The role of sural nerve reflexes during drop-landing in subjects with and without chronic ankle instability.

The purpose of this study was to investigate the functional role of cutaneous reflexes during a single-leg drop-landing task among healthy, neurologically intact adults, and to identify whether individuals with chronic ankle instability (CAI) demonstrate altered reflexes and subsequent ankle kinematics. All subjects were physically active adults and were categorized as control (n = 10, Male = 6, Female = 4) or CAI (n = 9, Male = 4, Female = 5) depending on whether they scored a 0 or ≥ 11 on the Identification of Functional Ankle Instability questionnaire, respectively. Subjects performed 30-40 single-leg drop-landing trials from a platform set to the height of their tibial tuberosity. Muscle activity of four lower leg muscles was collected via surface electromyography, while ankle kinematics were recorded via an electrogoniometer. Non-noxious stimulations were elicited randomly to the ipsilateral sural nerve at two unique phases of the drop-landing task (takeoff and landing). Unstimulated and stimulated trials were used to calculate middle latency reflex amplitudes (80-120 ms) and net ankle kinematics (140-220 ms) post-stimulation. Mixed-factor ANOVAs were used to identify significant reflexes within groups and differences in reflex amplitudes between groups. Unlike the CAI group, the control group experienced significant facilitation of the Peroneus Longus (PL) and inhibition of the Lateral Gastrocnemius (LG) when stimulated at takeoff, resulting in eversion immediately prior to landing. When stimulated at landing, the control group experienced significantly more inhibition of the PL compared to the CAI group (p = 0.019). These results suggest lower neural excitability for individuals with CAI, which may predispose them to recurrent injury during similar functional tasks.

Modulation of cutaneous reflexes during sidestepping in adult humans.

A common neural control mechanism coordinates various types of rhythmic locomotion performed in the sagittal plane, but it is unclear whether frontal plane movements show similar neural patterning in adult humans. The purpose of this study was to compare cutaneous reflex modulation patterns evoked during sagittal and frontal plane rhythmic movements. Eight healthy, neurologically intact adults (three males, five females) walked and sidestepped on a treadmill at approximately 1 Hz. The sural nerve of the dominant (and lead) limb was stimulated randomly every 3-7 steps at eight phases of each gait cycle. Ipsilateral electromyographic recordings from four lower leg muscles and kinematic data from the ankle were collected continuously throughout both tasks. Data from unstimulated gait cycles were used as control trials to calculate middle-latency reflex responses (80-120 ms) and kinematic changes (140-220 ms) following electrical stimulation. Results show that the cutaneous reflex modulation patterns were similar across both tasks despite significant differences in background EMG activity. However, increased reflex amplitudes were observed during the late swing and early stance phases of sidestepping, which directly altered ankle kinematics. These results suggest that the neural control mechanisms responsible for coordinating sagittal locomotion are flexibly modified to coordinate frontal plane activities even with very different foot landing mechanics.

Effects of chronic ankle instability on cutaneous reflex modulation during walking.

Chronic ankle instability (CAI) is characterized by persistent giving way at the ankle following an acute lateral ankle sprain and is associated with an early onset of osteoarthritis. Researchers have reported that the cutaneous afferent pathway from certain leg muscles is modified in people with CAI while in a seated position. However, we do not know if these reflex modulations persist during functional activities. The purpose of this study was to further explore sensorimotor function in patients with CAI by analyzing cutaneous reflex modulation during gait. CAI (n = 11) and uninjured control (n = 11) subjects walked on a treadmill at 4 km/h and received non-noxious sural nerve stimulations at eight different time points during the gait cycle. Net electromyographic responses from four lower leg muscles were quantified 80-120 ms after stimulation for each phase of the gait cycle and compared between groups. We found that cutaneous reflex responses between groups were largely similar from the late stance to late swing phases, but uninjured control subjects, and not CAI subjects, experienced significant suppression in the medial gastrocnemius and lateral gastrocnemius muscles during the early stance phase of the gait cycle. Our results indicate that people with CAI lack a protective unloading response in the triceps surae following high-intensity sural nerve stimulation during the early stance phase of the gait cycle. Evaluating cutaneous reflex modulations may help to identify neural alterations in the reflex pathways that contribute to functional deficits in those with CAI.

Perceived ankle instability and cutaneous reflex modulation during gait.

Cutaneous reflex modulation during rhythmic ambulation is an important motor control mechanism to help minimize stumbling following an unexpected perturbation. Previous literature found individuals with chronic ankle instability (CAI) experience altered reflex patterns compared to healthy controls. Considering CAI is characterized by intermittent feelings of ankle instability, researchers have speculated that these alterations are related to perceived instability. Our purpose was to determine whether variability and magnitude of cutaneous reflex amplitudes can predict perceived instability levels following sural nerve stimulation during gait. Forty subjects walked while receiving random stimulations and reported their perceived instability. Middle latency reflexes among lower leg muscles were calculated using data derived from surface electromyography. Hierarchical logistical regressions revealed a positive relationship between reflex variability of the peroneus longus and lateral gastrocnemius muscles and perceived instability during midstance. This suggests subjects with consistent reflexes following sural nerve stimulation develop a certain level of perceptual expectation resulting in generally lower feelings of ankle instability, while subjects with more variable motor outputs perceive greater instability at the supraspinal level. Cutaneous reflex variability during stance may be an important objective outcome measure to monitor neuromuscular recovery throughout a rehabilitation or as a potential predictor of future lateral ankle sprains.

Using Normative Data and Unilateral Hopping Tests to Reduce Ambiguity in Return-to-Play Decisions.

