Article Critique

Jou rna l o f S port R ehabilitation, 2019, 28, 752-757 https://doi.Org/10.1123/jsr.2018-0092 © 2019 Human Kinetics, Inc.

Human Kinetics ORIGINAL RESEARCH REPORT

Ankle Strength Deficits in a Cohort of College Athletes With Chronic Ankle Instability

Bethany Wisthoff, Shannon Matheny, Aaron Struminger, Geoffrey Gustavsen, Joseph Glutting, Charles Swanik, and Thomas W. Kaminski

Context: Lateral ankle sprains commonly occur in an athletic population and can lead to chronic ankle instability. Objective: To compare ankle strength measurements in athletes who have mechanical laxity and report functional instability after a history of unilateral ankle sprains. Design: Retrospective cohort. Setting: Athletic Training Research Lab. Participants: A total of 165 National Collegiate Athletic Association Division I athletes, 97 males and 68 females, with history of unilateral ankle sprains participated. Main Outcome Measures: Functional ankle instability was determined by Cumberland Ankle Instability Tool scores and mechanical ankle instability by the participant having both anterior and inversion/eversion laxity. Peak torque strength measures, concentric and eccentric, in 2 velocities were measured. Results: Of the 165 participants, 24 subjects had both anterior and inversion/eversion laxity and 74 self-reported functional ankle instability on their injured ankle. The mechanical ankle instability group presented with significantly lower plantar flexion concentric strength at 30°/s (139.7 [43.7] N-m) (P =.01) and eversion concentric strength at 1207s (14.8 [5.3] N-m) ( P= .03) than the contralateral, uninjured ankle (166.3 [56.8] N-m, 17.4 [6.2] N-m, respectively). Conclusion: College athletes who present with mechanical laxity on a previously injured ankle exhibit plantar flexion and eversion strength deficits between ankles.

Keywords: isokinetic, ankle sprain, eversion, plantar flexion, subtalar, talocrural

Ankle and foot injuries account for more than 3 million emergency room visits annually and are the second most com­ monly injured area of the body in sport.1-2 Although this number is extremely large, an estimated 55% of those who sustain an ankle sprain seek neither medical attention nor treatment.3 If these ankle injuries are ignored and not treated correctly, reinjury is likely to occur, as some reports indicate an 80% recurrence rate in high-risk sports.1-2 the conundrum from a clinical perspective is that despite proper treatment intervention and quality care, the recurrence rate is still alarmingly high. Compounding the high recurrence rate is the fact that most of these individuals (32%-47%) continue to suffer from chronic symptoms.1-4' 6 The residual symptoms and recurrent sprains can cause some patients to be involved in a continuous cycle of debilitating symptoms and reinjury.7

One of the residual and potentially long-lasting symptoms of lateral ankle sprains is mechanical laxity caused by ligamentous damage to the ankle after injury. The amount of separation to the lateral ligaments affects the extent of pathologic laxity of the lateral ankle.7 In addition, because these ligaments are a rich source of mechanoreceptors, feed-forward neuromuscular control could be impaired resulting in gait alterations in those with chronic laxity.8 Laxity, or objective mechanical ankle instability (MAI), can last from 6 weeks to 1 year after injury, with some cases extending multiple years.2-9 As mechanical laxity is thought to be a potential cause of residual symptoms and lateral ankle sprain recurrence, this evidence suggests that those with MAI may be at risk for recurring injury for months, if not years, after an initial ankle sprain.2-9

Wisthoff, Matheny, G ustavsen, Glutting. Swanik, and Kaminski are with the University of Delaware, Newark, DE, USA. Struminger is with Eastern Michigan University, Ypsilanti, MI, USA. Wisthoff ([email protected]) is corresponding author.

Although mechanical instability can be present after an ankle injury, it has been suggested that mechanical instability is rarely the cause of functional instability, which is defined as recurrent sprains, episodes of “giving way,” pain, swelling, or decreased function after an initial ankle sprain.10' 12 Functional instability in conjunction with mechanical instability has been implicated in producing symptoms associated with chronic ankle instability (CAI).7-10 Multiple studies have reported that those with CAI have increased ligamentous laxity, alluding to the mechanical instability factor of the diagnosis.10-13-14 To more clearly differentiate athletes with and without functional insta­ bility, clinicians use, among others, the Cumberland Ankle Instability Tool (CAIT).15 Correctly identifying athletes with CAI is an important first step in enabling clinicians the ability to develop intervention programs aimed toward decreasing articu­ lar degeneration of the joint by increasing physical activity; thereby, lowering the risk of osteoarthritis in the ankle joint later on in life.9-16

