STANDING THE HEAT: BIOHACKING FIREFIGHTERS FOR HOT WEATHER OPS
On April 29, 2009, Cadet Firefighter Cohnway Matthew Johnson collapsed during a fitness run. At the hospital, his body temperature was…
On April 29, 2009, Cadet Firefighter Cohnway Matthew Johnson collapsed during a fitness run. At the hospital, his body temperature was found to be over 105 degrees. When Firefighter Johnson died six days later, the cause was listed as complications of hyperthermia and dehydration.
March 31, 2016, during SCBA training in an air-conditioned house, Firefighter Cadet Steven Reid Whitfield II collapsed. In spite of aggressive cooling care, he did not recover. His cause of death was listed as hyperthermia and dehydration. NIOSH found that the physical exertion of training in full PPE/SCBA contributed to his death.
September 16, 2012, Captain Neal Wade Smith was participating in an advanced SCBA training class when he was found unresponsive. ALS crews found Captain Smith’s temperature to be nearly 108 degrees during transport. He was pronounced dead 24 hours later. The cause of death was listed as hyperthermia, and NIOSH investigators found insufficient rehab to be a contributing factor.
As firefighters, we sometimes imagine ourselves invulnerable to some degree. The fact is, though, that you can’t win an argument with your body: when subjected to exertion under thermal stress, certain physiological processes occur that “mind over matter” simply can’t change.
Blood becomes more viscous and the heart works harder as water from plasma is pulled for sweat. Blood is routed away from the core into the extremities and the skin, reducing oxygen transport to muscles, core organs and the brain, decreasing the capacity for work, altering mental status, and increasing risk of cardiovascular collapse. Without intervention, a systemic inflammatory response occurs that damages every system of the body.
Pre-incident planning: advance preparation for hot weather responses
We shouldn’t wait for operations to begin to think about mitigating thermal stress. Just like pre-planning our target hazards and updating box cards, we as departments and as individuals should be thinking about hot weather ops before they actually occur (and they’re already part of your SOGs, right?)
One of the latest growing wellness trends is “biohacking” — the manipulation of your body’s physiology to improve its health and performance. While this may sound like snake oil, biohacking is older, more common, and more science-based than you might think: athletes, for example, employ forms of biohacking when they manipulate the body’s physiological responses to train for increased speed, strength, or muscle.
Our bodies are amazingly adaptable and can learn to perform in a variety of conditions (which is why humans can live in locations from the Antarctic to the Sahara). Pro coaches know this, and for a long time have “biohacked” their athletes by using clothing layers, saunas, and hot baths to control core temperature during training. Evidence suggests this can improve hot weather performance by increasing blood volume, cellular energy production, and fatigue resistance.
One study found that a 60-minute soak in a hot tub right after exercise yielded the same cardio benefits as an hour of cycling. Another study found that regular use of a sauna immediately following exercise increased running endurance by 32 percent.
A common saying among competitive athletes is “train like you race.” Firefighters are athletes, and our training goals should include optimizing performance to work better and more safely under conditions we’re likely to encounter on duty. Heat acclimatization training (conducted under qualified supervision) can provide great benefits for personnel likely to encounter hot weather working conditions. And while sauna use for firefighters has received attention recently for its benefits in cancer prevention, evidence (like the studies mentioned earlier) shows it can also improve resilience under thermal stress with less strain on the body than exercising outside in the hot sun.
It should be noted that these types of training techniques are best employed with physically fit individuals. For deconditioned personnel, the focus should first be on improving overall fitness before adding heat acclimatization training. There is evidence that being overweight can negatively affect heat dissipation, and losing weight will improve resilience under thermal stress.
Other ways to “hack” the body’s response to hot weather stress can include:
Hydration. For shift firefighters, “pre-hydrating” with about 8 ounces of water per hour on the day before a shift can help you arrive for duty well hydrated and better prepared for hot work. The same applies for volunteer or paid-on-call firefighters who could be called to work at any time — while you should always stay adequately hydrated, it’s vital to stay on top of water intake when you know temperatures are higher and you could be responding to a call. Simply planning to drink water while on scene can put you behind the curve: the body can lose as much as two liters of sweat in 30 minutes of work, and is able to absorb far less than that from drinking, leaving you dangerously dehydrated.
