Fitness Testing

AEROBIC FITNESS TESTING

(This information has been adapted from my book, The 30-Day Heart Tune-Up. For details, please consult the book).

Worldwide, physicians rely on the MET scale on a standardized treadmill test to gauge cardiovascular function. They commonly use what’s known as the “Bruce Protocol,” increasing the speed and incline of the running surface every three minutes until the point you feel you are at maximum exertion. This means you will be pushing yourself on a stationary bicycle or treadmill (one that shows you a MET level on the screen) to the point where you are breathing hard, puffing, and just barely able to talk in short sentences but clearly unable to sing. Your stride is still steady (you aren’t stumbling), your color is good, and you could keep on going a few more seconds. Once you get to this point, you will know your MET level.

This protocol is designed to be done in a physician’s office under the supervision of a doctor who knows you personally. You should always consult your physician before considering this type of testing. The more medical problems that you have, the more important that you perform this type of testing with your own doctor.

You should have an accurate way to measure your heart rate to proceed. At the least, use a heart rate monitor with a chest strap to accurately measure your heart rate with exercise. Most physicians would use an ECG tracing that measure the actual rate and rhythm of your heartbeat.

How to Do the Bruce Protocol

Start the treadmill at 1.7 miles per hour with a 10 percent elevation. (This should be an easy walking warm-up speed.) After exactly three minutes, increase the speed to 2.5 miles per hour and the elevation to 12 percent. Continue to increase the settings every three minutes. When you reach your maximal, comfortable exertion level, (breathing hard and just barely able to talk in short sentences) check your pulse. This is your maximum heart rate, which is extremely beneficial for you to know.

Using a heart-rate-measuring tool such as a chest band and a wristwatch that shows your heart rate precisely. (Treadmills and exercise machines with measuring devices in the handgrips may not be accurate enough as they usually record only a three-beat sequence and yield varying heart rates.) Monitor your heart rate during each stage. Most exercise machines at the gym can calculate your MET score for you. Obviously, if you do this test with a trainer, he or she will ensure that your MET is calculated.

BRUCE PROTOCOL FITNESS CALCULATION TOOL.

Physicians typically use this treadmill exercise protocol to look for signs of heart disease, yet it can also be used to measure aerobic fitness. To calculate your score, you need to determine your MET level based on when you stop the treadmill test. The longer you last, the higher your score will be. But before you begin, ask your doctor if you are safe to do this test with a physician, an exercise physiologist, or on your own.

 Minutes           Completed SPEED           (mph)

ELEVATION           

(% grade)

MET LEVEL       Men MET LEVEL        Women
1 1.7 10% 3.2 3.1
2 4.0 3.9
3 4.9 4.7
4 2.5 12% 5.7 5.4
5 6.6 6.2
6 7.4 7.0
7 3.4 14% 8.3 8.0
8 9.1 8.6
9 10.0 9.4
10 4.2 16%* 10.7 10.1
11 11.6 10.9
12 12.5 11.7
13 5.0 18%* 13.3 12.5
14 14.1 13.2
15 15.0 14.1

*If your treadmill doesn’t go beyond 15 percent elevation, at 10 minutes adjust the incline to 15 percent and increase your speed to 4.4 miles per hour and at 13 minutes maintaining the 15 percent incline and increase the speed to 5.4 MPH.

Under proper supervision, for this type of evaluation, you should try to push yourself hard. You’ll be sweating, puffing, and nearly spent but still capable of running well without stumbling and able to talk in short sentences. This is your maximum heart rate zone, so record it and then stop.

Below is an example of results with a patient in my clinic. Jake has been my patient for three years. At the age of 58, he could sing for the first nine minutes on the treadmill using the Bruce protocol elevation and speed guide I outlined above. That meant he wasn’t exercising at an aerobic level. From ninth through the twelfth minutes he was moderately winded, sweating, and could talk in only two-word sentences. He felt he was working pretty hard, but he could still keep going. This is his best workout zone. He noted his heart rate. By 13 minutes he was spent. He couldn’t talk in two short phrases without taking a breath. We calculated his maximum heart rate and stopped. He scored 13.3 METS.

From the table below, you can see that if a woman lasts 14 minutes and stops, her score would be 12.5 METS. On average, women achieve a slightly lower score with this table partly because they are usually smaller than men so they have less weight to carry uphill. So in principle, a slim man might choose the score from the woman’s table and a heavy woman could choose a score from the men’s. Keep in mind these are only estimates and you’d have to do a real oxygen burning treadmill test with a physician like me to calculate your score with 100 percent accuracy.  Below are sample tables for men and women to help you calculate where you stand in METs compared to other people of your gender and age.

Aerobic Capacity Testing for Women

Maximum Aerobic Capacity Achieved (in METs) by age

Percentile        20-29              30-39              40-49            50-59          60+

  • 90                     12.5                11.7                 11.3              10.1           10.0
  • 80                     11.7                11.0                 10.4               9.2             8.9
  • 70                     10.9                10.5                 9.7                 8.8             8.4
  • 50                     10.0                 9.7                   8.8                8.1             7.4
  • 30                      9.2                  8.7                   8.1                7.3             6.8
  • 10                      8.1                  7.6                   7.2                6.4             6.0

 

Aerobic Capacity Testing for Men

Maximum Aerobic Capacity Achieved (in METs) by age

Percentile         20-29              30-39              40-49           50-59          60+

  • 90                     14.7                 14.4                 13.8             12.9           12.1
  • 80                     13.8                 13.4                 12.6             11.7           10.9
  • 70                     13.4                 12.7                 11.9             11.0           10.1
  • 50                     12.1                 11.7                 10.9             10.1            9.1
  • 30                     11.3                 10.7                 10.0              9.2             8.2
  • 10                      9.9                   9.3                   8.8                8.0             6.6

Tables were adapted with permission of the American College of Sports Medicines Guidelines for Exercise Testing and Prescription, 6th Edition, 2000. Data provided by Institute for Aerobics Research, Dallas, TX.

After performing your aerobic fitness test with a machine that can calculate your maximum MET score, compare your actual achieved score with your age and gender in the charts above. For example, if 45-year-old Michelle runs on the treadmill for 11 minutes and 15 seconds, she reaches 10.9 METS, just above the 80th percentile for her age group; this means she is in good but not excellent physical condition. In contrast, 58-year-old Jake ran for 13 minutes, scoring 13.3 METS, 90th percentile for someone 5-10 years younger, so he is in very good shape.

HEART RATE RECOVERY TEST

In the Bruce Protocol I described above, I asked you to take your pulse at your level of maximum exertion. Now, immediately decrease the speed to 1 mile per hour with no elevation. You’ll do this because another good predictor of your heart’s ability to accommodate varying levels of physical effort is to track how quickly your heart rate drops after peak exercise. Your heart can race as high as 160 to 200 beats per minute. When you stop, the quicker your heart rate drops the better. Here’s what to do:

After reaching your maximum exertion rate, walk 1 mile per hour without incline for one minute and take your pulse again. A minimum 25-beat drop at 60 seconds is normal, but I’d prefer more than a 30-beat drop, that would show good heart rate recovery. (However, if you have had heart surgery or are taking medication that alters your heart rate, then your recovery may not meet these guidelines and you should clarify your targets with your own physician.) Athletes will often observe their heart rate drops by 40-60 beats at one minute. On the other hand, if it drops less than 20 beats at one minute, this would be concerning, and if it drops less than 12 beats, I’d call that alarming. At two minutes, your heart rate should drop by at least 45 beats. This too indicates a good cardiac recovery level.

Steven Masley, MD