You may not consider yourself as having a sedentary lifestyle, but even a short period of bed rest or other inactivity can quickly age your muscles.
In a 2014 paper published in Advances in Nutrition (linked below), Professor Daniel Moore talks about the role that a lack of physical activity plays in the development of anabolic resistance.
So what is anabolic resistance and why is it important to you?
Ana- upwards + (meta)bolism- change or transition + resistance-to oppose refers to the body's reduced ability to synthesize muscle protein from the amino acids that make up the protein in your diet, meaning it’s harder to repair and build muscle tissue.
And it’s related to age. As we all know, it gets harder to maintain a lean body as we get older. Although our muscles are continually regenerating at the rate of around 1-2 per cent per day, there is a net loss of muscle mass of about 1 percent per year from age 35 onwards, and without any dietary or lifestyle intervention, this become of real concern in our senior years.
But it’s not just relevant to older adults; the absence of physical activity through bed rest, injury or periods of hospitalization results in a loss of muscle mass in otherwise healthy younger adults. Although the cause is not known exactly, and it’s at least partly due to the muscle simply not being exercised, there does seem to be a reduced sensitivity to the biochemical signals of muscle protein synthesis (known as the mTOR pathway).
In other words, the less active you are, the harder it becomes to put on muscle - or get your lean body back – when you recommence exercise. And according to Professor Moore:
“this observation that immobilization or reduced activity recapitulates the characteristic anabolic resistance of aging in both healthy young and older individuals, and can result in losses of both muscle mass and strength, could be viewed as an acceleration of the “biologic age” of skeletal muscle."
He goes to to say that:
“even inconspicuous forms of inactivity such as a restriction of daily step counts from ∼6000 to ∼1500 were recently shown to negatively affect insulin sensitivity, reduce lean mass, and increase fat mass in both young and older adults. Similar to observations after complete immobility, this decrease in habitual step count was also shown to blunt the dietary protein–induced stimulation of muscle protein synthesis in older adults…”
Of course, older adults are more likely to be hospitalized with acute illness or injury, for example from falls, but at any age, these brief periods of inactivity may
“ultimately compromise the ability to reverse any development of anabolic resistance during the immobilised period….”
When not addressed with diet and exercise, inactivity can lead to the loss of muscle tone, mass, strength and function, and ultimately to the development of sarcopenia, or muscle wasting, and further into frailty, functional dependence and greatly reduced quality of life.
So what can you do about it?
Professor Moore suggests:
“…even acute bouts of activity can restore the sensitivity of older muscle to dietary protein. Provided physical activity is incorporated into the daily routine, muscle in older adults should retain its capacity for a robust anabolic response to dietary protein comparable to that in their younger peers.”
However, dietary protein must be supplied at appropriate doses to overcome any anabolic resistance due to age or, as it turns out, a period of inactivity, whether voluntary or involuntary.
And that’s why Muscle Maintenance has been formulated with the higher dose of protein, specifically the amino acid L-Leucine, required to trigger muscle protein synthesis in both older and less active adults.
1. Moore, D Adv Nutr. 2014 Sep; 5(5): 599S–607S. Published online 2014 Sep 1. doi: [10.3945/an.113.005405]
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