You've got loads of applications flying across your desk and you need to determine how you are going to place these people on an appropriate level of trip. All of us have handled the Health History form pretty well and collect good medical information but very few programs have figured out how to effectively measure physical condition. At Princeton University we run one of the largest wilderness orientation programs in the world. Each year we bring over 600 incoming students back and send them out on 60-70 six-day backpacking trips. Assigning people to an appropriate trip activity level becomes a huge job. This is one of my biggest nightmares each summer. It can also be a major risk management issue. Placing someone on a trip that's too physically challenging can lead to injuries, evacuations, or an unsatisfactory experience. Over the years I've researched and experimented with a variety of methods trying to find a way to get an accurate rating on physical fitness of participants. This article will take you through some of the research I've done, show you how my methods have evolved, and explain what I've found that can help you assess physical fitness of your participants or your staff. I hope that it will benefit you in improving your fitness assessment approach.

Getting an Exercise History

One common approach is to gather information about the person's regular physical activity and using that to separate people into particular levels. This is what I started with years ago and many programs take similar approaches. Below are the basic questions I've used used for a number of years. As you can see from the sample application form below by gathering some basic information you can make a guess about the person's physical condition.

I would take the individual's self-rating of current physical level (1-4) and match it up with our trip difficulty level of 1-4. I used the reported physical activity as a confirmation of how the self scored. In recent years I added the trip level question since some people wanted to be on easier trips so I would factor this in as well. The problem with such assessments is that they are entirely subjective, both for the person filling out the questions and for the person on the program end trying to interpret the answers. I felt like I needed a more concrete and definitive measurement tool, one that would give me some form of accurate scoring of physical condition.

Other Physical Assessments

I began researching other physical assessment methods and discovered a range of tools within health assessment and exercise physiology. These can be separated into two basic types of assessment tools: actual exercise tests which calibrate real levels of physical exertion during exercise and paper & pencil tools that use certain body measurements and facts about the person to calculate some type of score.

Body Mass Index (BMI)

After reviewing more literature I came across Body Mass Index (BMI). BMI is not actually a measure of physical fitness, rather it is a measure of where a person is underweight, normal weight, overweight, or obese for their body size. BMI is based on an individual's height and weight and is calculated from the following formula (weight/height²). It is not an exact science since there are other variables besides just height and weight that contribute to defining your physical characteristics (bone density, muscle mass etc.) but it does give a ball park figure. Knowing the BMI by itself won't predict aerobic capacity or physical fitness but an individual that is rated on the BMI scale towards obesity and who shows little or no reported regular exercise is more likely to be less physically fit. The BMI score is not the same thing as calculating a person's percentage of body fat, although it does correlate to % body fat. That's because there are other factors that influence a person's level of body fat including age and gender. For example, women are more likely to have a higher percent of body fat than men for the same BMI. Also for the same BMI score, older people have more body fat than younger adults.¹

So I began to use BMI as another comparative factor in identifying people who might be on the low end of physical fitness. By collecting height and weight on the application form I was able to quickly calculate the BMI of all participants. This was really only helpful with people who had very high BMI's indicating people who were highly overweight or obese. If I found people who had high BMI's and little or no reported regular exercise I considered them to be in poorer physical shape. This served as a check for people who might have rated themselves too highly on the 1-4 scale (not unlikely when people want to avoid saying that they are in poor shape). It was of some limited use. So my search continued.

You can use the BMI calculators below to calculate your body mass index (English or Metric) then review the chart that indicates where BMI scores fall in terms of weight assessment.

