Nervous system excitability and joint stiffness following short-term dynamic ankle immobilization

Abstract

Joint immobilization has been demonstrated to modify neural excitability in subsets of healthy populations, leading to disinhibition of cortical and reflexive pathways. However, these findings may have limited clinical application as most models have investigated casting and rigid immobilization, while many musculoskeletal injuries often utilize dynamic immobilization devices such as boot immobilizers and pneumatic splints that allow for modified ambulation. We therefore aimed to determine the short-term effects of ambulation in ankle immobilization devices on nervous system excitability and stiffness in able-bodied individuals. A repeated-measures design was implemented where 12 healthy individuals were tested for cortical excitability to the ankle musculature using transcranial magnetic stimulation, reflexive excitability using the Hoffmann reflex, and ankle joint stiffness using arthrometry before and after 30min of ambulation with a boot immobilizer, pneumatic leg splint, or barefoot. Motor evoked potential (MEP), cortical silent period (CSP), H to M ratio, and ankle joint displacement were extracted as dependent variables. Results indicated that despite the novel motor demands of walking in immobilization devices, no significant changes in cortical excitability (F≥0.335, P≥0.169), reflexive excitability (F≥0.027, P≥0.083), or joint stiffness (F≥0.558, P≥0.169) occurred. These findings indicate that short-term ambulation in dynamic immobilization devices does not modify neural excitability despite forced constraints on the sensorimotor system. We may therefore conclude that modifications to neural excitability in previous immobilization models are mediated by long-term nervous system plasticity rather than acute mechanisms, and there appear to be no robust changes in corticomotor or spinal excitability acutely posed by ambulation with immobilization devices.

EMG Activity With Use of a Hands-Free Single Crutch vs a Knee Scooter

“…By maintaining in-phase cyclic muscle activation, we have established these neuro-motor pathways remain active regardless of immobilization and weightbearing status while using an HFSC, which is consistent with previous studies. 33 The neuroplasticity while using an HFSC is further demonstrated by the GM demonstrating no significant change in EMG activity. The GM is a primary extensor of the hip while maintaining a balanced pelvis.…”

Soleus arthrogenic muscle inhibition following acute lateral ankle sprain correlates with symptoms and ankle disability but not with postural control

“… 46 , 47 The use of external ankle support (e.g., taping, immobilization) has limited evidence for its effectiveness in reducing AMI in patients with CAI; however, its potential to minimize pain during stance may represent an important factor in patients with ALAS. 48 While the extended use of such implements has been hypothesized to negatively affect long-term neuromuscular function and, therefore, postural control, our results demonstrate that neurological adaptations are more critical for patient function than postural control at this stage of injury. Addressing these factors in the early stages of injury has been proposed as a key factor for determining whether patients will go on to develop CAI or if they will “cope” and return to full function after their injury.…”

Effect of three-hour ankle joint immobilization with an ankle foot orthosis on corticospinal excitability and ankle joint angle excursion during gait

“…Roberts et al 16) examined the effects of 10-day lower limb cast immobilization on corticospinal excitability in young participants and found that it increased up to 24 hours after cast removal. On the other hand, Stirling et al 12) investigated the 30minutes gait effects of ankle immobilization devices on cortical excitability, spinal reflexive excitability, and ankle stiffness, and found no significant changes in these variables. These findings suggest that changes in neural excitability by joint immobilization are the result of long-term nervous system plasticity, at least longer than 30 min.…”

“…This study employed a pre-test post-test design to examine the effects of AFO immobilization on corticospinal excitability and ankle joint excursions with an immobilization time of three hours based on previous studies 9,12) .…”