Physiology and Fitness

Being able to work comfortably in the great outdoors means understanding what happens to the human body under certain conditions. Biological processes have a profound impact on survivability. Being aware of these processes could mean the difference between life and death.

*The following information relies heavily on personal experience and the National Association for Search and Rescue's (NASAR) Fundamentals of Search and Rescue 2nd Edition handbook.*

Quick Lift

Activity Levels and Environmental Factors on Caloric Intake

How many calories an individual needs to perform while being active in the wilderness varies wildly. There are so many factors involved it is impossible to paint this subject with a broad brush. Instead, we will cover some basics and leave it up to the reader to delve deeper into their own personal needs. Essentially, the harder you work, and the colder it gets, the more calories you will need to consume to maintain your body's caloric needs.

This video is a great description of what to consider when thinking about how much you need to consume to maintain your body's processes in a healthy way:

Needless to say, it's a complex situation; however, there are some symptoms that may indicate a lack of calories could be the culprit. Some of the main symptoms are:

- Fatigue
- Hair Loss
- Constantly Feeling Cold
- Feeling Depressed or Anxious
- Constipation
- Feeling Irritable or Emotionally Unstable

To get an idea of how many calories you may need, here are a few online calculators to use:

Baylor College of Medicine: Adult Energy Needs Calculator
Active: Calorie Calculator

It may be necessary to consult a dietitian depending on your personal needs, but it is important to be aware of the symptoms and recognize when you may be going through a caloric deficit. If you find yourself experiencing any of the symptoms, take time to be mindful of what could be a potential cause.


Increasing Levels of Dehydration and Effects on the Body

The importance of water intake must be taken seriously. It is recommended that adult women consume 2.7 liters of water from food and beverages, and adult men consume 3.7. This amount can change based on activity level, climate, and a multitude of other factors.

Urine color is often a good indicator of how hydrated a person is. Pale-yellow to clear urine is indicative of being properly hydrated, while darker colors (usually in smaller amounts) indicate dehydration. There is a lot more to staying hydrated, including important chemicals the body uses to regulate our body (known as electrolytes), but the frequency of electrolyte consumption depends heavily on food intake and physical exertion. Watch the following videos to get a better understanding of how hydration and dehydration affect the human body:

Unfortunately, keeping your body working in proper order is not as simple as regularly drinking water. Cellular processes rely on other chemicals to operate at peak performance. One of the most common ways individuals participate in extended lengths of intense physical activity is with sports drinks, mainly for one purpose: electrolytes. The following video explains why and when electrolytes are important:
NASAR Hydration Tips:

  • Water is more essential than food, and lack of it will kill you quicker than lack of food.

  • It is impossible to physically perform at any reasonable level without the adequate intake of fluids.

  • Food should be eaten only when there is enough water to drink. Do not eat if water is scarce.

  • For long periods of exercise or when water must be treated, use flavored sports drink mixes to encourage fluid intake.

  • Use salt tablets with caution and, ideally, only under the direction of a physician.



Body Temperature Regulation
Since the human body is constantly generating heat, excess heat must be transferred to the surrounding environment to maintain a healthy temperature, approximately 99 degrees Fahrenheit. In order for humans to maintain this ideal temperature, we must stay well nourished, hydrated, and adjust our clothing depending on climatic conditions due to heat transfer.


Heat transfer can occur because of the following processes:


  • Conduction: heat which is transferred between two objects touching. An example of this is when you are lying on a cold surface such as snowy ground.

  • Radiation: the human body emits and receives energy through space without an intervening medium (such as clothing). Humans emit energy in the form of infrared radiation.

  • Convection: is a form of conduction enhanced by the movement of molecules in a gas or liquid. This is the reason windy weather in the winter can create potentially fatal conditions.

  • Evaporation: This is when water changes its state from a liquid to gas, such as when the human body perspires to cool the skin, or during respiration.

The following video explains these processes in a way that pertains to the human body in outdoor conditions:

Learn more about body heat loss (at rest) from here.

As the ambient temperature changes, the human body attempts to maintain its core temperature at a steady 98.6 degrees Fahrenheit/37 degrees Celcius. Extreme ambient heat can result in feeling uncomfortable, feeling pain, or even burned skin. Extreme ambient cold can result in numb skin, frostbite, or the skin freezing completely.

If the body cannot maintain a stable core temperature, symptoms will occur that negatively impact body function. An increase in core temperature (such as a fever) can result in drowsiness, coma or convulsions, and death. A decrease in core temperature can result in shivering, impaired cognition, coma, heart failure, and death.