Body Mass Index Scoring

VO2 max

Still searching for an actual numerical value of physical fitness I came upon VO2 max (officially written as VO_2max). VO2 max, also referred to as maximum oxygen uptake, is the maximum volume of oxygen consumed by the body each minute during exercise. Since the amount of oxygen we consume is directly related to the amount of energy we are burning, a measurement of oxygen consumption is actually a measure of aerobic fitness. The idea behind the MAX is that you are trying to measure the amount of oxygen you are consuming while exercising at your maximum capacity. VO2 max is expressed as the amount of oxygen in milliliters you consume in one minute per kilogram of your body weight (ml/kg/min) while exercising at near maximum capacity. (It's actually quite difficult to measure someone at maximum output since you'd assume that you can't sustain your true maximum output for very long. So people also refer to measure VO2 Peak or the peak level that you reached and sustained.) People who are more aerobically fit have higher VO2 max values.

VO2 max scores³

Below are charts showing how VO2 max scores correlate with physical condition for men and women of different age groups.

Women (values in ml/kg/min)

Men (values in ml/kg/min)

So VO2 max became a very promising measurement for evaluating the physical condition level of participants and staff. The question is then, how do you measure VO2 max? The answer is to do some form of physical fitness test.

Physical Fitness Tests

There are a variety of physical fitness tests used to establish a person's fitness level. The goal of these tests is to get the person to engage in some form of aerobic exercise, increase their heart rate and then perform some measurement to evaluate their fitness level. Test include running on treadmills, stationary bikes, walking, step tests and other aerobic activities. Some of these like treadmill tests require special testing or monitoring equipment and trained personnel to administer the test. These types of test may be hard to find and can be costly, which makes it hard to get participants to take them. For most programs, therefore, they are not a viable option. Only those programs that have extreme physical activity levels might decide that such documented testing is required before participating. There are however a number of tests which can be performed with minimal equipment and no special training. These are the ones that are most useful for the typical program. One of most well-known is the Harvard Step Test and there are others such as the Rockport Fitness Walking Test.

Harvard Step Test

The Harvard Step Test was developed by the Harvard Fatigue Laboratory. The test is simple. The idea is to step up onto the bench and down continuously for 5 minutes at the rate of 30 steps/minute (1 step every 2 seconds) or until the person can no longer maintain the rate of 30 steps/minute. At the end of the 5 minutes time the heart rate at three different times. The change in heart rate at Time 1, Time 2 and Time 3 shows the person's recovery time after the exercise. That is how quickly the person's heart rate returns to its normal resting rate after exercise. The step test is based on the premise that someone with a higher fitness level will have a smaller increase in heart rate and a faster recovery time. The values are strongly correlated with VO2 max but the Harvard Step Test score is not an actual measurement of VO2 max.

One of the benefits of the Harvard step test is that it only requires a bench of a certain size and a stop watch. The test is easy to do at home. A disadvantage is that there is some variation in the demands of the test based on the height of the step and the height or the person. Various step heights are quoted in the literature (40 cm, 45 cm, 50 cm). However it is obvious that it will require more energy for a 5 foot tall person to step up 50 cm than for a 6 foot person. Also body weight makes a difference so a heavier person is doing more work than a lighter person slightly skewing the results. The Harvard Step Test is conducted as follows: .

• Step up on to a standard gym bench (45cm high) once every two seconds for five minutes (~150 steps). Start with one foot (right or left ) and use that same foot as the starting "step up" foot throughout the exercise.
• Have someone to help you keep to the required pace. A counter or metronome can be helpful to maintain the rate (120 count on a metronome).
• One minute after finishing the test take your pulse rate for 30 seconds to get Beats per Minute (bpm). Have the person refrain from talking and unnecessary movement when heart rates are being counted since any activity can skew the heart rate and influence the results - Pulse 1
• Two minutes after finishing the test take your pulse rate for 30 seconds (bpm) - Pulse 2
• Three minutes after finishing the test take your pulse rate for 30 seconds (bpm) - Pulse 3

The score on the Harvard Step Test if based on the following formula:

Score = 100 * (300 seconds/ 2*(pulse1 + pulse2 + pulse3)

The Harvard Step Test is not the equivalent of VO2 max but is correlated with VO2 max. The correlation to VO2max is approximately 0.6 to 0.8. The Harvard Step Test has its own fitness ranking scale. Here are the range of scores for the Harvard Step Test and the physical condition rating based on the score

