Mitchell L. Cordova

Effect of knee joint effusion on quadriceps and soleus motoneuron pool excitability.

PURPOSE To examine changes in quadriceps and soleus MN pool activity resulting from knee joint effusion over a 4-h period and assess the relationship between the muscles. METHODS A repeated measures before-after trial design was used for this study. Eight, neurologically sound volunteers (age 23.3+/-2.1 yr, height 171.8+/-15.9 cm, mass 65.5+/-17.7 kg) participated in this study. An area superomedial to the patella was cleaned and anesthetized, and 30 mL of sterile saline was injected into the knee joint capsule to mimic mechanical joint effusion. The Hoffman reflex (H-reflex) was elicited by applying a percutaneous stimulus to the appropriate nerve and recording the response through surface electromyography. Soleus and vastus medialis H-reflex measures were collected from each volunteer before, at 30 min, 90 min, 150 min, and 210 min intervals over a 4-h period after knee effusion. RESULTS All soleus H-reflex measures after effusion (30 min 5.89+/-0.92 V; 90 min 6.16+/-0.48 V; 150 min 6.59+/-0.50 V; 210 min 6.70+/-0.56 V) were increased in relation to the preeffusion measure (5.01+/-0.79 V). All vastus medialis H-reflex measures after effusion (30 min 4.23+/-0.94 V; 90 min 4.15 +/-1.11 V; 150 min 4.16+/-0.57 V; and 210 min 4.99+/-1.23) were decreased in relation to the preeffusion measure (5.88+/-1.44 V; P < or = 0.05). CONCLUSIONS Afferent activity from the knee joint capsule resulted in an inhibitory effect on the vastus medialis and a facilitatory effect on the soleus. Facilitation of the soleus in cooperation with other lower extremity musculature could be a mechanism for compensation of the inhibited quadriceps to maintain lower kinetic chain function.

Arthrogenic muscle response to a simulated ankle joint effusion

Background: Arthrogenic muscle inhibition (AMI) is a continuing reflex reaction of the musculature surrounding a joint after distension or damage to the structures of that joint. This phenomenon has been well documented after knee joint injury and has been generalised to occur at other joints of the human body, yet minimal research has been conducted in this regard. The response of the muscles crossing the ankle/foot complex after ankle injury and effusion is not well understood. AMI may occur after an ankle sprain contributing to residual dysfunction. Objective: To determine if AMI is present in the soleus, peroneus longus, and tibialis anterior musculature after a simulated ankle joint effusion. Methods: Eight neurologically sound volunteers (mean (SD) age 23 (4) years, height 171 (6) cm, mass 73 (10) kg) participated. Maximum H-reflex and maximum M-wave measurements were collected using surface electromyography after delivery of a percutaneous stimulus to the sciatic nerve before its bifurcation into the common peroneal and posterior tibial nerves. Results: The H-reflex and M-wave measurements in all muscles increased (p⩽0.05) after the simulated ankle joint effusion. Conclusions: Simulated ankle joint effusion results in facilitation of the soleus, peroneus longus, and tibialis anterior motoneurone pools. This may occur to stabilise the foot/ankle complex in order to maintain posture and/or locomotion.

Six Weeks of Balance Training Improves Sensorimotor Function in Individuals With Chronic Ankle Instability