CONTEXT: After a lower extremity injury, patients often return to sport (RTS) when the injured limb's performance on unilateral hopping tests is similar to that of the uninjured limb. However, the exact target symmetry value patients must reach before the RTS is unclear. OBJECTIVE: To identify variables that predict limb symmetry index (LSI) values on 6 unilateral hopping tests in healthy, physically active adults. DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: In total, 275 healthy, physically active adults, consisting of recreational athletes (n = 198), National Collegiate Athletic Association Division I student-athletes (n = 56), and Army Reserve Officer Training Corps cadets (n = 21), volunteered to participate (143 men, 132 women, age = 20.16 ± 2.19 years, height = 172.66 ± 10.22 cm, weight = 72.64 ± 14.29 kg). INTERVENTION(S): Each participant completed 3 speed (6-m crossover-hop, side-hop, figure-8 hop) and 3 distance (triple-crossover-hop, lateral-hop, medial-hop) functional performance tests on both limbs. MAIN OUTCOME MEASURE(S): Mean performance of the dominant and nondominant limbs and LSI values. Two multiple regression models were used to find variables that might help to predict a participant's LSI for each functional performance test. RESULTS: The models helped to predict limb symmetry for 10 of the 12 multiple regressions. Unilateral limb performance was the best predictor of LSI values, as it was statistically significant in 11 of the 12 regression models. Sex and body mass index were significant predictor variables for the side hop and figure-8 hop, respectively. CONCLUSIONS: We found significant predictor variables that clinicians can use in the absence of baseline testing to determine patient-specific LSI values. Individualizing RTS decisions in this way may help to minimize subjectivity in the decision-making process and ensure a safe and timely return to competition.

Assessing Outcomes in People With Chronic Ankle Instability: The Ability of Functional Performance Tests to Measure Deficits in Physical Function and Perceived Instability.

Study Design Laboratory-based, cross-sectional study. Background Functional performance tests (FPTs) assess short bouts of unilateral hops for either distance or speed. More research is needed to identify specific FPTs that may be useful for measuring asymmetry outcomes related to functional performance and perceived instability deficits in individuals with chronic ankle instability (CAI). Objectives To identify FPTs that are sensitive to subjective and objective deficits associated with CAI. Methods Twenty-four subjects with unilateral CAI (10 male, 14 female; mean ± SD age, 20.7 ± 3.0 years) and 24 healthy, matched controls (10 male, 14 female; age, 20.1 ± 2.6 years) completed 5 unilateral FPTs in random order. Mean FPT scores and functional symmetry percentages were calculated and compared between groups using 2 separate 1-way multivariate analyses of variance (MANOVAs). Perceived instability symmetry percentages were compared between groups using a Mann-Whitney U analysis. Results There were no differences in the mean FPT scores (P>.05) or functional symmetry percentages (P>.05) between groups for any of the 5 FPTs. However, participants with CAI perceived greater instability when using their involved limb during the side hop (P = .02), 6-meter crossover hop (P = .003), lateral hop (P = .007), and figure-of-eight hop (P = .008). Conclusion There were no differences in mean functional scores between groups for all 5 FPTs, and each group performed symmetrically. Regardless, administering a visual analog scale following the completion of the side hop, 6-meter crossover hop, lateral hop, and figure-of-eight hop tests captures subjective reports of perceived instability in the involved limb that can be compared bilaterally throughout treatment. J Orthop Sports Phys Ther 2018;48(5):372-380. Epub 30 Mar 2018. doi:10.2519/jospt.2018.7514.

Patient-Reported Outcomes Measurement Information System Physical Function Item Bank, Version 1.0: Physical Function Assessment for Athletic Patient Populations.

CONTEXT: The Patient-Reported Outcomes Measurement Information System (PROMIS) item banks have been validated for general populations, but their application to high-functioning patient populations remains speculative. OBJECTIVE: To examine the measurement properties of the PROMIS physical function item bank, version 1.0, when applied to individuals representing high levels of physical ability. DESIGN: Cross-sectional study. SETTING: National Collegiate Athletic Association Division I and III collegiate athletic training rooms and intramural events. PATIENTS OR OTHER PARTICIPANTS: A heterogeneous sample of 215 adults from Division I or Division III collegiate or recreational sports volunteered for this study. Participants were divided into 4 groups depending on sport activity and injury status: healthy collegiate (HC; 33 men, 37 women; age = 19.7 ± 1.1 years), injured and currently active in sport (IP; 21 men, 29 women; age = 19.9 ± 1.2 years), injured and currently not active in sport (INP; 12 men, 18 women; age = 19.7 ± 1.3 years), and healthy recreational (HR; 47 men, 18 women; age = 20.1 ± 1.4 years). MAIN OUTCOME MEASURE(S): Participants completed 2 assessments: (1) an injury-history questionnaire and (2) the PROMIS physical function item bank, version 1.0, in computer-adaptive form. Mean PROMIS physical function scores were determined for each group. RESULTS: The PROMIS physical function score for the HC group (61.7 ± 6.0) was higher than for the IP (54.9 ± 7.5) and INP (44.1 ± 8.2) groups (P < .001). The IP group had a higher score than the INP group (P < .001). Mean PROMIS scores were not different between the HC and HR participants (mean difference = 1.9, P = .10). CONCLUSIONS: The computer-adaptive PROMIS physical function item bank, version 1.0, accurately distinguished injury status in elite-level athletes on a physical function latent trait continuum. Although it was unable to distinguish HC athletes from HR athletes, exposing a possible ceiling effect, it offers potential for use as an outcome instrument for athletic trainers and other sports medicine clinicians.