Monthly Archives: August 2013

Don’t pet the sweaty stuff

Tech shirts.  All of the major companies make them now.  Mostly polyester, they were designed originally to increase evaporation to provide a “cool” feeling and decrease the amount of sweat present in the clothing after a workout.  They were popular with military in the Middle East until they were banned due to the injuries they cause when burned. Living in south Texas, I’m infinitely familiar with clothing soaked with sweat.

This article took 3 different kinds of synthetic shirts and 1 ordinary cotton shirt (Fruit of the Loom!) and compared them.  The methods section makes me never want to be friends with these guys, as they made them start at 7 kph, going up 1kph per minute up to 14 kph.  Then inclination was increased by 1 degree per minute until exhaustion. This was to determine peak oxygen uptake.  Then for each individual fabric test they made them perform at 70% of that maximum uptake for 30 minutes, then increased the inclination to exhaustion again.  At least there was a fan blowing on them from the front.  Temperature was controlled at 31.7C and relative humidity was kept at 42%.

During testing, they measured

  • Temperatures (ambient, skin, body, and core)
  • Relative humidity (ambient, chest, and back)
  • Blood lactate (from the ear)
  • Ratings of
    • perceived exertion on a 6-20 scale
    • thermal sensation on a 1-9 scale
    • wettedness sensation on a 1-4 scale
    • shivering and sweating sensation on a 1-7 scale
  • Heart rate
  • Respiratory exchange ratio
  • Ventilation
  • Oxygen uptake
They found that 2 of the 3 synthetic shirts did lower body temperatures, decreased relative humidity, and made the runners “feel cooler” during exercise.  They did not demonstrate any increase in performance ability.  Thus, it is likely that this kind of shirt may make you feel less wet, but is unlikely to make you an Olympic athlete right out of the box.  Certainly they aren’t worth a huge premium over regular shirts.
Exercising in a Hot Environment: Which T-shirt to Wear?

See you later, alligator.

Alligators can be found from Florida to Texas, and north into North Carolina and possibly even Tennessee.  3 species are present, with the American alligator being predominant, followed by the American crocodile in southern Florida, and the caiman is an exotic species present in southern Florida.  

There have been 24 documented deaths from crocodilians in the United States.  This is in addition to the 567 reported adverse encounters in the same time frame (1928-2009).  The encounters are predominantly caused by human encroachment into alligator territory. All reported attacks are limited to the American alligator. 

This article gives some pointers on alligator attacks.  These include:

  • Don’t go to Florida.  91.6% of fatalities and 90.8% of documented attacks occur there.
  • Males represent 85.4% of attacks.
  • Most bites (81%) are single bites.
  • 80.8% of bites are on the hand or arm.
  • 26.5% of bites occur while handling alligators (shocking, I tell you). Wading and swimming combined make up 30%.
  • Noon to 6pm is the highest incidence of bites.
  • May to August are the worst months for alligator bites.
  • 54.8% of the bites were felt to be unprovoked, and 33% were felt to be provoked.
  • 29.2% of the cases were consistent with the alligators treating humans as prey.
  • Most fatal attacks involve alligators greater than 8ft in length, so avoid the big ones.
  • 38 bacteria and 20 fungal species have been cultured from alligator mouths, and overwhelming sepsis has been a cause of death after an attack.
  • Alcohol wasn’t reported commonly.
Sadly, no advice is given on how to survive an attack once it starts, and treatment descriptions are lacking. But the article does help reinforce common sense when it comes to animals that hunt humans. One last thing, don’t run away in a zig zag pattern. That’s a myth. Just run straight away as fast as you can.

Adverse Encounters With Alligators in the United States: An Update
http://www.ncbi.nlm.nih.gov/pubmed/20591380