A commonly used Heart Rate training zone calculation used by many people today is the old (220-age) x intensity level desired = Desired BPM (Beats Per Minute) during an aerobic exercise session. The problem with using this "standard" or generic calculation is it does not take into account the fitness level of the individual and can be as far as 10-12 BPM off. To clarify why this makes a difference is if you take two 30 year old males, one leads a sedentary lifestyle and has a resting heart rate of 90 and you take another 30 year old male that is a marathon runner with a resting heart rate of 50, logic would tell us they would not train at the same working BPM (Beats Per Minute) even if they are both working at 70% of their MHR (Maximum Heart Rate).

The Karvonen Heart Rate Calculator is a much more accurate assessment and is calculated by taking into consideration your Maximum Heart Rate (MHR), Your Age and your Resting Heart Rate (RHR). Within each training zone, subtle physiological effects take place to enhance your fitness. Following these guidelines you will see the most from your exercise program.

Once you have your calculations in hand you then need to decide which training zone is best for what you are wanting to accomplish in your exercise program. Below is a basic breakdown on how the different "exercise zones" use energy produced by your body. Keep in  mind these are standardized zones to help ensure you are not working too hard or not hard enough. In a healthy adult with no outstanding medical conditions there would be no reason to exercise below the 60% threshold.

You will probably recognize the "FAT BURNING ZONE" and the "AEROBIC ZONE" already. These two figures are on almost every piece of cardio equipment on the market today. If you look closely at their charts they use the mostly inaccurate (220-age) X desired percent I talked about earlier and may not fit your fitness level so you could be training at the wrong heart rate level.

You have probably also heard you MUST stay in the fat burning zone or you will use your muscles as energy, burn off all your muscle and not lose fat. Well this in a way, in my opinion, is false. Yes, when you push your heart rate above 70% your body does change its fuel source slightly from using mostly fat but if you think about it this way if you work harder you will use more calories and more calories means more weight loss. An example is, if you work in the 60% range and you burn 100 calories and 60 of those are fat calories that is great you did lose 60 calories of fat but if you push to 70% and you burn 200 calories and 120 of those are fat calories you just burned twice as much fat in the same amount of time using very little change in effort. Now this is not to say more is better because this is not the case but to lose weight you must have a calorie deficit each day (less calories  in, more calories out) so why limit how many calories you are burning by taking a casual stroll at 60%?

Resting Heart Rate
To determine your Resting Heart Rate (RHR) do the following. Find somewhere nice and quiet, lie down and relax. Position a clock where you can clearly see it while still lying down. After 20 minutes, remain where you are and check your pulse/heart rate (beats/min). If you have a heart rate monitor, put it on before you lie down. After the 20 minutes check the output from your monitor, use this value as your RHR.

Keep in mind the heart is a muscle so with regular exercise it will become larger, stronger and become more efficient as it pumps blood through your body. As a result you will find your resting heart rate should get lower over time so you will need to check your RHR on a regular basis (e.g. Monthly).

Below are basic guidelines and should be qualified for your use by your doctor or certified personal trainer to ensure you are working not only efficiently but more importantly safely.

The Energy Efficient or Recovery Zone - 60% to 70%
Training within this zone develops basic endurance and aerobic capacity. All easy recovery cardio training should be completed at a maximum of 70%. Another advantage to training in this zone is that while you are fat burning you could lose weight and you will be allowing your muscles to re-energize with glycogen (muscle fuel), which has been expended during those faster paced workouts.

The Aerobic Zone - 70% to 80%
Training in this zone will develop and strengthen your cardiovascular system. The body's ability to transport oxygen to, and carbon dioxide away from, the working muscles can be developed and improved. As you become more fit and stronger from training in this aerobic zone it will be possible to increase your longer cardiovascular training sessions at up to 75%, so getting the benefits of some fat burning and improved aerobic capacity is key for training in this zone.

The Anaerobic Zone - 80% to 90%
Training in this heart rate zone will develop your lactic acid system. In this zone, your individual Anaerobic Threshold (AT) is found - sometimes referred to the point of deflection (POD). During these higher heart rates, the amount of fat being utilized as the main source of energy is greatly reduced and glycogen stored in the muscle is predominantly used. One of the by-products of burning this glycogen is lactic acid. There is a point at which the body can no longer remove the lactic acid from the working muscles quickly enough. This is your Anaerobic Threshold (AT). Through the correct training, it is possible to delay the AT by being able to increase your ability to manage the lactic acid for a longer period of time or by pushing the AT higher.

The Red Line Zone 90% to 100%
Training in this zone will only be possible for short periods (cardio bursts). It effectively trains your fast twitch muscle fibers and helps to develop speed. This zone is reserved for interval running and only the very fit are able to train effectively within this higher heart rate zone.

Heart rate variations for a given intensity
A reduction in heart rate for a given intensity is usually due to an improvement in fitness but a number of other factors might explain why heart rates can vary for a given intensity:

• Dehydration can increase the heart rate by up to 7.5%
• Heat and humidity can increase the heart rate by 10 beats per minute
• Altitude can increase the heart rate by 10 to 20%, even when acclimatized.
• Biological variation can mean the heart rate varies from day to day by 2 to 4 beats/minute

Use This Karvonen Heart Rate Calculator to determine your exercise zone