From your third decade onward, several measurable markers of capacity begin a gradual decline. None of this is a verdict — it is a baseline, and much of it is modifiable.
Cardiorespiratory fitness (VO₂max)
VO₂max — the maximum oxygen your body can use during intense effort — declines roughly 10% per decade after age 25 [1]. It is among the strongest predictors of longevity, and structured training can slow the decline substantially [4].
Muscle mass & strength
Muscle mass decreases approximately 3–8% per decade after age 30, and the rate accelerates after 60 [2]. This loss — sarcopenia — quietly erodes strength, metabolic health, and independence.
Cognitive processing speed
A hallmark of cognitive aging is slowed processing speed — a decrease in the rate at which we perform perceptual, motor, and decision-making tasks [3].
These markers define your arc — but they are not fixed. A substantial portion of the decline is attributable to inactivity and other modifiable factors, which is precisely where targeted performance medicine intervenes.