Weather Notes | Knowt (2024)

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

        See Also

        Ear measurement of temperature is only useful for screening for fever in an adult emergency departmentFever in Adults - Infections - MSD Manual Consumer VersionFever in Infants and Children - Children's Health Issues - Merck Manual Consumer VersionBody Temperature Is 96, But I Feel Sick: Causes and More

      • 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