Check with your doctor before starting any exercise routine. One of the simplest and safest ways available to find your aerobic fitness baseline is by walking. If you are a jogger, you may want to jog instead. You can do this a couple of ways.
One option is to simply go for a walk. Record how many minutes you can go before getting tired. After going on three different days, total all your minutes and divide by three to get your average. Another option is to perform the Rockport Walk Test. The goal of this test is walk a mile as fast as you can and then record your total time and ending heart rate. Simply plug these numbers into this online calculator to determine your current level of fitness. This test is more accurate when you are able to measure your pulse with a heart rate monitor. If you need to measure it manually, check out how by watching this video.
Set a length of time, perhaps 10 minutes and walk as far as you can. Record the distance you were able to walk, either in terms of blocks if outside or exact distance if using a treadmill. Write your scores on your Fitness Results sheet. Keep walking as often as you can. As long as you are feeling up to it and have your doctor’s clearance, you can retest yourself every six weeks to help monitor your progress.