When designing a four zone model for cardiorespiratory training what range of intensity defines zone two?

calendar_today February 28, 2013

Establishing your Heart Rate Training Zones

So you have been going to the gym 3 times a week forever but nothing seems to be changing! Sound familiar? Have you ever thought that you might be wasting your time? Well if you are working at the right intensities you are guaranteed to get the benefit. But I wonder how many people really understand what is the right intensity for them and how do they find it. In this article, I discuss the concept and procedure for you to determine your own training zones to maximise your time spent exercising. Working smart not hard will get you results.

What is a Training Zone

A heart rate training zone is a range that defines the upper and lower limits of a training intensity . The values are expressed as a percentage of maximum heart rate (for example, 70% of HRmax), and the range is based on (1) the metabolic systems in your body that fuel your muscles during exercise, and (2) how hard you want to train. There are different schools of thought on how many zones there are. We will work on the principle that there are 5 –

Fitness Training Zone 1(50 – 60% of MHR) – The lowest level you can exercise in and still increase your fitness levels. This is ideal for beginners or people who have not exercised for a long period of time. This Fitness Training Zone can be for just improving your overall health or it can also be used as a recovery fitness zone for people who are over-training and need to take a break. This mode is very aerobic so is good for people who want to lose weight as the main source of fuel used by the body is fat stores.

Fitness Training Zone 2 (60 – 70% of MHR) – This is the zone where the heart begins to benefit. The heart will be over worked and therefore grow back bigger and stronger becoming more efficient and improving the hearts ability to pump blood and improve the muscle cells ability to utilize oxygen. In this zone stored body fat is the primary source of energy utilized hence this zone is referred to as the “weight management zone” or “fat burning zone”. This is a good Fitness Training Zone for long slow distance exercise as the body becomes more efficient at feeding the working muscles with fat as the main fuel source.

Fitness Training Zone 3 (70 – 80% of MHR) – This Fitness Training Zone is the most effective for overall cardiovascular fitness and is often called the “aerobic zone” or “target heart rate zone”. This is the optimal fitness training zone to workout in to increase your cardio-respiratory capacity or the body’s ability to transport oxygenated blood to the muscle cells and carbon dioxide away from the cells. After a while you will be able to cover more distance during workouts in less time. Your body will burn less glucose and more stored fat as fuel thereby working more efficiently. This Fitness Training Zone is also effective for increasing overall muscle strength.

Fitness Training Zone 4 (80 – 90% of MHR)(85-90%= Anaerobic Threshold) – This level is where you cross over from aerobic training to anaerobic training which is called the anaerobic threshold or AT. This is the point where the body cannot effectively remove lactic acid from the working muscles quickly enough. Lactic Acid is a by product of glycogen consumption by the working muscles. e.g. The body is predominantly using carbohydrates as its fuel source.
This Fitness Training Zone is primarily for people who want to increase their performance levels. You would characterise this zone as hard. During this Fitness Training Zone your muscles become tired, your breathing becomes heavy and you will become fatigued. The benefit of training in this zone is you can increase your body’s ability to tolerate and deal with lactic acid for a longer period of time as the enzymes in your muscles responsible for anaerobic metabolism are increased. For competitors it is good to know your anaerobic threshold as many fit athletes can compete at or about their anaerobic threshold.

Fitness Training Zone 5(90 – 100% of MHR)(VO2 Max) – You will only be able to train in this Fitness Zone for short periods of time. You should not train at this level unless you are very fit. In this zone lactic acid develops very quickly as you are operating with oxygen debt to the muscles. Training in this zone increases your fast twitch muscle fibres which ultimately will help increase speed. You will not be able to stay at this level very long and should be used primarily in interval training.

As stated above the primary fuel during aerobic and anaerobic training is fat and carbohydrate, respectively, but it is very important to understand that both fuels are burned simultaneously at virtually all levels of exercise; it is not just one fuel or the other, except at the very highest intensities (close to 100% of HRmax). Resistance exercise and sprinting are examples of anaerobic training, whereas walking and jogging are typically considered aerobic, although you could walk or jog fast enough to make it anaerobic. It’s likely that you are working anaerobically (above 85%) if you’re out of breath during a workout and working aerobically (less than 85%) if you’re only slightly out of breath.

What Range Should I Train At?

Most people train within an aerobic exercise training zone (40% to 85% of HRmax). Aerobic capacity (endurance) will improve faster if you train closer to 85% than if you train at 65%, but some individuals don’t have the capacity to start training at 85%, or they simply prefer to start training at lower values and gradually increase the intensity over the time. Some individuals may even need to start at levels as low as 40% or 50%, depending on their age, level of fitness, or body weight. But the level that you start at isn’t all that relevant. What matters most is that you get started, and then over time, as your endurance improves, you can gradually increase the intensity.