Because both mechanical and functional instability are related to recurring ankle injury and long-lasting symptoms, typical treatment attempts to correct both.7-10 Strength training is one method aimed at reducing the likelihood of reinjury and prolonged symptoms. Interestingly, Bleakley et a l17 compared an accelerated exercise protocol that included muscle strengthening to a tradi­ tional Protection, Rest, Ice, Compression, Elevation (PRICE) protocol and reported improvement in self-reported ankle function alter 1 week following an acute ankle sprain. Because sport activity requires muscles to work synchronously, it is important to stress strength training involving both concentric (CON) and eccentric (ECC) muscle actions. Athletes rely on muscular co-contraction, specifically ECC control during sports. This is especially irue following an ankle sprain, whereby, return to efficiency will require musculature to co-contract to dissipate forces associated with the sprain mechanism.18 Previous research examining the relationship

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between muscle weakness and CA1 has noted that those with self- reported CAI had significantly higher ECC peak torque (PT) dorsiflexion/plantar flexion (DF/PF) ratios than a healthy, control ankle. Those group differences in the PT ratios are most likely associated with a reduction in PF ECC torque.14-19’20 Reinjury to the ankle may also occur when the inversion/eversion (INV/EV) torque ratio is altered indicating muscle weakness.19-21-22 Ankle strengthening programs may restore normal INV/EV and PF/DF strength, which could possibly limit the effects of CAI and limit lateral ankle sprain reoccurrence.19

Both the mechanical and functional instability components of CAI may be important when looking at strength deficits in those with previous injury. In a homogenous group of subjects who have suffered unilateral ankle sprains, the question remains whether MAI and/or functional ankle instability (FAI) exists. Furthermore, it remains to be seen if there are associated deficits in ankle muscle strength in both subgroups. Therefore, the purpose of this study was to compare isokinetic strength measures of the ankles with or without FAI and the ankles with or without MAI, whereas second­ arily we aimed to determine how many subjects within the popu­ lation of those who have previous ankle sprain classify as having FAI or MAI.

M e th o d s

Study Design A retrospective cohort design was used to examine isokinetic strength of the ankle in 2 specific groups: (1) those identified with unilateral FAI, and (2) those identified with unilateral MAI comparing with the uninjured, healthy ankle. The dependent measures, isokinetic strength, involved PT values in PF, DF, INV, and EV in both CON and ECC at 2 velocities (30°/s and 1207s).

Participants Data files from a total of 553 student-athletes from National Collegiate Athletic Association Division I sports including football, men’s basketball, women’s basketball, men’s lacrosse, women’s lacrosse, men’s soccer, women’s soccer, field hockey, and volleyball were examined. Each subject was provided consent to participate using the university’s institutional review board approved consent form (UD IRB #131714-12). Prior to participa­ tion, all subjects completed an ankle study inclusion questionnaire detailing ankle injury history. Of the 553 student-athletes, parti­ cipants included in this study were only those subjects with a history of unilateral ankle sprains resulting in a total of 165 subjects, 97 males and 68 females (18.5 [0.7] y, 178.0 [10.3] cm, and 78.7 [17.1] kg). One or more previous unilateral lateral ankle sprains occurred at least 1 year from testing. Subjects were excluded from the study if they had a severe lower-extremity injury (<6 mo) resulting in surgery or not being fully cleared for athletic participation.

Procedures S u b je c t G ro u p in g s (FA I). The Cumberland Ankle Instability Tool15 was used to determine FAI status in those subjects identified as having unilateral ankle sprain history. The validity and reliability of the CAIT in discriminating those with FAI has been estab­ lished.15 Recently, Wright et al5 utilized a more accurate cutoff

score of 25 (sensitivity of 96.6% and specificity of 86.8%) in differentiating those with FAI. In this study, a CAIT cutoff score of equal to, or less than 25, was utilized to signify those with and without FAI. The opposite uninjured ankle would then serve as the control for all subsequent data analysis.

