The 33 trapped miners in Chile will spend the next few days in tunnels almost half a mile underground, eating a special diet recommended by NASA and doing exercises designed to aid their rescue by midweek.

Officials have “concerns” over the physical toll the extraction will have on the men as they are pulled up to the surface one by one in a steel tube 24 inches wide, Health Minister Jaime Manalich told reporters yesterday. Miners in coming days will have to perform “very hard” exercises and eat a special diet that includes saltwater supplements and aspirin to prevent them from suffering from hypertension, thrombosis or other forms of stress during the rescue, he said.

The men are in “good shape” physically and psychologically, Manalich said.