This is why it is extremely important to be prepared for weather conditions and be aware of what symptoms you may be experiencing. In cold environments, it is especially important to be aware of the effects of Wind Chill. Learn more about how the wind can amplify the effects of cold weather here.

Conversely, working in hot conditions also assumes risk depending on the ambient temperature and the humidity in the air. Using a Heat Index can help determine how heat and moisture in the air affect warm weather. Learn more about Heat Indexing here.

Immersion in cold water will also reduce the body's core temperature over time and can even result in something called "cold water shock". The colder the water, the faster the rate of internal cooling. Learn more about the impacts of cold water immersion here.


Being physically fit is one of the most important endeavors you can commit to, especially when contributing to SAR operations. Physical fitness is the ability of your body systems to work together efficiently to allow you to be healthy and perform activities of daily living. Search and rescue processes are physically demanding, and being prepared to endure those elevated physical demands will prevent injuries and make you more effective.

For example, if a missing person is incapable of moving themselves, SAR technicians must be prepared to move the incapacitated person over challenging terrain. This means the possibility of having to move someone weighing several hundred pounds. Needless to say, being in a state of fitness that allows you to perform normal daily tasks is not enough. You must be able to exert yourself beyond what is needed for normal daily functions and have enough energy left over for additional tasks. 


Not every volunteer SAR technician will be capable of performing every SAR task, regardless of how frequently they train for it, and that is okay. There are roles for anyone with SAR training, regardless of their physical capabilities. That being said, it is important for anyone serious about participating in SAR operations to make a commitment to continuously improve their physical fitness.

Depending on your individual circumstances, it might be a good idea to get a health check with a doctor before starting a fitness program. You should consult a physician if you have been inactive for several years, or have any underlying conditions. Some of those conditions may include having:

    - arthritis or bone problems 

    - high blood pressure 

    - heart trouble 

    - frequent dizziness 

    - family history of early stroke or heart attacks 

    - obesity 

    - extreme breathlessness after mild exertion

    - severe muscular, ligament, or tendon problems 

    - other known or suspected diseases

There are four main aspects of physical fitness: cardiorespiratory endurance, muscular strength, muscular endurance, and flexibility.

Cardiorespiratory endurance is the level at which your heart, lungs, and muscles work together when you're exercising for an extended period of time. How long you can run, hike or swim are examples of how this endurance can be observed.

Muscular strength is the amount of force you can put out or the amount of weight you can lift. You can gauge your strength based on how easy it is to lift or move something. When you are at the gym, weights are typically labeled in pounds or kilograms, and you can observe your muscular strength by high how the numbers are on a weight being used.


Muscular endurance is how many times you can move that weight. The more times you can repeat a muscular movement at any given weight is how you can observe your endurance.


Flexibility is defined as the range of motion of your joints or the ability of your joints to move freely. It also refers to the mobility of your muscles, which allows for more movement around the joints. Increased flexibility helps prevent injuries to muscles and joints.


One major positive side effect of muscle building is that it will help control unhealthy weight, as muscle tissue burns calories at a faster rate than fat tissue. Maintaining a healthy weight reduces stress on joints and cardiorespiratory processes. This makes you more effective in the field and reduces the likelihood of injuries. Additionally, exercising decreases stress, extends metabolic processes, and boosts self-confidence.

Some tips that will help get you started can be found here.


It is important, to be honest about your current limitations. Identifying areas that need improvement will help you learn ways to strengthen them. Maintaining a healthy diet and fitness routine will improve every aspect of your life, not just your ability to perform SAR operations.

Getting started on a physical fitness program is easier now than it ever was before. There are endless instructional resources available on the internet for every fitness level. For the average adult with little fitness training and no underlying conditions, the video below will be a great place to start:

Finally, NASAR has a great list of recommendations to help get you in the right mindset to be ready for search and rescue operations:

"In everything you do--work, play, school, relationships, etc.--mental preparedness can be accomplished by following some simple self" guidelines. The following tips also help in maintaining a proper attitude of safety, in life as well as SAR.

Be thorough. When you begin something, do it well and finish what you start. Perseverance is an essential survival tool. Do not give up.

Be confident and willing to learn. Confidence comes through training and experience. Learn essential skills and practice what you learn. If you do something right or do something wrong, apply what you learned when you are next confronted by a similar situation. Learn something from every experience.

Be conscientious. There is a good chance that no one will be around to watch what you are doing. Your activities must be guided by your own standards. Set them high. Your peace of mind and satisfaction in a job well done may be your greatest, and sometimes only, reward.

Be assertive. Take advantage of new experiences. Push yourself beyond what you have done in the past without being foolsih. Take the lead to get things accomplished. Do not be afraid to take a safer route, recheck your bearings, or change your mind."