S u b je c t G ro u p in g s (M A I). Ankle laxity measurements with an instrumented portable ankle artbrometer (Blue Bay Research Inc, Navarre, FL) were derived using our previously described testing protocol.23 Participants were assigned to the MAI group if bilateral differences equaled or exceeded 3 mm for anterior displacement and 3° of inversion rotation.24-26

S tre n gth Testing. The Kin Com 125 AP (Isokinetic International, Chattanooga, TN) isokinetic dynamometer was used to assess PT for all 4 ankle motions (PF, DF, INV, and EV). Kin Com dynamometers allow for precise and reliable measurement and storage of data from isokinetic, isotonic, and isometric muscular actions.27 The isokinetic procedures described below were derived from those previously performed by Kaminski et al27 and Morrison and Kaminski.28

Inversion/eversion ankle strength was tested with subjects seated in the dynamometer chair, hips and knees slightly flexed and lower legs secured using the universal stabilizer attachment. The shoe was securely fastened into the ankle INV/EV footplate attachment. A total of 45° of INV/EV motion was tested. Using the overlay protocol function on the Kin Com, both CON and ECC muscle actions were tested at velocities of 307s and 1207s. A total of 3 maximal repetitions were performed at each speed. PT was then derived from each of the CON and ECC torque curves. Gravity compensation was not necessary for this testing position. In addition, EV/INV PT ratios were calculated at both velocities and for each of the CON and ECC muscle actions in the MAI and FAI groups.

Plantar flexion/dorsiflexion ankle strength was tested with subjects seated in the dynamometer chair, hips flexed to 90° and knees completely extended. The thigh was held down to the dynamometer chair using the thigh stabilizer attachment. The shoe was securely fastened into the ankle PF/DF foot plate attachment. A total of 45° of PF/DF motion was tested. For PF testing, the start position was in 10° of DF pushing downward (CON) toward the stop angle of 35° of PF. For DF testing, the opposite occurred, whereas the motion started at 35° of PF moving upward (CON) into DF until they stopped at 10° of DF. Using the overlay protocol function on the Kin Com, both CON and ECC muscle actions were tested at velocities of 307s and 1207s. A total of 3 maximal repetitions were performed at each speed. PT was then derived from each of the CON and ECC torque curves. Gravity compensation was necessary for this testing position. In addition, DF/PF PT ratios were calculated at both velocities and for each of the CON and ECC muscle actions in the MAI and FAI groups.

Statistical Analysis The primary independent variable in this study is group status as determined by either MAI or FAI. The dependent measures were the isokinetic strength measurements involving the PT values for all 4 ankle motions (PF, DF, INV, and EV) both CON and ECC at the 2 velocities (307s and 1207s). The CON and ECC muscle actions were analyzed separately.

Differences in strength between the involved ankle and the uninvolved, healthy control ankle were examined utilizing a

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hierarchical linear model with a scaled identity error structure. This model included the strength measures as the dependent variables and the primary variables of ankle MAI and FAI as independent variables. Sex was included in the analysis to control for a potential covariate. All models were run using SPSS (version 22.0; SPSS, Inc, Chicago, IL). By using this analysis, it was possible to compare all variables simultaneously. Values that were 3 or more SDs past the mean were considered outliers and eliminated. In addition, subjects who did not have all necessary data for 1 dependent variable were excluded from the analysis in which the data were missing. These subjects were included in all other analyses. Cohen’s d effect sizes were used to determine the impact of significance, whereas 0.2 is a small effect, 0.5 a medium effect, and 0.8 a large effect.

Results Of the 165 participants with a history of unilateral lateral ankle sprains, 24 subjects (14.5%) had both anterior displacement and inversion rotation laxity and, thus, classified as MAI. Also, 74 subjects (45%) had self-reported FAI in their injured ankle at the time of testing. Therefore, 67 participants had a history of unilateral lateral ankle sprains but did not classify as MAI or FAI and were not included in further analysis.

Strength in MAI G roup

Participants with MAI presented with less EV CON strength at 1207s (? = —2.137, P = .03) than the opposite, uninjured ankle. PF CON strength at 307s was also significantly less in the MAI ankle compared with the ankle without MAI (t = - 2.567, P = .0 1 ) (Table 1). A trend toward significance was seen for ECC (7 = —1.905, P = .06) and CON PF at 1207s (r = —1.852, P = .0 7 ) when comparing ankles. Although no significant differences in strength were evident, there were moderate to large effect sizes (Cohen’s d) for ECC and CON PF at 1207s (0.44 to 1.11, respectively). Specifically, participants’ ankles with MAI exhibited lower strength values than the opposite, uninjured ankles (Tables 1 and 2). CON and ECC INV and DF strength values were not significantly different at either velocity (Tables 1 and 2). PT ratios in the MAI group are reported in Table 3.

