Alan R. Needle

Context : Transcranial direct current stimulation (tDCS) can enhance cortical activity and improve motor performance, potentially inducing synergetic effects when coupled with balance training. Yet, its effects during balance training in individuals with chronic ankle instability (CAI) remain unclear. This study aimed to evaluate whether tDCS has additive effects on static postural control, neural excitability, and perceived ankle function in individuals with CAI compared with sham stimulation. Design : Double-blind, pilot randomized controlled trial. Methods : Nineteen individuals with CAI were included. Participants were randomized to either active tDCS or sham tDCS. Participants and experimenters were blinded to group allocation. Twenty minutes of anodal tDCS (2 mA) was applied over the contralateral motor cortex of the CAI-injured side during balance training, 3 times a week for 4 weeks. The primary outcome was static postural control, assessed by center of pressure velocity and area during unipedal stance with eyes open and closed. Secondary outcomes included corticospinal and spinal reflexive excitability (soleus, fibularis longus, and tibialis anterior), evaluated via transcranial magnetic stimulation and Hoffmann reflex methods, respectively, during unipedal stance. Self-reported outcomes were assessed. All outcomes were assessed at baseline, during, and following a 4-week intervention. Individual analyses were conducted. Results : Individual analyses show changes in static balance, soleus corticospinal excitability, and ankle function over time, regardless of tDCS group. Effect size estimates indicated small group differences at weeks 2 and 4 in the active-tDCS group compared with sham for most measures. However, the center of pressure area under the eyes-closed condition and fibularis longus corticospinal excitability demonstrated potential moderate ( d = −0.62) and large ( d = −0.88) effects, respectively. Conclusion : This pilot study indicates that tDCS applied during balance training appears to provide no added benefit. However, potential changes in selected outcomes (center of pressure area and corticospinal excitability) warrant a larger clinical trial.

Background: Chronic ankle instability (CAI) may impair neuromechanical control during both gait initiation and initial-step stabilization when attentional resources are divided. However, the effects of cognitive-motor interference across these successive movement phases remain unclear.Methods: Thirty men (15 with unilateral CAI and 15 matched controls) completed gait-initiation trials under single-task and auditory 2-back conditions. Anticipatory center-of-pressure (COP) control and initial-step spatiotemporal characteristics were assessed before lead-limb initial contact. Vertical-force characteristics, mediolateral margin of stability (ML-MoS) at initial contact, and muscle-synergy characteristics were assessed during lead-limb initial stance. Outcomes were analyzed using two-way mixed ANOVA.Results: A common three-synergy solution yielded a mean total variance accounted for (VAF) > 90% in all four Group × Task conditions. Group × Task interactions were observed for total VAF, Synergy 2 full width at half maximum (FWHM), peak posterior COP displacement, and ML-MoS (p = 0.007-0.033, ηp2 = 0.153-0.231). Under the dual-task condition, men with CAI showed higher total VAF at the fixed three-synergy rank, shorter Synergy 2 FWHM, smaller peak posterior COP displacement, and smaller ML-MoS than controls (p < 0.001 to p = 0.045, d = 1.003-1.947). Across groups, the dual task prolonged foot-lift duration, shortened initial step length, reduced peak vertical ground reaction force, shortened Synergy 1 FWHM, and shifted the center of activity of Synergy 3 earlier (p < 0.001 to p = 0.028, ηp2 = 0.137-0.350).Conclusions: Cognitive-motor interference in men with CAI selectively affected anticipatory postural control during gait initiation and neuromuscular regulation during initial-step stabilization.

