What we've found so far suggests a link between higher activity of certain stress-related genes in muscle and weaker leg strength in older adults. The evidence we've reviewed leans toward this connection, based on one key assertion supported by 55.0 studies [1].
Our analysis of the available research shows that older adults who have increased activity in unfolded protein response genes—involved in how cells handle stress—tend to have lower leg strength [1]. These genes play a role in how muscle cells respond when proteins don’t fold correctly, which can happen more often with age. While this increased gene activity is associated with weaker legs, it doesn’t appear to affect heart and lung fitness [1]. This suggests the impact may be specific to muscle strength rather than overall endurance or cardiovascular health during physical activity.
We don’t yet know whether the increased gene activity directly contributes to muscle weakness or if it’s simply a marker of underlying muscle changes. The evidence we’ve reviewed does not tell us about cause and effect—only that these two factors tend to occur together. Also, no studies in this analysis refuted the link, and we have not found any evidence suggesting a benefit or harm from this gene activity.
Since our current analysis is based on a single assertion drawn from multiple supporting studies, we can’t rule out other factors that might influence both gene activity and strength. More research may help clarify the role these genes play in aging muscle.
Practical takeaway: If you're an older adult, maintaining leg strength through regular resistance training might be especially important, even if you feel generally fit. We don’t yet know how much control we have over gene activity, but staying active supports muscle health in ways that matter for daily life.
2 items of evidenceView full answer