The reality is that we lose strength as we age, especially if we don’t challenge our muscles through resistance training. You also lose muscle mass, an age-related problem called sarcopenia. Some experts believe that sarcopenia will reach epidemic proportions as the population continues to age. You start to lose muscle mass in the 30s and 40’s but this process accelerates after the age of 50. In fact, muscle mass decreases by 3 to 8% per decade after the age of 30 and accelerates in the late 50s and early 60s.
Sarcopenia isn’t just an aesthetic issue. Loss of muscle tissue leads to loss of strength and an increased risk of frailty and falls. Plus, it negatively impacts metabolic health as muscle cells absorb glucose from the bloodstream, helping to lower blood sugar. In addition, muscle is more metabolically active and gives your resting metabolic rate a slight boost.
You might try to blame the age-related loss of strength completely on the loss of muscle tissue – but that’s not the full story. Yes, muscle cross-sectional area declines with age and this explains some of the loss of strength we experience with aging but other factors contribute too. Let’s look at some of them.
Muscle Tissue Becomes Fattier
Muscle doesn’t turn to fat but muscle accumulates more fatty tissue with age. If you were to look at the muscles from an older person, you’d see that it has significantly more fat and connective tissue as the muscle of a youthful person. What causes this age-related change? Studies show that fatty infiltration of muscle tissue is partially brought on by hormonal changes, including a reduction in testosterone and estrogen as well as a rise in the stress hormone cortisol with age. It’s also due to lack of muscle stimulation, not challenging aging muscles with resistance exercise. What’s more interesting is these changes have other significance. As fat accumulates, you experience a drop in insulin sensitivity and that increases the risk of type 2 diabetes, obesity, and other health problems, including cardiovascular disease.
Reduced Synchronicity of Muscle Firing
Strength is more than muscle size. When you first start training with weights, you often see modest strength gains within the first few weeks, before your muscles have had time to grow. That’s because strength training improves communication between the brain and muscles. When a muscle fiber contracts, it does so in response to a command from your brain and central nervous system. The brain, through nerve pathways, signals motor units (a nerve fiber and the muscle fibers it connects with) to tell the muscle to contract. During the early phases of resistance training, this process becomes synchronous and this leads to the ability to generate more force. You also get greater activation of synergistic muscle fibers and less inhibition of the antagonists.
Unfortunately, the recruitment of motor units by the brain and central nervous system becomes less efficient with age as well as less synchronized. This leads to reduced force production by the muscle. So, it’s not just loss of muscle size that makes older people lose strength, the way their nervous system communicates with muscle fibers becomes more disorganized and less synchronous. The communication between the nervous system and muscle is more disjointed.
Reduction in Fast-Twitch Muscle Fibers
The muscle fibers that your muscles are made of are of two types: fast-twitch and slow-twitch muscle fibers. Slow-twitch fibers are often called endurance fibers as they’re resistant to fatigue. On the other hand, they also can’t contract with a great deal of force. These are the fibers you mainly use when you walk or run at a moderate pace or do a high number of reps with light weights when you weight train. Fast-twitch muscle fibers fatigue quickly but can contract with more force. They’re the speed and power fibers – the ones you recruit when you sprint, do a power move or lift heavy weights. Loss of muscle as you age over time affects your strength and power.
You don’t lose slow and fast-twitch muscle fibers at an equal rate as you age. You actually lose a higher ratio of fast-twitch to slow-twitch fibers. As a result, you become weaker and less powerful, whereas endurance and stamina are less negatively impacted.
Changes in Tendon Structure
You need healthy tendons, as tendons transmit force from muscle to bone. Tendons change with age as well. Tendons are mostly made up of collagen and with age, collagen synthesis declines and the collagen structure becomes more disordered. Plus, tendons lose some of their water content, causing the tendon to stiffen. As a result, the risk of tendon injuries goes up in women after menopause. Strength training, especially training that emphasizes the eccentric portion of the muscle contraction, may help preserve tendon health due to aging based on preliminary studies.
The Bottom Line
The reasons you lose strength with age are multifactorial. What we do know is that strength training reduces strength loss as well as loss of muscle tissue. What you don’t want to do is spend most of your time doing aerobic exercise and underemphasizing the strength component of your workouts. Remember, you lose more fast-twitch muscle fibers, ones involved with strength and power, as you age than slow-twitch, endurance fibers. So, you have to work harder to preserve the fast-twitch ones. You do that through strength training and by doing power moves where you move a resistance at a higher speed. Older people often get the message that they should walk – but they also need to strength train. So, make sure your workout is balanced and, if anything, is weighted more toward strength training. You need to reduce age-related muscle loss as much as possible to stay healthy and functional as you age.
References:
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Front Endocrinol (Lausanne). 2016; 7: 69. Published online 2016 Jun 20. doi: 10.3389/fendo.2016.00069.
J Cachexia Sarcopenia Muscle. 2012 Jun; 3(2): 95–109. Published online 2012 Feb 3. doi: 10.1007/s13539-011-0054-2.
Resistance Training: Adaptations and Health Implications By Len Kravitz, Ph.D.
Ortho Information. “Effects of Aging”
Curr Opin Clin Nutr Metab Care. 2004 Jul; 7(4): 405–410.
J Bone Joint Surg Am. 2013 Sep 4; 95(17): 1620–1628.
Muscles Ligaments Tendons J. 2014 Jul-Sep; 4(3): 324–328.
Related Articles by Cathe:
4 Reasons You Lose Muscle Size & Strength with Age
Lack of Exercise is More Harmful to the Muscles of Older People
How Imbalanced Exercising Training Contributes to Aging
