuracy and slower response times. These impairments may be related to functional reorganization in the motor cortical maps following leg amputation or the presence of chronic pain. However, the results are not consistent across all studies, highlighting the need for further research in this area. The implications for clinical practice include the use of motor imagery tasks as assessment tools, the development of individualized treatment plans targeting motor imagery impairments, and the integration of motor imagery interventions alongside other evidence-based treatments. Patient education, interdisciplinary collaboration, and regular monitoring of progress are also important considerations. Overall, while motor imagery shows promise as a tool for understanding and managing foot pain, more research is needed to establish optimal protocols, explore long-term effects, and determine the specific patient populations that may benefit most from motor imagery interventions.