By Ryan R. Reilly
The term athlete has applications beyond the realm of sports. Because the unique skill sets are combined with requisite physical conditioning and technical preparedness, members of various rescue professions have become known as tactical athletes.1,2,3 In particular, firefighters are a breed of tactical athletes that not only check the aforementioned boxes of conditioning and preparedness but also face extreme environmental factors with regard to immediately dangerous to life or health (IDLH) hazards.4 This article will examine the most common IDLH environment firefighters encounter—the fireground—and offer considerations for preparing these tactical athletes to take on this deadly setting.
The Environment
Temperatures within a structure fire can reach 1,400°C (2,552°F), with potential exposure resulting from not only the heated air itself but also radiant heat, heat conducted from hot surfaces, and the firefighter’s own body heat.5 It has been documented that during fire suppression activities, a firefighter’s core temperature can increase by more than 2°C (3.6°F),6,7,8 putting the individual at risk of thermal stress should his core temperature rise above 40°C (104°F).9 Typically, the human body can self-regulate core and shell temperature through physiological and behavioral responses, but the nature of firefighting challenges all innate responses to rising temperatures. Should core temperature rise above the typical point of 37±1°C (98.6±1.8°F) to 38.5°C (101.5°F), performance can be inhibited by the onset of hyperthermia.9,10 Interestingly, as environmental heat stress increases along with the duration of activity, metabolic heat production also increases, leading to increased sweating as an intended means of cooling, subsequently causing a greater deficit of total body water, further hindering performance.11
Such heat stress and dehydration are further compounded by the firefighter’s personal protective equipment (PPE), as the low water vapor permeability of the material impedes the evaporation of sweat and elevates heat storage, resulting in uncompensable heat stress.7,12,13,14,15 The added weight of thermal protective clothing (i.e., bunker gear) and the self-contained breathing apparatus (SCBA) further burdens the firefighter and decreases mobility and work capacity while also increasing perceived and respiratory effort, which can contribute to cardiac strain.12,16,17 In fact, it has been observed that the combined burden of firefighting PPE and SCBA increases energy cost by 25% and reduces tolerance time for work by as much as 75%.18
Knowing that the temperature of the environment and the various strains brought on by PPE can contribute to fatigue, it is important to consider these factors when designing a training program to prepare a firefighter for the demands of this occupation. The following sections will propose preparatory initiatives and examine possible interventions for improving a firefighter’s physical readiness for the demands of the fireground.
Preparation
Firefighting is made up of both short, high-intensity bouts of activity and sustained, low- to moderate-intensity work, requiring particular emphasis on aerobic energy systems throughout the time spent working on the fireground.1,17,18 Obviously, anaerobic pathways will play a role—particularly at the onset of fire suppression and rescue activities and for any work requiring explosive effort—but both anaerobic and aerobic capacity are notably higher in athletes with a high VO2 max, suggesting that a training program should focus on this metric. The aforementioned actions requiring power, however, are determinedly few by comparison to activities requiring strength (and, more specifically, strength endurance or the ability to create great amounts of force repeatedly for the duration of an event19), and a high lactate threshold is key to the endurant qualities required for firefighting.17,20
A distinct challenge for program design with regard to tactical athletes is that since their occupation does not have an off-season, training cycles cannot be periodized as they could with a traditional athlete.1,2 That is to say that a training program for a firefighter cannot follow the typical structure for preparing athletes in which phases of progressively modified exercise selection are structured around the demands and timing of competition; the demands of a firefighter’s job are ever-changing and unpredictable, and these aspects must be considered when designing a training program. However, since this discussion focuses on preparing a firefighter for the intense heat of the fireground, overall programming and specialization shall be omitted.
Fortunately for athletes of all stripes, heat acclimation is beneficial for withstanding the stressors of a hot environment, and this particular adaptation can occur with just 10 days of training, and the benefits can be retained for as many as 14 days.21 These benefits include reduced oxygen uptake, glycogen sparing, and reduced blood lactate—all indicative of improved metabolic efficiency.
In research trials, it was demonstrated that heat acclimation can be achieved in hot (38°C/100°F) environments with 30% relative humidity, and the adaptations were induced by 45-minute, steady-pace workouts on a cycle ergometer at 50% VO2 max, once a day for 10 days.21 This study demonstrates that heat acclimation training does not have to be specific to the intended activity, allowing for some variation in firefighter training.
Furthermore, the benefits of this training not only carry over to maintaining a low core temperature and reducing water loss in a hot environment, but the metabolic adaptations are maintained in cool and temperate climates as well, equating to measurably improved fitness from low- to moderate-intensity training.
However, the athletes in the aforementioned study already had high levels of fitness as noted by an average VO2 max of 67 ml/kg/min, in line with other findings that high aerobic fitness and regular training equate to successful and lasting heat acclimation.22,23,24 For this reason, it is equally if not more important that firefighters have a high level of fitness. To achieve this, it is suggested that interval training be incorporated to improve VO2 max.25,26
Interval training—whether it be in the form of high-intensity interval training, sprint intervals, or another variety—is marked by intense “all-out” periods of effort separated by periods of low-intensity activity or rest, and this method of training has been determined to improve VO2 max.25 Moreover, it has been proven that, in addition to aerobic power as determined by VO2 max, interval training of a high-intensity nature also improves aerobic capacity as measured by accumulated oxygen deficit and anaerobic capacity as measured by decreased lactate accumulation.27,28,29
The main point of contention with program design involving such intermittent maximal effort comes down to the rest periods in between the high-intensity rounds. According to tactical strength and conditioning facilitator guidelines from the National Strength and Conditioning Association, the sprint:rest ratio should be 1:1, emphasizing equal rest to work periods.30
The American College of Sports Medicine guidelines for interval training vary rest periods from equal to greater lengths in comparison to working bouts, with a work:rest ratio ranging from 1:1 to 1:9.31 Of particular note are the protocols used by Tabata et al,32 in which six to eight maximal-effort sprints lasting 20 seconds each are interspersed with periods of complete rest lasting 10 seconds, effecting a 2:1 work:rest ratio. Compared to intervals with longer rest periods (work:rest::1:4), this mode of training elicited the greatest improvements in aerobic and anaerobic capacity and aerobic power.
