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Author: Stan Reents, PharmD
Original Posting: 05/25/2013 03:37 PM
Last Revision: 10/16/2020 06:04 AM

If you are looking for a low-impact activity that can give you a good aerobic work-out, consider hiking. Even without wearing a back-pack, hiking can really drive your heart rate up.

In one study where young males marched while wearing a weighted back pack, the following improvements in aerobic capacity were seen (all subjects marched at a pace of 5 km/hour, for 30 min/day, 5 days per week) (Shoenfeld Y, et al. 1980):

• 3-kg back-pack x 3 weeks 15% improvement
• 3-kg back-pack x 4 weeks 18% improvement
• 3-kg back-pack x 3 weeks
then 6-kg for 1 more week
30% improvement


Scientists express the energy expenditure of various activities in terms of "MET's". One MET represents the number of calories you burn while sitting at rest. So, "2 MET's" would be twice that. Walking at a moderate pace (3 mph) burns about 3 MET's. "Back-packing" or "climbing hills" is generally reported at about 7 MET's (Ainsworth BE, et al. 2011):

• RUNNING, 6mph (10 min/mile) 10 METs
• WALKING, 3mph (20 min/mile) 3 METs

For the average person, calories are easier to understand than METs. Here is a comparison of hiking while wearing a back-pack vs. walking on a level surface:

(30 min.)
100-lb. PERSON
150-lb. PERSON
200-lb. PERSON
30-lb. PACK
235 calories 350 calories 470 calories
10-lb. PACK
180 calories 270 calories 360 calories
• WALKING 80 calories 120 calories 160 calories

OK, let's say you've never hiked before. Hiking has its risks. It does require some degree of advanced planning. Overnight, or, multi-day hikes require more gear and more planning. And, regardless of your skills, experience, and gear, it is always wise to tell someone where you're going and when you expect to be back. If you're lost or hurt, a delay of a single day might make a huge difference in the outcome.

This review will offer some suggestions.

GETTING READY: Knowledge and Skills

First, having the latest, coolest gear isn't much good if you don't know how to use it. Get familiar with it before the hike. For example, can you set up your tent, or, fire-up your stove without looking at the instructions?

Shelter: If you bring a tent, make sure you know how to set it up. It may not be that easy in a strong wind, or complete darkness. What tools does this task require? If you are not bringing a tent, learn how to make a shelter that will keep you warm and dry.

Fire: Can you make a fire if you had to? More importantly, can you make a fire that won't spread into a wild-fire?

Water: Humans cannot survive longer than 4-5 days without water. No one plans to get lost, but, nevertheless, you should have some method of purifying water in case you do. Assume that all natural sources of ground water could be contaminated with giardia and/or cryptosporidium (see below). Know how to sterilize water by boiling or by chemical disinfection. Or, carry a water bottle with a high-efficiency filter. (See my other review -- "Hiking Gear" -- for an in-depth discussion of water filter bottles.)

Plants: Learn to recognize 3-5 native plants that could be used for nutrition and/or hydration.

Navigation: Learn how to use the sun to navigate.

Prevent Altitude Sickness: If you plan to be hiking up to elevations above 9,000-10,000 ft, then altitude sickness is something to consider. In fact, one study reports that, of 3,158 visitors to the Colorado Rockies, 25% developed altitude sickness at heights as modest as 6,300 ft. Altitude sickness can affect the brain (ranging from simple confusion to cerebral edema) and the lung (ranging from coughing and shortness of breath to pulmonary edema). Either one can be fatal.

Strategies for preventing it include:

  • Go slow: as you ascend, give your body time to acclimate; the higher you go, the more time you should allow
  • Stay hydrated: drink water; minimize alcohol


This topic has been extensively summarized in my other review: "Hiking Gear". But, here is a short list of things to consider:

  • boots or shoes that are appropriate and that are broken in!
  • at least 2 pairs of socks
  • several shirts/tops that you can layer depending on the temperature
  • a hat
  • sunglasses and sunblock
  • a compass
  • a watch
  • some type of high-quality device for filtering or purifying water
  • a multi-tool that includes a can-opener
  • eating utensils
  • plastic bags of various sizes (to keep clothes dry, to carry trash out)
  • a flashlight or headlight
  • extra batteries or a solar charger with a USB connection
  • a mirror
  • a whistle

Medical Stuff

Bring at least some rudimentary medical supplies:

First-aid: Bring stuff you can use to clean and bandage a cut, MoleSkin and tape if you develop a blister, etc.

