Power vs Endurance Predisposition

The trade-off between power and endurance is wired into fiber-type biology and the broader aerobic-anaerobic gene set. ACTN3 (fast-twitch performance) and ACE I/D (oxygen delivery efficiency) sit at the center. Carriers of "power-dominant" combinations tend toward sprint and strength dominance; carriers of "endurance-dominant" combinations tend toward sustained-effort dominance.

Carriers of ACTN3 RR + ACE DD genotype are associated with the power-dominant pattern: strong sprint performance, high peak force, faster but less sustainable efforts. Carriers of ACTN3 XX + ACE II genotype are associated with the endurance-dominant pattern. Mixed genotypes (most clients) produce intermediate patterns that lean one way or the other but respond to training in both directions.

Sport selection is the biggest practical lever: distance running, cycling, and triathlon reward endurance-dominant variants; sprinting, weightlifting, jumps, and team sports rich in repeated short bursts reward power-dominant variants. Training time invested toward the variant pattern compounds faster than training time spent against it. Both phenotypes can train both qualities, just with different starting points and different responses.

Most athletes aren't told their wiring leans one direction or the other. They discover it through which sports felt natural and which felt like fighting their body. Which ACTN3/ACE combination you carry decides which direction the wiring actually rewards, and whether your past sport gravitations were preference or biology.