sarcopenia is a very common problem with aging and is a leading cause of frailty
it is characterized by progressive and generalized loss of skeletal muscle mass and strength
it has high correlations with physical disability, poor quality of life and death
presarcopenia stage is characterized by low muscle mass without impact on muscle strength or physical performance
loss in muscle mass may be associated with increased body fat so that despite normal weight there is marked weakness, this is a condition called sarcopenic obesity.
sarcopenia is different to cachexia which may be defined as a multifactorial syndrome characterized by severe body weight, fat and muscle loss and increased protein catabolism due to underlying disease
Epidemiology
pronounced changes in muscle tissue begin from around 50 years of age
muscle mass and strength begin to deteriorate at an annual rate of 1–2% and 1.5–5% respectively
up to 10% of 60-69 yr olds have sarcopenia
40% for adults over 80 years of age
Aetiology
primarily a syndrome of old age
risk factors include:
age
gender
low level of physical activity
protein malnutrition
sleep quality
alcohol intake
smoking status
chronic inflammatory conditions
genetic factors:
genetic factors account for 46–76% and 32–67% of fat-free mass (FFM) and muscle strength variability, respectively and thus far it seems 24 genes and 46 DNA polymorphisms whose expression is significantly associated with muscle phenotypes in older adults have been found 1)
ACTN3 (the “sprint gene”):
1 in 5 people have genetic α-actinin-3 deficiency due to homozygosity for the premature stop codon at the rs1815739 (R577X) polymorphism which is associated with significantly lower strength and higher frailty scores as they age2)
a meta-analysis using two large independent cohorts of Caucasian postmenopausal women showed that even heterozygous carriage of the ACTN3 577X allele increases the risk of falling by 33%3)
muscle resistance training combined with creatine supplements appear to build muscle mass more effectively than resistance training alone and may add an extra 1.4kg mass compared to no creatine supplementation 4)
estimated daily requirement of creatine is about 2 g/day for a 70-kg male however endogenous synthesis of creatine may be inadequate under pathological or certain physiological conditions
creatine-rich foods include fish and meat
supplementation protocols, such as an initial loading phase of 20 g/day for 5–7 days followed by a maintenance dose of 3–5 g/day, have shown consistent benefits in enhancing muscle performance and lean mass.
exercise programs should include progressive weight training, with up to 10 exercises targeting major muscle groups and 8–12 repetitions per exercise.
both high- and low-frequency resistance training can effectively improve skeletal muscle mass, muscle strength, and quality in older females with sarcopenia