Gait & Posture 41 (2015) 282–287

Effects of focal ankle joint cooling on unipedal static balance inindividuals with and without chronic ankle instability

Kyung-Min Kim a,*, Joseph M. Hart b, Susan A. Saliba b, Jay Hertel b

a Texas State University, San Marcos, TX, United Statesb University of Virginia, Charlottesville, VA, United States

A R T I C L E I N F O

Article history:

Received 27 April 2014

Received in revised form 5 September 2014

Accepted 16 October 2014

Keywords:

Cryotherapy

Postural control

Center of pressure

A B S T R A C T

Application of cryotherapy over an injured joint has been shown to improve muscle function, yet it is

unknown how ankle cryotherapy affects postural control. Our purpose was to determine the effects of a

20-min focal ankle joint cooling on unipedal static stance in individuals with and without chronic ankle

instability (CAI). Fifteen young subjects with CAI (9 males, 6 females) and 15 healthy gender-matched

controls participated. All subjects underwent two intervention sessions on different days in which they

had a 1.5 L plastic bag filled with either crushed ice (active treatment) or candy corn (sham) applied to

the ankle. Unipedal stance with eyes closed for 10 s were assessed with a forceplate before and after each

intervention. Center of pressure (COP) data were used to compute 10 specific dependent measures

including velocity, area, standard deviation (SD), and percent range of COP excursions, and mean and SD

of time-to-boundary (TTB) minima in the anterior–posterior (AP) and mediolateral directions. For each

measure a three-way (Group–Intervention–Time) repeated ANOVAs found no significant interactions

and main effects involving intervention (all Ps > 0.05). There were group main effects found for mean

velocity (F(1,28) = 6.46, P = .017), area (F(1,28) = 12.83, P = .001), and mean of TTB minima in the AP

direction (F(1,28) = 5.19, P = .031) indicating that the CAI group demonstrated greater postural instability

compared to the healthy group. Postural control of unipedal stance was not significantly altered

following focal ankle joint cooling in groups both with and without CAI. Ankle joint cryotherapy was

neither beneficial nor harmful to single leg balance.

� 2014 Elsevier B.V. All rights reserved.

Contents lists available at ScienceDirect

Gait & Posture

jo u rn al h om ep age: ww w.els evier .c o m/lo c ate /g ai tp os t

1. Introduction

Chronic ankle instability (CAI) is a debilitating collection ofsymptoms that persists following an initial ankle sprain [1,2]. It hasbeen documented that approximately 30% of ankle sprain patientsdevelop CAI [2]. CAI is primarily characterized by repetitive boutsof the ankle giving way, feeling of ankle instability, and recurrentankle sprains [3]. Although CAI has been associated with a varietyof mechanical and sensorimotor deficits [1,2], postural controlimpairments have been suggested as a primary contributing factor[4]. Rehabilitation programs with an emphasis on postural controlfor patients with CAI have been shown to lead to improved clinicaloutcomes [5].

* Corresponding author at: Department of Health and Human Performance, Texas

State University, San Marcos, TX 78666, United States. Tel.: +1 512 245 4373;

fax: +1 512 245 8678.

E-mail address: kmk102@txstate.edu (K.-M. Kim).

http://dx.doi.org/10.1016/j.gaitpost.2014.10.017

0966-6362/� 2014 Elsevier B.V. All rights reserved.

Cryotherapy is one of the most common modalities used insports medicine. Traditionally, it is used for a variety of treatmentpurposes including decreased inflammation, pain, swelling, andmuscle spasm [6,7]. Application of cryotherapy over a joint usingone or two ice bags has been shown to increase muscle activation[8–12] and potentially lead to muscle strength gains[10,12,13]. These studies [10,11] attributed the improved musclefunction to increased alpha motoneuron recruitment followingjoint cooling. Recently, cryotherapy applied to the ankle joint hasbeen found to facilitate alpha motoneuron pool excitability of thesoleus and fibularis longus in individuals with CAI [8,9]. Further-more, knee cryotherapy was found to restore deficits in quadricepsmuscle fiber conduction velocity [13], and also negated thefunctional movement deficiencies associated with experimentallyinduced knee joint effusion [14]. These results suggested that jointcryotherapy might have therapeutic potential to enhance func-tional outcomes in patients with joint pathology.

