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.*
After reviewing all of the contents of this page, you must be able to:
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:
- Hair Loss
- Constantly Feeling Cold
- Feeling Depressed or Anxious
- 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.