Inflexibility is genetically determined and makes you fast

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Last year I blogged about some cool findings from the University of Cape Town on a gene called COL5A1, a certain variant of which seems to predispose people to be (a) inflexible and (b) efficient distance runners. That initial study looked at participants in the South African Ironman triathlon; the same research group now has a new study in press at the International Journal of Sports Physiology and Performance looking at 72 runners in the 56km Two Oceans ultra-marathon.

The results confirm the previous findings: runners with the “TT” variant of the COL5A1 genotype ran faster (5:41 versus 6:05 on average), and that group was also overrepresented in the “fast and inflexible” quadrant of subjects. The genotype accounted for about 7% of performance variance.

It’s worth emphasizing that the effect of this gene is still quite small overall — there are so many genes that affect performance that any one gene is unlikely to have a large effect. As the paper puts it:

[T]he magnitude of the effect of the COL5A1 gene on endurance running performance was calculated as being “moderate” in this study. Due to the polygenic nature of the endurance phenotype3, it is highly unlikely that a single gene would have any greater magnitude of effect.

There are plenty of other questions that remain to be answered — for instance, does this genotype allow you to directly run faster, or does it (for example) make you more injury resistant so that you can train more? This study apparently represents just one part of a larger cohort being studied, so perhaps there will be further insights before long.