Ankle cryotherapy resulting in increased alpha motoneuronpool excitability (aMNPE) may have the potential to improve

K.-M. Kim et al. / Gait & Posture 41 (2015) 282–287 283

postural control. There are multiple studies determining thatdecreased aMNPE is associated with postural control deficits inindividuals with postural instability due to various pathologiesincluding CAI [15–17]. There is also evidence that an intervention,electrical perturbation during bipedal standing, directly aimed atevoking aMNPE did restore the diminished aMNPE, and lead toimprovement in postural control [18]. There was a strongcorrelation between changes in aMNPE and postural controlfollowing the intervention [18]. These findings indicate thatdecreased aMNPE may play a role in postural control deficits.

Two previous studies [19,20] have assessed unipedal posturalcontrol performance following ankle joint cooling, and bothreported that balance was not adversely affected. However, thesefindings are not convincing because of methodological limitationsincluding the lack of a control condition. This warrants a follow-upstudy with a sound design and more outcome variables of posturalcontrol to confirm or refute the previous findings. We wereinterested in how the ankle cryotherapy would affect not onlynormal postural control in healthy subjects, but also impairedpostural control in subjects with CAI because focal ankle jointcooling has been demonstrated to increase aMNPE in both groups[8–10,21]. Therefore, the purpose of the present study was todetermine the effects of a 20-min focal ankle joint cooling on quietunipedal postural control in individuals with and without CAI. Wehypothesized that the ankle cryotherapy would significantlyimprove static postural control in individuals with and withoutCAI.

2. Methods

We performed a laboratory study that employed a crossoverdesign. Independent variables were group (CAI and healthycontrol), intervention (ankle cryotherapy, sham), and time (pre-and post-intervention). Primary dependent variables were 10 pa-rameters of center of pressure (COP) excursions recorded during aquiet unipedal stance for 10 s. Secondary outcomes were scores ona visual analog scale to represent subject’s perceived level ofpostural control during the 10-s unipedal stance and the number offailed trials of the unipedal task. All subjects received the anklecryotherapy and sham treatments on separate days at least 24 hapart. The order of treatment sessions was randomly assigned. Alloutcomes were collected before and immediately followingintervention.

2.1. Subjects

Fifteen subjects with CAI and 15 healthy controls without anyhistory of ankle sprains recruited from a university communityparticipated in the present study. Subject demographics are shownin Table 1. Subjects were assigned to either the CAI group orhealthy control group based upon their current ankle status and ahistory of ankle injury. We utilized the previously reported

Table 1Subject demographics (mean and standard deviation).

Group CAI Healthy control

Subjects 15 15

Sex 6 females, 9 males 6 females, 9 males

Age (yrs) 22.6 � 5.8 23.8 � 5.8

Height (cm) 174.7 � 8.1 171.9 � 9.9

Mass (kg) 74.9 � 12.8 68.9 � 15.5

FAAM-ADL (%) 82.7 � 6.5 100

FAAM-Sport (%) 65.0 � 9.3 99.7 � 1.3

Number of previous ankle sprains 4.9 � 4.8 0

Months since the latest ankle sprain 13.5 � 7.3 N/A

Abbreviation: CAI, chronic ankle instability; FAAM, foot and ankle ability measure;

ADL, activity of daily living.

inclusion criteria for each group [22,23]. Subjects were excluded ifthey reported current lower extremity injuries within the past6 weeks, any history of lower extremity surgery, neuropathies,diabetes, balance disorder, Raynaud’s diseases, and any coldinduced circulatory problems, and other conditions known toaffect balance. For subjects with bilateral CAI, their self-reportedworst limb was used, and limbs of healthy controls were side-matched to CAI subjects for analysis purposes. All subjectsprovided informed consent and the study was approved by theUniversity’s Institutional Review Board.