Strength in FAI G roup

No significant findings were observed for the strength values between the ankles with or without self-reported FAI (Tables 1 and 2). All CON and ECC strength measurements in males were significantly greater than those in females (P< .001). PT ratios in the FAI group are reported in Table 3.

Discussion Our primary aim was to examine isokinetic strength measures in both our FAI and MAI groups. Interestingly, we only detected differences in strength among those who were mechanically unsta­ ble. Our results indicate that participants with MAI presented with less EV CON strength at 1207s. Tropp29 previously reported that those with unilateral instability had peroneal muscle weakness in isokinetic testing. Even though mechanical laxity may occur naturally in the population at large, it still appears to affect strength values in athletes with a previous unilateral ankle sprain.1-7-14-18’30 Although ligaments provide a static restraint and help maintain the bony integrity of the joint, it is the surrounding musculature that needs to act efficiently to provide the necessary dynamic joint stability.30 Previous research has reported that the primary me- chanoreceptors involved in an acute injury to the lateral ankle ligaments are the sensory nerve endings, which are involved in pain response, and the Ruffini endings, which are involved in main­ taining joint position and kinesthesia.31 Thus, a disruption in the integrity of the lateral ankle ligaments, or the presence of MAI, may disrupt muscular co-contraction involved in maintaining proper ankle joint position. Once ligament integrity is restored via healing, sensory re-education through the addition of proprioceptive ex­ ercises can begin to stimulate the sensory nerve endings and improved proprioceptive function.11 Holmes and Delahunt32 deter­ mined that subjects with CAI show deficits in frontal plane ankle joint position sense. Similarly, Terada et al33 concluded that kinematic movement patterns during a drop jump with a feed­ forward visual intervention were altered in those with CAI. There­ fore, clinicians should focus their treatment interventions in those with mechanical deficits on feed-forward neuromuscular control versus a feedback intervention. These treatment interventions would involve visual feedback during neuromuscular control or

Table 1 Average Sagittal Plane Peak Torque (N m) Strength Measures

____________________Plantar flexion Dorsiflexion

Concentric_______ Eccentric Concentric Eccentric 30 m/s 120 m/s 30 m/s 120 m/s 30 m/s 120 m/s 30 m/s 120 m/s

Functional ankle instability Without 164.4 (57.6) 102.7 (47.4) 240.3 (82.9) 227.4 (83.5) 45.7 (17.9) 29.0 (13.0) 69.3 (23.7) 70.3 (23.6) With 161.9 (50.4) 99.33 (38.4) 239.5 (84.7) 2 16.1 (76.8) 45.6 (14.7) 27.5 (10.0) 67.5 (21.8) 68.5 (19.8) P .90 .82 .70 .12 .32 .94 .91 .67 t -0.133 -0.225 -0.389 -1.57 0.994 -0.081 0.109 -0.428

Mechanical Without

ankle instability 166.0 (56.5) 103.2 (46.3) 242.0 (83.6) 227.2 (83.0) 45.5 (17.3) 28.8 (12.5) 68.5 (23.1) 69.8 (23.0)

With 136.1 (41.0) 86.01 (31.2) 215.6 (75.0) 194.2 (62.5) 48.1 (15.9) 27.3 (11.0) 74.6 (25.6) 70.8 (20.8) P .01* .07 .1 1 .06 .80 .36 .57 .74 t -2.57 -1.85 -1.59 -1.91 0.255 -0.922 0.567 -0.337

Note: Values are presented as mean (SD). ♦Significant difference between those with or without FAI and those with or without MAI ( P c . 05).

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Table 2 Average Frontal Plane Peak Torque (N-m) Strength Measures

Inversion Eversion Concentric Eccentric Concentric Eccentric

30 m/s 120 m/s 30 m/s 120 m/s 30 m/s 120 m/s 30 m/s 120 m/s F u n ctio n a l a n k le in sta b ility

W ith o u t 2 3 .2 (8 .5 ) 17.2 (6 .6 ) 2 8 .3 ( 1 2 .2 ) 2 7 .9 (1 2 .0 ) 2 3 .0 (7 .6 ) 17.3 (6 .5 ) 2 9 .5 ( 1 2 .3 ) 2 9 .4 ( l 1.2)