STUDY DESIGN Prospective cohort study. OBJECTIVE To assess the effect of 6 weeks of balance training on sensorimotor measures previously found to be deficient in participants with chronic ankle instability (CAI). BACKGROUND CAI is the tendency toward repeated ankle sprains and recurring symptoms, occurring in 40% to 70% of individuals who have previously sustained a lateral ankle sprain. Recent studies have found deficits in sensorimotor measures in individuals with CAI. As balance training is a common component of ankle rehabilitation, understanding its effect on the sensorimotorsystem in individuals with CAI may enable us to optimize protocols to better utilize this rehabilitation method. METHODS Twelve participants with CAI and 9 healthy volunteers participated. Independent variables were group (CAI, control) and time (pretraining, posttraining). Participants with CAI who completed a 6-week balance training program and healthy controls who did not get any training were pretested and posttested at the beginning and at the end of 6 weeks. RESULTS The individuals in the CAI group who performed balance training demonstrated better performance than control participants on baseline adjusted posttraining measures of dynamic balance in the anterior medial (P = .021), medial (P = .048), and posterior medial directions (P = .030); motoneuron pool excitability Hmax/Mmax ratio (P = .044) and single-limb presynaptic inhibition (P = .012); and joint position sense inversion variable error (P = .017). It may be of note that no systematic differences were detected for static balance or plantar flexion joint position sense tasks. CONCLUSIONS After 6 weeks of balance training, individuals with CAI demonstrated enhanced dynamic balance, inversion joint position sense, and changes in motoneuron pool excitability compared to healthy controls who did not train. LEVEL OF EVIDENCE Therapy, level 2b.

Contributing Factors to Medial Tibial Stress Syndrome: A Prospective Investigation

PURPOSE To conduct a prospective, multisite, cohort study investigating the possible risk factors for medial tibial stress syndrome (MTSS) in college athletes. METHODS One hundred and forty-six healthy, collegiate athletes from NCAA Division I and Division II institutions participated in the study. Subjects first completed a health history questionnaire to establish previous history of injury and underwent a physical examination to assess their ankle/foot strength, ankle/foot range of motion, tibial varum, and navicular drop before the start of their respective athletic season. Athletes were instructed to report to a certified athletic trainer if they developed pain on their tibia. If MTSS was present, subjects were then placed into the symptomatic group. Independent t-tests and chi-square analyses were used to determine whether differences existed between MTSS and healthy athletes for the continuous and the discrete dependent variables, respectively. The significant dependent variables were then used in the discriminant function analysis. RESULTS Twenty-nine subjects developed MTSS during this study. Athletes that had been participating in athletic activity for fewer than 5 yr were significantly more likely to develop MTSS (P = 0.002). Additionally, athletes with a previous history of MTSS (P = 0.0001), a previous history of stress fracture (P = 0.039), and the use of orthotics (P = 0.031) were more likely to develop MTSS compared with those who did not develop MTSS. CONCLUSION This study established that the factors most influencing MTSS development were previous history of MTSS and stress fracture, years of running experience, and orthotic use. These data demonstrate the importance of establishing a thorough history before the start of the season so that athletes who might be at risk for MTSS development can be identified.

Effects of ankle support on lower-extremity functional performance: a meta-analysis.

UNLABELLED Clinicians surmise that the application of external ankle support reduces the ability to perform functional skills and movements, but the outcomes from some of these studies have been inconclusive. PURPOSE To meta-analyze studies regarding the effects of external ankle support on lower-extremity functional performance measures. METHODS A total of 93 effects from 17 randomized controlled trials utilizing predominantly crossover designs with recreationally active participants and competitive athletes were subjected to a random-effects meta-analysis. The treatment variable was external ankle support with three levels: adhesive tape, lace-up style, and semirigid style. Differences between mean changes in treatment and control groups were computed as standardized effect sizes for sprint, agility, and vertical jump performance with their 90% confidence intervals (CI). Effect sizes >0.20 were considered substantial. RESULTS The greatest effect of ankle support on performance was a negative effect of lace-up style brace on sprint speed (effect size -0.22, 90% CI -0.47 to 0.03), equivalent to approximately 1% impairment of speed. The other effects of external ankle support on performance were insubstantial, though most were negative, and their lower confidence limits allowed for realistic chances of impaired performance. Substantial true variation between studies, although poorly defined, was also present for some effects, further increasing the likelihood of performance impairment in some settings. CONCLUSIONS More research is needed to reduce the uncertainty in the effects of external ankle support on performance. In the meantime, it is our opinion that the benefit in preventing injury outweighs the possibility of substantial but small impairment of performance when athletes use external ankle support.

Arthrogenic muscle inhibition is not present in the limb contralateral to a simulated knee joint effusion.

