BY DAN SENN
The fire service has long advocated cardiovascular training as an essential, life-saving, and job performance-enhancing activity. Examples of the suggested activities include running, biking, and swimming. But, is this type of training functionally applicable to prepare us for on-scene activities? Do we regularly run, bike, or swim to the scene? Do on-scene operations usually involve running, biking, or swimming? These questions are not by any means meant to underestimate the importance of cardiovascular training. It’s hard to argue the life-saving benefit of cardiovascular training with the high prevalence of cardiovascular-related on-duty deaths.
However, when it comes to overall job performance, cardiovascular training falls short of preparing our bodies for the physiological and mechanical stress encountered on the emergency scene. By looking at cardiovascular training in the proper perspective and reevaluating our approach to fitness program design, we can develop a program that improves job performance and reduces the risk of injury and cardiovascular-related death. The purpose of this article is to help you gain a better understanding of and perspective on how implementing variation within a physical conditioning program is required to prepare us for the physical demands of our profession.
Cardiovascular health and performance are important at a basic level. Your entire body relies on the heart and corresponding vasculature to perform throughout the entire spectrum of physical activity, whether that be meeting perfusion needs through flow work or pressure work (for a review of cardiovascular dynamics, see “The Human Heart is Like a Fire Pump,” Fire Engineering, December 2010). Much of the exercise information we preach in the fire service is limited to focusing on the flow aspect of cardiovascular dynamics. Addressing the flow aspect through aerobic cardiovascular training helps to prevent and reduce the health-restricting effects of cardiovascular diseases such as chronic heart failure, hypertension, arteriosclerosis, and atherosclerosis. Additional training adaptations include an increase in stroke volume, increased plasma and blood content volume, enhanced capacity to use oxygen, and enhanced recovery from fatigue.
However, our heart also must function in a pressure mode as well. Above a certain intensity of physical activity, the heart transitions to a pressure mode, where the heart is pumping not only at a high rate but also at higher pressures to circulate blood through the vascular system. At a basic level, our heart must maintain its ability to pump blood under high-volume and high-pressure demands, and the vascular system must maintain its ability to dilate and constrict to augment blood flow. These reasons establish the importance of cardiovascular training as a basic foundation on which to build.
Although cardiovascular health is important, a simple job-task analysis makes it apparent that firefighting involves physical stress that requires methods of physical conditioning that extend beyond the benefits limited to aerobic cardiovascular training. Remember, the goal of program design is to better prepare our bodies for the physical demands of job tasks and to enhance our overall performance on scene. There are two major aspects to address when designing the specifics of a job-applicable training program: the metabolic systems that support the required activities and the mechanical characteristics of job tasks. Identifying these two task profiles allows us to determine what exercises will better prepare us and how we should be performing these exercises. It’s important to start by reviewing the differences in metabolic systems and how they contribute energy for physical activity.
Our body produces energy aerobically (dependent on oxygen) and anaerobically (not dependent on oxygen). Thus, we have both aerobic and anaerobic energy production mechanisms that provide energy for activity and determine our total work capacity. All muscle action and subsequent body movement requires energy. The energy cost of that activity is paid for with the body’s energy currency, adenosine triphosphate (ATP). ATP, as you guessed, is produced by both aerobic and anaerobic mechanisms. For the purposes of this article, energy and ATP will be used interchangeably. When our muscles need currency to pay for an activity, it concurrently receives ATP from three major production sources: immediate, glycolytic, and aerobic. Both the immediate ATP-creatine phosphate (ATP-CP) and the glycolytic sources quickly produce ATP without the use of oxygen and thus are part of the anaerobic metabolic system. The aerobic mechanism, of course, uses oxygen in the production of ATP.
Immediate Energy System
The immediate energy system is the first energy source depleted by a muscle cell when initiating an action. This system maintains a small storage of ATP in muscle cells for immediate use and reconstructs “spent” ATP within the cell rapidly in response to when the muscle increases the use of ATP and depletes the stored supply. The importance of this system is the immediate contribution of energy and its influence on our short-duration, maximal-intensity work capacity [such as a maximal squat repetition or a 100-meter (m) sprint]. The limitation of this energy system is that it is rapidly depleted and is unable to produce ATP at a rate and an amount that match the muscles’ ability to use energy. In fact, this system provides energy for all-out effort of only five to 15 seconds. This is why you are able to maintain a maximal effort activity for only a few seconds. In other words, you can’t maintain a 100-m sprint pace for very long. Similarly, you can’t perform two or more repetitions of your maximum squat load within one set. Your immediate and glycolytic systems must “reload,” so to speak, before a repeat performance.
