Summarize:

The less fit you are, the more slowly you will need to ease into your workout routine, but the quicker you will see gains. If you are already very fit, you will have to work extremely hard to further improve your cardiovascular fitness. Before you can determine your maximum heart rate a key number for creating efficient workouts - you'll need to estimate your overall fitness level. Remember to start low and go slow. You do not want to overdo your workouts initially. This prevents injury and allows your body to catch up. Poor Shape If you do not exercise at all, or have not exercised in the last eight weeks. Remember: it does not matter how thin you are. You can be very thin and still in poor cardiovascular condition. Average Shape You participate in any aerobic activity walking, running, biking, swimming, rowing, etc. 3 times a week for 20 minutes. Good Shape You run or walk at least 5 miles a week, and have regular training sessions that total over 1 hour a week. Your HRmax is just what it sounds like: the fastest your heart can beat while exercising. It is the baseline for determining the heart rate ranges you will want to hit while working out, and differs for different types of exercise highest while running and lower while biking and swimming. The traditional way to calculate your HRmax is to subtract your age from 220. However, this method can be off by as many as 20 beats per minute (bpm). The HeartZones "best fit" formula to find your running HRmax: 210 minus 50% of your age minus 5% of your body weight (pounds) + 4 if male and 0 if female. Or try the following formula: 217 (.85 x age) and then add/subtract as follows: Subtract 3 beats for athletes in excellent shape under 30. Add 2 beats for a 50 year old athlete in excellent shape. Add 4 beats for athletes in excellent shape who are 55 and older. Subtract 3 beats for rowing training. Subtract 5 beats for bicycle training. There are two options for the SubMax test: The 1 Mile Walking Test Walk four continuous laps on a track as fast as is comfortable. During the last lap, take your pulse four times (while still walking), or use your heart rate monitor to determine your average heart rate.Then, add as follows: +40 bpm if in poor shape. +50 bpm if in average shape. +60 bpm if in good shape. The 3 Minute Step Test Use an 8" step. Step up and down in a four-count sequence, alternating between right and left foot (aka up, up, down, down) for one full set. Do 20 sets per minute for 2 minutes and then a third set of 20 while monitoring your heart rate. Add as follows: +55 bpm if in poor shape. +65 bpm if in average shape. +75 bpm if in good shape. You can have your physician supervise your test, or pay $75-100 for a test with an Exercise Test Technologist, certified by the ACSM. Or, you can do one of the following tests yourself: 800 Meter Track Test Wearing a heart rate monitor, run 400 meters (1,000ft) (1 lap) at 90-95% of your HRmax. For the second 400 meters, run as hard as you can. Record your maximum heart rate when you reach on the second lap. Hill Test Find a hill that takes about two minutes to run up, and is steep enough that you are breathing hard at the summit. Start the test about a 5 minute run from the hill. Start with a slow jog, then gradually accelerate so that you are running at 85% of your HRmax when you hit the base of the hill. Try to maintain your speed as you climb the hill. Note your highest heart rate on your way to the top of the hill.
Determine your starting level in order to know how frequently and hard you can work out. Decide what kind of shape you are in. Estimate your maximum heart rate (HRmax). Test your maximum heart rate with a SubMax test. Perform a max heart rate stress test for the most accurate number.