Palmieri RM, Ingersoll CD, Edwards JE, Hoffman MA, Stone MB, Babington JP, Cordova ML, Krause BA: Arthrogenic muscle inhibition is not present in the limb contralateral to a simulated knee joint effusion. Am J Phys Med Rehabil 2003;82:910–916. ObjectiveThe purpose of this investigation was to estimate bilateral neuromuscular activity in the vastus medialis on induction of a unilateral knee joint effusion. DesignEight subjects each were assigned to effusion or control groups. The effusion group had 60 ml of sterile saline injected into their superolateral knee joint capsules. The control group rested for 8 mins. Bilateral recruitment curves for the Hoffmann reflex (H-reflex) and muscle response (M-wave) were obtained before and 10, 20, and 30 mins after the effusion or rest. The maximum H-reflex (Hmax), maximum M-wave (Mmax), and the Hmax/Mmax ratio were utilized for data analysis. ResultsBoth Hmax and Hmax/Mmax ratios decreased from the baseline measure in the effused vastus medialis, whereas no changes were detected on the contralateral side. Effused subjects demonstrated decreased motoneuron pool excitability in the effused limb, whereas control subjects did not differ from baseline. ConclusionsKnee joint effusion results in ipsilateral but not contralateral impairment of quadriceps function. Rehabilitation protocols after knee joint injury should focus on ipsilateral neuromuscular and mechanical alterations that occur as the result of joint damage.

Ground reaction forces and EMG activity with ankle bracing during inversion stress.

PURPOSE The purpose of this investigation was to evaluate the effects of external ankle support on ground reaction forces and myoelectrical activity of selected lower extremity muscles during dynamic inversion stress. METHODS Twenty-four healthy males performed five trials of a lateral dynamic movement at a rate between 80-90% of their maximal speed under three ankle brace conditions (no brace--control, Aircast Sport-Stirrup, Active Ankle). Ground reaction forces along the mediolateral axis and EMG activity of the peroneus longus, tibialis anterior, and medial gastrocnemius were simultaneously recorded during force plate contact. RESULTS Ankle bracing did not affect peak impact force (P > 0.05), maximum loading force (P > 0.05), or peak propulsion force (P > 0.05) in the lateral direction compared with the control condition. Ankle bracing reduced the EMG activity of the peroneus longus during peak impact force compared with the control condition (P < 0.05), although no differences were noted between the two braces. Furthermore, peroneous longus activity during maximum loading force and peak propulsion remained unaffected (P < 0.05). Ankle bracing did not affect the EMG activity of the tibialis anterior and medial gastrocnemius at the point of peak impact force, maximum loading force (P > 0.05), and peak propulsion force (P > 0.05). CONCLUSIONS These data suggest that ankle bracing may not affect the forces experienced at the foot and ankle, but helps reduce the strain placed on the peroneus longus during peak impact force. Furthermore, ankle bracing does not alter the function of the tibialis anterior and medial gastrocnemius during dynamic inversion stress.

Mechanical Instability After an Acute Lateral Ankle Sprain

OBJECTIVE To examine the natural recovery of mechanical laxity after an ankle sprain over an 8-week period. DESIGN Prospective cohort study. SETTING Biodynamics research laboratory. PARTICIPANTS Subjects with an acute lateral ankle sprain (n=16; 7 men, 9 women; age, 19.5+/-0.7y; mass, 64.6+/-8.1 kg; height, 171.9+/-9.6 cm) and healthy controls (n=16; 7 men, 9 women; age, 20.4+/-1.7y; mass, 76.9+/-11.1 kg; height, 176.5+/-11.1 cm) participated. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Subjects with acute ankle sprains were tested 3 days after injury and again 8 weeks later. Anterior and posterior displacement (mm) and inversion and eversion rotation ( degrees ) were measured with an instrumented arthrometer. For each dependent variable, a 2 x 2 x 2 repeated-measures multivariate analysis of variance was performed. RESULTS A significant interaction was found between group, time, and side for anterior translation (F=4.24, P=.05). There were also significant main effects for group. There was significantly more anterior displacement at day 3 (F=19.52, P=.001) and at week 8 (F=8.45, P=.010) in the injured group compared with the healthy group. There was also significantly more inversion rotation at day 3 (F=2.70, P=.002) and at week 8 (F=5.4, P=.033) in the injured group compared with the healthy group. CONCLUSIONS The lack of significant differences in mechanical laxity over an 8-week period suggests that natural recovery of laxity takes longer than 8 weeks. Further research needs to be conducted to examine how long this laxity persists and the role ankle rehabilitation plays in mechanical stability restoration.

