Abstracts

A majority of studies documented areduced ankle muscle activity, particularly of the peroneus longusmuscle (PL), in patients with functional ankle instability (FI). Itis considered valid that foot orthoses as well as sensorimotortraining have a positive effect on ankle muscle activity in healthyindividuals and those with lower limb overuse injuries or flatarched feet (reduced reaction time by sensorimotor exercises;increased ankle muscle amplitude by orthoses use). However, theacute- and long-term influence of foot orthoses on ankle muscleactivity in individuals with FI is unknown. AIMS: The presentthesis addressed (1a) acute- and (1b) long-term effects of footorthoses compared to sensorimotor training on ankle muscle activityin patients with FI. (2) Further, it was investigated if theorthosis intervention group demonstrate higher ankle muscleactivity by additional short-term use of a measurement in-shoeorthosis (compared to short-term use of shoe only) afterintervention. (3) As prerequisite, it was evaluated if ankle muscleactivity can be tested reliably and (4) if this differs betweenhealthy individuals and those with FI. METHODS: Threeintervention groups (orthosis group [OG], sensorimotor traininggroup [SMTG], control group [CG]), consisting of both, healthyindividuals and those with FI, underwent one longitudinalinvestigation (randomised controlled trial). Throughout 6 weeks ofintervention, OG wore an in-shoe orthosis with a specific PLstimulation module, whereas SMTG conducted home-based exercises.CG served to measure test-retest reliability of ankle muscleactivity (PL, M. tibialis anterior [TA] and M. gastrocnemiusmedialis [GM]). Pre- and post-intervention, ankle muscle activity(EMG amplitude) was recorded during normal unperturbed (NW) andperturbed walking (PW) on a split-belt treadmill (stimulus 200 mspost initial heel contact [IC]) as well as during side cutting(SC), each while wearing shoes only and additional measurementin-shoe orthoses (randomized order). Normalized RMS values (100%MVC, meanSD) were calculated pre- (100-50 ms) and post (200-400ms) - IC. RESULTS: (3) Test-retest reliability showed a highrange of values in healthy individuals and those with FI. (4)Compared to healthy individuals, patients with FI demonstratedlower PL pre-activity during SC, however higher PL pre-activity forNW and PW. (1a) Acute orthoses use did not influence ankle muscleactivity. (1b) For most conditions, sensorimotor training was moreeffective in individuals with FI than long-term orthoticintervention (increased: PL and GM pre-activity and TAreflex-activity for NW, PL pre-activity and TA, PL and GMreflex-activity for SC, PL reflex-activity for PW). However,prolonged orthoses use was more beneficial in terms of an increasein GM pre-activity during SC. For some conditions, long-termorthoses intervention was as effective as sensorimotor training forindividuals with FI (increased: PL pre-activity for PW, TApre-activity for SC, PL and GM reflex-activity for NW).Advisors/Committee Members: Mller, Steffen (advisor).