How do our muscles change with advancing age?
We’ve discussed the benefits of exercise (here, here, here, here), including health benefits (this). Until now, this discussion has admittedly focused on young and middle aged folks. Whether we want to admit it or not, we’re all going to get older. In journal club today, we synthesize two studies that look at our muscles as we age, and what exercise can do to them.
The first study is from 2009. It examined 813 males and 865 females, aged 70 to 79. The participants were followed over 5 years to learn how their muscles changed over time. They completed lifestyle surveys and were confirmed to be healthy and active at the start of the study. They had DEXA scans done before/after, as well as CT scans of their mid-thighs. The CT scans quantified their muscle and fat levels (including subQ and the fat marbling their muscle). They did strength tests for their legs. Below are the descriptive stats for the groups. As always, they’re group averages and rounded to the nearest whole number for the ease of viewing.
The second study was published in 2011 and took a different approach to this topic. Knowing the results of this previous study, these researchers sought to find out how regular intense exercise affects muscle over time in older adults. Rather than follow a group over time, though, they looked at people from a wide age span. They examined 20 males and 20 females, aged 40 to 81 years. These participants trained in some kind of athletics 5 days a week for many years, if not their whole adult lives. They completed a survey, had their body composition measured, and had an MRI scan of their thighs. Below are the descriptive stats for the groups. As always, they’re group averages and rounded to the nearest whole number for the ease of viewing.
The 2009 study of “normal” active folks found that leg muscle mass went down over the 5 years while the amount of fat marbling the leg muscles went up, for both males and females. In both, gaining or losing weight was correlated with the loss of leg strength. Such folks had a 4-fold faster annual decline in strength. The loss of muscle over 5 years was correlated with the loss of leg strength. For females, even the loss of total and subQ body fat correlated with the loss of strength. For males, the increase in marbled fat over 5 years correlated with the loss of leg strength.
Because of previous studies finding a link between diabetes and marbled fat, the researchers examined that connection in these participants. They found that males who got diabetes had over 10% more marbled fat than males who did not. No difference was found for females.
How did the participants of the 2011 study fare?
Increasing age in the highly athletic folks was associated with higher BMI/body fat %/subQ fat, along with lower amounts of leg muscle/strength. The participants of any age that had higher body fat % were more likely to have less LBM/leg muscle/leg strength and more subQ/marbled fat. Participants of any age with more LBM were more likely to have less subQ fat and more strength. As anyone would expect, more leg muscle was associated with more leg strength. When the researchers examined leg strength by each decade, from 40 to 81 years, they saw a decline in average strength start with 60-69 year olds. There was no further decline in strength during 70-81 year olds.
I must make something very clear. The 2011 older athletes were literally not the same as the 2009 Gen Pop folks. While they were not the same participants, they were also not in the same category. The older athletes may have had a little less strength, a little less muscle, and a little more subQ fat than their younger athletic friends, but they were heads and shoulders above the 2009 Gen Pop participants. The following figure, taken directly from the 2011 paper, is what has given these studies their notoriety. The figure says it all.
Thoughts & Implications
For the Gen Pop folks, the results found that marbled fat increased over time, regardless of whether male or female or weight went up or down. The researchers cited other work that has found that marbled fat in muscles, like visceral fat, is associated with diabetes, insulin resistance, and metabolic syndrome. That this kind of fat increased in the non-athletic elderly over time is concerning for long-term health.
Honestly, everything about the 2009 Gen Pop results over time is concerning, including the fact that these participants were “active,” “independent” elders. At the start, they seemed great for their age. While marbled fat increased in everyone, those that changed overall weight in any way had the most increase. It appears that change in weight during 70-79 years is not a good sign of internal health, unfortunately.
On the flip side, athletic folks fared so much better over their advancing years of life. The oldest athletes had only slightly less muscle mass than the “younger” athletes. The oldest athletes also managed to hold on to their strength as they got further from 60 years old. That is a good thing, as the researchers cited studies that have shown a decrease in strength for 70-79 year olds is associated with a higher mortality rate.
Plain & Simply
A huge limitation of these studies is that they jump from Gen Pop to legitimate athletes that train 5 days a week and compete in their sports. This journal club leaves the question open, what about in between? Does less intense/less frequent exercise help manage body composition in the aging population? We know that it improves the health and quality of life for younger folks. Given studies that have shown aging muscle can still respond to acute resistance exercise, we can hope! Future journal clubs will examine the possibility of a middle ground.
If you have any questions about this study or anything I said, please feel free to leave a comment. I will get back to you and others may have insight to offer, too. If you have any questions or topic suggestions that you would like answered as a post, then please email me at email@example.com.
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