It should be noted that, because the body stores extra water with glycogen, personnel following low-carb diets (including keto, Atkins, paleo, etc.) will likely have lower total water stores and, as a result, may dehydrate more quickly.
Nutrition. What you eat can have a dramatic impact on the body’s ability to tolerate thermal stress. Fried foods, processed meats, alcohol, and caffeine (anything more than 1 or 2 regular-sized cups of coffee in per day) can each affect the body’s ability to regulate core temperature. On the other hand, foods that are high in water and mineral content like melons, tomatoes, berries, summer squash, celery, and cucumbers can help maintain adequate levels of water and electrolytes in the body.
There is also evidence that some dietary supplements like creatine, glycerol and alpha lipoic acid can improve cardiovascular response and the body’s ability to regulate temperature (though you should check with your doctor before adding any supplements).
In addition, firefighters should get an annual physical. Your doctor will be able to detect problems like cardiovascular irregularities and hypertension, each of which can increase your risk of having a cardiac incident on the fireground even without the added thermal stress.
ICS (Incident Cooling Strategies): mitigating fireground heat stress
Once the alarm bells ring, the time for advance preparation is past, and we must shift our focus to cooling strategies.
Some cooling techniques that have been studied include cold gel packs, ice towels, and cooling fans. Neither helmet-based cold gel packs nor ice towels applied to the forearms showed any significant core cooling benefits. Cooling by fan airflow, however, does help by aiding the natural evaporation of sweat, and has even been shown to mitigate heat-related decreases in VO2max (the body’s ability to uptake oxygen). Like heaters are set up to keep crews warm during cold weather ops, electric fans may be beneficial in keeping crews well when temperatures rise.
One of the most beneficial and effective cooling techniques studied is forearm immersion (with arms up to the elbows in a tub/trough of cool or cold water), which shows fantastic benefits for mitigation of thermal stress. Evidence shows forearm immersion can quickly lower not only core body temperature, but also heart rate. In addition, one study showed it increased work tolerance time by as much as 60%. Forearm immersion may be a useful addition not only to rehab stations, but also as “pre-hab” for personnel in staging areas.
Whenever possible, attention should also be paid to the types of food and beverages made available to personnel during hot weather ops or when risk of heat-related illness is otherwise elevated. High-protein foods may need to be limited, as they are more difficult to digest and could increase the potential for GI distress in firefighters who go from eating directly to a working environment. Easily digestible carbs will provide quicker and more stomach-friendly replenishment of energy stores. In addition, the thermogenic effect (heat generated due to digestive processes) is greater with high protein foods, which can raise the body’s core temperature and increase the risk of heat-related illness.
Ice-cold sodas may be refreshing in rehab, but can have negative effects on heat tolerance and thermoregulation. Caffeine (from soda, tea, and coffee) is a diuretic, and can reduce the body’s stores of water, increasing the risk of dehydration. Cool or cold water is the best on-scene choice.
Ice may be more beneficial still: an October 2018 study at the School of Health and Sport Sciences found that drinking a “slurry” of water and crushed ice before exercise resulted in lower core body temperatures and better exercise performance in hot conditions. While a crushed ice slurry may not always be a practical offering at incident rehab, it may be a viable option for cooling before and during hot weather training drills, where there is more time for advance preparation.
Hot or cold, we need to keep in mind the effect environment has on working crews. While company officers and incident safety personnel should always be watching for signs & symptoms of heat stress, remember that safety is everyone’s responsibility: crews should be watching and accountable to each other, so we can make sure everyone goes home safely.
Roy is a certified Firefighter I/II, a company Health & Safety Officer, and Certified Personal Trainer. Your questions and thoughtful comments are always welcome.