HEAT ACCLIMATIZATION

Armstrong, L.E. (1998). Heat acclimatization. In: Encyclopedia of Sports Medicine and Science, T.D.Fahey (Editor). Internet Society for Sport Science: http://sportsci.org. 10 March 1998.

Physiological Responses
Heat Illness
Factors Affecting Acclimatization
Loss of Acclimatization
References

Subsequent to repeated bouts of exercise in a hot environment, there is a marked improvement in the physiologic responses of healthy humans. This improved tolerance to exercise in heat is known as heat acclimatization. When accomplished in an artificially controlled environmental chamber, this process is known as heat acclimation. The primary benefit of heat acclimatization is improved tolerance of exercise in the heat, evident as a reduction of the incidence or severity of symptoms of heat illness, and increased work output concurrent with reduced cardiovascular, thermal, and metabolic strain.

Physiological Responses

Heat acclimatization is specific to the stress imposed on the human body. For example, passive exposure to heat induces some responses, notably an improved ability to dissipate heat. In contrast, physical training in a cool-dry environment results in metabolic, biochemical, hematologic, and cardiovascular adaptations. Heat acclimatization via strenuous exercise induces responses attributed to both passive heat exposure and training in cool environments. Table 1 illustrates these relationships.

Complete heat acclimatization requires up to 14 days, but the systems of the body adapt to heat exposure at varying rates. The early adaptations (initial 1-5 days) involve an improved control of cardiovascular function, including expanded plasma volume, reduced heart rate, and autonomic nervous system habituation which redirects cardiac output to skin capillary beds and active muscle. Plasma volume expansion resulting from increased plasma proteins and increased sodium chloride retention, ranges from +3 to +27%, and is accompanied by a 15-25% decrease in heart rate. This reduction of cardiovascular strain reduces rating of perceived exertion, which is proportional to central cardiorespiratory stress, also decreases during the first five days of exercise-heat exposure. Plasma volume expansion is a temporary phenomenon, which decays during the 8th to 14th days of heat acclimatization (as do fluid-regulatory hormone responses, see below), and then is replaced by a longer-lasting reduction in skin blood flow that serves to increase central blood volume.

The regulation of body temperature during exercise in the heat is critical, because of the great potential for lethal hyperthermia. Thermoregulatory adaptations (i.e., increased sweat rate, earlier onset of sweat production), coupled with cardiovascular adjustments, result in a decreased central body temperature. This response is maximized after 5 to 8 days of heat acclimatization. However, the adaptations of eccrine sweat glands are different during humid and dry heat exposures. Heat acclimatization performed in a hot-humid condition stimulates a greater sweat rate than heat acclimatization in a hot-dry environment. Also, the absolute rate of sweating influences thermoregulation. If hourly sweat rate is small (<400-600 ml), a peripheral adaptation of whole body sweat rate may not occur.

Conservation of sodium chloride (NaCl) also occurs during heat acclimatization. The NaCl losses in sweat and urine decrease during days 3-9 of heat acclimatization, resulting in an expanded extracellular fluid volume. Subsequently, NaCl losses in sweat and urine increase toward pre-acclimatization levels, once physiologic strain (i.e., cardiovascular, thermal) moderates. Francesconi and colleagues (1993) recently demonstrated that NaCl losses, during a strenuous 10-day heat acclimatization protocol, were related to plasma renin (PR) and plasma aldosterone (A) concentrations. When subjects consumed a low salt diet (4g NaCl per day) and a moderate salt diet (8g NaCl per day), both PR and A increased during the first four days of heat acclimatization, but decreased during the remaining 6 days of heat acclimatization. The improved cardiovascular stability, which occurred on days 1-4 of heat acclimatization, allowed equivalent exercise performance with both diets and apparently reduced the stimulation and need for large elevations of PR and A. No change in plasma levels of arginine vasopressin (AVP) were observed across time, in either dietary group, possibly because hourly water intake matched the fluid lost in sweat. Usually, AVP synthesis is stimulated by an increase in plasma osmolarity or alterations in blood pressure, plasma volume, and renal or hepatic blood blow. Therefore, it is unlikely that the ability to successfully sustain exercise, during the latter days of the heat acclimatization process, is specifically related to the action of hormones that regulate fluid-electrolyte balance. This is particularly true when salt balance has been achieved.