2.2. Instruments

Postural control during unipedal stance was assessed with theAccusway Plus forceplate (AMTI, Watertown, MA). COP wascalculated from the three dimensional forces and moments arisingfrom the foot/forceplate interface through the Balance ClinicSoftware (AMTI, Watertown, MA). COP data were sampled at a rateof 50 Hz and a fourth-order low zero lag, low-pass filter with acutoff frequency of 5 Hz was used to filter the COP data [24,25]. Acustom software program processed in MatLab (MathWorks, Inc.,Natick, MA) and the Balance Clinic were used to calculate10 specific COP parameters [24,25].

Skin surface and ambient air temperatures were collected usingPT-6 surface thermocouples (Physitemp Instruments Inc, Clifton,NJ) interfaced to Physitemp Thermes USB electrothermometer(Physitemp Instruments, Inc., Clifton, NJ). The temperature datawere stored through the MCC DAQ Software (MeasurementComputingTM, Norton, MA).

2.3. Procedures

2.3.1. Postural control in Unipedal stance

Subjects performed three trials of unipedal stance with eyesclosed for 10 s on a forceplate. Subjects were instructed to performa unipedal stance on the involved limbs of subjects with CAI or theside-matched limbs of healthy controls. Specific foot positions onthe forceplate and balance assessment were consistent with apreviously reported manner [25].

2.3.2. Ankle cryotherapy and sham treatments

Subjects were positioned supine on a table to receive eitherankle cryotherapy or sham treatments on different days at least24 h apart. The ankle cryotherapy consisted of one plastic bag filledwith 1.5 L of crushed ice that was applied to the anterior aspect ofthe ankle with an elastic bandage to secure it for 20 min. The shamtreatment consisted of the same size bag, but filled with the samevolume of room temperature candy corn that was placed on thesame location of the ankle with an elastic bandage for 20 min. Allparticipants were asked to avoid any forms of cryotherapytreatments at least 24 h prior to study participation.

2.3.3. Surface temperature

Two surface thermocouples were used to measure skin surfacetemperatures at two sites: one over the sinus tarsi of the ankle andthe other over the soleus muscle belly 2–3 cm distal to thegastrocnemius. Another surface thermocouple measured ambientair temperature in the laboratory. Three measurements at each sitewere collected before and immediately after removing an ice bagfrom the ankle joint. These temperature measurements wererecorded to ensure that the ankle cryotherapy cooled only theankle joint, not the surrounding muscles.

2.3.4. Visual analog scale

Visual analog scales [22,26] were used to quantify a perceivedlevel of balance performance during unipedal stance. After each

K.-M. Kim et al. / Gait & Posture 41 (2015) 282–287284

trial of the postural task, subjects were rated the level of theirbalance performance by drawing a vertical line across a 100 mmhorizontal line ranging from 0 to100 with 0 representing ‘‘worstbalance’’ and 100 indicating ‘‘best balance’’.

2.4. Data processing

Postural control of unipedal stance was assessed with10 specific COP measures. There were 6 traditional COP measuresand 4 time-to-boundary (TTB) measures utilized. The traditionalCOP measures included the mean velocity, area, standarddeviation, and percent of available range used for COP excursions.For all of these measures, a larger value indicates greater posturalinstability.

In addition to the traditional measures, TTB measures werecalculated to provide insight into the spatiotemporal aspects ofpostural control as these measures have been shown to besensitive to detecting balance deficits associated with CAI[25,27]. The methods used to compute TTB measures in theanteroposterior (AP) and mediolateral [28] directions have beenpreviously described in detail [24,25,27]. Specific TTB measuresserving as dependent variables were mean of the minima and thestandard deviation of the minima in the AP and ML directions. Alower TTB measure indicates greater postural instability[24,25,27].

