The Sarcopenia Clock and Why Muscle Mass Is the Organ of Longevity
Sarcopenia — the progressive, age-related loss of skeletal muscle mass and function — begins around age 30 and accelerates after 60, averaging 1-2 percent of muscle mass per year and 3 percent of strength per year in sedentary adults. Stuart Phillips at McMaster University describes skeletal muscle as the organ of longevity: it is the primary site of insulin-mediated glucose disposal, accounting for approximately 80 percent of post-meal glucose uptake. Reduced muscle mass is mechanistically connected to the insulin resistance underlying type 2 diabetes, cardiovascular disease, and the cognitive decline associated with hyperglycaemia.
After 40, recovery becomes the primary training variable and training becomes the gap between recoveries. Post-exercise mTORC1 pathway activation is both reduced in magnitude and shorter in duration in older adults. The anabolic window is narrower, the recovery requirement longer, and the consequence of accumulated fatigue more pronounced. Recovery time between heavy sessions targeting the same muscle group should increase from 48 hours to 72-96 hours. Training frequency should be maintained — two or more stimuli per muscle group per week produces superior hypertrophy — but with reduced volume per session. Protein intake should increase to 1.8-2.2g per kg bodyweight to compensate for reduced anabolic signalling efficiency.
The Exercises With the Best Evidence
The exercises with the best evidence for muscle preservation in masters athletes are compound movements: trap-bar deadlifts with lower spinal compression than conventional deadlifts at equivalent posterior chain stimulus, goblet squats, chin-ups, and horizontal rowing. These movements preserve the highest proportion of functional muscle mass relative to the joint stress they impose. Testosterone declines approximately 1-2 percent per year from age 30 — real but modest in its direct training implications. The more impactful hormonal variable is growth hormone release during deep sleep, which declines with age and is significantly impaired by poor sleep quality, making sleep optimisation the most underrated component of masters athlete programming.