The Study
Longitudinal decline of lower extremity muscle power in healthy and mobility-limited older adults: influence of muscle mass, strength, composition, neuromuscular activation and single fiber contractile properties
This study watched a group of older people for three years and saw that their muscle power went down. But because they didn't split people into groups randomly, it can't prove that one thing caused another. So we can say some things are connected, but not that they caused the change.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
Researchers followed older people for 3 years to see how their leg muscle power changed. They found that both healthy and less mobile older people lost similar amounts of leg power, but for different reasons. In healthier people, the brain's ability to activate muscles declined, while in less mobile people, muscle size and strength decreased. Interestingly, the remaining muscle fibers got stronger to compensate, but not enough to prevent overall power loss.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 540 / 100
Quality score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Key takeaways
Summary
Based on the study abstract and findings.
- 1The loss of leg power can make everyday activities harder and increase fall risk, so even a 9% decline over 3 years is significant for older adults.
- 2Both groups lost about 8-9% of leg power over 3 years.
- 3Healthy older adults had a 25.6% drop in neural activation, while mobility-limited had 3.8% less muscle size and 5.9% less strength.
- 4Single muscle fibers increased peak force by >30%, peak power by >200%, and shortening velocity by >50%.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
European journal of applied physiology
Year
2013
Authors
K. Reid, Evan P Pasha, G. Doros, D. Clark, C. Patten, E. Phillips, W. Frontera, R. Fielding
Related Content
Claims (6)
Over three years, people aged 70 to 85 lost about 8-9% of the strength in the muscles that straighten their knees. This happened similarly for those who were healthy and those who already had trouble moving around, meaning both groups declined at about the same rate.
Older adults who lose leg power over three years also show a slower electrical signal from their nerves to their muscles—about 25% slower—but their muscle size and strength stay the same.
In older adults who already have trouble moving, losing power in the leg muscles over three years goes along with the muscles getting smaller and weaker, but the nerve signals that tell the muscles to work stay the same. That suggests the power loss is mostly due to the muscles themselves shrinking and weakening, not to problems with the nerves.
In older adults, even those with limited mobility, whole muscles get weaker over three years, but the surviving individual muscle cells keep their size and actually get stronger and faster: they produce more force and move more quickly, helping to keep muscles working.
In older adults, weaker nerve signals to muscles cause a loss of muscle power. This nerve signal decline happens before the muscles shrink or get weak, so the nerve issue is the first step in age-related muscle decline.
As people age past 35, the muscle fibers used for quick, powerful movements (like sprinting) waste away faster than the fibers used for endurance. This causes muscle power to drop by about 3-4% every year.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.