2.5. Statistical analysis

The mean of each outcome measure was used for statisticalanalysis. For each COP measure, a three-way ANOVA (Group,Intervention, and Time) with repeated measures were performedto determine the effects of ankle cryotherapy on postural control.Another three-way ANOVA was conducted for VAS scores to assesssubjective intervention effects on balance performance duringunipedal stance. Post hoc simple contrasts were conducted toidentify specific differences in the presence of significant inter-actions or main effects. Consistent with contemporary statisticalrecommendations [29], we elected to not apply corrections to thelevel of significance for multiple comparisons. The number of failedtrials was analyzed with nonparametic statistical tests because thedata were not found normally distributed. Mann–Whitney U testswere used to determine group difference at each of measurementpoints: pre-and post-intervention (ankle cryotherapy and sham).Additionally, Wilcoxon Signed Rank tests were utilized to assesswhether pre-intervention numbers of failed trials were differentfrom post-intervention. For the control variable of temperature,dependent t tests were performed for differences in temperature

Table 2Center of pressure (COP) measures taken during unipedal stance for 10 s (mean and st

COP parameters Chronic ankle instability

Ankle cryotherapy Sham

Baseline Follow-up Baseline Fo

Velocity (cm/s)a,b 8.55 � 2.5 7.75 � 1.7 8.47 � 2.1 8

SD ML 0.53 � 0.26 0.50 � 0.25 0.54 � 0.28 0

SD AP 0.71 � 0.40 0.65 � 0.31 0.66 � 0.31 0

Area (cm2)a 26.3 � 9.7 23.6 � 7.5 24.8 � 5.1 2

Percent range ML (%) 22.6 � 11.5 21.5 � 10.3 22.3 � 10.5 2

Percent range AP (%) 13.7 � 7.9 12.6 � 7.7 13.1 � 6.6 1

Mean Min. TTBML(s) 1.98 � 0.92 2.02 � 0.95 1.89 � 0.75 2

Mean Min. TTBAP(s)a 4.66 � 1.66 4.80 � 1.51 4.63 � 1.77 4

SD Min. TTBML 1.70 � 0.91 1.80 � 1.07 1.71 � 0.72 1

SD Min. TTBAP 3.04 � 1.52 3.32 � 1.55 3.20 � 1.54 3

Abbreviation: SD, standard deviation; ML, mediolateral; AP, anteroposterior; TTB, time-a A group main effect indicates that the CAI group had postural control deficits comb A time main effect indicates that postural control improved over time.

measurements between pre- and post-intervention. Alpha levelwas set a priori at p � 0.05. All statistical analyses were performedusing SPSS 19.0 statistical software (SPSS Incorporated, Chicago, IL,USA).

3. Results

Descriptive statistics for all measures are presented in Tables 2–5. There were no

significant interactions (all Ps > 0.05) found for any of the COP measures, however,

there were significant group main effects found in the mean COP velocity

(F(1,28) = 6.46, P = .017), COP area (F(1,28) = 12.83, P = .001), and mean of TTB minima

in the AP direction (F(1,28) = 5.19, P = .031). The CAI group was found to sway

significantly faster (8.3 � 0.41 cm/s) and over a larger area (25.2 � 1.2 cm2) than the

healthy control group (6.8 � 0.41 cm/s, 18.5 � 1.3 cm2). The mean of TTB minima in

the AP direction was significantly lower in the CAI group (4.7 � 0.36 s) than in the

healthy group (5.9 � 0.36 s). Additionally, there was a significant time main effect for

mean COP velocity (F(1,28) = 4.83, P = .036) with baseline measures (7.7 � 0.33 cm/s)

being significantly greater than follow-up measures (7.4 � 0.27 cm/s).

Significant interactions were not found on the VAS scores for subjective balance

performance, however, a group main effect (F(1,28) = 5.05, P = .033) was observed.

The CAI group (44.1 � 4.0 mm) reported worse perceptions of postural stability than

the control group (56.9 � 4.0 mm). The CAI group also had more failed trials than the

healthy group at all measurement points (all Ps < .029). Neither group significantly

changed the number of failed trials following either ankle cryotherapy or sham

(Table 4).

Our cooling method using an ice bag applied to the ankle joint significantly

decreased the skin surfaces overlying the ankle in both CAI (t(14) = 17.30, P < .001)

and healthy groups (t(14) = 18.23, P < .001), but no significant changes in soleus

surface temperature were noted. As expected, our sham treatment using candy corn

did not change skin surface temperature at either location. The ambient room

temperatures remained unchanged before and after intervention (Table 5).

