Heteroplasmy—the fraction of mutated mitochondrial DNA—acts as a true clock of aging. As defective genomes rise, oxidative capacity, VO₂ Max, and metabolic water production fall. Crossing threshold levels disrupts gradients, accelerates decline, and raises disease risk. Training and light can reshape the mitochondrial pool.
VO₂ Max naturally declines with age—about 10% per decade after 30. But research shows that 50–70% of this decline is preventable with consistent aerobic training. Zone 2 and Zone 4 workouts can preserve heart function, mitochondria, and muscle, keeping VO₂ Max above the independence threshold (20 ml/kg/min) well into later decades. In other words, aging lowers your ceiling—but training decides how steep the slope gets.