W ith 2 3 .2 (8 .8 ) 16 .6 (5 .6 ) 2 7 .2 ( 1 2 .1 ) 2 8 .0 (1 2 .2 ) 2 2 .7 (6 .7 ) 16.8 (6 .0 ) 2 8 .5 ( 1 0 .1 ) 2 7 .7 (9 .6 )

P .5 2 .2 2 .1 4 .6 6 .37 .3 3 .35 .1 4

t - 0 . 6 4 4 - 1 . 2 2 - 1 . 4 8 - 0 . 4 3 8 - 0 . 8 9 5 - 0 . 9 8 2 - 0 . 9 4 6 - 1 . 4 9

M ec h a n ic a l a n k le in sta b ility

W ith o u t 2 3 .3 (8 .6 ) 17 .2 (6 .4 ) 2 7 .9 ( 1 2 .1 ) 2 8 .0 ( 1 2 .0 ) 2 3 .0 (7 .4 ) 17.3 (6 .4 ) 2 9 .3 ( 1 2 .0 ) 2 9 .1 ( 1 0 .9 )

W ith 2 1 .2 (7 .6 ) 1 6 .0 (6 .3 ) 2 9 .9 ( 1 4 .0 ) 2 6 .9 ( 1 2 .1 ) 2 1 .0 (6 .8 ) 14.8 (4 .8 ) 2 8 .4 ( 1 0 .3 ) 2 7 .2 ( 1 0 .2 )

P .18 .2 3 .9 3 .51 .1 0 .03* .5 0 .2 6

t - 1 . 3 6 - 1 .2 1 0 .0 8 5 - 0 . 6 6 2 - 1 . 6 3 -2.13 - 0 . 6 7 4 - 1 . 1 4

Note: Values are presented as mean (SD). ^Significant difference between those with or without FAI and between those with or without MAI (P < .05).

Table 3 Peak Torque (N-m) Strength Ratios

DFCON/ DFCON/ DFECC/ DFECC/ DFCON/ EVCON/ EVECC / EVCON/ EVCON/ PFCON PFCON PFCON PFCON PFECC INCON INCON INECC INECC

30 120 30 120 30 30 120 30 120 F u n ctio n a l a n k le in sta b ility 0 .3 1 (0 .2 0 ) 0 .2 9 ( 0 . 2 1) 0 .4 9 ( 0 .2 7 ) 0 .7 7 ( 0 .3 9 ) 0 .2 4 (0 .2 1 ) 1 .1 0 ( 0 .4 6 ) 1.68 ( 0 .7 2 ) 0 .9 0 ( 0 .3 5 ) 0 .6 9 ( 0 .3 4 )

M e c h a n ic a l an k le in sta b ility 0 .3 0 (0 .1 3 ) 0 .2 7 ( 0 .1 5 ) 0 .5 1 ( 0 .1 9 ) 0 .7 4 (0 .3 0 ) 0 .2 4 (0 .1 2 ) 1.23 ( 0 .8 3 ) 1.78 ( 0 .7 7 ) 0 .9 4 ( 0 .2 9 ) 0 .7 4 ( 0 .2 6 )

Abbreviations: CON, concentric; DF, dorsiflexion; ECC, eccentric; EV, eversion; IN, inversion; PF, plantar flexion. Note: Values are presented as mean (SD).

balance tasks, asking the patient to keep their eyes open while focusing on an object.

Our study reports no significant strength deficits in participants with FAI. However, previous research has hypothesized that a proprioceptive deficit may result from a partial deafferentation caused by damage of sensory nerve endings, resulting in FAI and leading to loss of position sense, delayed peroneal reaction time, strength deficits, and impaired postural control.11-31 Conversely, the dynamical systems theory postulates that an ankle sprain can alter biomechanics by limiting motion due to acute symptoms, thus reducing the degrees of freedom for the joint to move.34 These biomechanical alterations may also appear bilaterally.34 If recur­ ring ankle sprains affect an athlete bilaterally, comparing an athlete's injured ankle to their uninjured ankle may be an inappro­ priate comparison as strength deficits may exist in both ankles. The lack of significant differences in FAI subjects related to strength at the ankle also alludes to compensation, based on the dynamical systems theory, at sites other than the ankle because of injury.35 Previous research has concluded that those with FAI show varia­ tions in shank to rearfoot joint coupling34-36 and hip to ankle coordination37 in walking and running gait. This theory, along with our findings, may indicate that clinicians should focus less on asymmetric exercises in previously injured athletes with FAI and instead focus on rehabilitation encompassing more bilateral kinetic chain exercises. Utilization of a kinematic strategy may change the rehabilitation process to look at the limb and body working in tandem, which may be more of a problem in athletes with FAI, instead of focusing solely on the injured ankle.