The body accommodates to both low and high-intensity workouts by increasing the activity of respiratory enzymes and other biochemical reactions in the muscles. Anaerobic training-like intervals, fartlek and High Intensity Interval Training (HIIT) are helpful if you want to improve your time or perform optimally in an event like a 10K run or a 50-mile bike ride because the training prepares your body for the specific anaerobic demands of the event (like when you have to sprint or climb a hill). This type of training, called “specificity of training,” is effective because it mimics the type of exertion experienced during the event.

On the other hand, if health and general levels of fitness are the goal, and not performance in a road race, then there’s no need to train anaerobically unless you like to push. Instead, substantial gains in health and fitness can be accrued by aerobic training between 40% and 85% of HRmax. Volumes of research prove this.

A traditional method of aerobic training is to start at the low end of the aerobic training range, say 50% or 60%, and as training continues and the heart and muscles adapt to the challenge, the intensity is progressively increased. For example, a sedentary individual might start at 60% of HRmax and remain at that level for four weeks, and then during the fifth week increase the intensity to 65% (increases of 10% of intensity and/or duration is the standard recommendation). Again, the body accommodates to the work over time, and when higher levels of fitness are desired, the intensity needs to be increased. Training heart rate zones offer a quantifiable method of guiding workouts and determining exercise intensity.

Fat Burning vs. Cardio Mode?

Perhaps no other training “technique” is more gimmicky and misleading than the “fat burning” and “cardio” modes on the control panels of exercise equipment. They are based on the biology that at lower levels of exertion a higher percentage of fat is burned compared to carbohydrate. That’s because:

1. Fat is denser fuel than carbohydrate (9 calories per gram vs. 4 calories).

2. It takes more oxygen to burn fat than carbohydrate because fat is denser.

3. At lower levels of exertion, you presumably breathe in and deliver more oxygen to the muscles to burn fat.

All of the above may be true given the right circumstances, but there are problems with it when it comes to real world exercise scenarios. First off, lots of fat is burned at all intensities within the aerobic training zone. Secondly, the terminology “fat burning” and “cardio” can confuse individuals into thinking that fat is burned only during exercise in “fat burning” mode and that no fat is burned in “cardio” mode. The fact is that you burn fat during both modes. But the major problem is that the fat-burning mode is typically too slow a workout for many people to maximize benefits. In fact, at the end of a fat-burning workout, you could end up burning fewer calories and less total fat than during a cardio-mode workout. Here’s an example of what I mean.

Suppose a 150 lb moderately fit man walks on the treadmill for 60 minutes at 3.0 mph in his “fat burning zone” that’s 300 calories for a 150-pound man (a 150-pound man burns approximate 100 calories per mile when he walks). Since this man is moderately fit, he will burn approximately 60% of the calories from fat (180 calories) and 40% from carbohydrate (120 calories).

Now let’s say the same 150-pound man walks on the treadmill for 60 minutes at 4.0 mph in his “cardio zone”. That’s 400 calories burned, with approximately 50% of the calories from fat (200 calories) and 50% from carbohydrate (200 calories). The percent of fat burned may be less at 4.0 mph than 3.0 mph because the exertion is higher and so theoretically less oxygen is delivered to the muscles.

If you examine the example carefully, you will notice that at the slower fat-burning mode the man does indeed burn a higher percentage of fat compared to cardio mode (60% v. 50%), but in cardio mode, he burns more total calories (400 v. 300) and more total fat (200 calories v. 180 calories). My suggestion is to ignore the fat burning zone (unless you want a less intense workout). You’re not going to burn more fat in this zone than in cardio zone, and it could end up being an inefficient use of your time. I suggest training as hard as you comfortably can without risking injury so that you maximize the calorie and fat burn and gain the overall cardiorespiratory training effect.

Calculating a Target Heart Rate Zone

Most Heart Rate Zone predictions use complex maths and equations to calculate your zones. The maths is often centred on a predicted maximum heart rate. To actually find your maximum heart rate you would need to train to maximum exertion, i.e. to you physically couldn’t go any further or harder often causing collapsing and vomiting. We wouldn’t recommend you attempt this but also wouldn’t recommend relying on a predicted maximal heart rate that is focused on your age. We all know that everyone is different and no two 40 year olds will have the same heart, so why use age as a measure for your maximal heart rate?

You will see people predicting your maximal heart rate as 220 – age, or

FOR FIT WOMEN (in beats per minute): MAX HR = 211 – (YOUR AGE/2)
FOR FIT MEN: (in beats per minute) MAX HR = 205 – (YOUR AGE/2)

There are even more complicated versions and equations out there. The truth is you don’t need to know your maximal heart rate to calculate your zones.

Errors in Predicting Maximum Heart Rate

Calculating target ranges in individuals over age 40 can be inaccurate because of errors in estimating HRmax due to considerable heart rate variability in older adults. This means that the popular equation to estimate HRmax, “220-age”, may not be accurate in individuals older than 40 years. The error is probably due to the origin of the equation which was derived from volunteers who were most likely not representative of the general population.

In an important study published in The Journal of the American College of Cardiology in 2001, researchers examined data from 351 studies (18,712 subjects) and determined that the “220-age” equation underestimates maximum heart rate in older adults (the older the individual the more the error).

