As quadriplegics, their cooling and heating systems are compromised.
"When you start to get hot, your brain sends a message to sweat right?" Canadian veteran David Willsie explains. "We don't get that message."
So there's a danger of heat exhaustion when they propel their wheelchairs across an indoor court at ramming speed for four eight-minute quarters. They take steps to cool themselves off before, during and after matches at the Paralympic Games.
The players might wear ice vests or ice towels around their necks before games or during breaks in games. They mist themselves with spray bottles. Post-game, they may immerse their arms in an ice bath.
"If I find myself getting overheated and start to get a headache, I go for ice in my armpits," says Mike Whitehead. "The major arteries are there and that will help me to cool down."
Willsie says he and his teammates have each swallowed a microchip to measure their core temperature at some point in their careers with the national team. That helps them and the team's medical staff figure out what each player needs to do to regulate his thermals.
"Everybody is different. Mother Nature is a mad scientist," Willsie says. "You figure out your own system that works.
"I try to heat up really fast and then plateau. My warmup is short and intense to get my heart rate up."
The rugby venue at the Paralympic Games, also used for basketball, is cool and airy. Bench-side fans weren't required in Canada's game against Belgium on Thursday.
"This is a perfect environment. The temperature is ideal," Whitehead observed. "We were in Montreal recently and we were in a gym with no air conditioning, so we're in heaven right now."
Willsie says because the Canadian players rotate in and out of games they're less likely to overheat in an international matches compared to playing an entire game with their club teams in gyms at home.
Still, a players turned the spray bottle on himself after pre-game warmup. The players reached for their water bottles the moment they wheeled off court.
The human body has sensors to tell the brain what's going on temperature-wise and that information passes through nerves in the spinal cord, according to Canadian team chief medical officer Richard Goudie.
All players on Canada's wheelchair rugby team are quadriplegics. All four limbs have impaired sensation because of an injury to their upper spine.
"So they have all their legs, most of their trunk and part of their arms that's not dealing well with sensing temperature changes and also managing it," Goudie explains.
"On the court, because your muscles generate heat then you're going to become very hot, but you can't sweat very well below the level of your injury.
"A lot of them have to create pre-cooling, so they'll wear ice vests before to try and decrease their temperature by cooling the skin, which is still taking up a lot of the cold blood flow to the core. That decreases your body temperature before you start. You have more room to get hotter before you get into trouble and overheat."
Regulating body temperature is less of an issue on the men's wheelchair basketball team, for example, because many of them are paraplegics with just their legs affected, or amputees.
"It's all about the amount of your body that still has adequate sensors," Goudie says. "The guys in basketball, especially the ones who have amputations, they've got a completely normal thermoregulation. It's the spinal cord injury individuals (most affected)."
Canada defeated Belgium 58-50 on Thursday to set up an important match Friday versus Sweden. With both countries 1-1, the winner advances the semifinal. Former Canadian team coach Benoit Labrecque coaches the Swedes.
"Benoit was my coach from 2001 to 2008," Whitehead said. "Having Benoit coach Sweden, we know they'll be prepared. It's a definite advantage for us to know him well, but he is a smart guy."