title: Peroneal electromechanical delay and fatigue in patients with chronic ankle instability.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effect of chronic ankle instability (CAI) on electromechanical delay times (EMD) before and after fatigue. Understanding the mechanisms that contribute to CAI is essential for the development of effective rehabilitation programmes. It was hypothesized that patients with CAI will demonstrate prolonged EMD times compared to healthy subjects and that fatigue will cause greater increases in EMD times in the CAI group.
  
  
  METHODS
  Twenty-one male volunteers participated in the study providing data on 16 ankles with CAI and 26 with no history of ankle injury. EMD was measured on an isokinetic dynamometer. Measurements were taken with the ankle in neutral (0°) and at 30° of inversion. All subjects followed an isokinetic fatigue protocol until eversion torque fell below 50 % of initial torque for three consecutive repetitions. A 2 × 2 × 2 ANOVA was used to calculate the effect of ankle status (CAI vs. healthy), fatigue, angle (0° vs. 30°) and their interactions on EMD.
  
  
  RESULTS
  Fatigue caused a significant increase on EMD [non-fatigued: 122(29)ms vs. fatigue 155(54)ms; p < 0.001]. EMD times were shorter at 30° of inversion compared to neutral [neutral: 145(39)ms vs. 30° of inversion: 132(40)ms, p = 0.015]. An interaction effect for ankle status and angle was found (p = 0.026) with CAI ankles demonstrating longer EMD [CAI: 156(45)ms vs. healthy: 133(40)ms] in neutral but not at 30° of inversion [CAI: 133(46)ms vs. 132(33)ms].
  
  
  CONCLUSIONS
  Patients with CAI had longer EMD times in neutral, but not when the ankle was placed in inversion. This suggests that rehabilitation programmes may be more effective when retraining occurs with the ankle in neutral position. It is likely that low EMD times prevent ankle acceleration at the beginning of the mechanism of injury, but they are less important when the ankle has already inverted at 30°. Both CAI and healthy subjects demonstrated longer EMD after fatigue, emphasizing the importance of proper conditioning in the prevention of delayed peroneal response and subsequent ankle injury. Improving resistance to fatigue of the peroneals may prove to be an effective prevention tool of ankle sprain recurrence in patients with CAI.
  
  
  METHODS
  III.
authors.affiliation: Orthopaedic Sports Medicine Center, Department of Orthopaedic Surgery, University of Ioannina, Ioannina, Greece. dflevas@hotmail.com.
authors.forename: Dimitrios A
authors.initials: DA
authors.lastname: Flevas
authors.affiliation: Department of Orthopaedic Surgery, Klinik Sanssouci Potsdam - Berlin, Berlin, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Bernard
authors.affiliation: Orthopaedic Sports Medicine Center, Department of Orthopaedic Surgery, University of Ioannina, Ioannina, Greece.|Metropolitan Hospital, Athens, Greece.
authors.forename: Stavros
authors.initials: S
authors.lastname: Ristanis
authors.affiliation: Orthopaedic Sports Medicine Center, Department of Orthopaedic Surgery, University of Ioannina, Ioannina, Greece.
authors.forename: Constantina
authors.initials: C
authors.lastname: Moraiti
authors.affiliation: Orthopaedic Sports Medicine Center, Department of Orthopaedic Surgery, University of Ioannina, Ioannina, Greece.
authors.forename: Anastasios D
authors.initials: AD
authors.lastname: Georgoulis
authors.affiliation: Orthopaedic Sports Medicine Center, Department of Orthopaedic Surgery, University of Ioannina, Ioannina, Greece.|Discipline of Physiotherapy, Faculty of Health Sciences, University of Sydney, Sydney, NSW, Australia.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Pappas
mesh_terms: D000293:Adolescent; D000328:Adult; D016512:Ankle Injuries / Q000150:complications / Q000503:physiopathology / Q000534:rehabilitation; D000843:Ankle Joint / Q000503:physiopathology*; D002908:Chronic Disease; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013180:Sprains and Strains / Q000150:complications / Q000503:physiopathology / Q000534:rehabilitation; D055815:Young Adult
keywords: Ankle instability; Ankle sprain; Electromechanical delay; Peroneal delay; Reaction time