Somewhere around 40, the conversation about exercise shifts.
Performance matters less; the consequences of its absence matter more.
The body is a cold bookkeeper. Muscle is a costly luxury, and the system refuses to pay for what isn't used. Take away the demand and the body begins to trim the ledger. Quietly. Over the years, these small subtractions become a total loss.
The clients I work with aren't always training for the mirror. The goal is to keep the body's resource allocation working in their favor - strength, glucose regulation, bone density, postural integrity - the things that determine what 75 actually feels like.
Progressive resistance training is the signal. The body responds to what arrives consistently - and ignores everything else.