What is sarcopenia?



Sarcopenia is an age associated loss of muscle mass, strength, and function.  Clinically, it is defined as a loss of muscle mass coupled with functional deterioration (loss of walking speed, walking distance, and grip strength can be used to assess). It can begin as early as the 4th or 5th decade of life and is a major contributor to poor health and disability in older adults.  


Our muscles are made up of many individual muscle fibres bundled together. Like all cells in the body, muscle tissue is not static, it shows a continuous cycle of synthesis and breakdown. In sarcopenia, both the number and size of these individual fibres decrease. There is also a corresponding reduction in the quality of muscle fibres. This occurs through mechanisms that alter the biology of the muscle, including metabolic, cellular, vascular, and inflammatory changes.


Importantly, we are not talking about having big muscles like a bodybuilder, we are talking about having adequate muscle mass and strength to perform your activities of daily living comfortably and confidently, well into older age. Maintaining adequate muscle mass also has a positive impact on several components of health, as we shall see.


The good news is, research demonstrates that the processes involved in sarcopenia may be slowed, interrupted, and even reversed. At present, resistance exercise and appropriate protein intake (supplementation if required) have been established as the basic treatment of sarcopenia.  

Contributing factors

The causes of sarcopenia are multifactorial. The main underpinning physiological mechanisms are:

  • A lack of appropriate physical activity (in particular, loaded activity and resistance exercise)

  • Age related hormonal changes (a decrease in hormones that regulate muscle growth)

  • A negative energy balance through inadequate nutrition (particularly reduced protein intake)  

Older adults who are less physically active are more likely to have lower skeletal muscle mass and strength and have an increased risk of developing sarcopenia. A more sedentary lifestyle is associated with poor functional performance and early disability.


As previously mentioned, in sarcopenia, there is not only a reduction in the number and size of individual muscle fibres, there are also changes to existing muscle biology. 

Biology of sarcopenia

​   Changes within existing muscle can include:

  • Decreased number of motor units (these are the areas where our nerves meet our muscles and tell them to work)     

  • Increased oxidative stress

  • Chronic inflammation

  • Decreased cellular repair

  • Decreased mitochondrial quality (these are the engines of the cells)

  • Decreased capillarisation (therefore decreased blood flow)

  • Insulin resistance (affecting blood glucose control and a risk factor for diabetes)

  • Fat infiltration within and between muscle fibres 

  • Decreased mTOR (a natural substance involved in protein synthesis)

   Appropriate physical activity and exercise has a positive effect on ALL of the above biological changes.



Health and lifestyle conditions associated with sarcopenia

The loss of muscle mass and strength with sarcopenia are associated with a diverse group of health conditions, including:

  • Frailty and disability 

  • Risk of falls and fractures 

  • Loss of physical independence

  • Cognitive decline and depression  

  • Type 2 diabetes

  • Cardiovascular disease 

  • Immune function 


Role of physical activity and exercise

It is well established that regular exercise throughout the lifespan reduces the severity of sarcopenia and its associated comorbidities.  

Current evidence suggests that resistance training should be considered of prime importance in attempting to halt and even reverse the progression of sarcopenia. Further evidence suggests that the benefits of resistance exercise can be augmented by the addition of sufficient protein intake, with protein supplementation if required


The Health, Aging, and Body Composition study, which was conducted over 3 years, showed that older adults in the highest quintile of protein intake lost significantly less muscle mass than those in the lowest quintile of protein intake.  


Appropriately prescribed exercise can promote increased muscle strength and positive changes to the internal biological structure of sarcopenic muscle.  

A resistance program aimed at combating sarcopenia should be individualised to suit current circumstances, including health and medical status, functional ability, contraindications, and personal objectives. For those with, or wishing to prevent, sarcopenia, it is recommended that a resistance training program include:

  • At least 2-3 sessions a week  

  • Exercises incorporating all the major muscle groups 

  • Loads sufficient enough to elicit a strength response.

  • Incremental progression, as tolerated.  

  • Supervision by a professional

The earlier resistance programs are integrated into daily life, the longer we have to improve muscle mass, strength and delay the onset of sarcopenia. However it is never too late to start, everybody can benefit from resistance training, regardless of age or previous training. Beginning resistance training in middle or later life can reduce the effects and delay the progression of sarcopenia, while improving muscle strength and subsequently daily living activities.


‘Skeletal muscle displays features of plasticity, enabling growth over the life course in response to the stimulus of physical activity’.