4. Discussion

Our hypothesis that ankle joint focal cooling would improvepostural control during unipedal stance in groups with andwithout CAI was rejected as the ankle cryotherapy did notsignificantly affect any of the postural control measures in eithergroup. The findings were consistent with an absence of changesfound in VAS scores and the number of failed trials followingcryotherapy. The CAI group did demonstrate worse posturalcontrol than the control group regardless of the administration ofcryotherapy. These results clearly showed that the individualswith CAI had postural control deficits compared to the healthycontrols, which agrees with the conclusions recently made inmultiple systematic reviews [30–32]. Our method to cool the anklejoint with an ice bag was found to significantly decrease the skinsurface temperatures at ankle joint, but not the soleus muscles,indicating the hypothermal effect was given only to the ankle joint.

Our results clearly showed ankle joint cryotherapy did notnegatively affect postural control. To our knowledge, only two

andard deviation).

Healthy control

Ankle cryotherapy Sham

llow-up Baseline Follow-up Baseline Follow-up

.36 � 1.8 6.93 � 1.3 6.73 � 1.5 6.88 � 1.6 6.65 � 1.3

.54 � 0.28 0.51 � 0.27 0.50 � 0.25 0.51 � 0.30 0.52 � 0.27

.70 � 0.36 0.59 � 0.28 0.57 � 0.29 0.64 � 0.39 0.61 � 0.37

6.1 � 6.1 19.0 � 4.6 18.3 � 6.3 18.7 � 7.5 17.8 � 4.6

2.4 � 11.3 22.8 � 12.6 23.1 � 11.3 23.1 � 13.1 23.5 � 12.3

3.6 � 7.2 11.3 � 5.9 10.4 � 5.6 12.3 � 8.3 10.6 � 5.7

.00 � 0.89 2.15 � 1.24 1.99 � 0.94 2.02 � 1.04 2.08 � 0.94

.74 � 1.62 5.86 � 1.35 5.92 � 1.47 5.78 � 1.39 5.98 � 1.27

.81 � 1.01 1.90 � 0.50 1.85 � 0.46 1.92 � 0.59 2.13 � 0.51

.23 � 1.31 3.86 � 1.81 3.93 � 1.50 3.92 � 1.47 4.52 � 1.74

to-boundary; Min, minima.

pared to the healthy control group.

Table 3Visual analog scale scores (mm) of subjective levels of postural control during

unipedal stance for 10 s (mean and standard deviation).

Ankle cryotherapy Sham

Baseline Follow-up Baseline Follow-up

Chronic ankle instabilitya 42.3 � 18.1 44.27 � 15.8 45.80 � 17.5 44.00 � 13.3

Healthy control 54.3 � 18.2 58.40 � 19.8 58.47 � 19.28 56.33 � 20.9

a A group main effect indicates that the CAI group perceived less levels of balance

performance than the healthy control group.

Table 4Numbers of failed trials of a 10-s unipedal stance (median and range). It is noted

that there were no differences before and after intervention.

Ankle cryotherapy Sham

Baseline Follow-up Baseline Follow-up

Chronic ankle instability 2 (0–8)a 2 (0–6) 1 (0–8)a 1 (0–7)a

Healthy control 0 (0–2) 0 (0–2) 0 (0–3) 0 (0–2)

a A group difference indicates that the CAI group failed more numbers of trials

than the healthy control group.

K.-M. Kim et al. / Gait & Posture 41 (2015) 282–287 285

studies previously assessed unipedal postural control followingankle joint cooling in healthy subjects [19,20]. They both reportedthat postural control in healthy subjects was not substantiallyaffected after cryotherapy. Although the methodology of the twoprevious studies may be criticized, combined with the results ofour current study with a more robust design and additionalpostural control measures, there appears to be mounting evidenceindicating the ankle cryotherapy does not adversely affect posturalcontrol.

