In a new study, researchers found new evidence to support the belief that the nervous system plays an important role in age-related weakness.
The results suggest that physical weakness in aging may be due, at least in part, to impairments in brain and nerve function, rather than changes in the muscles themselves.
The research was conducted by a team the Ohio University and elsewhere.
The study looked at a group of 66 older adults (average age in their 70s), who were first categorized as severely weak, modestly weak or strong based on their measured performance on a standardized physical test.
The people were asked to push against resistance with their leg extensor muscles, using as much strength as they could generate.
When they reached their self-perceived limit, the muscle they were using was then stimulated electrically.
If this caused the muscle to put out more force, it was a sign that the strength limitation the person experienced came from somewhere other than the muscle itself.
The team found when the added force that came from electrical stimulation was expressed as a percentage increment, it showed that the weaker the test people, the larger a boost their muscles got.
The people in the “severely weak” group (who were on average older) got an increase of 14.2%—twice the 7.1% increase shown by those in the “strong” group.
The team says it’s confirmatory evidence that the nervous system is a key culprit in weakness.
The study has implications for addressing the age-related loss of muscle strength, which can seriously reduce seniors’ mobility
When the conventional scientific wisdom linked such weakness mainly to loss of muscle mass, many drug companies looked for medications that acted directly on the muscles—but few proved effective.
The new study provides further evidence that the nervous system plays a significant role in the problem.
One author of the study is a professor of physiology and neuroscience Brian Clark, Ph.D.
The study is published in JAMA Network Open.
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