Whether you lift weights or work your body against resistance using body weight or resistance bands, you do it to increase the size of your muscles, or at least preserve what you have. However, there’s another aspect of muscle health and function you hear less about – muscle quality. It might surprise you to learn that muscles can be equal in size but one is of higher quality than the other.
What determines the quality of a muscle? Scientists define it as the amount of force a given muscle can generate relative to its size. A smaller muscle that can muster up lots of force is higher quality than a weak muscle regardless of size.
Here’s the bad part. As you age, assuming you don’t weight train, you gradually lose muscle strength and muscle mass. However, research shows you lose muscle strength BEFORE your muscles become smaller. So, loss of muscle quality precedes loss of muscle mass. This further illustrates the point that muscle strength and size aren’t always correlated.
Muscle Quality: Muscles Get Fat Too
How do you lose muscle quality? If you looked at an imaging study of the quadriceps of a 25-year-old, healthy person and compared it to a 60-year-old, sedentary individual, you’d see a marked difference in how the muscles look. The 60-year-old quadriceps would have a much higher proportion of fat relative to functional muscle tissue.
Why might this be? As you age, fat begins to accumulate within the muscle. Fat builds up in various locations – between the bundles of muscle fibers that make up your muscles and within the fibers themselves. Along with this accumulation of fat, your muscles become weaker because you have less functional muscle tissue per unit area of muscle.
Not only do you lose strength, but your muscles lose the ability to generate power. At an extreme, your muscles can lose enough power that you have problems lifting yourself out of a chair. If you were to look at the quadriceps muscles of nursing home residents confined to wheelchairs, you’d see most of the muscle has been replaced with fat and they no longer have enough functional muscle tissue to get around.
Sounds bleak, doesn’t it? The good news is you can preserve the size and quality of your muscles by staying active and working them regularly against resistance. Research even shows older people who have problems getting out of a chair can become functional through resistance training. At one time, scientists thought the loss of muscle quality and size was an inevitable part of aging, but more research shows it’s mainly a consequence of being too sedentary.
Inflammation and Muscle Aging
Another reason scientists propose that older muscles accumulate more fat has to do with a phenomenon you hear a lot about these days – inflammation. No wonder. Inflammation is the driving force behind many health problems. Inflammation becomes more common with age, and inflammation boosts the release of inflammatory chemicals called cytokines. These cytokines impair fat metabolism at the cellular level and lead to the accumulation of fat. What’s just as disturbing is fat builds up inside the aging muscle, it interferes with the activity of insulin, leading to one of the most common age-related problems – insulin resistance. Lean muscle is more sensitive to insulin and better for your metabolic health.
Fortunately, exercise addresses these problems on several fronts. For one, it helps preserve muscle size and quality. In one study, the quadriceps muscles of older triathloners were similar in terms of fat accumulation of a person in their 20s. Therefore, exercise seems to reduce fat accumulation in the muscle, which, in turn, preserves muscle quality. Exercise also improves insulin sensitivity and reduces inflammation. These are also some of the ways exercise reduces the risk of chronic health problems like metabolic syndrome, heart disease, and type 2 diabetes.
Another factor that increases fat accumulation inside muscles is obesity and weight gain. This makes sense since body fat produces inflammatory cytokines that contribute to further fat accumulation in the muscles and elsewhere on your body. It’s a vicious cycle – fat increasing inflammation and inflammation further contributes to fat storage and metabolic problems. Exercise and eating a clean, unprocessed diet that’s low in sugar helps break this brutal cycle.
How do you know how much fat you have in your muscles? You can measure it via ultrasound or with other imaging studies such as a DXA scan or MRI.
The Role of Aerobic Exercise
Yes, you need to work your muscles against resistance to preserve muscle tissue as you age, but aerobic exercise is important too. One of the characteristics of aging muscles is they have fewer mitochondria. It’s mitochondria that produce ATP, the energy source muscles use to contract. Aerobic exercise helps increase the number of mitochondria inside muscle cells and makes them more efficient energy producers. When you have healthy muscle mitochondria you have more energy and stamina too. So, resistance training AND aerobic exercise is the key to preserving the quality of your muscles.
The Bottom Line
You not only want ENOUGH muscle – you want the quality of the muscle you have to be high. A combination of resistance and aerobic training, a clean diet, unprocessed diet, and keeping your weight from increasing is the key to preserving muscle quality as you age. By doing these things, you have a good chance of staying fully functional as you age and avoiding diseases associated with aging such as metabolic syndrome, type 2 diabetes, and heart disease.
References:
Egg Nutrition Center. “Muscle Quality: What Does It Mean to Your Health?”
Eurekalert Science News. “Ultrasound-Estimated Fat Content in Muscles May Be an Indicator of Physical Health”
Front. Physiol., 29 October 2015 | http://dx.doi.org/10.3389/fphys.2015.00302
Phys Sportsmed. 2011 Sep;39(3):172-8. doi: 10.3810/psm.2011.09.1933.
PLoS One. 2010 Oct 12;5(10):e13307. doi: 10.1371/journal.pone.0013307.
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4 Reasons We Lose Strength as a Result of Loss of Muscle as We Age
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Can You Build Muscle Size Through Aerobic Exercise?
Can You Still Get the Benefits of Exercise if You Start Later in Life?
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STS Strength 90 Day Workout Program
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