For gastroenteritis: If you are worried about the possibility of developing diarrhea from drinking contaminated water, then bring some Pepto-Bismol and loperamide. Many people don't realize how effective Pepto-Bismol is for bacterial causes of gastroenteritis. The active ingredient in Pepto-Bismol -- bismuth -- is most often used to prevent traveler's diarrhea, but it can also be effective for treatment (Steffen R. 1990). However, bismuth is not effective against giardia.

Altitude sickness: The August 2006 issue of National Geographic's Adventure magazine describes a "personal hyperbaric chamber" to deal with altitude sickness. Essentially, it looks like a sleeping bag, but it has a foot pump that is used to inflate it, thereby increasing the air pressure inside the bag. The bag described in this article ("The Gamow Bag") was invented by Igor Gamow, a former chemical engineering professor at the University of Colorado, but several other pressurized bags like this also exist: the Certec® Bag, and the PAC® Bag. The PAC® Bag (shown here) was designed by Jim Duff, MD, an expedition physician.

All 3 bags are reviewed at:

Don't forget bug repellent containing Deet or Picaridin and sunblock. Several years ago, National Geographic's Adventure magazine recommended the skin protection products from Dermatone.

Survival Gear

Have you heard of "Personal Locator Beacons"? You might want to give these devices some serious consideration, particularly if you like to hike alone. Leading manufacturers are:

But, low-tech works, too. A mirror and a whistle are absolutely critical. In lieu of a mirror, a knife blade, a credit card, or even the aluminum foil from a gum wrapper might work to reflect sunlight and help someone find you.

Also, worth considering:

  • a folding knife or a multi-tool
  • 30-50-ft of rope
  • several feet of duct tape
  • a solar charger device
  • a solar-powered or crank-powered weather radio


Excessive Liquids: Obviously, you're going to need water during a long hike, but keep in mind that 1 gallon of water weighs 8.4 lbs. So, consider using a filtration / sterilization system to minimize the amount of water you carry. If you are bringing water, and you are going to hike the same trail out and back, stash some of your water along the trail going out so you can retrieve it on the return trip.

Glass: Unless they are very small, don't bring glass containers. Glass is heavier than plastic, and, you certainly don't want broken glass inside your backpack!

Alcohol: Alcohol will dehydrate you. However, a cold brew after a long day of hiking is pretty satisfying. Here's a thought: if you bring vodka instead of beers, you can get the same, um, "effect" with much less volume (= less weight to carry). And, vodka could conceivably be used to disinfect a wound (though that stings like hell!!)

A Chair: Even though there are some nifty little camp chairs available, they're bulky to carry. I don't think they're worth the aggravation.


As mentioned above, having some type of water purification may be the most important item you bring with you on a hike.

Here is a summary of 220 cases of "water-borne illnesses" reported to the CDC between 1972-1985. Although these are older data, it shows that giardia is the most common infectious agent:

Giardia lamblia parasite 38.6%
• Shigella bacteria 11.8%
• Hepatitis A virus 7.7%
• Norwalk virus virus 6.8%
Campylobacter jejuni bacteria 4.5%
• Salmonella, non-typhi bacteria 4.5%
Salmonella typhi bacteria 2.3%

There are 4 ways to purify water: boiling, chemical, filtration, and UV light:


According to the medical text "Principles and Practice of Infectious Disease" by Mandell, to kill giardia requires boiling for at least 1 minute, longer if at higher altitudes:

• at sea level: 1 minute 5 minutes
• at higher altitudes: 5 minutes 20 minutes


Chlorine and iodine are the 2 main types of chemical disinfection used in water-purification systems. Some are stand-alone systems. The internal cartridge in some water bottles combines a filter with a chemical system. According to "Principles and Practice of Infectious Disease," to kill giardia requires a chlorine minimum concentration of 4-6 mg/L.