Technology

However, everyone is different and it is important to understand your own heart and what it can do. To establish you own zones, it is recommended you purchase a heart rate monitor; alternatively most gyms will have cardio equipment that can measure your heart rate through touching sensors on the handles of a bike or cross-trainer. This method is not 100% accurate however it will allow you to calculate a zone to give you benefit, especially if you use the same equipment periodically.

Heart rate monitors are devices that measure heart rate in real time. They have grown wildly in popularity over the past 10 years partly due to the miniaturisation and accuracy of computer chips. Many athletes use heart rate monitors during their workouts to determine if they are in the proper training zone. But heart rate monitors aren’t just for elite athletes. I recommend a heart rate monitor if you like gadgets or think you might like the heart rate data and real-time feedback from your body that these devices provide. The standard design is a strap with a transmitter that you wear around your chest and a wristwatch with a receiver. The chest transmitter detects your heart rate during exercise and wirelessly sends the signal to the wristwatch display for you to see. You can purchase all the bells and whistles with functions like downloading the entire workout to your computer or alarms that let you know when you go too high or too low in your training zone, or you can go minimalist and purchase the basic model that just reads your heart rate. Nike, Polar, and Garmin are just three reputable companies that manufacture heart rate monitors. You can find recommended heart rate monitors at www.nltraining.co.uk/shop.

Perceived Exertion

Heart rate monitoring and training zones aren’t for everyone. But don’t worry, you can still get a great workout and gain all the benefits of exercise. All you need to do is listen to your body. You’re working out if you feel your heart pumping and you’re slightly out of breath. You can also use the Borg Scale of Perceived Exertion (RPE) to measure intensity. Simply select the number from below that best describes your level of exertion.

6 No exertion at all
7
7.5 Extremely light
8
9 Very light
10
11 Light
12
13 Somewhat hard
14
15 Hard (heavy)
16
17 Very hard
18
19 Extremely hard
20 Maximal exertion

An exertion level from 13-14 will get you to the middle of your aerobic training zone.

Using a combination of your Heart rate and RPE it is possible to calculate your heart rate zones very accurately without the use of assumptive equations. Establishing your heart rate zones this way can also be fun and let you understand your body a lot more.

Accurately calculate your Heart Rate Training Zones

Firstly select a piece of exercise apparatus, e.g. a bike or cross-trainer. You will need to work through a range of exercise intensities so be prepared to work yourself hard. There are many variables on a piece of equipment – speed, incline, resistance, etc. You will need to keep them all constant through the test except one. It is recommended that you keep the speed constant, so RPM on a bike or cross-trainer needs to be set at a comfortable level to start then maintained throughout. You can then use resistance to vary the workout intensity. Undertake a 6-8 gradual progressive warm up, starting very easy increase the resistance slowly at 2 minute intervals. At the end of the workout you should feel about a 12 on the scale of perceived exertion. From here you will need to record your heart rate at a range of different resistances that give you different perceived exertions. If possible have a friend or Personal Trainer record your heart rates while you are exercising. Record the resistance, RPE and your heart rate at 2 minute intervals (use the example table below) Remember to keep the level the same for 2 minute intervals to ensure your heart rate plateaus against the resistance then record your heart rate and you level of perceived exertion.

You can then plot your heart rates against the RPE scale to give you your actual zones.  See the working example below.

Joe is 40, his maximal heart rate would traditionally be calculated as 220-40=180. However in reality it may be a lot higher or lower. His zones would be calculated as

When undertaking his own tests Joe uses a bike and records his exercise below –

Notice that Joe doesn’t work in Zone 5, this is really only for serious athletes in specific training. Exercising at this intensity can be dangerous if not supervised.

Joe then plots his results against the RPE in the table below producing his accurate heart rate training zones

Joe’s heart rate zones are therefore higher than predicted. Had Joe not completed this method of establishing his heart rate zones he would have been exercising at too low an intensity and missed out on several key benefits to exercise. Arguably it would take him a lot longer to reach his goals as well.

Summary

Heart rate training zones and heart rate monitoring is:

1. helpful for individuals who want to maximise the benefit from their exercise. Working efficiently to achieve your goals

2. real-time feedback for individuals who like to know how their body responds to exercise, and

3. Important data for athletes who want to get their intervals right.

But even if you never get hooked on the idea of a training zone, you can still get a great workout by listening to your body or using a scale like the RPE. The important point is to get out there and move no matter how you monitor your workout,

New Life Training typically uses High Intensity Interval Training (HIIT) with their workouts to ensure maximum benefit from your Personal Training sessions. We use Heart Rate Monitors provided to each Personal Training client to ensure you maximise the benefit from your workouts and don’t waste your time when your train!

If you would like to establish your own heart rate training zones or would like to know more about how to train at the right intensity for you please call New Life Training on 07771 985015.

What range of intensity defines Zone 2?

What percentage of predicted heart rate max is used in Zone 2 of cardiorespiratory training?

What is the intended outcome of Stage 2 training?

What RPE range on a scale of 1 to 10 aligns with training in Zone 2?