Excess dietary water and electrolytes do not speed the process of heat acclimatization. When dehydration or salt deficits exist, however, cardiovascular and thermoregulatory responses may be negatively affected, and the theoretical risk of heat illness increases. Consistent daily monitoring of body weight will allow athletes to recognize water deficits which require consumption of fluid (-2 to -3% of body weight), reduction of training duration/intensity (-4 to -6%), or consultation with an experienced physician (in excess of -7%).

Plasma cortisol concentration generally indicates the strain experienced by the body. Heat-acclimated, well-hydrated humans exhibit no change in plasma cortisol when exercise in a hot environment is mild. Under the same conditions, the lack of heat acclimatization and dehydration can result in large plasma cortisol increases. When exercise is intense and core body temperature rises markedly, the plasma cortisol concentration increases during the initial days of heat acclimatization, but returns to control levels after 8 days of heat acclimatization, reflecting the reduction in total body strain.

Physical training in a cool environment may or may not improve exercise economy. Metabolism can be affected by heat acclimatization, in that oxygen uptake during submaximal exercise is reduced. Large effects have been reported for stair stepping; treadmill and cycle-ergometer exercise produce smaller, but statistically significant, changes. The physiologic mechanism has not been defined exactly, but three theories exist: (a) blood flow to the skin increases, thus reducing central blood volume, venous return to the heart, and cardiac output; (b) the portion of cardiac output perfusing muscle decreases; and (c) the recruitment of muscle fibers shifts from predominantly oxidative to glycolytic fibers. Heat acclimatization reduces muscle glycogen utilization and post-exercise muscle lactate concentration.

Heat Illness

Heat acclimatization is of interest to physicians as well as athletes, because it reduces the incidence of heat illness and the intensity of symptoms. The most common heat illnesses among athletes are heat cramps, heat syncope, and heat exhaustion.

Heat cramps are usually unheralded and occur in the voluntary muscles of the legs, arms, and abdomen, after several hours of strenuous exercise in individuals who have lost a large volume of sweat, have drunk a large volume of hypotonic fluid, and who have excreted a small volume of urine. Sodium depletion probably causes heat cramps. Heat acclimatization decreases the risk of experiencing heat cramps.

Heat syncope (e.g., fainting) occurs most commonly during the first 3-5 days of heat exposure. This illness is related to the shunting of blood through dilated cutaneous vessels, postural pooling of blood, diminished venous return to the heart, reduction of cardiac output, and cerebral ischemia. Heat syncope typically occurs when the ambient temperature or humidity rises suddenly, or when a non-acclimatized individual performs exercise in a hot environment. Heat acclimatization reduces the incidence of heat syncope to nearly zero, after 3-5 days of exercise-heat exposure. This period corresponds with cardiovascular stabilization, early in the course of heat acclimatization (see above). Heat syncope is a syndrome distinct from heat exhaustion, because water and salt depletion do not always contribute to heat syncope.

Heat exhaustion is the most commonly diagnosed form of heat illness among athletes, despite the fact that its symptoms are often vague and differ greatly from one situation to another. Clinical descriptions include various combinations of headache, dizziness, fatigue, hyperirritability, tachycardia, hyperventilation, diarrhea, piloerection, hypotension, nausea, vomiting, syncope, heat cramps, as well as “heat sensations” in the head and upper torso. This explains why heat exhaustion is defined as the inability to continue exercise in a hot environment, and involves a diagnosis of exclusion. Heat acclimatization significantly reduces the signs and symptoms of heat exhaustion, after eight days of strenuous, intermittent running.

The three aforementioned heat illnesses all involve either fluid-electrolyte balance, extracellular volume and tonicity, or cardiovascular adaptation. This emphasizes the importance of (a) ample dietary intake of NaCl and fluids, and (b) fluid-electrolyte hormone regulation during heat acclimatization.

Factors Affecting Acclimatization

It is believed that host factors may influence the capacity to acclimatize to exercise in a hot environment. For example, older persons were previously thought to be less heat tolerant than their younger counterparts. Middle aged men (>45 yr) were shown to have higher heart rates, higher rectal temperatures, and lower sweat rates than young men, during exercise in the heat, both before and during exercise in the heat, both before and after heat acclimatization. Similarly, studies conducted in the late 1960s suggested that women were less tolerant of exercise in a hot environment than men. However, recent research has qualified and/or reversed these viewpoints. It is now recognized that few gender-related differences exist, when female and male subjects are matched for pertinent physical and morphological characteristics. It is also recognized that differences between older and younger subjects are not necessarily due to aging per se, but may be due to other factors such as decreased training volume and lower maximal aerobic power (VO2max)

Most experts agree that intense physical training in a cool environment improves physiologic responses and speeds the process of heat acclimatization. During training in cool conditions, optimal physiologic adaptations may be achieved if strenuous interval training or continuous exercise, at an intensity above 50% of VO2max, is performed for 8-12 weeks. Maintenance of an elevated core body temperature appears to be the most important physiologic stimulus.

