It is estimated that people lose around 3-5% of their muscle mass per decade after they reach 30, with this rate of decline higher in inactive individuals and accelerating in all of us after the age of 60. This loss of muscle mass and strength is a serious cause for concern, as it contributes to the overall increased frailty and reduced mobility that can strike in advanced years, both of which lead to a higher risk of falls and injuries.
Why do we lose muscle in old age?
There are a number of factors that contribute to age-related muscle loss, a phenomenon which is also referred to as sarcopenia. As we grow older, our muscles become resistant to normal growth signals (nutrition and exercise), in a process known as anabolic resistance. When studying the muscles of older individuals, we do not see the normal increases in muscle protein synthesis (the repair and growth of muscle tissues) after exercise. Although this phenomenon is more common in older populations, it is becoming increasingly common in younger people, a fact that is likely caused by our steady decline in physical activity and increasing rates of chronic inflammation (which is itself a major contributory factor to muscle loss).
Other causes of muscle loss as we age include hormonal changes, specifically of those hormones that have a role to play in muscle mass maintenance, including testosterone and oestrogen.
The menopause and muscle loss
While age-related muscle loss impacts both men and women, women are particularly vulnerable. Studies have shown that after the menopause, the loss of muscle force relative to muscle mass accelerates at a much faster pace than in men of the same age.
This is primarily due to a steep decline in the release of ovarian hormones, with the decrease in oestrogen playing a key role in the loss of both muscle and bone mass. A decrease in muscle mass exacerbates postural issues and contributes to the deterioration of bone health, both factors which increase the risk of osteoporosis (a medical condition in which the bones become brittle, fragile and prone to fractures).
The oestrogen deficiency that occurs around menopause coincides with other lifestyle changes that often appear as we approach our later years. Most notably, levels of physical activity tend to drop, causing us to become more sedentary. As fitness becomes less of a priority, poor nutrition habits may also start to creep in. Combined with the poor sleep quality and high stress levels that many of us are facing across all age groups, we have a “perfect storm” for not only muscle loss, but also fat gain. The result is the loss of muscle tone and weight gain around the middle that we often see in middle age and beyond.
Countless studies have shown that across all age groups, women are consistently less physically active than men and participate much less in resistance training, which will accelerate their already higher rate of muscle loss and place them at an even higher risk of losing muscle mass, experiencing weight gain in middle age and ultimately suffering from increased frailty due to poorer bone health in their advanced years.
Can we prevent losing muscle as we get older?
Losing muscle is generally accepted as an unfortunate, but normal, part of the aging process, however that does absolutely not mean that we are powerless to stop it. While some of the factors that contribute to age-related muscle loss are largely beyond our control (hormonal and neural changes), all the evidence agrees that it is massively compounded by inactivity and poor nutrition. Meaning that there is a great deal that we can do to maintain our muscle as we get older. Studies have also demonstrated that we can continue to build muscle well into our eighties (!) so it is absolutely never too late to start.
The importance of resistance training
Working with weights in the gym is hugely beneficial across all stages of life, but it should remain a key part of our exercise regimes in later years. As our muscles become less responsive to normal growth stimuli, regular resistance training can help to counteract this and encourage our body to maintain muscle mass. Resistance training not only serves to build muscle, but also to burn fat, meaning that we can help to optimise our body composition well into our retirement.
When it comes to maintaining bone health, weight training again has a huge role to play, with a higher rate of bone formation associated with mechanical loading. Frost’s mechanostat theory was the first to propose that bones will grow stronger in response to stress, and stated that “the bone possesses an inherent biological system to elicit bone formation in response to high mechanical strains, thereby strengthening the bone”. His theory, which has been supported by a large number of studies, suggests that bone formation is site-specific, in other words it is increased in areas of high strain.
This kind of research is highly relevant when we consider the menopause and high prevalence of fractures caused by osteoporosis. One particular study looked at postmenopausal women and concluded that resistance training successfully reduced bone loss in the hip and spine. Hip fractures are one of the most debilitating and life-changing injuries in later life, as they almost always have a severely detrimental impact on independence and quality of life. Weight-bearing exercises that elicit physical loading to the lower limbs can therefore promote bone strength in the hip region
The decline of skeletal muscle with age is one of the key causes of functional decline and loss of independence in older populations. Women are particularly vulnerable to the effects of this, primarily due to the steep decline in oestrogen that occurs around the time of the menopause, triggering deterioration of both bone strength and muscle mass.
Resistance training benefits us at all stages of life, but it should remain a key part of exercise regime in later years. As well as maintaining muscle mass and strength and promoting strong and healthy bones, resistance training has a positive effect on body composition, hormonal and stress regulation, sleep and cognitive function.
Volpi, Elena et al. “Muscle tissue changes with aging.” Current opinion in clinical nutrition and metabolic care vol. 7,4 (2004): 405-10. doi:10.1097/01.mco.0000134362.76653.b2 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2804956/
Walston, Jeremy D. “Sarcopenia in older adults.” Current opinion in rheumatology vol. 24, 6 (2012): 623-7.doi:10.1097/BOR.0b013e328358d59b https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4066461/
Edwards, Elizabeth Skidmore, and Sarah Carson Sackett. “Psychosocial Variables Related to Why Women are Less Active than Men and Related Health Implications.” Clinical medicine insights. Women’s health vol. 9,Suppl 1 47-56. 4 Jul. 2016, doi:10.4137/CMWH.S34668 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4933535/
Hong, A Ram, and Sang Wan Kim. “Effects of Resistance Exercise on Bone Health.” Endocrinology and metabolism (Seoul, Korea) vol. 33,4 (2018): 435-444. doi:10.3803/EnM.2018.33.4.435
Martyn-St James M, Carroll SA. Meta-analysis of impact exercise on postmenopausal bone loss: the case for mixed loading exercise programmes. British Journal of Sports Medicine 2009; 43:898-908 https://bjsm.bmj.com/content/43/12/898
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