Muscle mass and strength start to decline around the fourth decade of life and the rate of decline accelerates with advancing age.^[15][16] With that said, the process is heterogeneous in when it begins and the magnitude of decline, especially since lifestyle factors like frequent resistance exercise and adequate daily protein intake can help to delay and attenuate losses in muscle mass and strength with aging. Beyond the age of 50, a loss of leg muscle mass of 1%–2% per year and a loss of muscle strength of 1.5%–5% per year have been reported.^[17]

The SARC-F is a screening tool used to quickly identify probable cases of sarcopenia. It is a self-reported questionnaire containing five components: strength, assistance in walking, rising from a chair, climbing stairs, and falls. Each component is scored from 0 to 2, with higher scores indicating greater functional impairment. A total score ≥ 4 is predictive of sarcopenia and adverse outcomes.^[13][14]

To confirm the presence of sarcopenia, strength and muscle mass are assessed. The cut-off for low muscle strength is a grip strength of < 27 and < 16 kilograms for men and women, respectively, or taking > 15 seconds to complete the chair stand test.^[1] The cut-off for low muscle mass, which is quantified as appendicular skeletal muscle mass divided by height squared, is < 7 and < 5.5 kilograms/meters2 for men and women, respectively.^[1]

Lastly, physical performance is assessed to determine the severity of sarcopenia. The cut-off for low physical performance is a gait speed of ≤ 0.8 meters per second, a score ≤ 8 on the Short Performance Battery, taking ≥ 20 seconds to complete the Timed-Up and Go test, or taking ≥ 6 minutes to complete the 400-meter walk test.^[1]

There are three main conditions that overlap with sarcopenia: frailty, malnutrition, and cachexia. Frailty is a state of increased vulnerability due to cumulative decline in multiple physiological systems^[18] and involves adverse effects to physical, cognitive, and social dimensions.^[19] Sarcopenia contributes to the physical aspect of frailty, but it differs from frailty because it only affects the musculoskeletal system, whereas frailty is a much broader condition.

Both malnutrition and sarcopenia are characterized by low muscle mass, but sarcopenia also includes impaired muscle function. Additionally, reduced fat mass is typically present in malnutrition, but not sarcopenia.^[1]

Cachexia is described as severe weight loss and muscle wasting associated with conditions such as cancer, HIV/AIDS, or end-stage organ failure. Cachexia and sarcopenia may coexist, but the presence of the aforementioned conditions suggests that cachexia is more likely.^[2] Unlike sarcopenia, cachexia is characterized by systemic inflammation, as indicated by low serum albumin and elevated C-reactive protein levels.^[20] The diagnosis of cachexia also typically requires unintentional weight loss of at least 5% of body weight in the past six months.^[20]

Animal-based proteins are generally higher quality than plant-based proteins because they contain adequate amounts of all the essential amino acids (EAA) and are better digested and absorbed.^[21] Consequently, studies typically report a greater increase in muscle protein synthesis (MPS) following the ingestion of animal-based proteins.^[22]

To overcome the lesser anabolic properties of plant-based proteins, a greater amount of protein can be consumed.^[23][24] In a 3-day study in older adults (average age of 66), daily MPS rates did not differ between a high-protein (1.8 grams of protein per kilogram of body mass per day) vegan diet that provided 57% of protein as mycoprotein and a high-protein omnivorous diet.^[25]

An alternative (or even additional) strategy is to combine different plant-based proteins to provide a balanced EAA profile,^[26] as plant-based proteins typically contain an inadequate amount of one or more EAA.

While studies looking at acute changes in MPS are informative, they do not directly reflect longer-term changes in muscle mass and strength, which is what we’re really concerned with.

Evidence suggests plant- and animal-based protein supplements have a similar effect on changes in muscle mass and strength in older adults (≥ 50 years).^[27] However, consuming an omnivorous diet and obtaining 25–50 grams of protein per day from a plant-based protein supplement is very different from consuming a vegan diet.

A 12-week study in young men demonstrated that a high-protein (1.6 grams per kilogram of body mass per day) vegan diet promoted comparable increases in leg lean mass and muscle strength as a high-protein omnivorous diet.^[28] Unfortunately, a similar study has yet to be conducted in older adults, so the consequences of consuming a vegan diet on muscle mass and strength in this population remains unclear.

As it stands, the source of protein doesn’t seem to matter all that much, as long as enough total protein is consumed each day.

Lifting weights, or resistance training, has numerous benefits to the muscles and skeleton that are uniquely attributed to this form of training.

There are some cognitive benefits associated with exercise in general, but this FAQ entry will be more focused on what resistance training can give that other forms of exercise cannot.

Resistance training?

Resistance training is a form of training where the muscles and skeleton are pit against a large force, either induced by external resistance (lifting weights) or by gravity (maximal jumping or sprinting). Resistance training tends to be focused on power, and tends to be anaerobic (intense) in nature.

Anything with maximal exertions can be considered resistance training. Things like Tennis and racquetball show some benefits as well due to some strides being full exertion, but weightlifting tends to have the most dramatic effects.

Benefits to Muscles

Most notably weight lifting, but all forms of resistance training, can increase muscle mass.

This can reduce the occurrence of sarcopenia (the age-related decline in muscle mass not associated with pro-inflammatory cytokines)^[29] when elderly,^[30][31] although all activity can reduce rates of sarcopenia, resistance training seems most effective.^[32][33]

Benefits to Bone

Exercise in general tends to be associated with better bone mineral density and/or bone width in athletes when compared to a non-athletic control group.^[34][35][36] Greater bone health and an exercise regimen are inversely associated with falls in the elderly, which suggests that exercise is a good preventative measure.^[37][38][39]

It might also slightly protect against further reductions in bone mineral density in those already diagnosed with osteoporosis or osteopenia,^[40] although in general activity is encouraged.^[41]

In older age, those who practice Sprinting have been shown to have better bone density and size relative to jogging and walking activities.^[42] Although beneficial bone adaptations seem to be better in the young, they can still occur even if one starts a physical exercise program later in life.^[43]

It should be noted that swimming does not tend to increase bone density or mass, as the person is suspended in a pool of water rather than actively forcing power against gravity. It may increase bone health slighty in some persons, but is much less reliable than other forms of exercise.^[41][44][45]

Health Promoting effects

Involvement in exercise for at least 150 minutes a week in associated with a reduced risk of diabetes in men, with a protective effect existing for both aerobic exercise and weight training with persons participating in both having least risk.^[46]