Weather

Hyperthermia vs. Hypothermia

  • Hyperthermia = elevated body temperature

  • Hypothermia = drop in body temperature
     

  • Heat Stress

    • Variable based on the person and their body's ability to dissipate heat; variation in sweat rates

    • Metabolic heat production - normal metabolic function

    • Conductive heat exchange - physical contact with other objects

    • Convective heat exchange - dependant on temperature/presence of circulating medium

    • Radiant heat exchange - from sunshine

    • Evaporative heat loss - sweat glands --> evaporates
       

  • Exertional heat illness

    • Heat rash - red, raised rash with prickling and tingling feeling with sweating

    • Heat syncope - rapid physical fatigue during overexposure to heat

    • Heat cramps - muscle spasms due to excessive loss of water and electrolytes

    • Exertional heat exhaustion - environmental heat stress + strenuous physical exercise

    • Exertional heatstroke - CNS abnormalities + potential tissue damage; elevated body temperature

    • Malignant hyperthermia - genetically inherited muscular disorder --> hypersensitivity to anesthesia and extreme exercise in hot environments

    • Acute exertional rhabdomyolysis - sudden catabolic destruction and degeneration of skeletal muscle

      • Preventing heat illness

        • Dehydration - loss of <2% of body weight

        • Fluid and electrolyte replacement

        • Gradual acclimatization

        • Identify susceptible individuals

        • Appropriate uniform/clothing

        • Weight records (weigh-ins, weight-outs)

        • Monitor temperature and humidity
           

  • Cold injuries

    • Frostnip - high wind, severe cold --> ears, nose, cheeks, etc

    • Frostbite - length of exposure; ranges in severity and prognosis

      • Preventing cold injuries

        • Proper clothing

        • Monitor weather and conditions

        • Hydration

Heat index

  • Heat + humidity + bright sunshine

  • Universal Wet Bulb Globe Temperature (WBGT) index:

    • Dry bulb temperature (DBT) - standard mercury thermometer

    • Wet-bulb temperature (WBT) - wet wick wrapped around the end of thermometer that is swung around in the air

    • Globe temperature (GT) - measures the sun’s radiation with a black metal casing around the end of a thermometer

      • WBGT: (0.1 x DBT) +( 0.7 x WBT) + (GT x 0.2)

      • WBGT: (0.3 x DBT) + (0.7 x WBT)

        • Record temperatures for 90 seconds

        • Psychrometer = two thermometers – dry and wet – when the cloth is soaked and thermometers are properly ventilated, WBT < DBT (cooling due to evaporation) --> drier the air = lower the WBT 

      

                                                                  Easy Work                         Moderate Work                   Hard Work

               Heat Category |  WBGT (F) | Work/Rest | Water per hour | Work/Rest | Water per hour | Work/Rest | Water per hour

                         1           |    78-81.9 |    No limit |      1/2 quart     |    No limit |      3/4 quart     |  40/20 min |      3/4 quart    

                         2           |    82-84.9 |    No limit |      1/2 quart     |  50/10 min |      3/4 quart     |  30/30 min |        1 quart       

                         3           |    85-87.9 |    No limit |      3/4 quart     |  40/20 min |      3/4 quart     |  30/30 min |        1 quart       

                         4           |    88-89.9 |    No limit |      3/4 quart     |  30/30 min |      3/4 quart     |  20/40 min |        1 quart       

                         5           |       >90     |   50/10min |       1 quart       |  20/40 min |        1 quart     |  10/50 min |        1 quart      

 

  1. No flag = <78.0F - nonacclimatized: exterme extertion may lead to heat illness; fully acclimatized: normal activity

  2. Green flag = 78.0F - 82.0F - nonacclimatized: discretion with intense exercise; fully acclimatized: normal activity

  3. Yellow flag = 82.1 - 86.0F - unacclimatized: limit intense exercise to 1 hour with total outdoor exercise less than 2.5 hours; fully acclimatized: use discretion in planning

  4. Red flag = 86.1 - 89.9F - nonacclimatized: no outdoor session; fully acclimatized: limit outdoor sessions to 1 hour (total outdoor time less than 4 hours)

  5. Black flag = >90F - nonacclimatized: cancel all outdoor session; fully acclimatized: cancel all outdoor session

Other environmental factors

Altitude

  • Loss in maximum oxygen uptake = a 4-8% deterioration in performance

  • Hyperventilation

  • Fewer RBC to adequately capture available oxygen in the air

    • Altitude illness can occur: acute mountain sickness; pulmonary edema; Sickle cell trait

Sun exposure

  • Use sunscreen!

  • Can increase rates of skin cancer

Lightning

  • Take extreme caution; develop EAP

  • See/hear lightning = immediate danger; should seek shelter

  • Lightning always accompanied by thunder --> Flashbang method - count number of seconds from a sighting of lightning to hearing thunder, ÷ by 5 (ex: 30 = 6 miles away)

  • Lightning Detectors - hand-held or automated systems

Pollution

  • Photochemical haze - nitrogen dioxide + stagnant air react with sunlight to produce ozone

  • Smog - carbon monoxide + sulphur dioxide

    • Decrease activity during high pollution

    • Ozone levels rise during dawn, highest at midday, and reduce after late-afternoon

    • Avoid activity in high pollution areas

Jet lag

  • Physical and mental effects caused by traveling across time zones

    • Hydrate!

    • Younger individuals adapt quicker than older

    • Traveling west - light meals early, heavy meals late; consume caffeine; exercise/train later in the day

      • Faster adaptation

    • Traveling east - heavy meal earlier; avoid caffeine; exercise/train earlier in the day

Synthetic turf

  • Common injuries - ex: turf toe

  • No increased incidence of injury vs natural surfaces

  • More durable than natural grass and easier to maintain