It’s an unpleasant fact of life that most mass-participation endurance events start at (and sometimes before) the crack of dawn. But it’s not equally unpleasant for everyone: the world is divided into morning types (“larks”), evening types (“owls”), and those who don’t have a pronounced preference either way. What if you’re a wonderful endurance athlete, but you just hate getting up in the morning? Will this make it less likely that you persist in the sport?

That’s basically the question that a group of South African scientists from the University of Cape Town tackled in a recent study published in Chronobiology International. They compared four groups of people: 125 cyclists, 120 runners, 287 Ironman triathletes, and 96 active but non-competitive controls. The first test they did was to administer the “Horne-Ostberg Morningness-Eveningness Questionnaire,” which is used to distinguish larks from owls. Here are the results (where MT is morning type, NT is neutral type, and ET is evening type):

Pretty big difference in the number of morning people in the athlete groups compared to the control group. But this doesn’t distinguish between cause and effect: maybe years of pre-dawn rides have convinced those cyclists that they really like getting up in the morning (because if they didn’t tell themselves that, they’d go crazy). So the researchers also did a series of genetic tests; here are the results of one of them:

In this case, the “5 allele” is associated with shorter circadian rhythms, which in turn translates to morning preference — so people born with morning preference are indeed (at least in this particular sample of white South African men) more likely than the general population to end up getting addicted to endurance sports, presumably because of the time of day when most people train and compete.

So… who’s going to found the first Evening Triathlon Association, bringing endurance sports to the neglected owls of the world?