One previous study [33] has examined the effects of cryothera-py on single leg balance in patients with lateral ankle sprainswithin the 4–7 days. The balance performance, as assessed by MLpostural sway variability, was impaired following lower-legimmersion cryotherapy in which the injured ankle was immersedfor 20 min in a tub containing an ice water mixture [33]. This resultconflicts with our findings of no influence of ankle joint cooling onpostural control in patients with CAI. This discrepancy may be dueto the difference in body area being cooled (lower limb immersionversus focal cooling of the ankle joint) or the nature of the jointpathology (acute versus chronic) [33]. We attempted to locally coolthe skin surface overlying the ankle joint with an ice bag because ofpreviously reported favorable outcomes on muscle activationfollowing cold application with an ice bag to a joint [8–14]. Ourjoint cooling technique significantly decreased only the jointsurface, but not the soleus muscle surrounding the joint. Incontrast, the immersion cooling technique used in the previousstudy likely cooled all structures in the lower leg including theentire foot, ankle, and extrinsic muscles and tendons in thelower leg. The immersion cryotherapy likely decreased sensitivityof cutaneous, articular, and musculotendinous receptors thus

Table 5Skin surface temperatures (8C, mean and standard deviation).

Group Site Ankle cryotherapy

Baseline

Chronic ankle instability Ankle 30.86 � 2.1

Soleus 31.47 � 1.9

Room 23.64 � 1.6

Healthy control Ankle 30.49 � 1.7

Soleus 30.92 � 1.9

Room 22.95 � 1.8

a A difference indicates that ankle cryotherapy significantly decreased the skin surfa

resulting in alterations in single leg balance [33–35]. Posturalcontrol impairments following the ice water immersion have alsobeen found in healthy participants [36]. However, focal ankle jointcooling has not resulted in postural control deficits in healthyparticipants [19,20]. These results suggest that ice water immer-sion that cools both joints and their surrounding muscles may havedifferent effects than focal joint cooling. We surmise that posturalcontrol in unipedal stance may be impaired following cooling thelower leg due to direct muscle cooling, but not after focally coolingthe ankle joint.

It is believed that the multiple sensory inputs from afferentstructures in the ankle joint are necessary for the central nervoussystem (CNS) to execute successful postural control, and altera-tions in these sensory activities may cause alterations in posturalcontrol [2,25]. Three categories of mechanoreceptors responsiblefor sensing postural information to CNS in the ankle joint includescutaneous, articular, and musculotendious receptors. It is reason-able to assume that both focal ankle joint cooling and ice waterimmersion would affect cutaneous, articular, and tendonousreceptors on the anterolateral aspect of the ankle. The ice waterimmersion would also influence articular receptors elsewherearound the ankle and foot, but probably more importantly, itwould also cool the muscle spindles in the intrinsic and extrinsicfoot muscles. Muscles spindles, especially in the triceps surae, areextremely important in regulating postural control [34,35,37]. Thestudy utilizing mechanical vibration applied to the triceps surae asa perturbing tool demonstrated considerable postural deviations,indicating a vital role of muscle spindles in contributing toproprioception that is essential for accurate postural control[38,39]. Thus, the differing results on postural control betweenfocal ankle joint cooling and ice water immersion are likely due tothe influence that postural control has on the muscle spindles.

In addition to potential sensory effects of ankle joint cooling,there is evidence that ice bags applied to the knee or ankle jointsignificantly enhance motor function including muscle activation[8–13], muscle fiber nerve conduction velocity [13], force output[10,12,13], and functional performance [14]. It has been suggestedthat these improvements are due to increased motoneuronrecruitment following joint cooling [10,11]. We hypothesized thatankle joint cryotherapy would enhance postural control inindividuals both with and without CAI because the CNS wouldbetter accommodate to postural demands with the expandedalpha motoneuron pool of the ankle stabilizing muscles. However,our results did not support this hypothesis. One likely explanationfor these results may be the absence of changes in motoneuronpool excitability (MNPE) of ankle muscles after the similar icetreatment while standing [40]. Recently, Kim et al. [40] assessedMNPE of the soleus and fibularis longus, as assessed by Hoffmannreflex while their subjects laid prone and then stood in bipedal andunipedal stances. They found a 20-min ice bag application to theankle joint significantly increased MNPE in both muscles whileprone in a manner consistent with previous investigations [8,9],but they did not find any changes in MNPE in either standing

