After a 20min warm up, followed by a 2min recovery, run for 20min on a flat course (grade of less than 3%). Begin the test at a high, but somewhat conservative effort. You should feel as if you could go much faster. The most common mistake athletes make when doing this test is starting out too fast because it feels so easy for a few minutes. The first 5 minutes should feel relatively easy. After every 5 minutes, decide whether you should go somewhat faster or more slowly for the next 5 minutes. These changes should be slight.
This test is especailly risky on the bike. Keep your head up so you can see ahead throughout the test while being especially mindful of traffic. Do not take risks to get good data.