Irrespective of physical training, VO2max generally influences physiologic responses during the development of heat acclimatization. Individuals with a high VO2max (>60 ml.kg^-1.min^-1) exhibit superior heart rate and rectal temperature responses, and usually reach a stable heat acclimatization state faster, when compared to those with a low VO2max (<40 ml.kg^-1.min^-1). However, maximal aerobic power per se may not be as important in conferring heat tolerance as the underlying physiologic adaptations (i.e. altered blood volume, vasodilation/vasoconstriction, and muscle metabolism) which result in VO2max differences between individuals. A recent publication by Pandolf et al. (1988) demonstrates this concept well. They exposed nine young men (21 y) and nine middle-aged men (46 y) to a 10-day heat acclimatization protocol (100 min treadmill walking per day, 49°C air temperature). The results of testing on Day 1 indicated that middle-aged men were able to exercise longer, had lower heart rates and rectal temperatures, and exhibited greater whole-body sweat rates than young men. The differences persisted for the first few days of heat acclimatization, but were absent by day 10 of heat acclimatization. Both groups were closely matched for body mass, surface area, percent body fat, and maximal aerobic power (51 versus 53 ml.kg^-1.min^-1, respectively). The factor that distinguished these two groups was their level of regular weekly physical training: middle-aged men ran an average of 39 km per week, whereas young men averaged only 8 km per week.

The phrase “heat intolerance” has been used in a wide variety of contexts. Interestingly, heat intolerance has been defined by some experts as an inability to develop normal physiologic adaptations, during repeated days of exercise in a hot environment. Some humans do not show the classic decreases in heart rate and rectal temperature that exemplify successful heat acclimatization. This has been of particular concern among persons with cardiovascular disease and prior heat stroke patients. One recent publication (Armstrong et al., 1990), however, reported that 9 out of 10 prior heat stroke patients exhibited normal heat acclimatization responses (90 minutes treadmill walking per day, 7 days, 40°C air temperature), 61 days after experiencing heatstroke.

Loss of Acclimatization

The physiologic adaptations to exercise training in a cool environment are lost after several weeks or months of inactivity. In contrast, heat acclimatization adaptations may vanish after only a few days or weeks of inactivity (i.e., 18-28 days). The first adaptations to decay are those that develop first: heart rate and other cardiovascular variables. The rate of decay of adaptations is affected by the number of heat exposures per week, the number and format of training sessions, and the degree to which core body temperature is elevated. Athletes with high VO2max usually will lose heat acclimatization adaptations slower than individuals with low VO2max.

References

Armstrong, L E, J P De Luca, and R W Hubbard. Time course of recovery and heat acclimation ability of prior exertional heatstroke patients. Med. Sci. Sports Exerc. 22: 36-48, 1990.

Armstrong, L E and C M Maresh. The induction and decay of heat acclimatization in trained athletes. Sports Med. 12: 302-312, 1991.

Armstrong, L E and K B Pandolf. Physical training, cardiorespiratory physical fitness, and exercise – heat tolerance. In: Human Performance Physiology and Environmental Medicine at Terrestrial Extremes, K.B. Pandolf, M.N. Sawka, and R.R. Gonzalez (Eds.). Indianapolis: Benchmark Press, 1988, pp. 199-226

Francesconi, R P, L E Armstrong, N M Leva, R J Moore, P C Szlyk, W T Matthew, W C Curtis, R W Hubbard, and E W Askew. Endocrinological responses to dietary salt restriction during heat acclimation. In: Nutritional Needs in Hot Environments, B.M. Marriott (Ed.). Washington, D.C.: National Academy Press, 1993, pp. 259-276.

Greenleaf, J E and C J Greenleaf. Human acclimation and acclimatization to heat: A compendium of Research. Moffett Field, CA: Ames Research Center, Technical Memorandum no. TM X-62008, 1970, pp. 1-188.

Hubbard, R W and L E Armstrong. The heat illnesses: biochemical, ultrastructural, and fluid-electrolyte considerations. In: Human Performance Physiology and Environmental Medicine at Terrestrial Extremes, K.B. Pandolf, M.N. Sawka, and R.R. Gonzalez (Eds.). Indianapolis: Benchmark Press, 1988, pp. 305-359.

