In an earlier forum post, Scott Johnston gave a more in-depth explanation of how the step-test works:
First thing in the AM, put on your HR monitor and step up and down on/off a step at a moderate cadence till your HR climbs to somewhere in the range of 100-120 or so. The step cadence should be easy to moderate effort and you probably only need to do this for a minute. Once you elevate the HR to 100+ immediately sit down and note your HR in 1 minute.
The rate of drop in HR will bear almost a perfect inverse correlation to your recovery state. The faster your HR recovers from the mild stressor the more recovered you are.
This takes little time, involves very little stress and is very portable. The step height and the cadence need to be the same each test. Establish a base line during a period of low training load and then note your perception when you train following test where the HR recovery is less during the 1 min.
A slow HR recovery indicates poor recovery. How poor only you can decide by testing yourself. You may find that 10 beats slower recovery will still allow you to train as normal but 15 beats means you need a day off. It’s very individual.
Recovery State and Techniques for Deciding Base Training Workout Intensities
Does that help?