The glycolytic or nonoxidative system rapidly breaks down glucose to produce ATP. This system is also commonly referred to as the “lactic acid system.” The significance of this system is the quick response to depletion of the immediate energy stores (ATP-CP system) and the ability to provide a large amount of ATP quickly to sustain a high-intensity activity for a longer duration than the immediate system.
The glycolytic system sort of picks up where the immediate system left off during an activity. An example of an activity relying heavily on glycolytic energy production would be a 400-m sprint or a quick ascent up four flights of stairs. By the time the immediate energy system is depleted and overrun by energy demand, the glycolytic system kicks in to contribute energy. The downfall of this system is similar to that of the immediate system: It can support a sustained intensity for a limited duration. In other words, you can’t maintain a 400-m race pace for 1,600 m. A full-effort 400-m sprint requires maximum output from both immediate and glycolytic processes. So, our body’s performance quickly declines as anaerobic energy sources are exhausted.
The oxygen-dependent system uses oxygen in the production of ATP. The significance of this system is that it can produce very large amounts of ATP over an extended time. The aerobic energy production system can use sugars, carbohydrates, fats, and certain amino acids for energy production. Oxidative metabolism is much more extensive than anaerobic metabolism and, therefore, is able to extract larger amounts of ATP from “raw materials.” However, this system is limited to producing ATP at a much slower rate and cannot support enough energy by itself to support a high-intensity workload. This is the main energy system that allows a person to maintain a steady pace in a longer race.
The combined significance of these energy systems is that they all work together and simultaneously. In fact, all systems are working at all times—when we are sleeping, exercising, watching TV, and so on. Our body continuously demands energy ranging from a low amount during rest to a large amount during activity.
However, two factors determine the productivity of each system—intensity and duration of physical activity. As the intensity of an activity increases, energy demands from anaerobic metabolism increase; and as the duration of an activity increases, energy demands from aerobic metabolism increase.
Let’s look at this from, let’s say, a grocery store supply-demand perspective. Think of ATP as ice cream. Imagine that the immediate ATP supply is on the store shelves or in the back room. When ice cream (ATP) starts flying off the shelf, more ice cream (ATP) is readily brought from the back room to replenish the shelves. This all takes place within the store and is similar to immediate metabolic mechanisms that provide energy within a muscle cell. The store must also order more ice cream to meet consumer demand. Glycolytic mechanisms are quickly able to meet the store’s demand for a short period during a sharp spike in consumer demand. Think of the supplier as the small local creamery that can readily deliver what it has on hand and fires up the ice cream production line.
But, our muscles must also rely on aerobic mechanisms to provide a more stable and consistent, but slower, supply of ATP. Think of this as a large-scale, out-of-town distributor that is able to deliver a consistent supply of small truck loads of ice cream. Of course, when the store puts in an initial order, it takes a while for the trucks to start showing up.
With anaerobic training, we can essentially expand the store, increase shelf and back room space, hire more employees to restock shelves, and expand the capacity of the local creamery. With aerobic training, we essentially increase the size or the number of arriving out-of-town ice cream delivery trucks. Training adaptations enhance our metabolic systems in a way so that we can support a “greater market demand,” hence a greater capacity to perform work. However, each mode of training is specific to improving a respective metabolic supply chain.
Energy production in each system is stimulated by the rate and amount of ATP being used for activity. Each activity has an energy value that requires a given amount of energy currency. The proportionate contribution of each energy system to support the required amount of currency (ATP) to meet the price (ATP requirement) of the activity depends on the intensity and duration of that activity. For example, let’s say you have 400 m to travel by foot. If you sprint the 400 m as fast and as hard as you can, the vast amount of energy used to travel that distance was provided anaerobically through the immediate and glycolytic system. But if you walked that same distance, much of the energy used was provided by aerobic metabolism. In both cases, 400 m of work was performed, but the majority of energy provided to perform that work was supplied by different sources, which was dictated by the intensity and duration of the activity. In other words, how you attempt to complete a task determines the type of metabolic stress incurred.
If we are to improve all-around performance, it is important that the conditioning program include a plan to enhance work capacity through all three energy systems. Enhancing the work capacity of the anaerobic systems will allow you to improve performance in short-duration, high-intensity activities such as those tasks you perform during emergency operations. Improving the work capacity of the aerobic system will improve performance in long-duration, lower-intensity activities and speed recovery between bouts of activity.
