DUBAL Beat the Heat Prevention Method
Introduction The body is required to get rid of excess heat to maintain a constant internal temperature (37 C) The body s s best mechanism for removing any excess heat is through the evaporation of sweat
How does heat alter this? High humidity stops/decreases the evaporation of sweat and therefore no heat is lost Muscular strength declines due to increased blood circulation to the skin, resulting in decreased flow to muscles Overheating decreases alertness and mental capacity
Blood - the key component Blood has the essential functions of providing oxygen and nutrients to vital organs and working muscles However it also carries heat from working muscles and the body s core to the skin so heat can be dissipated The blood volume is about 5 L for males and about 4 L for females
So what happens when I work in the heat? Thermal stress results in sweating: sweat evaporates producing cooling all sweat comes from blood supply initially, so increased sweat results in decreased blood volume
Dehydration: the impact If blood volume decreases you become dehydrated: there is less blood available to go to the skin and to ability to dissipate heat is lost heart rate increases because of this smaller volume, resulting in excessive fatigue blood supply to the gut is reduced resulting in decreased fluid absorption less blood is available to supply working muscles mental capacity is compromised due to decreased blood flow to the brain
Dehydration facts Single biggest cause of heat illness Thirst only starts at 2% dehydration of body weight Start drinking fluid immediately, don t t wait until thirsty Sweat rate can reach up to 1 litre per hour Drink small amounts and often (program drinking) Typically 40% of workers come to work dehydrated Drink plenty of water before coming to work Aim for clear to straw coloured urine when at work Drink so as to urinate frequently (~ 4 times a day)
Dehydration: the impact 1 to 2% dehydration 6 to 7% reduction in physical work rate 3 to 4% dehydration 22% to 50% reduction in work rate, for moderate and hot environments Mental performance begins to decrease at 2% dehydration and beyond that decrease proportionally to the level of dehydration
Summary The best way to maintain blood volume and therefore your capacity to stay cool is to prevent dehydration by maintaining fluid intake This is the same as ensuring a radiator is topped up with coolant before going on a trip. If the radiator is full the engine won t t overheat, if its only half full its performance will be limited and it will overheat
So what exactly is in sweat? Water Sodium (salt) Potassium Magnesium, Calcium larger amount small amount Virtually none
Fine, but how much fluid do you lose? 1000 900 800 700 600 Sweat Rate 500 (ml.h -1 ) 400 300 200 100 0 Sweat Rate Hour 1 Hour 2 Hour 3 Hour 4 Hour 5 Hour 6 Hour Hourly Sweat Rate over 6 Hours at 35 C C and 50% RH Average sweat rate ~ 600 mls/hr Working for 10 hrs : 6 L lost in a day
What about salt? Sodium (mmol.l -1 ) Sweat Sodium Concentration per Hour 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 Hour 1 Hour 2 Hour 3 Hour 4 Hour 5 Hour 6 Arms Legs Sodium Concentration changes in Arms and Legs over 6 hours (Mean+/- SD) Average sodium loss: ~ 40 mmol/l/hr Working for 10 hrs at a rate of 600ml/hr = 240mmol 240 mmol = 5.52 g lost in a day About 13 grams of salt which is about 3 teaspoons!
What s s wrong with caffeine and alcohol? Caffeine and alcohol are diuretics (i.e. they cause increased rate of urination)
Alcohol : an example If you are dehydrated by 3 Kg (3 L): -And you drink 3 litres of fullstrength beer -you produce 3.5 kg urine Net LOSS = 0.5 kg -End up 3.5 kg dehydrated -And you drink 3 litres of pure water -you produce 0.0 kg urine. Net GAIN = 3 kg -End up hydrated
Caffeine Coffee (per 250 ml mug) Percolated 100-200 mg caffeine Instant 70-180 mg caffeine Tea (per 250 ml mug) 1 minute brew 15-55 55 mg caffeine 5 minute brew 30-80 mg caffeine
Caffeine (cont.) Caffeinated drinks (per 375 ml can) Coke Pepsi Energy drinks (per 250ml can) 75 mg caffeine 60 mg caffeine Red Bull 80 mg caffeine V 78 mg caffeine
What you can do to limit these effects Drink tea in preference to coffee Drink weaker coffee or tea Reduce or eliminate intake of cola and energy drinks Drink a cup of water every time you drink a cup of tea or coffee When drinking alcohol make sure you are hydrated when you start
Can hydration status be tested? Simple test ; Urine Specific Gravity using a refractometer Takes less than one minute Measures concentration of urine compared to water
Specific Gravity : what it means 1.000 1.010 Excellent 1.010 1.015 Okay 1.015 1.020 Need fluid 1.020 1.025 Hypo-hydrated 1.025 1.030 Dehydrated
So what are the health problems associated with heat stress? Heat Stroke body s s system of temperature regulation fails body temperature rises to critical levels deep body temp. exceeds 40 C primary signs: confusion, irrational behaviour, loss of consciousness, convulsions, lack of sweating, hot dry skin
Heat stroke first aid call medical attention immediately move person to shade remove clothing and wet skin increase local air velocity increase fluid intake if possible can lead to permanent brain damage and death
