Polymers: a champion’s secret weapon

Marie Dorin-Habert and Vincent Defrasne are both biathlon champions. Each has enjoyed a successful career, with Marie winning four Olympic medals and five world titles, and Vincent taking part in three Olympics, culminating in a gold medal in Turin in 2006. Now retired from competitive biathlon, they discuss the importance of equipment in their sport.

How does your equipment impact your sporting performance?

The biathlon is a sport that combines cross-country skiing and rifle shooting. We need to be able to ski quickly and shoot precisely, so aside from our strength and aim, our equipment also affects our performance. This is even more true at the elite level, where the difference between first and second place boils down to little more than a few small details, including the choice of equipment. We need maximum reliability and the latest technology to ensure we are not penalised and our performance is not hindered in any way.

Is this particularly true for the skis?

Yes, but not just them! But let us start with the skis. Not many people know this, but an athlete competing in the World Cup has between twenty and forty pairs of skis to choose from when selecting the pair they will use on race day — and this decision is only made an hour before the start to make sure the chosen skis are as well suited to the day’s conditions as possible. A ski is so much more than a simple board. It is comprised of a core, laminates and a base. In competition skis, the core is a honeycomb structure made of Nomex, a stable, rigid aramid. The laminates are usually an epoxy resin carbon composite that guarantees excellent rigidity and watertightness.

As for the base, this is arguably the most important part of the ski because it is the part that comes into contact with the snow, so it must glide well. It is made from extruded or agglomerated polyethylene. Agglomerated polyethylene is generally the material of choice since it makes for a more durable base. It also makes it more porous so that it can better absorb wax (a paraffin-based paste coated on the base to improve glide). To further ensure a good glide, the base features fine grooves which, just like on a car tyre, help eject water. The skis glide thanks to the hydrophobic properties of the wax, which transforms the water in the snow into micro-droplets that the skis can “roll” over. The type of base you use should be adapted to the snow’s texture and temperature on the day. There aren’t any all-purpose competition skis; that is why we bring along a couple dozen pairs.

Next, the components need to be put together correctly, stiffening certain parts of the ski depending on the desired qualities and the athlete’s skiing style. This makes the skis more responsive and able to glide correctly during active skiing as well as during passive descent.

Are the boots as important as the skis?

Absolutely! All the athlete’s power travels through them into the skis. We saw the introduction of carbon and epoxy-based composites, which was a huge development. This material created ski boots that were lighter, thinner and more rigid, making them more responsive. On the downside, this rigidity could lead to fatigue fractures in some athletes, which is obviously not great at the height of a season. Manufacturers have since improved them by only using carbon in strategic parts of the boot, which provides good thrust without compromising on comfort. The rest is made from different kinds of polymers like polyurethane and EVA (ethylene-vinyl acetate).

Ski boots are generally covered with a watertight shell, often made from PVC. Comfort is also key because a course can last for several hours. Ski boots are pretty warm and comfortable now, thanks to synthetic materials like polyester. Of course, we have our own little tricks, too (says Vincent). One of my instructors had the idea of slipping a little plastic wedge under my toes to raise them up and allow my tibia to move forward, gaining a little extra power without foregoing comfort. It was a well-kept secret for a long time…

Did rifles undergo the same kind of evolution?

Not so much: they are still made of wood and metal today, and plastics are rarely used. Although Jean-Pierre Amat, one of the French team’s coaches, did add a little something. He designed small plastic parts that he glued to the rifle, adding extra support on the top and against the hollow of the shoulder. This provides a fixed reference point to help hold the rifle on the shoulder correctly. It is so simple, but it had never been done before. Now everyone on the course uses it!

And what about the clothes?

In competition, comfort comes first, and clothing should never restrict movement. That is why all our gear is synthetic — it needs to be made from extremely flexible materials. These materials are made from polymers like polyester, polyamide and elastane. The latter has a major advantage in that it is more breathable than the others.

Gore-Tex (polytetrafluoroethylene (PTFE)) membranes have also been a major innovation since they are waterproof while still allowing skin to breathe. We need a range of equipment because we face a wide variety of temperatures, and the cold is our enemy. You can lose a race because your fingers are cold. You lose the sensitivity required to execute the shot correctly — it happens all the time! You need gloves that are not too thick but still thick enough to retain heat. Synthetic materials do a pretty good job of this, although we think there is definitely still room for improvement.

What is your relationship with equipment manufacturers?

It all depends on the athlete’s level. If they are a “medallist”, all their equipment will be made to measure according to their technical skills (skiing technique, strength, position on the shooting range, etc). Although we develop equipment together, brands don’t often reveal their secrets because they are afraid that the athlete will switch to rival brands.

Do you think elite sport is compatible with environmental sustainability?

It should be! Back when we were competing, it was not something that concerned many people. The terms “carbon footprint” and “eco-design” were little more than vague and unfamiliar concepts. However, that is not the case now; things are changing for the better. The French Ski Federation is trying to limit air travel, though these restrictions are still quite light. In the same way, skis that used to be thrown away at the end of a season are now distributed to clubs to be used by young hopefuls. Today, we are all in favour of eco-design, and competitors are keen to choose eco-designed equipment. However, for it to be accepted, every team has to get on board to ensure a level playing field in case this equipment turns out to be less efficient — something that has not been proven. Ideally, the International Ski Federation should impose eco-design standards.

What is life like after elite sports?

Marie Dorin-Habert has teamed up with other elite skiers to create Zecamp, a hotel with a sporting twist where everyone can learn how to complete a biathlon.
https://zecamp.fr/

Vincent Defrasne has launched Ayaq, a brand of eco-responsible performance clothing designed for outdoor sports.
https://ayaq.com/