Tech feature – Keeping cool at the Tour
By Zack Vestal
Until reaching Barcelona and heading for the Pyrénées, the first six days of the Tour de France were held in hot weather. Road races in the heat present challenges for riders and staff in terms of hydration and electrolyte supplementation. But because “warming up” for the race usually happens in the first few kilometers, overheating isn’t a factor.
Time trials are another matter, because warming up on trainers prior to the start is critical. Any coach or physiologist will tell you that activating the muscle and energy systems prior to the start of a hard TT effort will yield the best outcome, but in hot temperatures, riders can overheat quickly and become dehydrated.
One famous example of a rider overheating during warm up is Lance Armstrong himself, who lost a key time trial to Jan Ulrich in the 2003 Tour de France, which he blamed partly on dehydration due to warming up in the heat.
The importance of keeping cool
Team Garmin-Slipstream team physiologist Allen Lim described the importance of keeping cool during warm up (and exertion in general). “In my opinion,” he said, “It’s the single biggest bottleneck in the Tour, or any other sport.”
Lim went on to describe how the human machine is powered and how it regulates itself. As it turns out, athletes are not unlike internal combustion engines, in that they require fuel (energy) and oxygen (air) to create work (power). Also like a gasoline engine, humans produce waste, principally excess nitrogen in the form of urea, but also in the form of excess heat. As it turns out, again much like an engine, Lim said that humans are only about 25 percent efficient. Fully 75 percent of the air and fuel burned by an athlete is converted to heat—some of which is necessary for life, but an excess of which can be detrimental.
Lim pointed out that “blood is not just for carrying oxygen but also for dissipating heat. Blood flows to the periphery of the body for heat exchange on the skin.”
When a person is cold, blood is retained in the core to preserve heat. When a person is hot, blood moves to the skin to help transport heat out of the body.
It sounds like a good system, and it is. But when blood is needed at the muscles for oxygen and energy transport during exercise, and it’s not available because it’s being shunted to the body’s extremities for heat transport, the efficiency of the human machine declines. Lim called the phenomenon “physiological steal.”
“Power dropoff in the heat is huge,” he said.
“Anything you can do to externally cool the human machine while performing work allows more blood for delivering oxygen to working muscles rather than keeping cool,” Lim said. “The cooler the rider, the more power he can produce.”
Lim also noted that a cooler rider also enjoys a hydration benefit due to reduced perspiration.
Lim went as far as to say that keeping cool is like a legal performance enhancer.
“When you think of all the ways that riders try to cheat, using drugs, it seems totally ridiculous,” he said. “Because all they really have to do is keep cool. Find ways to keep cool.”
So, what strategies did teams use to keep their cool?
The stage four team time trial started in the mid-afternoon sun of Montpellier. Temperatures ranged in the low to mid 80s. Every team had riders set up on trainers for warm up, and all were in the shade. However, only a few had visible strategies for keeping cool.
The Italian Liquigas team used four electric fans to cool its riders. The principal cooling mechanisms at work in this case are evaporation and convection. Lim described how perspiration (or water) evaporating from skin offers cooling benefit. Convection (a current of air moving across and away from the heat source) is also at work to transport heat from the body.
Evaporation and convection are essentially what help cool riders while actually moving, so the fans simulate moving through the air.
Team Rabobank used what appeared to be medical devices that relied on electrically powered pumps to circulate cold water through Lycra shirts with water bladders sewn in. While very elaborate and rather restrictive (riders must remain tethered to the pumps while wearing the cooling jerseys), the cooling effect is probably significant.
The cooling mechanism in this case is primarily conduction, in which direct contact with the colder surface (water contained in the bladders) pulls heat from the body.
Plus, because the jerseys are worn around the core of the body, the benefit is extra, according to Lim. “The paradox (of warming up) is that you want to get muscle temperature higher, because muscles work better when warm. But despite that, you want to keep the core cool,” he said. The goal is suitable warm up for muscles, without causing the body to regulate itself for higher core temperature. External cooling of the core “tricks the brain into thinking it’s cooler, so it doesn’t regulate to a higher set point,” and thus shunt blood away from working muscles, explained Lim
Team Garmin riders were clearly focused on the team time trial. In addition to the careful choices in bike setup prior to the event, they faced the team bus rather than onlookers during their warm up. They also declined media and interviews prior to the race.
Allen Lim and team staff employed every cooling mechanism in the book to keep the nine Garmin athletes climate-controlled for warm up. They wore stretchy cooling vests with long pockets stuffed with ice to keep cool by conduction and evaporation. “We have fans that blow on them as well, which is convection,” said Lim. Direct contact with the ice counts as conduction, and as the resulting melt water evaporates, evaporative cooling adds effect. “We’re using all three mechanisms to keep them cool,” he said.
The particular vests worn by team Garmin are not commercially available, although similar cooling vests can be found on the market. “We custom make each one for the guys. I designed them and we have a friend sew them by hand,” said Lim. The material is stretchy but tight, and just thick enough to prevent burns from the ice, but thin enough to offer conductive cooling.
Additionally, the Camelbak-sponsored Garmin team starts off the races with large, insulated ChillJacket water bottles. Lim pointed out that feeding from team cars is not permitted in the first 50 kilometers of road races. “It’s better to stay on top of hydration than to play catch up. So for the first hour they are able to have cold drinks,” said Lim. He noted that colder liquids are absorbed more effectively by the body, and the insulated Camelbak bottles keep their drinks cold in the hot weather.
“We’ve been doing this for about four or five years now but few teams have caught on,” said Lim.
He hopes it stays that way, so his chilled-out Garmin-Slipstream riders can keep one of their biggest advantages to themselves.