Now that we have established a better understanding of our body’s demand for energy and how that demand is met through the different metabolic systems, we can now develop a metabolic and mechanical job analysis. To construct a metabolic and mechanical profile of our “in-action” performance, we evaluate the typical tasks and the intensity of those tasks that we would expect to perform during training drills or at an emergency incident. The typical nature of fireground operations varies by department, based on available personnel, equipment, and the predominant property characteristics in your district. But regardless of these factors, on-scene objectives are accomplished in a similar fashion.
Fireground operations involve a sequence of various nonrepetitive movements and activities of various ranges of intensity. A first-in engine company may expect to perform a list of tasks in succession—for example, carrying and operating tools and equipment, placing and climbing ladders, pulling and advancing hose, climbing stairs, wrestling a hose stream, pushing and pulling ceiling and wall, and—above all—hopefully, just an appliance or furniture drag as opposed to a victim drag. In fact, doesn’t this appear similar to the entrance physical agility test you had to perform at one time? In some departments, an engine company may be called on to accomplish all these tasks within its first bottle of air. This scenario is similar to an exhausting full-body workout requiring muscle strength, muscular endurance, and pressure and flow stress on the cardiovascular system.
Emergency medical services (EMS) and rescue tasks are often not as physically exhausting as the high-paced, high-intensity fireground operations. Objectives are often accomplished with more thought and care. However, lifting and assisting patients, extricating victims, and moving and operating equipment in a trench or at a collapse scene may all require the rescuer to function in awkward and vulnerable positions and postures. Crawling or reaching into a vehicle to maneuver a patient onto a backboard requires core strength to protect from back injury. Sometimes a rescuer can be in an uncomfortable position for an extended time, requiring stamina and mobility. I can think of multiple times when I was stuck inside a vehicle cringing from shoulder pain just from maintaining C-spine! Past injuries and chronic wear and tear, such as in my case, often require some form of rehab to be performed indefinitely for pain management and maintaining structural integrity of the joint and supporting musculature. Core and joint stability and strengthening exercises are especially important when training for EMS and rescue tasks.
From what we know about our energy systems and our task analysis, it is evident that cardiovascular training alone does not prepare us for all the physical stress we encounter on scene. Metabolic similarities between aerobic cardiovascular training and fireground tasks are limited. This type of training enhances our ability to recover between bouts of activity but does little to prepare us for the intensity and mechanical stress of expected tasks. Little of what we do resembles the continuous cyclical movement of running, biking, or swimming. Only during higher-intensity cardiovascular training, such as interval training, do the heart rate response and metabolic stress become more similar to those of fireground tasks.
However, the type of work done during fireground tasks involves an intermittent, nonrepetitive nature with much greater variation in body and limb movements that require a greater output capacity from our anaerobic mechanisms in the form of muscular strength and muscular endurance. This is especially true when body weight is increased and limb movements are restricted by the gear we wear. Remember, this added weight and resistance increase the relative intensity of an activity when compared with performing that same activity without gear. For example, imagine yourself walking on a treadmill at four miles per hour. This task represents a specific intensity based on your fitness level. This same task increases in intensity considerably when performed when wearing turnout gear and self-contained breathing apparatus.
Differences in mechanical stress between cardiovascular training and fireground tasks are much more obvious. Running presents a moderate repetitive stress throughout the lower body joints. However, mechanical stress to the body during all emergency operations is often more severe and acute and is as various as the movements we perform. Acute back, shoulder, elbow, and knee injuries are common during on-scene operations.
With the variation in the physical demands of our profession, the importance of functional variation in our conditioning programs is clearly evident. We push our bodies through a wide variation of physiological and mechanical stress. Our physical conditioning program must reflect this variation to maintain our health and work capacity and to prevent injury. Our conditioning program must reflect the mechanical variation of the job tasks we perform and train the metabolic systems that support the way we perform these tasks on scene.
Continuous aerobic exercise can be used as a means of establishing a base cardiovascular health, managing a healthy weight, and preventing cardiovascular disease. The continuous work method usually involves a lower-intensity activity performed at a relatively constant heart rate over a prolonged duration—for example, a 30-minute jog at a “conversation” pace. To further improve cardiovascular performance, higher intensities must be achieved in training. Interval training is a common means of training in bouts of higher intensities alternated with active recovery periods. This is a means of overloading the aerobic and, in higher intensities, the glycolytic metabolic systems, which will result in an increase in your body’s ability to use oxygen, more commonly known as an increase in your VO2 max.
HOW TO PROCEED
If you are currently in poor cardiovascular health or are just starting a fitness program, you should use cardiovascular training as a primary means to improve cardiovascular health and prepare you for higher-intensity activities. If you already have a base level of cardiovascular health and fitness, use cardiovascular training to augment the performance of your anaerobic metabolic mechanisms for on-scene operations.