Context : Trail running involves navigating complex and unstable terrains, increasing the risk of falls or ankle rolls. We aimed to determine the incidence and the role of a multitask assessment in the prediction of injurious mechanisms in trail races ranging from 20 to 50 km. Design : Prospective cohort. Methods : A total of 227 runners (41.4 [11.2] y) across 9 trail-running races completed a prerace multitask neurocognitive assessment evaluating motor and cognitive performance. After the race, participants reported perceived exertion and any events experienced (falls and ankle rolls), and finish times were recorded from the race clock. Course characteristics, including elevation gain, single-track percentage, and median finish time, were used to describe race difficulty. Results : Falls and ankle rolls were reported by 27.3% (95% CI, 21.5 to 33.1) and 23.3% (95% CI, 17.8 to 28.8) of runners, respectively. Event frequency was higher in races with faster finishing times, less elevation gain, and a higher proportion of single-track trail. Mixed-effects negative binomial regression models showed that higher motor accuracy was associated with a greater fall rate (incidence rate ratio = 1.12, 95% CI, 1.00 to 1.25, P = .04), whereas cognitive accuracy and reaction time were not significant predictors. A modest cognitive × motor accuracy interaction ( P = .03) suggested limited interplay between attentional and motor control processes. Faster running pace and greater perceived effort were the most consistent predictors of falls and combined outcomes (pace incidence rate ratio ≈ 0.88, P < .05; effort incidence rate ratio ≈ 1.31, P < .02). Conclusions : Falls and ankle rolls were common in trail races, occurring most often in faster and more technical events. Although neurocognitive performance showed limited contribution, the relationship between cognitive and motor accuracy may modestly influence fall risk. Injury-related mechanisms in trail running appear to be multifactorial, with pace, terrain, and perceived effort exerting stronger influence than prerace neurocognitive performance.

Background: Acute lateral ankle sprains (ALAS) are linked to altered spinal-reflexive excitability that may predicate sensorimotor dysfunction. However, sensorimotor control is influenced by spinal and supraspinal mechanisms, necessitating examination of each following ALAS. We aimed to investigate the effects of ALAS on neural excitability during unipedal stance, relating these neural adaptations to clinical outcomes. Methods: Twenty-six young adults were enrolled (13 ALAS: 19.6 ± 1.9 yr; 13 uninjured controls: 20.7 ± 2.4 yr). Spinal-reflex excitability was assessed at the soleus using the Hoffmann reflex, evoking maximal reflexive (H _max ) and motor (M _max ) responses from electrical stimulation. Corticospinal excitability was assessed via motor evoked potentials (MEP) from transcranial magnetic stimulation, recording responses at 100%, 120%, and 140% of active motor threshold, and normalized to background EMG prior to stimuli and M _max . For clinical outcomes, area and velocity of unipedal center-of-pressure measurements were recorded, along with acute symptoms (pain and swelling) and ankle disability. Results: Independent t -tests revealed no significant differences in spinal-reflex excitability between ALAS and uninjured control (CON) groups. However, corticospinal excitability was significantly higher in patients with ALAS across all stimulus intensities (MEP _100% : ALAS = 2.7 ± 1.2, CON = 1.2 ± 0.6, P < 0.001; MEP _120% : ALAS = 3.9 ± 1.1, CON = 2.6 ± 1.8, P = 0.033; MEP _140% : ALAS = 3.9 ± 1.9, CON = 2.4 ± 1.6, P = 0.031). Patients with ALAS exhibited impaired postural control, as shown by larger area (ALAS = 2.9 ± 0.7, CON = 2.2 ± 0.6, P = 0.049) and higher velocity (ALAS = 3.3 ± 1.0, CON = 2.7 ± 0.5, P = 0.005). Pearson’s product – moment correlations found that increased corticospinal excitability did not significantly correlate with impaired postural control or acute symptoms; however, higher corticospinal excitability was associated with more severe ankle disability ( r = −0.607 to −0.721, P = 0.028 to 0.005). Conclusions: This study provides initial evidence that ALAS affects neural excitability during unipedal stance predominantly at the corticospinal level, which may contribute to ankle disability.

To identify, critically appraise, and synthesize the existing evidence regarding the effects of therapeutic interventions on arthrogenic muscle inhibition (AMI) in patients with chronic ankle insta... Therapeutic interventions on arthrogenic muscle inhibition (AMI) in patients with chronic ankle instability are scarce.Current studies incorporate mainly short-term therapeutic interventions.Focal ...

