Why do some people respond to endurance training so much better than others? Lund University researchers Ola Hansson and Kristoffer Ström, with international partners, began with muscle tissue and DNA from just over 600 Swedes and identified a variant in the gene RAB3GAP2 associated with the number of capillaries in muscle. More capillaries mean better delivery of oxygen and nutrients, one of the physiological foundations of endurance performance.
The team then tested the finding in elite athletes from six countries. The variant turned out to be roughly twice as common in Swedish endurance athletes, at about 10 per cent, as in non-athletes, at about 5 per cent, and it is strikingly rare in explosive-sport specialists: under 1 per cent of world-class Jamaican sprinters carry it. The association replicated in athlete cohorts across Europe, America and Asia, though not in Africa. The study appears in Cell Reports.
Mechanistically, the variant lowers production of a protein that restrains capillary formation, so carriers build more vessels, and high-intensity training suppresses the same brake further. The variant also tracks with a stronger inflammatory response and, in some contexts, higher injury risk, a reminder that such trade-offs are the norm in human physiology. Beyond sport, the researchers are collaborating with AstraZeneca on whether easing this brake pharmacologically could improve sugar uptake in muscle, a potential route to treating insulin resistance in diabetes.