Training for muscular power, strength, and endurance conditions the anaerobic metabolic systems. Each training adaptation is specific to the mode of training. For example, if you want to increase strength, you must train with heavier loads. If you want to improve muscular endurance, you must train with lighter loads and perform repetitions to fatigue. Power is developed by performing multijoint exercises at high velocities and moderate loads. Power may not be used a whole lot in our job tasks, but it is a bonus. Olympic-type lifts are a great way to develop power, but they’re not for everyone. There are other applicable and more entertaining ways of training for power with medicine balls. Medicine balls may be used in various ways that provide a means of increasing full-body power and for developing core strength and stability as well.
The role of muscular endurance is often overlooked and underestimated. Training for muscular endurance enhances your anaerobic capacity, resulting in the ability to resist and recover from muscular fatigue. Circuit training is an easy way to develop muscular endurance and implement a wide variation of exercises. Circuit training is probably the most applicable type of training for fireground operations because of the ability to mimic metabolic stress and mechanical movements. Circuit training involves a series of exercises, usually anywhere from five to 25 exercises performed in consecutive order with little or no rest between exercises. Each exercise may have a repetition or time goal such as 45 seconds. The key design consideration is to ensure you have a balance of exercises among all planes of movements. Core exercises may be divided into dynamic and static exercises and balanced among the frontal, sagittal, transverse, and diagonal planes of movement. Foundational exercises should be balanced between lower-body pushing and pulling exercises such as squats and hip bridges or leg curls, respectively; upper-body horizontal pushing and pulling exercises such as push-ups and rows, respectively; and upper-body vertical pushing and pulling exercises such as shoulder press and lat pull-down, respectively. Creativity is encouraged when planning these workouts. You can implement just about any type of exercise into a circuit, and the format can be as basic or as novel and as entertaining as you wish to make it.
Strength training involves heavier loaded exercises performed for repetitions often between one and 12 repetitions. This type of training goes beyond building muscular strength. Bone and other attaching structures like ligaments and tendons also adapt to the mechanical stress applied. However, the focus of strength training should be on foundational exercises such as squats, Romanian dead lifts, bench press, shoulder press, lat pull down, horizontal pull, upright pull, and so on. These exercises involve basic, multijoint, foundational movements that we perform regularly in our daily lives.
Designing an appropriate and well-balanced conditioning program can easily turn into an overwhelming, complex task. Seeking advice from a fitness professional is a good decision. However, finding the right one may be priceless. A well-experienced and creative fitness professional (often, preferably one who has experience with athletes) can provide appropriate specific guidance on balancing different types of training and making the best use of your department’s current equipment resources and facility. That person may also provide suggestions for obtaining additional equipment resources that are inexpensive and versatile to fit within your program needs.
Firefighting, EMS, and rescue tasks involve a variation of movements and energy system production. Our fitness training should reflect the movement and metabolic demands encountered during emergency operations. With a better understanding of metabolic systems and task analysis, we are better able to assemble a fitness program that is functionally more applicable and appropriate.
Bjornaraa, B. S. (2001). Systematic applications of strength training and conditioning. Mound: StrengthCon, LLC.
Brooks, G. A., Fahey, T. D., & Baldwin, K. M. (2005). Exercise physiology: Human bioenergetics and its applications (4th Ed.). New York: McGraw Hill.
Guyton, A. C. & Hall, J. E. (2006). Textbook of medical physiology (11th ed.). Philadelphia: Elsevier Saunders.
Kales, S. N., Soteriades, E. S., Christophi, C. A., & Christiani, D. C. (2007). “Emergency duties and deaths from heart disease among firefighters in the United States,” The New England Journal of Medicine; 356:1207-1215.
Rhea, M. R., Alvar, B. A., & Gray, R. (2004), “Physical fitness and job performance of firefighters,” Journal of Strength and Conditioning Research; 18: 348-352.
Senn, D. S. (2010), “The human heart is like a fire pump,” Fire Engineering; 163(12):73-77.
Sheaff, A. K., Bennett, A., Hanson, E. D., et al. (2010), “Physiological determinants of the candidate physical ability test in firefighters,” Journal of Strength and Conditioning Research; 24:3112-3122.
DAN SENN, MS, CSCS, NSCA-CPT, is a firefighter/EMT for Fargo, North Dakota. He trains young athletes for sport performance and works with firefighters on job-related physical fitness and injury rehabilitation. Senn also serves his department as an instructor for firefighter physical fitness and injury prevention and provides program guidance to the department. His background is focused in exercise physiology, motor learning, biomechanics, and sports medicine.