Same workout, my friend builds muscle and I barely change

Roughly half of how you respond to training is genetic, and ACTN3 helps decide whether you are built more for power or for endurance.

Why it happens

ACTN3 makes a protein in fast-twitch fibres, the ones that fire in sprints and heavy lifts. People with the working version gain explosive strength quickly. Many South Asians carry two non-working copies and lean toward endurance. Doing the wrong style for your wiring is training against yourself.

One thing to try

Do one strength session and one endurance session this week. Notice which leaves you energised and which wrecks you. That gap is data.

Each decode is a research-backed tendency, not a diagnosis. A tap tells you how your body is likely wired and what to try, it does not label you, and nothing here is a substitute for a doctor where a medical question is involved.