Orthopedic Projects
Paul LaStayo, PT, PhD leads a team of investigators exploring the influence of eccentric (lengthening) muscle contractions following orthopedic surgical procedures and how these muscle actions influence locomotion and sport activities. Past investigations have focused on how progressively increasing high force eccentric exercise impacts the outcome of anterior cruciate ligament reconstruction (ACL-R) and total knee joint replacement (TKR) respectively.
During normal locomotion and mobility tasks, muscles do much more than produce useful work by shortening. When the force acting on muscle, such as gravity, exceeds the force produced by the muscle, it will lengthen eccentrically, absorbing mechanical work. In tandem with Stan Lindstedt, PhD at Northern Arizona University, Dr LaStayo is investigated how these "lengthening contractions" are used both to convert kinetic energy to heat, like a shock absorber (e.g., hiking downhill) or to store elastic recoil (i.e., elastic strain) energy for subsequent use, like a spring (e.g., running).
Research Focus
Quadriceps atrophy is a major impairment after ACL-R and TKR. This atrophy, coupled with strength and functional deficits is evident primarily during the first 3 months following ACL-R but can persist for several months or years. Similarly those with TKR have chronic atrophy and weakness. The weakness following TKR, however, is also due in large part to a neural inhibition. Because eccentric resistance exercise is a potent stimulus for increasing muscle size and strength, we are interested in the structural, functional and neurological effects of eccentric exercise acutely after ACL-R and chronically after TKR.
Large gains in strength and power are accompanied by changes in the "tuned" frequency of muscle use in response to chronic eccentric training. Shifts in a number of structural and functional properties within the muscle fiber are evident, though the exact mechanisms of these adaptations have not been elucidated. The ability of high force resistance exercise to influence neurologic inhibition is also not clear, though we are actively pursuing this question. We are also exploring the many structural and functional changes that can be attributed to the gigantic cytoskeletal protein titin.
Current Projects
The current research aims are to determine whether the addition of high force eccentric resistance exercise to traditional physical therapy can amplify the return of muscle structure (quadriceps muscle volume), influence the cytoskeletal protein titin, enhance neurologic recruitment and force production while carrying over to whole body performance and mobility.
The methods used to achieve these aims include whole and cell muscle imaging (MRI, light and electron microscopy), strength/power testing (with and without superimposed electrical stimulation) a battery of whole body performance tests and self-report questionnaires. A novel form of resistance training, eccentric ergometry, is the human experimental model and rats running downhill on a treadmill has been used as our non-human model.
Collaborators
Lee Dibble, PT, PhD, ATC
Associate Professor, Department of Physical Therapy
University of Utah
Robin L. Marcus, PT, PhD, OCS
Associate Professor, Department of Physical Therapy
University of Utah
Robert Burks, MD
Patrick Greis, MD
Christopher Peters, MD
Department of Orthopedics
University of Utah
Stan Lindstedt, PhD
Department of Biological Sciences
Northern Arizona University
