It may not be obvious from his tall, sturdy frame but Tim Jarvis has been starving himself.

The explorer and environmental scientist put on an altitude mask to deprive his lungs of oxygen to prepare for his ascent of three mountains in Ecuador including Cotopaxi, a 5897-metre active volcano whose summit is off-limits due to the threat of imminent eruption.

“I sit there for maybe half-an-hour in the morning, half-an-hour in the evening,” Jarvis says. “I stick on the mask and turn it up, in the old money, to 18,000 feet, which is just shy of 6000 metres and sit there and read the paper.

“It’s hard doing it but it starts to get you accustomed to the level of breathing difficulty you get at that altitude.”

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