Recent literature has highlighted altered spinal-reflex excitability following acute lateral ankle sprain (ALAS), yet there is little information on the conduction velocity of spinal reflex pathways (CV-SRP) in these patients. Therefore, we aimed to investigate the effects of ALAS on the CV-SRP. We employed a cross-sectional study with two groups: ALAS (n = 30) and healthy controls (n = 30). The CV-SRP of the soleus, fibularis longus, and tibialis anterior was assessed using the H-index method. As secondary outcomes, H-reflex and M-wave latencies were assessed as well as acute symptoms including ankle swelling, pain, and self-reported ankle function. Separate group-by-limb ANOVA with repeated measures revealed a significant interaction for soleus CV-SRP (p < 0.001) and H-reflex latency (p < 0.001), showing significant slower CV-SRP and longer H-reflex latency in the involved limb of the ALAS group compared with both limbs in the control group. However, there was no significant interaction or main effect in any other ankle muscles (p > 0.05). A further correlation analysis showed a significant relationship between CV-SRP and acute symptoms, including ankle swelling (r = −0.37, p = 0.048) and self-reported ankle function (r = 0.44, p = 0.017) in ALAS patients. These results suggest a disrupted functionality of the afferent pathway and/or synaptic transmission following ALAS. Level of Evidence: 4.

Neural changes in the ankle stabilizing muscles following ankle sprains are thought to be one contributing factor to persistent ankle dysfunction. However, empirical evidence is limited. Therefore, we aimed to examine spinal reflex excitability of lower leg muscles following acute ankle sprains (AAS). We performed a case-control study with 2 groups consisting of 30 young adults with AAS and 30 aged-matched uninjured controls. Hoffmann reflex (H-reflex) testing was performed to estimate spinal reflex excitability of lower leg muscles: soleus, fibularis longus (FL), tibialis anterior (TA). Maximal H-reflex (H_max) and motor responses (M_max) were determined by delivering a series of electrical stimuli at the sciatic nerve. H_max/M_max ratios were calculated to represent normalized spinal reflex excitability. Separate group-by-limb analyses of variance (ANOVA) with repeated measures found there were no significant interactions for any of the muscles (SL: F_1,56 = 0.95, p = 0.33, FL: F_1,51 = 0.65, p = 0.42, TA: F_1,51 = 1.87, p = 0.18), but there was a significant main effect of group in the soleus (F_1,56 = 6.56, p = 0.013), indicating the H_max/M_max ratio of soleus in the AAS group was significantly lower bilaterally (AAS = 0.56 ± 0.19, control = 0.68 ± 0.17, p = 0.013), with no significant group differences in the other muscles (FL: F_1,51 = 0.26, p = 0.61, TA: F_1,51 = 0.93, p = 0.34). The bilateral inhibition of the soleus spinal reflex excitability following AAS may be significant in that it may explain bilateral sensorimotor deficits (postural control deficits) following unilateral injury, and provide insights into additional therapies aimed at the neural change.

Clinical Scenario: The impact of concussion in baseball athletes is far reaching although typically less studied than collision sports. The neuromotor sequelae of these injuries can have lasting effects on the high level of coordination needed in baseball skills. In professional athletes, the long-term effects of concussion combined with the high demands for performance can potentially shorten athletes’ careers. Clinical Question: Do Major League Baseball players who have had a concussion compared with those with no history of concussions have decreased batting performance after they return to full participation? Summary of Key Findings: Seven articles meeting criteria for level 2 evidence were identified in this critically appraised topic. Four of 7 studies found deficits in batting performance following concussion. However, the 3 studies that did not identify differences lacked a comparative control group. Clinical Bottom Line: Evidence supports a relationship between concussion and decreased batting performance. This suggests there is a demand for screening and rehabilitation strategies aimed at improving sport-specific neuromotor and coordination skills in these individuals. Strength of Recommendation: Collectively, the body of evidence included to answer the clinical question aligns with the strength of recommendation of B.