Based on these findings, it is strongly encouraged that firefighters engage in such training two to three times per week. The added advantage is time: With a working period of four minutes (eight 20-second intervals followed by 10-second rest periods), such a workout—even when considering time for warming up and cooling down—makes for a very short time commitment that can easily be incorporated into a firefighter’s schedule.
Overall, preparation for taking on the extremely hot environment of the fireground is twofold: improving VO2 max and acclimating to intense heat. In a training academy setting for new recruits, 10 days of heat acclimation21,22,23,33 can be included in physical training programming after at least six weeks of interval training to improve candidate fitness.25,26,28
It is further suggested that both protocols be maintained at least once per week to prevent decay of training-induced adaptations. In the case of firefighters already working in the field, heat acclimation training sessions may have to be relegated to off-days from work, which is admittedly more ideal for those individuals attempting to maintain existing acclimation, but there is no evidence that taking a day off from heat acclimation training will necessarily result in setbacks.
Further, if 14-20 minutes can’t be reasonably set aside for sprint interval training while at work, this particular protocol is not impeded, as it is recommended that participants employ this workout method two to three days per week as scheduling allows. Combined, these two protocols should adequately prepare firefighters for the rigors of working in a hot environment. Further, more specific training modalities should also be employed for the requisite strength and endurance components of the job, a prescription that is beyond the scope of this article.
Interventions
Hydration is crucial to performance; this cannot be stressed enough for fire suppression activities. Even mild hypohydration (a loss of water equal to less than 2% bodyweight) unrecognized by an individual can impair performance in a hot environment,15,34 further emphasizing the need for proper hydration. As a rule of thumb, at least 1,400 milliliters (ml) of water over a 24-hour period is the basis for adequate hydration,35 equivalent to nearly 48 ounces (oz.). This number is close to the amount of expected water loss during firefighting of 1.5 liters (l) (50 oz.), enforcing the need for hyperhydration to stave off the effects of heat stress-induced dehydration; this can be countered by ingesting 29.1 milliliters per kilogram (ml/kg) of water with optional 1.2 grams per kilogram (g/kg) of glycerol prior to firefighting activities.12 Further, ingesting five servings of 100 g of ice slurries before participating in firefighting can assist in maintaining a stable core temperature during time spent in the hot environment.15,36
Another intervention that has been supported by science is menthol ingestion.37 Menthol has been shown to reduce airway discomfort and induce bronchodilation, subsequently improving performance and reducing fatigue in firefighters. However, the effect of this on the rate of air intake and thus available working time as limited by SCBA air supply may require further research before this intervention can be fully realized.
Compression clothing is popular among a variety of athletes, particularly as a means of assisting with thermoregulation, especially in terms of hemodynamic adjustment and moisture-wicking potential.38,39 However, current data does not support the use of compression clothing underneath bunker gear as a means of maintaining or reducing body heat; admittedly, the data does not necessarily refute the possibility either.38
Finally, it is important to address skip-breathing, a method of respiration some firefighters encourage as a means of prolonging SCBA air supply. This practice involves holding the breath following inhalation, resisting the urge to exhale, and inhaling a second time before finally exhaling. This is not only contraindicated for individuals on any kind of SCBA (overland, underwater, or otherwise), but it is outright anathema, as skip-breathing can result in abnormally high levels of carbon dioxide throughout the blood and tissues—a condition known as hypercapnia—and this can result in unconsciousness or even death.40 In fact, skip-breathing is one of the major causes of death in scuba divers. It is important that the danger of this practice be disseminated throughout the fire service.
Extreme heat can play havoc on performance and metabolic processes, but such environments cannot be avoided in the fire service. As tactical athletes facing such intense environmental factors, it is important for firefighters to prepare accordingly, using a combination of sprint intervals to improve aerobic power and training at low intensity (50% VO2 max) in controlled, hot (38°C/100°F) settings to acclimate to the rigors of extreme heat. Hydration is equally important, and drinking what essentially amounts to double the recommended minimum for adequate hydration—1.5 l (50 oz.) during a 24-hour period and an additional 1.5 l (50 oz.) prior to firefighting activities—is key to preventing or at least limiting dehydration.
Other interventions have been and are continuing to be studied, but no clear adjuncts to fitness and hydration preparation have yet been supported. Finally, despite prevailing advice from concerned firefighters, skip-breathing is dangerous to the point of being deadly and should not be used as a means of preserving air supply; improved fitness, however, can accomplish that aim.
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Ryan R. Reilly is a fire marshal with the Chicago (IL) Fire Department and a fire investigation technician in the Office of Fire Investigation. A personal trainer since 2007, he is a corrective exercise specialist and a graduate student in applied exercise science at Concordia University—Chicago.
