Why do some people find marathon running easy, while others shine in sprint or strength sports but suffer when jogging? The answer often lies not only in training, but in muscle fiber composition, oxygen uptake and regeneration capacity – factors that are strongly genetically co-determined.
The best-known "sport gene" is ACTN3. It encodes alpha-actinin-3, a protein found only in fast muscle fibers. About 18% of the world's population have a variant (XX genotype) that completely switches off this protein. These people are often "born endurance athletes".
Insights into these genes help to optimize training and avoid frustration. Power types benefit disproportionately from interval training and heavy weights. Endurance types respond better to high volume and steady load.
Genetics is not fate. Knowing your predisposition allows you to get the best out of your biology through a targeted lifestyle.