The Gerkin Test for Treadmills

Often used to measure the fitness of firefighters and military personnel, the Gerkin treadmill test helps you estimate your cardiovascular endurance. The test makes a treadmill run incrementally more difficult for a specified amount of time, during which you measure your heart rate until you exceed your target rate. How long it takes you to exceed that rate helps you measure your fitness level.

You're allowed to warm up for three minutes for the Gerkin test, all of which count toward your overall time on the treadmill. The first measure is your resting heart rate before your warm up begins. The warm up can be a walk or run at 3 mph with the machine set at no incline.

Leave the speed at 3 mph but up the incline by 2 percent for one minute. Then, increase the speed by half a mile per hour, and raise the incline by 2 percent for one minute. Increase your speed and incline in one-minute increments until you reach your target heart rate. To get your maximum heart rate, subtract your age from 220, then multiply that number by 50 to 85 percent. You should only exercise at 50 to 85 percent of your maximum heart rate. Cool down for three minutes with a zero grade at 3 mph.

If you're taking the test to pass a physical fitness exam, it's likely you must run for at least 13 minutes but no more than 17 minutes, including the warmup, before you go over your target heart rate. Your heart rate might be monitored as you cool down as well, which helps the scoring professional determine an estimated maximal oxygen consumption during exercise, or VO2 max.

In 2004, an Occupational Medicine journal article called "Evaluation of a Treadmill Test for Predicting the Aerobic Capacity of Firefighters" took a shot at the Gerkin's reputation. Researchers found it led to VO2 max rates being overestimated by 25 percent and recommended organizations cease using the Gerkin test. As of 2013, many high-risk occupations, such as firefighters, still used the Gerkin test. However, some were moving toward a test introduced by the International Association of Fire Chiefs: the Wellness-Fitness Initiative. It includes a treadmill test where the participant walks at a constant speed and grade for 10 minutes. The grade is then increased until the participant reaches exhaustion. A 2011 Journal of Occupational Medicine and Toxicology article found this method more effective than the Gerkin, although not always completely accurate.