Rockport Fitness Walking Test (RFWT)⁵

The Rockport Fitness Walking Test is a timed test to walk (not jog on run) for one mile (1609 meters). It is named after the Rockport Shoe Company which developed the test. You need to have an accurate measured mile and the subject needs to be accurately timed in minutes and hundredths of seconds required to complete the walk. The goal is to move as quickly as possible but still at a walk. At the end of the mile the time is taken and the person's heart rate at the end of the walk is recorded. Having someone else do the actual timing is helpful. The advantage of the test is that it requires little equipment. The disadvantage of the RFWT is that the test is too easy for people in excellent physical shape. After the test the following variables are used to calculate VO2 max.

• Weight
• Age in years
• Gender (women are given a value of 0 and men a value of 1)
• Time to complete the one mile walk (in minutes and hundreds of seconds)
• Heart rate in beats per minute (recorded immediately after stopping)

The formula for the VO2 max calculation is:

VO2 max = 132.853 - (0.0769 * Weight) - (0.3877 * Age) + (6.315 * Gender) - (3.2649 * Time) - (0.1565 * Heart rate)

For programs that have advanced physical requirements, who stress this to participants in marketing materials, and can require tests like the Harvard Step Test or the Rockport Fitness Walking Test on your application or health form this may be a useful solution. The problem is actually getting people to do the tests. In my case I knew that a majority of incoming students simply wouldn't complete the test so I decided that the only way for me to be successful at this was to find a pure "paper and pencil test" where after collecting some basic known facts about a person I could make some sort of calculation on their fitness level. This became my "holy grail" of fitness assessment tools.

Non-Exercise Measurements

I continued to wrestle with finding a paper and pencil test that would give a more accurate picture of a person's fitness level. After en extensive search I was lucky enough to come across a paper in the journal Medicine and Science in Sport and Exercise (Vol. 22, No. 6, pp. 863-870, 1990). The article, Prediction of Functional Aerobic Capacity without Exercise Testing by Jackson, Blair, Mahar, Wier, Ross and Stuteville⁶ sounded like it was just what I was looking for. When I got the copy on interlibrary loan it turned out to be the "holy grail." I felt like Indiana Jones.

The authors decided to use VO2 max as their index of aerobic capacity and hence a measurement of physical fitness level. In the study they compared two different Non-exercise based assessments against the actual VO2 max levels of their test subjects. The goal of their study was to see if they could develop a predictive formula for VO2 max without requiring an actual exercise test. They identified a number of important factors that are determinants of physical condition--age, gender, BMI or % body fat, and a ranking of the person's regular physical activity. For this ranking they used a Physical Activity Rating questionnaire (PA-R) developed by NASA and the Johnson Space Center for evaluating the physical condition of employees (see the PA-R questions below). Using these different values they developed two different formulas which predicted VO2 max without an exercise test.

In the first case the formula which they developed used the score from the PA-R, measured percentage of body fat, age, and gender to predict VO2 max. This was called the N-Ex % Body Fat model. The second formula, referred to as the N-Ex BMI model, uses the score from the PA-R, Body Mass Index (BMI), age and gender to predict VO2 max. This suddenly provided me with an assessment tool that is completely "paper and pencil." In order to calculate the predicted VO2 max all that is needed is weight and height (for BMI), age, gender, and the score from the PA-R questionnaire. Based on the study results both the N-Ex BMI model or the N-Ex % Body Fat model are valid predictors of VO2 max. The formulas are as follows (note that there is a different formula for women and men). The first number in each formula is a constant that was developed based on the person's gender which standardizes the results into the normal VO2 max values.

NASA/JSC Physical Activity Rating (PA-R)

The NASA/Johnson Space Center Physical Activity Rating (PA-R) scale was developed to provide an assessment score of 0-7 on a person's level of regular physical activity. There are a series of eight statements about routine physical activity. Participants are to select only one response that best describes their physical activity level. Each response is given a numerical value which you can see in parentheses next to the selection button.

