What do Mathieu van der Poel, Sren Wrenskjold and Mauro Schmid all have in common? If you said theyre all stage winners of this edition of the Tour de France youd be right. But theres also something else, a detail so subtle you might not have spotted on the TV: they all shave their arms. Though not a new practice, arm-shaving has seemingly become more common in big races. Cycling Weekly carried out a visual survey on the ground at this year's Tour, assessing riders' forearms as they passed through the pre-stage media zone, and found that around half of the peloton now shave their arms maybe even a slight majority.It got us wondering why. The advantages of smooth legs are well known in cycling less aerodynamic drag equals seconds saved but why the arms too? Their surface area is smaller, they dont block the air flow as much as the legs, and if the riders bike position is low enough, they barely poke up above the handlebars. Surely theres no point in shaving them? In search of answers, we asked the riders themselves. Caja Rural-Seguros RGA's Fernando Gaviria, a two-time Tour stage winner, said this is the first Tour for which he has shaved his arms. I spoke with [my team-mate, Alex] Molenaar about whether we should do or not, he said. Then we spent a night in the room and we said, Ok, lets do it. As a sprinter, Gavirias main motive is to go faster. Its just for more aerodynamics, the Colombian said. I dont feel the difference in the climbs. I get dropped all the same. But what does the science say? Is there an aero advantage? (Image credit: Getty Images)In 2015, bike brand Specialized carried out a test in their wind tunnel, and found that shaved arms saved 19 seconds over 40km. Though the study wasnt far-reaching (their sample size was a single rider), its conclusion was clear enough: the aero gains are small, negligible even, but they exist all the same. According to Casper von Folsach, performance director at Uno-X Mobility, the impact of arm-shaving is very individual, and depends on how much arm hair a rider has. Overall there is for sure a much more significant aero penalty in leg hairs as most people have more significant hair growth on their legs, legs make up a larger surface area and are more exposed, he said. But that doesn't mean there's not a difference for arm hairs. Its partly for this reason that the entirety of Von Folsachs Uno-X Mobility squad came to this years Tour with smooth arms. Gaviria did the same because he has a lot of hair on his body. But even riders who arent so naturally hirsute are shaving their forearms. This is because theres another, perhaps more important reason to do so, as stage 13s winner Schmid explained. It makes it a bit more clean in case you get a little road rash. Its not only for aero gains, the Jayco AlUla rider said. Its the same thing with the legs; in case you crash, I think it makes it much easier because then youre not ripping all the hairs out if you get bandages.Lotto Intermarchs Baptiste Veistroffer, this editions breakaway hero, concurs. Its because of crashing, firstly, he said. If you crash and you need to clean it, or you need surgery, its easier without hair. It was fortunate, then, that Gavirias arms were hairless when he crashed on stage 12, and shredded his skin on the asphalt.(Image credit: Getty Images)Veistroffer, pressed for more information on his arm-shaving habits, was understandably perplexed by Cycling Weekly's questioning. This is not expected, he laughed, but conceded he shaves his arms every one to two weeks only when Im racing, not when Im home. Conversely, Schmid doesnt shave his arms as routinely as he does his legs, and only originally did so to copy another rider. I think Marc Hirschi normally does it, and I saw him do it and thought, Maybe thats the reason why hes so good, he says. So there you have it: riders shave their arms for a few reasons, namely the perceived aero advantage, and for ease in case of road rash. Oh, and there's another minor reason, as Von Folsach points out. For what it's worth, many riders also report that sun screen application becomes easier, he said, so that's also something I guess.