Effect of Ankle Taping on Mechanical Laxity in Chronic Ankle Instability

Background: The high percentage of re-injury after an initial ankle sprain necessitates examination of preventative methods. The purpose of this project was to investigate the effect ankle tape has on mechanical laxity in subjects with CAI. Materials and Methods: Twenty subjects with unilateral CAI (seven males and 13 females; age, 20.6 ± 1.8 years; mass, 69.9 ± 13.7 kg; height, 172.3 ± 9.3 cm) and 20 healthy subjects (seven males and 13 females; age, 21.9 ± 4.3 years; mass, 72.0 ± 14.6 kg; height, 171.1 ± 6.7 cm) participated in the study. Both ankles of each subject were tested under two conditions: 1) before the application of tape; and 2) immediately after 30 minutes of exercise with the ankle taped. Mechanical laxity was measured with an instrumented ankle arthrometer. Two (group) x two (time) repeated measures ANOVA analysis was used for analysis. Results: There were significant group by time interactions (p = 0.014) for anterior displacement with significantly increased anterior displacement in the involved ankle of the CAI group relative to the matched control limb both before and after tape application. Similarly, there were significant time main effects for posterior displacement (p = 0.004), inversion (p = 0.001) and eversion (p = 0.043) rotation. Specifically, tape application decreased posterior displacement, inversion and eversion rotation only in the CAI group. Additionally, a significant group main effect for inversion rotation (p = 0.001) was also noted. Followup testing indicated significantly greater inversion rotation for the CAI ankle compared to the matched healthy ankle before tape application. Conclusion: Mechanical laxity significantly decreased in CAI subjects after tape application. Although there was still a significant difference in mechanical laxity between the involved ankle vs. the uninvolved ankle of the CAI group, as well as the matched healthy group, laxity decreased in the CAI ankle after the application of tape. Clinical Relevance: Ankle taping may be able to improve mechanical instability in those with CAI.

Segmental Spinal Reflex Adaptations Associated With Chronic Ankle Instability

OBJECTIVE To further understanding of the role that segmental spinal reflexes play in chronic ankle instability (CAI). DESIGN A 2 x 2 repeated-measures case-control factorial design. The independent variables were ankle group with 2 levels (healthy, CAI) and stance with 2 levels (single, double legged). SETTING University research laboratory. PARTICIPANTS Twenty-two participants with CAI and 21 matched healthy controls volunteered. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES The dependent variables were 2 measures of motoneuron pool excitability: paired reflex depression (PRD) and recurrent inhibition. RESULTS A 2 x 2 repeated-measures multivariate analysis of variance revealed a significant interaction between group and stance on the linear combination of PRD and recurrent inhibition variables (Wilks lambda=.808, F(2,40)=4.77, P=.014). Follow-up univariate F tests revealed an interaction between group and stance on the PRD (F(1,41)=9.74, P=.003). Follow-up dependent t tests revealed a significant difference between single- and double-legged PRD in the healthy participants (t(20)=-3.76, P=.001) with no difference in CAI participants (t(21)=-0.44, P=.67). Finally, there was a significant difference in recurrent inhibition between healthy (mean, 83.66) and CAI (mean, 90.27) (P=.004). CONCLUSIONS This study revealed that, compared with healthy participants, CAI participants were less able to modulate PRD when going from a double- to a single-legged stance. Additionally, CAI participants showed higher overall levels of recurrent inhibition when compared with healthy matched controls.