Hiker dies from heat while hiking Palm Springs Trail 6/29/15

[climbant]

Hypothermia and Hyperthermia can both come on pretty quickly. Normal range for humans is IIRC 97.8-99, below or above that effects can start taking place. Previous medical conditions, medications, hydration, and fuel available will play a roll in the seriousness of those changes and how your body responds. But no matter who we are, our body temperature will fluctuate. There was a study a few years ago that looked at the effects of hypothermia on mental/physical skills on test subjects. They used some Navy SEALS, the SEALS were tolerating body temperatures that should have rendered them unconscious and they were still performing pretty well. Conversely an older person with several medical problems/medications may become unresponsive when most people would only be having very mild effects. The scientists were very surprised as this wasn't what they were looking into. As a firefighter here in the valley for over a decade, I see new firefighters to the desert having a harder time in the heat, they are not as acclimated. Conversely how many of us have been up the mountain in pants, jacket, and beanie while others are in shorts and short sleeves.

Studies on marathoners have found optimal temperatures are in the mid 40's. Temperatures above that started effecting performance.
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0037407

Where this couple is from, the average high in July is a hair under 60. What was the temp when they started, mid 80's? Once again a very sad story.

[scotts]

Yes climbant. I think a big part of fitness is the capacity to regulate body temperature. This is going to vary with training, age, acclimatization, etc, but if you don't have it, you just don't have it.

For hot weather hiking (especially) good advice would include not trying to 'tough it out'.

[momphrare]

Yes cynthia23,
The body can only regulate itself for so long. The biggest factor like climbant has mentioned is the persons mental and physical abilities. An additional factor is the humidity in the air. If it is very humid out then the body loses its ability to cool itself. So you can become hyperthermic very quickly in medium to high heats.