Examining Neuromuscular Control During Landings on a Supinating Platform in Persons With and Without Ankle Instability Gregory M. Gutierrez, * y PhD, Christopher A. Knight, z PhD, Charles B. Swanik, z PhD, ATC, Todd Royer, z PhD, Kurt Manal, § PhD, Brian Caulfield, || PhD, and Thomas W. Kaminski, z PhD, ATC Investigation performed at the Human Performance Laboratory, Department of Health, Nutrition & Exercise Sciences, University of Delaware, Newark, Delaware Background: Ankle instability is a costly public health concern because of the associated recurrent sprains. It is evident there are neuromuscular control deficits predisposing these individuals to their ankle ‘‘giving way.’’ Individuals with a history of lateral ankle sprain, who did not develop instability, may hold the key to understanding proper neuromuscular control after injury. Hypotheses: On the basis of previous research, the authors hypothesized that individuals with ankle instability would demon- strate reduced peroneal activation, causing a more inverted position of the ankle, before and after landing. Study Design: Controlled laboratory study. Methods: This study aimed to evaluate preparatory and reactive neuromuscular control when landing on a custom-designed ankle supinating device in individuals with ankle instability (AI), individuals with a history of lateral ankle sprains without instability (LAS), and uninjured controls (CON). Forty-five participants (15 per group) were asked to land on a device built to simulate the mechanism of a lateral ankle sprain (supination) while kinematics and muscle activity of the lower extremity were monitored. Results: Contrary to our hypotheses, the AI group displayed significantly increased preparatory (P = .01) and reactive (P = .02) peroneal activation, while the LAS group demonstrated a trend toward increased preparatory tibialis anterior muscle activation (P = .07), leading to a decreased plantar flexion of the ankle at landing. Conclusion: The AI group was likely acting in a protective fashion to a potentially injurious situation, indicating these individuals can activate the peroneals if needed. The LAS group’s strategy may be a safer strategy in that a less plantar-flexed position of the ankle is more close-packed and stable. Further, it appears the long-latency response of the peroneals may be enhanced in these individuals, which indicates motor learning at the supraspinal level to promote dynamic restraint. Clinical Relevance: Individuals with AI can increase peroneal activation when necessary to dynamically stabilize the ankle, indicat- ing the potential for training/rehabilitation. Further, the LAS group may deploy a different control strategy after injury to protect the ankle from subsequent sprains, which deserves investigation during activities of daily living. A greater understanding of these strat- egies will lead to the development of more appropriate treatment paradigms after injury to minimize the incidence of instability. Keywords: sensorimotor control; biomechanics; copers; ankle sprain Lateral ankle sprains are among the most common orthopae- dic injuries, estimated to occur at a rate of 1 injury per 10 000 people daily. 19 The disruption of the lateral ligament complex often leads to mechanical instability (ligamentous laxity), pain, swelling, peroneal muscle weakness, and neuromuscu- lar dysfunction, leaving it particularly susceptible to further injury. 13 The result of these residual symptoms is often recur- rent ankle sprains, which have been linked to an increased risk of osteoarthritis and articular degeneration. 8,12 In 1965, Freeman et al 7 were the first to describe func- tional ankle instability (as opposed to mechanical instabil- ity) as a condition characterized by repeated episodes of the ankle ‘‘giving way’’ after an initial lateral ankle sprain event. They postulated that ankle instability was attribut- able to articular deafferentation after injury to the lateral ankle ligaments. Many researchers have studied this closed-loop mechanism of ankle instability. 2,6,20,23 Most of this research has involved testing in static conditions, despite the fact that most injuries occur during dynamic activities (running, cutting, and landing). More importantly, *Address correspondence to Gregory M. Gutierrez, PhD, Assistant Professor, Department of Physical Therapy, Steinhardt School of Culture, Education, and Human Development, New York University, 380 Second Ave, #423, New York, NY 10010 (e-mail: gmgutierrez@gmail.com). y Arthur J. Nelson, Jr Human Performance Laboratory, Department of Physical Therapy, New York University, New York, New York. z Human Performance Laboratory, Department of Health, Nutrition & Exercise Sciences, University of Delaware, Newark, Delaware. § Center for Biomedical Engineering Research, Department of Mechanical Engineering, University of Delaware, Newark, Delaware. || Institute for Sport and Health, School of Physiotherapy and Perfor- mance Science, University College of Dublin, Belfield, Dublin, Ireland. The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. The American Journal of Sports Medicine, Vol. XX, No. X DOI: 10.1177/0363546511422323 Ó 2011 The Author(s) 1 AJSM PreView, published on September 14, 2011 as doi:10.1177/0363546511422323