There is a common assumption that muscle mass is naturally lost with aging. Indeed, research shows that individuals lose an average of eight percent of their muscle mass between 40 and 50, and tend to lose muscle at an even higher rate after the age of 75. This is a cause for concern, as it has been observed that older adults with low muscle mass are more likely to have mobility problems and be at a higher risk for falls or other incidents. However, it is unclear why muscle mass is lost as we age, since older adults tend to be more sedentary/inactive. A recent article uses a subset of physically active older adults to examine whether muscle mass is a result of muscle aging or inactivity.
The study involved 40 masters athletes—top-level recreational athletes who participate in high-intensity activities. The researchers recruited five men and five women of four different age categories (40 to 49; 50 to 59; 60 to 69; and 70 or better) at a university health clinic, at bike shops, and competitive athletic events. Chosen participants—those who exercise at high-level intensity four to five times per week—were between the ages of 40 and 81 and involved in sports such as track and field, biking, and swimming. By choosing a sample of active individuals, the researchers were able to compare age groups without the confounding influence of inactivity.
For the study, participants completed an intensive survey about their health and sports history, and data was collected regarding their performance (arm strength tests) and body composition (measurements of body fat and MRI scans to examine muscle density). The researchers then statistically compared body composition and performance measures across age groups.
The analysis of these measures suggested that by staying active, individuals are able to maintain muscle mass and strength as we age. While age was associated with slightly higher body fat among the participants, the researchers found that there was no decrease in muscle mass or muscle density. Individuals 60 and better had slightly lower strength than those between 50 and 59, but those 70 and better were as strong as those between 60 and 69, suggesting that the benefits of activity remain as we age.
Because the number of participants in each age group was relatively small, it should not be assumed that the differences between age groups found in this study would be the same across these age groups in the general population. However, the high degree of muscle mass and strength found across age groups is a significant finding. While it was important for the study design to include only masters athletes, these findings may not apply to individuals who are not involved in high-intensity activity. Despite this, these findings strongly suggest that muscle mass can be maintained as we age.