Your maximum heart rate is an important guideline to measure your workout success. For many years, we have all been conditioned to use the simplest formula available. That is the formula 220 minus your age.
From there it was easy to calculate your correct work out zones by simply multiplying the first number by the percentage you wanted to be at. (MHR x .5 to .7 or more depending on desired intensity.) However, this is not all that accurate due to fitness level and body size, or other factors.
To truly know your maximum heart rate, you really do need to turn to a testing facility where they can hook you up to several machines and work you out until you drop from exhaustion. Then they can determine your maximum heart rate.
For most people this is impossible. A simple search engine inquiry can show you many methods that people use to attempt to calculate their maximum heart rate. (Such as the Karvonen Method of calculating THR.)
Once you have a good idea want your maximum heart rate is and what your target heart rate is, you need to figure out how to know when you have reached your target heart rate while working out. A combination of one of the following methods should help you out.
The Talk Test
If you can sing, joke, and carry on while you are working out, chances are you are not working out much at all. This would be the easy level or a light stroll.
If you can maintain a conversation with someone, then you are probably in the moderate range. If you find maintaining a conversation challenging but still doable, you are working out at a good hard level and are probably burning fat and working your cardio.
If you can barely get out a word or two, or cannot carry on a conversation at all, you are working out at a very intense level and if you are not an athlete, then this is the wrong level for you unless you are in training or doing something like intervals.
Rate of Perceived Exertion
This is similar to the talk test and can easily be performed while you are working out. Many professional trainers use this test frequently. The scale is from 1-10 with one being nearly comatose and on a couch or asleep. You are not making an effort at all.
A rate of three would be light housework or an easy stroll, say through a store.
A rate of four to six is a moderate effort and is where most beginners start out. A rate of seven if pretty hard and is probably only for runners and those in training for events. A rate of eight to ten is unsustainable and is the equivalent of dodging a danger or sprinting for a bus.
Wearing a heart rate monitor or trying to take you heart rate with a stopwatch in hand is another method. If you have a ballpark figure of what your maximum and target heart rates are, you can take your heart rate while still in motion and doing the exercise.
If you use one or more of the methods above to keep a check on your rate during your workouts and at every workout, you can gauge your success and have a more effective fat-burning or cardio workout each time.
If you want to get the most out o your workouts and know how to tell when you are in the workout zone, fat burning zone, and Cardio zone, then you need to be able to calculate your heart rate on the fly. Your general target zone for your maximum heart rate is generally between 50-80% of your maximum heart rate.
If you are just starting out, a beginner to working out, then you should take it slow at first. Start out between 50-60% and slowly, over a few weeks or months, work up your target heart rate to 70-80%. Start out with the lowest intensity you feel good at for about 10 to 20 minutes per session three to four days per week.
Once you reach a certain point, you will be at a midway between workout guru and just new to the concept. In general, you want to keep your target heart rate roughly between 60-70%. You should be perfuming 30 to 45 minutes of cardio or fat burning exercise four to five times per week.
Eventually you will become somewhat fit and start wanting more from your workouts. By this time, your target heart rate should be about 70-80% of your maximum heart rate. You should be performing about six 30-minute sessions of cardio per week OR you could perform three 60-minute session of cardio or fat burning work outs per week and spending the session in between burning even more fat by building muscle strength and endurance.