The siblings are well aware of the projected temperatures, which is why they are doing all they can to ensure that they acclimatise as much as is possible, determined that if their rivals are to better them in the quest for an Olympic medal, they will have to beat them without the help of the searing Brazilian sun.
But given that they are a couple of lads more used to the Scottish climate, they had to get creative.
“We have been trying to figure out what to do about training camps,” said elder brother Derek. “We want to compete in the European half marathon event in July, then hopefully go to Spain for a few weeks but, after that, we will do most of our training at home.
“We will do occasional runs in a heat chamber, which could be crucial. We have not actually used one yet but, from what I’ve heard, they are quite accurate at recreating whatever conditions you’ll be facing.
“I did a half-marathon once when the temperature was 33 degrees, so I have done an endurance race in hot weather. But twice that distance, it’s a step into the unknown.”
“The average temperature in Rio at the time we’ll be running is 26 degrees, which is hot,” agreed 23-year-old Callum. “It’s probably a bit too hot for the marathon but nothing too extreme.”
Callum was the first Briton over the line at the London marathon, guaranteeing his place on the plane to Rio, while, Derek was the third home athlete to finish, earning him the nod from the selectors as well.
But despite the relative youthfulness as exponents of the 26-mile race, they are hoping that, if they can race to their maximum potential, then they would be able to deal with a decent pace. But that will only happen if the can adapt to the sweltering heat.
“I did a 10k in Macedonia when it was 36 degrees,” recalled Callum, “and it did not go well. I had to drop out of that race. It was Commonwealth Games year. I was in a bad place and I didn’t want to put myself in a real hole with such a big event coming up. I had a feeling that, if I finished it, I would have been wrecked. Definitely pretty close to being in a very bad condition.”
But two years on and with the experience of Glasgow 2014 to build on, they are relishing the opportunity to pull on the GB vest at an Olympic Games and willing to leave it all on the line. They will also be tapping the brains of guys who have been there before.
“I’ve emailed Richard Nerurka, who finished fifth in the marathon at Atlanta, back in 1996, to see if he can offer us some advice,” said Derek. “I don’t expect conditions in Rio will be as tough as they were in Georgia that summer but I am keen to pick his brains.
“There is also the option to speak to some of the athletes who ran in Athens, which was just mental, especially the conditions for the marathon there.”
But, at least they are not in it alone, with all three marathon runners coming from the Scottish athletics stable and the brothers primed to attack every challenge together.
For Callum that means cashing in on being the baby of the duo and getting his older brother to leap into the unknown first.
“Yes, I can throw him into the heat chamber first!” he said. “But seriously, it is good to have someone else going through the same experiences, and being there at the holding camp, which can be quite a boring time. It’s good to have someone to talk to, someone to help eat up the hours.” “Yeah, it’s pretty horrible, especially the last week before the race,” agreed Derek. “You are scared to push yourself in case you use up all your energy. It’s the most stressful week.”
The pair, who had started out as promising young shinty players before swapping that for athletics after they realised that hand-eye co-ordination was not their forte and admitting that they were more suited to running, have found ways to cope with the nerves and the monotony.
“Usually we watch films, read, stay quiet. If you go out you think, ‘Oh, am I using up too much energy”? So we just stay in and watch boxsets,” said Callum. “Fortunately, we like the same kind of things. Sit-coms. Something light.”
Given the temperatures, they want to preserve as much energy as possible. But the pair have shown that, metaphorically at least, they can handle the heat.