Background

There has been extensive sportsmedicine research investigatingthe residual effects of lateralankle sprains and chronic ankleinstability (CAI). While there area plethora of studies of neuro-muscular control in CAI subjectsusing instrumented methods,there is a clear lack of non-instru-mented clinically applicable teststo assess neuromuscular andfunctional deficits in patientswith CAI. There also appears tobe a relationship between alter-ed neuromuscular control andmuscle fatigue. Deficits in staticpostural control related to CAIand fatigue have been investi-gated separately, but there is lit-tle evidence to link these factors

to performance measures ofdynamic postural control.

Objective

To investigate the effects offatigue and CAI on performancemeasures of the Star ExcursionBalance Test (SEBT), a measureof dynamic postural control.

Design and Setting

For each of the three designatedreaching directions, four separate 5[Day] x2 [Side] x2 [Time] ANOVA’swith a between factor of Groupwere performed for normalizedreach distance, maximal ankle dor-siflexion, knee flexion, and hip flex-ion angles. All data were collectedin a research laboratory.

Practical Implications:

The results of this study demonstrate that chronic ankle instability

disrupts dynamic postural control most noticeably by altering neu-

romuscular control proximal to the knee. This effect is magnified with

the presence of fatigue.

Grant Information Summary:

The Effects of Chronic AnkleInstability and Fatigue on DynamicPostural Control

N A T I O N A L A T H L E T I C T R A I N E R S ’ A S S O C I A T I O N

Subjects

Thirty subjects (16 Healthy, 14CAI) participated.

Measurements

All subjects completed 5 testingsessions during which sagittalplane kinematics and reachingdistances were recorded whileperforming 3 reaching direc-tions (anterior, medial, and pos-terior) of the SEBT (Figure 1)with the same stance leg beforeand after different fatiguingconditions. The procedure wasre-peated for both legs duringeach session.

Results

The involved side of the CAI sub-jects displayed smaller reachdistance values for all threereaching directions compared tothe non-injured side and theHealthy group. (Table 1). Theeffects of fatigue amplified thistrend.

Conclusions

The results demonstrate thatCAI and fatigue disrupted SEBTperformance (MAXD) mostnoticeably by altering control ofsagittal plane joint angles prox-imal to the ankle.

Principal Investigator:

Phillip A. Gribble,PhD, ATC

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Table 1: Group by Side Interaction:MAXD [reach distance (cm)/leg length (cm)] ± standard error

Figure 1: Star Excursion Balance Test

CAI: injured side CAI: un-injuredside

Healthy: matchedinjured side

Healthy: matchedun-injured side

Anterior Reach(F1,28=5.56,

P=.026)0.784 ± .016 0.818 ± .017 0.768 ± .015 0.771 ± .016

Medial Reach(F1,28=5.88,

P=.022).875 ± .015 .900 ± .018 .877 ± .014 .871 ± .017

Posterior Reach(F1,28=7.01,

P=.013).890 ± .024 .909 ± .024 .908 ± .023 .899 ± .022