The size of microorganisms is measured in units called "microns." The pore size of a filter is also measured in microns. So, it's relatively easy to determine what a filter will remove when you know the following:

• giardia
• cryptosporidium
4-12 microns generally yes
• BACTERIA • E. coli
• Shigella
• length: 1-10 microns
• diam: 0.5 - 1.2 microns
depends on the
pore size
• VIRUSES • hepatitis A
• Norwalk virus
extremely tiny MOST DO NOT**
(see discussion)

I have a water bottle with a filter and an iodine system built into it ("Exstream Orinoco"). I bought it years ago. On the label, it says the filter will remove anything larger than "1 micron" and it specifically identifies giardia and cryptosporidium. I've written an extensive discussion of "scoop-and-go" water bottles (containing built-in filtration systems) in my other review: "Hiking Gear".

**A hand-held (aka "scoop-and-go") water filter bottle that removes viruses??!!:

For individual use, if you want what appears to be the best "scoop-and-go" water filter bottle on the market, you would be hard-pressed to do better than the LifeSaver. This personal-use water purification system claims to have the smallest filter pore size: 0.015 microns (= 15 nanometers) and boasts the highest removal rates. Note that this product does NOT use chlorine or iodine, yet, claims to be able to remove viral pathogens. Their most dramatic claim is that it can eliminate the polio virus, which is 25 nanometers in size. They provide on their web site some laboratory test results backing up these claims. It meets the standards of the EPA and a slew of other ratings agencies. Very impressive! It has been on the market since 2007 and is used by military personnel around the world.

Of course, the Lifesaver is one of the more expensive scoop-and-go water filter / water purifier bottles on the market: sells their 4000 model for $130 - $145 and their 6000 model for $169 (as of 4/20/17). I could not find the LifeSaver on


American Hiking Society: The American Hiking Society ( was founded in 1976 and is based in Silver Spring, MD. It is the only national, recreation-based nonprofit organization dedicated to promoting and protecting America's hiking trails, and their surrounding natural areas. It represents 37 million hikers. Each year, on the first Saturday of June, they promote National Trails Day to encourage people to get out and enjoy hiking.

National Parks Pass: The National Parks and Federal Recreational Lands Pass ( will get you into more than 2000 federal recreation sites. If you plan on visiting even just a couple national parks in a calendar year, it is worth the money ($80/yr for adults, $10/yr for seniors, free to US Military and children under 15). And even if you don't, you're supporting something good (well, at least we think so!).....

Survival School: The oldest and largest survival school in the world is the Boulder Outdoor Survival School ( They have been in existence since 1968 and offer courses from 3-28 days in length. The classes are held in southern Utah.

Readers might also be interested in these reviews:


Stan Reents, PharmD, is available to speak on this and many other exercise-related topics. (Here is a downloadable recording of one of his Health Talks.) He also provides a one-on-one Health Coaching Service. Contact him through the Contact Us page.


Ainsworth BE, Haskell WL, Herrmann SD, et al. 2011 Compendium of physical activities: a second update of codes and MET values. Med Sci Sports Exerc 2011;43:1575-1581. Abstract

Principles and Practice of Infectious Diseases, 3rd ed., Mandell GL, Douglas RG, Bennett JE, editors, Churchill Livingstone, 1990.

Shoenfeld Y, Keren G, Shimoni T, et al. Walking: A method for rapid improvement of physical fitness. JAMA 1980;243:2062-2063. (no abstract)

Steffen R. Worldwide efficacy of bismuth subsalicylate in the treatment of travelers' diarrhea. Rev Infect Disease 1990;12 Suppl 1:S80-S86. Abstract


Stan Reents, PharmD, is a former healthcare professional. He has been a member of the American College of Lifestyle Medicine (ACLM) and a member of the American College of Sports Medicine (ACSM). In the past, he has been certified as a Health Fitness Specialist by ACSM, as a Certified Health Coach by ACE, as a Personal Trainer by ACE, and as a tennis coach by USTA. He is the author of Sport and Exercise Pharmacology (published by Human Kinetics) and has written for Runner's World magazine, Senior Softball USA, Training and Conditioning and other fitness publications.

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