Pandolf, K B, B S Cadarette, M N Sawka, A J Young, R P Francesconi, and R R Gonzalez. Thermoregulatory responses of matched middle-aged and young men during dry-heat acclimation. J. Appl. Physiol. 65: 65-71, 1988.

Sawka, M N, C B Wenger, A J Young, and K B Pandolf. Physiological responses to exercise in the heat. In: Nutritional Needs in Hot Environments, B.M. Marriott (Ed.). Washington, D.C.: National Academy Press, 1993, pp. 55-74.

Sciaraffa, D, S C Fox, R Stockmann, and J E Greenleaf. Human acclimation and acclimatization to heat: a compendium of research, 1968-1978. Moffett Field, CA: Ames Research Center, National Aeronautics and Space Administration Technical Memorandum no. 81181, 1981, pp. 1-102..

Wenger, C B Human heat acclimatization. In: Human Performance Physiology and Environmental Medicine at Terrestrial Extremes, K.B. Pandolf, M.N. Sawka, and R.R. Gonzalez (Eds.). Indianapolis Benchmark Press, 1988, pp. 153-198.

The following letter and information was written and sent to us by James Baker from Shell Oil. As you can see from the information below James has been in the petrochemical industry for 40 years and has had the experience of wearing FRC clothing for many years and  shares  some vital information about the proper undergarments to be worn with FRC’s.

Bryan,

Below is a document with some general comments about FRC use.

I have been in the petro/chemical business for 40 years. The first 5 years was in construction, then 32 years in process operations, and the last nearly 3 have been as a HEO/Rigger.

During the early/mid 70′s man made material clothing was very popular. There was an explosion and fire on the unit I was working. Every man that had on synthetic clothing had it melted to his body.

Fire is a great motivator. One man jumped from the third floor, hitting different equipment on the way down. It was said that he broke all of the ribs on one side, his arm, and both legs. He then got up on broken legs and ran some 2 or 3 hundred feet before collapsing. He was then carried to the control room to be administered first aid. The sight of him was so terrible that when the board operator saw him, he had a heart attack. The man that jumped did not survive.

The outside operator was found trapped in the elevator. His coveralls were not FRC material. I think they were a cotton/polyester blend. They did not melt to his body, but they were smoldering in different areas.

Through my career PPE has constantly been improved. FRC’s is one of the many. PPE is no longer an option, it is mandatory as it should be.

In my opinion if you are exposed to 2000 degree plus fire, you are going to get burned, period. With FRC’s, at least your clothes should not flame up or melt on you.

The purpose of Fire Retardant Clothing (FRC) is to protect personnel against flash fire.

Nylon or other synthetic materials can melt to your body when exposed to a flash fire. This is a very ugly sight to see. Melted material on skin is nearly impossible to remove.

Normally, FRC shall be worn as the outermost garment.  Specific jobs may preclude this requirement such as jobs working with:

• Asbestos

• Chemicals/Hydrocarbons that require chemical protective clothing or special personal protective equipment (PPE).

In such cases, FRC must still be worn beneath the outermost layer in FRC designated areas.

Rain gear is acceptable as an individual’s outermost garment (over FRC) for inclement weather or when testing sprinkler and deluge systems.

Duct tape, masking tape, or other types of material should not be used to seal FRC arm cuffs or leg cuffs openings. This material can catch on fire or melt.

Mosquito repellent containing DEET has been found to adversely affect the properties of FRC.

It is recommended by Dupont (manufacturer of Nomex) that flame-resistant undergarments or undergarments made only of cotton, silk, or

wool worn beneath the FRC to reduce the risk of flash fire burns.

Heavily soiled or contaminated garments should not be taken home and handling such garments in a manner that prevents exposure to personnel from contaminated garments. 

Such garments should be tagged and placed in dedicated plastic bags and bins at the drop off locations.  A MSDS Summary Sheet of the contaminating material shall also be included.

FRC are not to be used in lieu of approved Bunker Gear as PPE for fire fighting activities.  (FRC is designed to offer protection against flash fires, not extended exposures.)

If performing spark-producing activities such as welding or grinding, the wearer should verify they are wearing FRC appropriate for such activities (IE. FR treated cotton).