Heat Exhaustion symptoms resemble heat stroke and include headache, nausea, weakness, thirst and giddiness caused by loss of large amounts of fluids as sweat skin is clammy and moist complexion is red with rapid pulse body temperature is normal or slightly elevated Heat exhaustion first aid rest in cool place drink plenty of fluids severe cases could take one or two days to recover no known permanent side effects
Heat Cramps painful muscle spasm that occurs when sweating profusely in heat electrolyte imbalance caused by sweating water may be drunk but person must replace lost electrolytes Avoidance of heat cramps thirst cannot be used as a guide for the need to drink fluid water must be taken every 15-20 min in hot environments drink electrolyte replacement fluids muscles being used are most susceptible
Heat Collapse (fainting) workers not accustomed to hot environments who stand upright and immobile for long periods of time blood pools inadequate venous return resulting in decreased blood pumped to brain prevented by keeping workers moving and an acclimatisation program
Heat Rash (prickly heat) occurs most commonly in hot, humid environments sweat is not easily removed from skin sweat ducts become blocked, causing rash prevent by cool breaks and regular bathing and drying of skin Heat Fatigue temporary state of mental or psychological strain resulting from prolonged heat exposure decline in task performance, coordination, alertness reduced by heat acclimatisation
Long term health effects of heat stress Kidney stones is the most common Cancer of the bladder has recently been reported Possibly other effects in certain individuals from too much sugar i.e. when sweat replaced with full strength soft drinks and caffeinated drinks
Other benefits Thermal Comfort Exercise Performance Core Temperature Sweating Skin Blood Flow Body Heat Production Heart Rate Thirst Salt Losses (sweat & urine) Organ Protection Improved Improved Reduced Earlier & Greater Earlier Lower Lowered Improved Reduced Improved
Air-conditioning Alternating hot and cold conditions: Does not cause colds Can result in chill to kidney area: thermal shock Will not cause any permanent problems Do not set air-conditioning temperature too low Aim for about 25 C inside
What factors will affect our ability to remove excess heat? Physical factors age weight physical fitness acclimatisation metabolism use of alcohol or drugs hypertension general health
Why does my weight matter? The best measure of your weight status is Body Mass Index or BMI BMI= weight (kg)/ height (m)² A guide to risk of chronic health problems, life expectancy, and likelihood of poor quality of life in old age BMI : <19 UNDERWEIGHT 20-25 ACCEPTABLE 26-30 OVERWEIGHT >31 OBESE
BMI the impact 7690 workers injury reports examined 29% where injured over 3 yrs 85% of these were overweight (25-30) or obese (>30) 28% were overweight and 64% obese Those with BMI >40 were twice as likely to sustain an injury (am j epidemiol 2007 pollock et al)
The importance of physical fitness Heat stress places additional cardiovascular strain, hence superior aerobic capacity is a big advantage Workers who are selected for hot jobs that are in good general health and physical condition have less chance of getting heat stroke and other heat related illnesses Short term and minor illnesses should also be considered - flu, diarrhoea, vomiting, hangover Workers on medication should seek medical clearance
What else can you do outside the workplace? Drink water outside of work not just caffeine (tea, coffee, Coke) or alcohol (beer, spirits, wine) Good diet Good quality sleep
Heat Stress and Prevention Methods
Recognition & treating Heat Stress If heat stress is not recognized & treated in the early stages, it can have serious effects on the body such as: Hash Rash Heat Exhaustion Heat Cramps Heat Stress Heat Stroke
Heat Stress: Normal human body can maintain temperature between 36 C 38 C. By any chance the body heat rise, automatically that body will try to reduce the excess heat gained, but if the body gaining the heat faster that reducing it then we will have heat stress situation. This may happen in high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects, or strenuous physical activities.
Drink Plenty of Fluids
During hot weather you will need to increase your fluid intake, regardless of your activity level. Don t wait until you re thirsty to drink. During heavy exercise in a hot environment, drink two to four glasses (0.5 1 Litre) of cool fluids each hour. Heavy sweating removes salt and minerals from the body. These are necessary for your body and must be replaced. A rehydrating solution (Pocari Sweat) can replace the salt and minerals you lose in sweat. (One small cup every 15-20 minutes)
Stay Cool & Keep your skin Healthy Wash hot body areas by cold water Take shower Change wet clothe
Take Frequent Breaks Take more frequent breaks in cool, shaded areas when working in extreme temperatures or at the first sign of heat stress symptoms. If possible, try to schedule your tasks around the weather. Complete more physical tasks in the morning.
Avoid hot foods and heavy meals
In summer period try to have light meals. Hot foods and heavy meals adding heat to your body
Heat Rash Prevention Method
Use Heat Rash Prevention Cream
Use T-Shirt T with long sleeve and long Johns to avoid heat rash
Heat stress is 100% avoidable and preventable as long as you recognize the signs and take proper precautions.