Sham

Follow-up Baseline Follow-up

12.08 � 2.8a 30.23 � 2.1 30.68 � 1.7

31.90 � 1.5 31.03 � 1.9 31.19 � 1.8

23.86 � 1.5 23.21 � 2.1 23.69 � 2.2

12.21 � 2.7a 30.16 � 1.5 30.25 � 1.7

30.74 � 1.8 30.78 � 1.4 30.83 � 1.2

22.89 � 1.3 22.86 � 1.2 22.93 � 1.2

ce overlying the ankle joint.

K.-M. Kim et al. / Gait & Posture 41 (2015) 282–287286

postures after cryotherapy. These results indicate that theincreased MNPE associated with ankle joint cooling found in anon-weight bearing position may not translate to weight bearingpositions. This discrepancy may have important applications forthe use of cryotherapy as a disinhibitory modality prior totherapeutic exercise.

In addition to the neurophysiological explanations of ourresults, our methodological choices may have influenced ourresults. First, we used a 20-min ice bag application to the anklejoint while some authors [8–10] found improved muscle functionwith 30-min of cold application. However, it should be noted that20-min of ice treatment has been shown to elicit MNPE of thesoleus and fibularis longus in both individuals with and withoutCAI [40]. Secondly, it has been suggested that exercise interventionfollowing an ice bag application to a joint would facilitate musclefunction [10–12], but the present study did not include an exerciseprotocol because it focused on isolated effects of joint cooling onpostural control. Finally, the present study did not utilize a truecontrol condition (no intervention), but had two treatmentconditions of cryotherapy and sham. In both conditions the bagcontaining either ice or candy corn was secured to the ankle withan elastic bandage. It is possible that joint compression with anelastic bandage may affect single leg balance performance,however, it must be noted that the compression wrap wasremoved when the treatment time elapsed and all balance testingwas performed without compression.

The results of the current study may be important in clinicalsettings where there is an impression of potential detrimentaleffects of cryotherapy on muscle function. We agree that directmuscle cooling may impair postural control [33,36], however, ourresults showed that focal cooling of the ankle joint did not impairpostural control. It does not appear that cryotherapy to either theankle joint or its surrounding musculature can enhance unipedalpostural control. On the other hand, focal joint cooling may be safeto use prior to therapeutic exercises aimed at improving muscleactivation and strength [10–13]. When cryotherapy is necessary inthe beginning of a rehabilitation session, it is important to focus onankle joint cooling to avoid deleterious effects on postural balanceassociated with more global cooling procedures including thesurrounding muscles as would occur with cold water immersion.

Surprisingly, we found an improvement in postural controlregardless of which intervention was applied, as there was asignificant decrease in the mean COP velocity after interventions.This result may reflect a learning effect and indicate the COPvelocity measure may be more sensitive to change than other COPmeasures, requiring a practice trial. It is also possible to speculatethat joint compression provided by elastic bandage used to securea plastic bag of ice or candy corn (sham) plays a role in slowing theCOP excursions. However, it is noted that the ankle joint wasreleased from the compression during postural control assess-ments.

In conclusion, we found that postural control during unipedalstance was impaired among individuals with CAI, but posturalcontrol was not altered following a 20-min focal ankle joint coolingin individuals both with and without CAI. These findings indicatethat a single session of ankle joint cryotherapy is neither beneficialnor harmful for single leg balance performance.

Acknowledgements

National Athletic Trainers’ Association Research and EducationFoundation funded the present study through Doctoral GrantProgram. The study sponsor does not play any role in the studydesign, in the collection, analysis and interpretation of data, in thewriting of the manuscript, and in the decision to submit themanuscript for publication.

Conflict of interest statement: There is no conflict of interests forany of the authors.

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