Heat Stress Awareness and Prevention

Share This Article

 (0)

Aug 1, 2005 12:00 PM, By Sara Hornik, Summit Training Source

Learn how to beat the heat before it beats you down

Working in high-temperature environments is not only uncomfortable, it can be harmful to your health. The combination of high temperatures and stresses such as physical labor, fluid loss, and fatigue sets a breeding ground for heat rash, exhaustion, and stroke. Heat-related illnesses are often attributed to outdoor work during summer months, but they can happen just as easily at any time of the year in poorly ventilated indoor facilities. Preventing them requires an understanding of how your body regulates temperature, the ability to recognize the symptoms, and knowing how to treat them.

Heat release and absorption. The body constantly works to maintain a core temperature of 98.6°F (37°C). The human body compensates for small changes in temperature, either upward or downward, through a thermoregulatory system controlled by sensors in the skin. When warm, your skin may become flushed because your body is increasing blood circulation to the skin so excess heat can escape. However, if you’re using your muscles for physical activity, they receive most of the blood and less is available for the skin. Sweating, or perspiration, is the next step your body takes to cool itself. However, excessive heat puts stress on the body’s cooling system, rendering it unable to adequately protect you.

Almost 60% of all body heat is lost by radiation, which is the constant emission of heat to nearby objects that have a cooler temperature. As mentioned above, sweat is another cooling system used by your body. As sweat evaporates, it cools the skin. However, sweating is only effective if humidity levels are low enough to allow evaporation and if you thoroughly replace the fluids you have lost.

Conduction is the transfer of heat away from the body by items or substances with which the body comes in direct contact. If you hold a metal rail for a few minutes, it will be warm from your touch. Convection heat occurs whenever air or water that has a temperature below that of your body comes into contact with the skin, then moves away. The body heats the air upon contact.

Relative humidity not only makes a hot day more unbearable, it can make it more dangerous.

Identifying and treating heat illness. If the body is unable to reduce its core temperature through sweat, it will begin to store heat. When this occurs, the risk of serious health hazards is present. Heat-related illnesses vary in severity, but even a mild case is a good indication that factors necessary to cause more serious problems are present.

Heat rashes, sunburns, and heat cramps — Heat rashes and heat cramps can be very painful. However, they aren’t life threatening. Sunburns and heat rashes can be treated topically with a steroid cream or aloe lotion. Heat cramps are muscle spasms in the arms, legs, and stomach caused by the loss of salt and fluids through heavy sweating. Treat heat cramps by resting in a cool place and drinking fluids. A normal diet should provide the right amount of salt your body requires, but sports drinks infused with electrolytes can help you replenish what you lose when you’re exerting yourself in the heat.

Heat exhaustion — Heat exhaustion is what happens when the body’s cooling system shuts down from lack of fluids. When your body loses more fluids than you take in you’ll experience symptoms such as heavy sweating, cool moist skin, and a weak pulse. A victim of heat exhaustion may begin to feel weak, clumsy, confused, or upset. If you notice a co-worker is suffering from the above symptoms, move them to a cool or shaded area, help them loosen or remove excess clothing, make sure they ingest fluids, and fan and spray them with cool water. If not properly addressed, heat exhaustion can lead to heat stroke.

Heat stroke — When your body’s internal thermostat can no longer deal with the stress caused by heat, heat stroke occurs. In extreme temperatures, there may be little warning before a victim reaches this level. The body quickly stops sweating and begins storing the heat. Symptoms include a lack of sweating, hot dry skin (even though the person may have been sweating earlier), and a rise in body temperature to 105° or higher. The victim may also become weak and confused, dizzy, nauseated, or even fall unconscious.

Time is critical when administering aid to a heat stroke victim. Cool the person immediately by submerging them in water or pouring cold water over them. Fan the victim, and if he or she is still conscious, have them take small sips of water. Do whatever it takes to cool them down, and do it quickly. While you cool the victim down, another co-worker should call for professional medical attention immediately.

Understanding the causes and symptoms of heat stress disorders can help you to recognize them when they occur. However, the more effective approach is to take preventive measures that will reduce the hazard.

Heat-related illness prevention. Heat stress isn’t just a summer phenomenon; it can also happen in the middle of winter in an enclosed area with a high temperature. Preventing problems in indoor environments is easier because more options exist for lowering the ambient temperature. Engineering measures are the primary means of control when it comes to preventing heat disorders indoors. The most effective way to reduce the effects is to lower the temperature of the work environment by opening a window, using a fan to increase air movement, or relying on ventilation systems to rid the space of excess heat.

