Christopher A. Knight, Ph.D. at the University of Delaware is seeking
applicants for Doctoral training with a research focus on the control of
muscular force at the level of the motor unit. Students will begin their
training in September of 2007 with NIH support to work on a project
described below. Competitive applicants will have earned a relevant,
research-oriented MS degree and exceptional applicants will possess
competency in statistics, computer programming, implementation of laboratory
hardware, and written and oral communication of research findings. Dr.
Knight is within the Department of Health, Nutrition and Exercise Sciences
in the College of Health Sciences:
. The Ph.D. program is organized within an
interdisciplinary program entitled Biomechanics and Movement Science (BIOMS) Potential applicants to the BIOMS
program should contact Dr. Knight directly at

1 R03 AG026322-01
Motor unit discharge and slowed motor output in elderly

The elderly are often frustrated by poor control during precision tasks, and
slower production of muscular force has specific importance in fall
prevention. Motor unit research is in dire need of expanded paradigms to
provide new information about control mechanisms during real-world tasks.
We will examine age-related differences in two relevant motor unit discharge
behaviors and provide information that can be used to improve movement
quality in older adults and also in patient populations. Aim 1 is about
rate coding during the precise control of sinusoidal isometric contractions.
It is hypothesized that that the amplitude of firing rate modulation is less
in older adults, perhaps due to enhanced twitch summation of aged muscle
fibers with slowed contractility. Aim 2 is about motor unit discharge
behavior during rapid force production from rest as well as from a
submaximal force level. It is hypothesized that during the initiation of
rapid contractions, the initial firing rates of aged motor units will be
slower and there will be fewer doublet discharges, as compared to young
adults. Motor unit and muscular force recordings, surface electromyography
and contractile properties will be obtained from the first dorsal
interosseous muscle of 20 young (65 years) adults.
Successful experiments in these conditions can be considered significant
progress in motor unit research. In addition to furthering knowledge of
normal aging at the level of the motor unit, this project will provide vast
new information about motor unit discharge behavior in general. Consider
for example: 1) the value of this normative data for similar research in
patient populations, and 2) a better knowledge of neural commands in healthy
individuals can help to improve the functional electrical stimulation of
paralyzed muscle. This project also provides the basis for future research
on the adaptability of these neural factors and function in older adults and
patient populations.