Our secondary aim examined the percentage of an athletic population that presented with FAI or MAI. The results of this

study demonstrated that 45% of the participants with a history of at least 1 unilateral lateral ankle sprain reported FAI. This indicates an accurate depiction of the current literature reporting that FAI is present in 32% to 47% of those who have suffered from at least 1 lateral ankle sprain.5-6-26 However, it is interesting that this per­ centage is this high especially given the fact that our population of college athletes involve highly active individuals with access to specialized sports medicine care. In addition, we identified 14.5% of our subject pool to have MAI in their involved ankle. It is interesting to note that our results are similar to the frequency noted in the general healthy population who present with asymmetric laxity (11 %).38 Based on our findings, it appears that MAI and FAI are separate entities and lends support to the model proposed by Hiller et al39, whereby mechanical and functional instabilities coexist separately to one another in most subjects with the inclusion of recurrent ankle sprains.

The groups for FAI were determined based on a self-reported questionnaire, with the total participants who classified as having FAI topping out at 45%. The CAIT, although showing high sensitivity and specificity, is not without flaws. For example, this tool does not provide a way to control for copers or those with FAI but not experiencing any clinical symptoms, such as episodes of “giving way.” Therefore, the subject pool used in this study did not control for the presence of copers, as copers also have a history of a previous ankle sprain.40 In addition, the cutoff score of 25 was utilized for this study based on a recalibration by Wright et al5; however, this score may have limited the number of subjects with FAI that were included. In the future, it would be wise to use the CAIT as an adjunct with other diagnostic questionnaires such as the Functional Ankle Instability Questionnaire, Ankle Instability

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Instalment, or even the Ankle Joint Functional Assessment Tool to have a confident inclusion of those with FAI.41-42 Donahue et al42 previously concluded that the combination of the CA1T and Ankle Instability Instrument would be more accurate at depicting ankle instability status (sensitivity and specificity 0.82) than any single measure alone. Simon et al43 later developed the Identification of Functional Ankle Instability, based on the questions from the CA1T and Ankle Instability Instrument, and reported its accuracy to be 89.6%.

To measure laxity, we used a portable instrumented arthrom- eter. Ankle arthrometry, or instrumented measurements of subtalar joint laxity, is more reliable than manual testing with high intra­ tester and intertester reliability coefficients (ICC = .80-.97).44 However, throughout the collection of our data, 2 separate arth- rometers and multiple testers were utilized, so laxity data may have been confounded.45-46 We attempted to control for this limitation by comparing bilaterally within subjects, instead of between sub­ jects. Thus, all comparative variables were derived from the same arthrometer and tester.

The results of this study indicate that athletes who have MAI of their injured ankle exhibit deficits in EV and PF strength. We can speculate that the reduced strength of the plantar flexors and evertors of the ankle in athletes who have suffered a unilateral ankle sprain may be potential cause of these performance deficits. Witchalls et al4 found deficits in explosive power, agility, and proprioception in those with laxity of the ankle joint. Therefore, explosiveness and agility deficits may be observed due to strength impairments. Our results may affect clinical treatment by suggest­ ing that clinicians target lower leg musculature, specifically the gastrocnemius, soleus, and peroneals, during rehabilitation. Clin­ icians should continue to be cognizant of lingering laxity differ­ ences in athletes with a previous ankle sprain and enhance focus on PF and EV strength during the rehabilitation process. The obser­ vation that strength is not affected by FAI grouping status indicates a need for a more accurate diagnostic tool or a tool in combination with the CAIT, incorporating functional deficits using the Identifi­ cation of Functional Ankle Instability and the Foot and Ankle Ability Measure, which has been recommended by the Interna­ tional Ankle Consortium.1

Conclusion College athletes who present with mechanical laxity on a previ­ ously injured ankle exhibit PF and EV strength deficits between ankles; in contrast to those with FAI who do not demonstrate strength deficits. These data indicate that clinicians should focus on challenging and focused strength rehabilitation in individuals with MAI and focus on other modalities, such as neuromuscular control and dynamic balance, in athletes with reported FAI. Further research should attempt to determine how a targeted rehabilitation and treatment plan affect those with MAI and FAI after a unilateral ankle sprain.

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JSR Vol. 28, No. 7, 2019

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