<P> Master - class athletes maintain a high level of fitness throughout their lifespan . Even among master athletes, performance of marathon runners and weight lifters declines after approximately 40 years of age, with peak levels of performance decreased by approximately 50% by 80 years of age . However, a gradual loss of muscle fibers begins to occur at around 50 years of age . </P> <P> Exercise is of interest in treatment of sarcopenia; evidence indicates increased ability and capacity of skeletal muscle to synthesize proteins in response to short - term resistance exercise . A 2009 Cochrane review also found evidence that in older adults progressive resistance training can improve physical performance (gait speed) and muscular strength, which are two key components of sarcopenia . </P> <P> As of July 2015, there are no approved medications for the treatment of sarcopenia; however, β - hydroxy β - methylbutyrate (HMB), a metabolite of leucine which is sold as a dietary supplement, has demonstrated efficacy in preventing the loss of muscle mass in individuals with sarcopenia . A growing body of evidence supports the efficacy of HMB as a treatment for reducing, or even reversing, the loss of muscle mass, muscle function, and muscle strength in hypercatabolic disease states such as cancer cachexia; consequently, as of June 2016 it is recommended that both the prevention and treatment of sarcopenia and muscle wasting in general include supplementation with HMB, regular resistance exercise, and consumption of a high - protein diet . Based upon a meta - analysis in 2015, HMB supplementation appears to be useful as a treatment for preserving lean muscle mass in older adults . More research is needed to determine the precise effects of HMB on muscle strength and function in this age group . </P> <P> DHEA and human growth hormone have been shown to have little to no effect in this setting . Growth hormone increases muscle protein synthesis and increases muscle mass, but does not lead to gains in strength and function in most studies . This, and the similar lack of efficacy of its effector insulin - like growth factor 1 (IGF - 1), may be due to local resistance to IGF - 1 in aging muscle, resulting from inflammation and other age changes . </P>

Which of the following is defined as age-related loss of muscle mass and strength