(ATHENS, Ohio – April 27, 2015) Declining muscle strength is common
as people age, which can lead to falls and affect a person’s ability
to move and function independently. It’s often believed that a
muscle’s strength is directly tied to its mass. However, researchers
at the Ohio University Heritage College of Osteopathic Medicine have
discovered that muscle weakness in aging populations occurs in part
due to a breakdown in communication between the motor cortex, the
part of the brain that controls voluntary movement, and muscles.
Historically, the motor cortex was thought to affect movement and
coordination but not muscle strength.
“Several previous studies
compared young adults with seniors and found no differences in the
ability of the nervous system to activate muscles,” said Brian
Clark, Ph.D., professor of physiology and neuroscience at the
Heritage College and executive director of the Ohio Musculoskeletal
and Neurological Institute (OMNI). “When we ran the same comparison,
we didn’t see differences either. However, we went a step further
and grouped older adults by their level of muscle strength. When we
did this, the differences between our stronger and weaker seniors
For the study, research participants were asked to flex their
wrist before, during and after receiving electrical pulses to
stimulate the nerves in their forearm, which flexes the hand.
Additionally, Clark’s team used transcranial magnetic stimulation, a
non-invasive and painless way to explore brain physiology, to
examine the relationship between weakness and levels of brain
excitability. Significant differences were found when comparing
senior groups, with weaker seniors having higher levels of
inhibition in the brain and an impaired ability to voluntarily
activate their muscles. While several age-related factors contribute
to dynapenia (age-related loss of muscle strength), this study found
that degradation of the motor cortex is also partially responsible.
Although the study did not identify what happens in other muscle
groups or how aging alters the way the motor nerves fire, Clark is
currently conducting a four-year research project funded by the
National Institutes of Health to better identify the specific
neurological mechanisms that play a role in weakness in older
“Our results have major implications for clinicians and
scientists who are developing interventions to enhance muscle
strength in older adults. The most effective approach will most
likely employ multiple strategies, including ones that work with the
nervous system as well as the muscular system,” said Clark.
The results from the study have been published in the
Journals of Gerontology Series A: Biological Sciences and Medical
Sciences. Along with Clark, the paper is co-authored by S. Lee
Hong, Ph.D., Timothy D. Law, D.O., and David W. Russ, P.T., Ph.D. of
OHIO as well as Janet L. Taylor, M.D. from Australia.
“Many people are adversely affected by age-related muscle
weakness,” said Heritage College Executive Dean Kenneth H. Johnson,
D.O. “Through innovative research projects like this, we build a
better understanding of the body, which may lead to interventions
that improve strength and mobility in older adults.”
The study was supported in part through several grants from the
National Institutes of Health.
OMNI is an interdisciplinary institute that brings together
scientists from several Ohio University colleges and schools to
study disorders of the musculoskeletal and nervous systems. OMNI has
strong programmatic efforts in two research divisions: 1)
musculoskeletal and neurological pain disorders and 2) healthy
aging. The research across these two divisions has an overarching
aim of developing interventions that remove barriers to independent
physical mobility and ultimately reduce disability.
About Heritage College
The Ohio University Heritage College of Osteopathic Medicine is a
leader in training dedicated primary care physicians who are
prepared to address the most pervasive medical needs in the state
and the nation. Approximately 50 percent of Heritage College alumni
practice in primary care and nearly 60 percent practice in Ohio.
CARE LEADS HERE.