LESSONS IN SURVIVAL

The toughest part of the 19-day training takes place in a secret location at Camp Mackall called the Resistance Training Laboratory. Translation: a mock prisoner-of-war camp where students have the chance to put into practice what they have learned in the classroom phases of survival school. Everything is modelled on real enemy encampments,including guard towers,razor-wire fences,concrete cells and metal cages. They claim that they dont use torture,but sessions are known to be very rough.

During mock interrogations,the prisoners heart rates skyrocket to more than 170 beats per minute for more than half an hour,even though they arent engaging in any physical activity. Meanwhile,their bodies pump more stress hormones than the amounts actually measured in troops awaiting ambushes in Vietnam or patients awaiting major surgery. The levels of stress hormones are sufficient to turn off the immune system and to produce a catabolic state,in which the body begins to break down and feed on itself. The average weight loss in three days is 22 pounds.

Morgan looked at two different groups going through this training: regular Army troops like infantrymen,and elite Special Forces soldiers,who are known to be especially stress hardy. The two groups released very different amounts of a chemical in the brain called neuropeptide Y. NPY is an abundant amino acid in our bodies that helps regulate our blood pressure,appetite,learning and memory. It also works as a natural tranquiliser,controlling anxiety and buffering the effects of stress hormones like adrenaline.

Morgan found one very specific reason that Special Forces are superior survivors: they produce significantly greater levels of NPY. In addition,24 hours after completing survival training,Special Forces soldiers returned to their original levels of NPY while regular soldiers were significantly below normal.

Morgan also found that the best underwater navigators release a lot of a natural steroid called DHEA,which buffers the effects of the stress hormone cortisol and helps the brains hippocampus with spatial relationships and memory. Divers with the most NPY and DHEA graduated at the top of the class at the elite Navy Diving and Salvage Training Center in Panama City. Those with the lowest amounts did poorly.

Morgan has discovered a simple and accurate way of predicting who will survive and perform the best under extreme stress. The best survivors have metronomic heartbeatstheir hearts thump steadilywith almost no variability between beats. Morgan analysed the heartbeats of soldiers and sailors before they experienced major stress. The ones with metronomic heartbeats performed the best in survival school and underwater navigation testing. They also did the best in whats called close-quarters combat training. Morgan analysed their heart rates right before they went into mock battle. They were all suited up in combat gear,waiting for a buzzer to ring that would send them running into a building to kill the enemy and rescue hostages. They use simunitions,simulated ammunition that hurts but doesnt cause real harm. The ones with metronomic heartbeats,Morgan says,shoot more bad guys and kill fewer hostages.

Unfortunately,this metronomic effect is usually associated with early heart disease and even sudden death. Morgan wonders whether the same thing that makes you really good at surviving under high stress may not translate into excellent heart health when youre 50. Without it,though,these elite forces might never even make it that far.

Sherwood is author of The Survivors Club: The Secrets and Science That Could Save Your Life.