Outdoor environments present more problems because you can’t just dial down the heat. Instead, you must rely on measures such as shielding or special clothing.

Proper clothing can play a critical role in heat stress prevention. When hazard protection isn’t a factor, select clothing such as lightweight cotton that breathes. Light colors tend to reflect heat, and hats should be worn when working in sunlight if possible. Some protective clothing manufacturers offer ice vests that, although heavy, can provide several hours of cooling without hindering movement. The moisture vapor transport rating of material used for protective clothing should also be considered when using PPE.

Regardless of whether you’re working indoors or not, the loss of fluids is a major contributor to heat illnesses. And thirst isn’t a reliable indicator of the body’s need for fluids. A person can lose as many as 1.6 quarts of fluid per hour through sweating, so it’s important to drink plenty of liquids before, during, and after working in warm environments. Health experts recommend drinking 8 ounces of fluids for every 20 to 30 minutes of work being performed. Most sporting goods stores sell water bottles with measurements printed on the side to help you ensure you’re drinking the proper amount.

Another important factor to consider is the amount of time it takes to adjust to high temperatures. Humans can acclimate to a temperature change in about seven days. When temperatures change from warm to hot, gradually increase your exposure. The National Institute for Occupational Safety and Health suggests that workers who have had previous experience in jobs where heat levels are high enough to produce heat stress should begin with 50% exposure on day one and then increase exposure to 60% on day two, 80% on day three, and 100% on day four. For new workers who will be similarly exposed, the regimen should be 20% on day one, with a 20% increase in exposure each additional day.

Take more frequent breaks 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 and evening when the sun isn’t at its peak and the temperature is cooler. Reduce manual labor by using mechanical assistance when possible.

The best defense against heat disorders is common sense and a healthy body. Excessive weight traps heat in your body and forces your heart and glands to work harder to dispose of it. Exercise and eat a nutritious, balanced diet. Exercise may help you to acclimate to warmer temperatures as well. A nutritious diet will ensure your body received the right amount of salt to keep it functioning properly.

Heat stress is 100% avoidable and preventable as long as you recognize the signs and take proper precautions. Remember, you don’t need to be working outdoors or living in a warm climate to be exposed to the hazards of heat stress. When the heat index rises above 80° preventable measures need to be taken. By understanding how your body controls temperature you’re more able to recognize the symptoms of heat stress. Take immediate action if you or a co-worker develops heat cramps, heat exhaustion, or heat stroke. Use engineering controls whenever possible to reduce the hazards, and allow your body to acclimate to warmer temperatures before you overexert yourself.

Hornik is the marketing director for Summit Training Source in Grand Rapids, Mich.

Sidebar: Safety Side Effects of Extreme Heat

The hazards of heat aren’t restricted to heat illnesses. The frequency of industrial and construction accidents also tends to rise as the mercury does. Be aware of the following potential problems as you’re on the job this summer:

·         Hot thoughts — Just as exhaustion can cause you to feel sluggish or lose track of what you’re doing, severe heat and dehydration can hinder your physical performance and mental alertness. Take breaks, drink plenty of fluids, and be responsible enough to stop what you’re doing if you start to feel disoriented or clumsy.

·         Butter fingers — Even though sweat is meant to help you, it can be a detriment by causing your hands to be slippery, thereby increasing the chances you’ll drop tools or lose your hold on hand railings. Gloves may make your hands hotter, but they’ll improve your grip.

·         Clouded vision — Sweaty brows and the heat that radiates from your face can cause your safety goggles to fog up, reducing their effectiveness. Don’t take them off just because it’s annoying. Keep a rag on hand, and use it to clean them often.

Sidebar: Here Comes the Sun

When working outdoors in the summer, heat isn’t the only thing you have to worry about. Prolonged exposure to ultraviolet (UV) radiation can cause premature aging of the skin, cataracts, and skin cancer. Those with fair skin and light hair are more susceptible to the sun’s harmful rays, but everyone should keep the following tips in mind.

·         Cover up — Wear tightly woven clothing that prevents UV rays from reaching your skin.

·         Lather up — SPF 15 sunscreen can block 93% of UV rays and prevent your exposed parts from baking.

·         Heads up — Baseball caps are useless for protecting your neck, ears, eyes, forehead, nose, and scalp. Choose something with a wider brim.

·         Don’t look up — Prevent long-term eye damage by finding some sunglasses or safety glasses that block 99% to 100% of UVA and UVB radiation.