Heritage College of Osteopathic Medicine study reveals key insights into leg weakness in older adults

Researchers at the Ohio University Heritage College of Osteopathic Medicine led a groundbreaking study that sheds light on the mechanisms leading to leg weakness in older adults. Findings from this study provide crucial insights that could influence future interventions and treatments for age-related muscle weakness, which is a major public health concern because it often leads to debilitating physical limitations, diminished quality of life and increased health care costs for older adults.

The study finds that in older adults with leg extensor weakness, motor neurons fire less frequently. Motor neurons are cells found throughout the body that send signals from the brain and spinal cord to the muscles, leading them to move and perform actions like walking or standing. When this signaling is reduced, it leads to weaker muscle contractions and overall muscle weakness.

Researchers specifically focused on firing rates in the vastus lateralis muscle, which is part of the quadriceps in the upper thigh. It was found that older adults with leg weakness had significantly reduced motor unit firing rates in this region of the body compared to those without weakness. Additionally, using a computer model to simulate how changes in firing rates could affect muscle strength, researchers were able to predict that decreased motor neuron signaling could reduce muscle strength by up to 26 percent.

This novel discovery highlights the critical role motor unit firing rates play in maintaining muscle health and function. By identifying this relationship, the study opens new avenues for targeted therapies to preserve and improve muscle function in the aging population.

"Understanding what causes muscle weakness is essential if we want to develop effective interventions," said Brian Clark, Ph.D., Osteopathic Heritage Foundation Harold E. Clybourne, D.O., Endowed Research Chair, co-author and executive director of the Ohio Musculoskeletal and Neurological Institute (OMNI). "Now that this link has been identified, we can begin to focus on strategies to maintain muscle health in aging patients. These strategies may include specific types of exercise training as well as neurotherapeutics to enhance firing rates.”

Decreased motor nerve firing can occur naturally as the body ages. However, engaging in regular physical activity—particularly strength training—and maintain a nutritious diet can help maintain or improve muscle function as we age, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

The study’s lead author is Nathan Wages, Ph.D., a former post-doctoral fellow at Ohio University and currently an assistant professor of rehabilitation and movement sciences at Rutgers University. In addition to Clark, co-authors from the Heritage College are Leatha Clark, D.P.T. and Dallin Tavoian, Ph.D. Additional collaborators are Mohamed Mousa, Ph.D., Wright State University; David Arnold, M.D., University of Missouri; and Sherif Elbasiouny, Ph.D., Wright State University.

The Ohio Musculoskeletal and Neurological Institute (OMNI) works to improve the diagnosis, treatment, and prevention of musculoskeletal and neurological disorders through its two research centers: OMNI’s Center for Healthy Aging and OMNI’s Injury and Pain Research Center. The research across these centers seeks to enhance physical function and well-being, and ultimately reduce disability and pain-related suffering. OMNI is home to scientists across Ohio University with an interest in aging, pain, muscle, injury, bones, joints and brains. Its multidisciplinary research team draws widely from fields including neuroscience, skeletal muscle physiology, gerontology, musculoskeletal disease, functional biomechanics, health psychology and behavioral medicine. Ten OMNI researchers have been placed within the top five percent of scientists worldwide based on their lifetime citations as highlighted by the latest Scholar GPS rankings.