Calculate your VO2 max using the N-Ex BMI model

Based on the research N-Ex % Body Fat approach is slightly more accurate but still requires an physical measurement of percent body fat. Since this would be hard for most programs to get participants to do pre-course I did not choose this option. That means that the N-Ex BMI model wins hands down as the best pure paper and pencil test. So that was the 'holy grail" of my search, a complete paper and pencil based test that required only gathering a few basic facts from participants that would allow me to calculate a valid approximation of the person's VO2 max.

Since this study was done other similar ones have been performed (see the Bibliography) with similar results.

Summary

As you can see there are numerous ways to assess physical condition. I touched on only a few. The goal for this article (and the goal in my search) was to find a paper and pencil test that would give me an accurate score of physical fitness for a large group of participants with the least amount of staff intervention. The study by Jackson et. al provides such a measurement. My first large-scale use of the scoring will be this summer and I'll update this article with anything I learn.

On the technical side I collect height, weight, age, and gender on the application form. Using height and weight I calculate the BMI and then calculate the person's VO2 max. The information is entered into our participant database and the database performs the actual calculation and displays a VO2 max score. Using the VO2 max table above I have created a five-point scale of physical fitness of participants to match to the physical difficulty level of our trips. As you can see I combined Excellent and Superior into one number since none of our trips is that difficult. (anyone over 5 would have no problems on even the most strenuous of our trips). If you run very difficult trips you would probably want to have a 6th category. Another benefit of this testing approach (as you can see if you calculated your own score) is that you can actually have the person score themselves on the Web. This can be helpful if you want to track people into particular activity levels. Have the person calculate the score and then suggest appropriate trips for them on line.

I hope that this approach may be useful for other programs who have wrestled with this issue. If you have suggestions for other tests that you have used, please email them to OutdoorEd.com

Rick Curtis

Footnotes

1. Gallagher D, et al. How useful is BMI for comparison of body fatness across age, sex and ethnic groups? American Journal of Epidemiology 1996;143:228-239.

2. BMI calculator code - Center for Disease Control (www.cdc.gov/nccdphp/dnpa/bmi/calc-bmi.htm)

3. VO2 Max Chart - www.bodyresults.com/e2vo2max.asp

4. Harvard Step Test Calculator Code - Sports Coach UK - www.athleticscoach.co.uk

5. Rockport Fitness Walking Test - www.rockport.com/scripts/cgiip.exe/WService=rkptlatin1/09_walkingtest.html

6. Rockport Fitness Walking Test Calculator Code - Sports Coach UK - www.athleticscoach.co.uk

Bibliography & Resources

Jackson A.S., Blair S.N., Mahar M.T., Wier L.T., Ross R.M., Stuteville J.E. Prediction of functional aerobic capacity without exercise testing. Med Sci Sports Exerc 1990; 22(6): 863-870.

George J.D., Stone W.J., Burkett L.N. Nonexercise VO2max estimation for physically active college students. Med. Sci. Sports Exerc., 29:415, 1997.

Heil D.P., Freedson P.S., Ahlquist L.E, Price J., Rippe J.M. Nonexercise Regression Models to Estimate Peak Oxygen Consumption. Med Sci Sports Exerc 27(4): 599-606, 1995

Peter J. Maud, The Physiological Assessment of Human Fitness, Human Kinetics.

Web Sites

Sports Coach UK - www.athleticscoach.co.uk

Polar Hear Rate Monitors (Korea) - www.polarkorea.co.kr/resech/Performanceandfitnes.htm

SUA Fitness Center - shapeup.org/fitness/assess/fset2.htm

A non-exercise, cardiorespiratory prediction model for Hispanic women -
www.coe.ohio-state.edu/rsuminski/files/Professional%20info/current%20abstracts.htm