University of Oregon


The main research interest of the Neurophysiology Lab is age-related changes in neuromuscular function. The goal of this research is to better understand the mechanisms of reduced force production and increased fatigue resistance in aging muscle, and their role in changes in physical function. We aim to gain a clearer picture of “healthy aging” and to develop strategies to maintain physical function.

Approximately 37 million people in the United States are 65 years of age or older. Within this population there is a striking decline in physical function, with over 40% of older individuals reporting limitations in one or more activities of daily living. These functional limitations severely impact the quality of life in older individuals, and have a significant economic impact in terms of health care costs. A better understanding of the mechanisms of physical function decline, and the development of feasible interventions to prevent such deleterious changes, is therefore important.

Current studies in the lab are designed to test age-related changes in sensory feedback from the working muscles to the central nervous system (CNS). We are using a variety of techniques, including ischemia and muscle vibration to manipulate sensory feedback from the muscles and measuring the impact on the output of the central nervous system. Measures of CNS function are obtained with a combination of electromyography techniques, peripheral nerve stimulation and transcranial magnetic stimulation (TMS). We are also working with individuals at the Lewis Center for Imaging to establish protocols using magnetic resonance imaging and spectroscopy to couple anatomical and energetic information with our neurophysiological measures. These studies are aimed at a mechanistic understanding of age-related changes in muscle function. We also have an ongoing interest in the functional role of changes in the neuromuscular system. Specifically, we are interested in how these changes impact physical function, and how manipulation of sensory feedback may improve performance.

Recent publications

Peer-reviewed articles:

1.      Christie A, Snook EM, Kent-Braun JA. Systematic review and meta-analysis of skeletal muscle fatigue in old age. Medicine and Science in Sports and Exercise, 43: 568-577, 2011.

2.      Christie A, Gabriel DA. A comparison of models for calculating reliability of the H-reflex. Measurement in Physical Education and Exercise Science, 14: 164-175, 2010.

3.      Christie A, Kamen G. Short-term training adaptations in maximal firing rate and motoneuron AHP duration. Muscle & Nerve, 41(5): 651-660, 2010.

4.      Christie A, Inglis JG, Kamen G, Gabriel DA. Relationships between surface EMG variables and motor unit firing rates. European Journal of Applied Physiology, 107(2): 177-185, 2009.

5.      Christie A, Kamen G. Motor unit firing behavior during prolonged 50% MVC dorsiflexion contractions in young and older adults. Journal of Electromyography and Kinesiology, 19(4): 543-552, 2009.


Book Chapters:

1.      Kent-Braun JA, Fitts, RH, Christie AD. Skeletal muscle fatigue. In: Comprehensive Physiology, Wiley-Blackwell, Hoboken, NJ, in press.

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