Simple resistance training may help counteract age-related nerve deterioration that puts seniors at risk of injuries from falls and other accidents, according to cross-institutional research led by Syracuse University postdoctoral researcher JoCarol Shields and Department of Exercise Science Professor Jason DeFreitas .
The nerves that control our muscles naturally degrade and become slower as we age, a process referred to as denervation. This degradation is especially problematic in sedentary individuals. Counteracting this deterioration with exercise could help seniors enjoy greater independence and improve their quality of life.
"For people in their 70s and 80s, it's about preserving what you have," says Shields, who is working in the Neural Health Research Laboratory at the David B. Falk College of Sport at Syracuse University. "The aging process is going to happen no matter what, but can we slow it down."
The study was published Sept. 16 in the Medicine & Science in Sports & Exercise (MSSE), the leading multidisciplinary research journal for the American College of Sports Medicine and one of the flagship journals within the fields of sports medicine and exercise physiology.
"Shields and colleagues show that nerve function in older adults is trainable, which may also have long-term implications for nerve health, motor function, independence, and quality of life," Editor-in-Chief Andrew Jones wrote in MSSE's current issue. "This work could stimulate investigations into whether resistance training is an effective countermeasure for other, non-age related, sources of nerve degradation (for example, nervous system disorders)."
For their study, the researchers sought to determine the effects of resistance training on nerve conduction velocity (NCV), and if changes in NCV are dependent on age. Testing 48 subjects ranging from 18 to 84 years old, the researchers recorded NCV in the forearm and maximal strength before and after four weeks of handgrip training in both arms (training was conducted three times a week).
To measure each subject's NCV, the researchers used nerve conduction tests that stimulated the nerves in the muscles of the forearm and measured how fast it took to activate the muscle.
In the post-training tests, every senior that performed the training showed improvement in their nerve conduction. A nerve contains both fast and slow motor neurons, and the fast neurons are the first to deteriorate, disconnect from muscle, and become inactive with age. The researchers hypothesize that the training reactivated these fast neurons in the older participants, a process called reinnervation.
"When you lose fast neurons, you also lose the fast muscle fibers that are activated by them, and then your power, or the speed at which you can produce force, decreases," said DeFreitas, chair of the Department of Exercise Science at Falk College. "If you can reactivate those lost neurons, you can produce force faster again and that has practical implications so that a slip or a trip doesn't become a terrible fall."
The research team plans to conduct further studies to determine the role that exercise interventions play in mitigating age-related nerve deterioration, and if the reactivation of fast neurons translates to other parts of the body.
"If we're reactivating those neurons that started to die, that can play a significant role in the preservation of strength and avoiding disability with aging," DeFreitas said. "That to me is the likely hypothesis, so that's the premise of the follow-up work we're conducting."
In addition to Shields and DeFreitas, the research team included Claire Smith , graduate research assistant at Falk College; Shawn Reese, assistant professor of exercise science at Fairmont State University ; Marcel dos Santos , assistant professor of kinesiology and recreation at Illinois State University; and Maria Parodi , a master's student at Oklahoma State University.
This project was funded in part by a Doctoral Research Grant awarded through the Central States Chapter of the American College of Sports Medicine.
