Getting Into The Training Zone

exercise girl on back

By John Kain

We all have to do our cardio even though some of us like it more than others, personally I prefer a mix of different training methods and types of cardio to keep my mind occupied and normally in smaller, more intense chunks. Some people prefer to switch off and relax with long treadmill or road running sessions or lose themselves in their music on a bike or cross trainer.

Whichever method you choose, one important aspect is the intensity of the workout as this will have significantly different effects on the body. So before you start your cardio session or a new training programme it is well worthwhile thinking about what your end goal is.

Once that has been established, investing in a heart rate monitor would be a good idea, especially if you are new to training and unsure about what easy, moderate or intense exercise feels like.

Before you start training it is necessary to find your maximum heart rate, this is a fairly standardised calculation that is fairly accurate for most people and is based on the fact that as we get older our body’s maximum heart rate slowly comes down at a rate of about 1 beat per year. From numerous studies the relationship is actually a very linear one, and it is a very trustworthy calculation and is shown below.

220 – Age = Maximum Heart Rate (e.g. for a 40 year old, 220 – 40 = 180BPM max HR)

This is your starting point to calculate your training zones, whether you are a man or woman. This is also the basis for the numbers you see on a cardio machine that show you the CARDIO zone or FAT BURNING zone.

Like I said it’s a very reliable calculation to predict your max heart rate, but what it doesn’t take into account is your resting heart rate which could be very different between different individuals. By incorporating the HEART RATE RESERVE into the equation, in theory a more accurate training zone can be determined. Heart rate reserve is simply the difference between your maximum heart rate and your resting heart rate.


Heart rate has a relation with oxygen consumption especially when intensities rise to reach ranges between 50-90% VO2 max (VO2 max refers to the maximum amount of oxygen that an individual can utilise during intense or maximal exercise. It is measured as millilitres of oxygen used in one minute per kilogram of body weight).

Thus exercise intensity as it is normally prescribed is the percentage of maximum heart rate (calculated using the formula 220 – age) so;

  • A 30 year old who has a maximum heart rate of 190bpm thus may want to train at 75% of his intensity at 143bpm.
  • The formula “220 – age” makes no allowances for variations in resting heart rate among individuals.
  • The formula for heart rate reserve allows a better target heart rate to be determined for optimum training capacity based on both maximum and resting heart rate.

Calculating Target Heart Rate with Karvonen Formula

220 – age = maximum heart rate Maximum heart rate – resting heart rate = heart rate reserve (Heart rate reserve X training%) + resting heart rate

Comparing the two formulas

To compare the two formulas, an example of a 45 year old man who has a resting heart rate of 60 beats per minute and who wants to train at 70% maximum is assessed. Target heart rate in this individual:- 220 – 45 = 175 beats per minute. This is the maximum heart rate.

According to Karvonen formula

(115 x 0.7) + 60 = 140.5 Thus 140.5 beats per minute is the target heart rate using this method. Using the traditional 220 minus age formula this same person would have a target heart rate of (220-45 X 0.7) or 122.5

You can see from the above comparison that there can be quite a large disparity between the two methods, I personally believe the Heart Rate Reserve to be more accurate and this figure will almost always be higher than the 220 – age formula and this is the one I use.


Now we know our max heart rate and our heart rate reserve percentages we can be sure we are training at the correct intensity for the desired effect. But what is it that happens at the different training intensities that is so important? Well the body reacts differently depending on the demands placed upon it and at the different training zones there are different physiological factors that are going to be improved.

You may have seen FAT BURNING zones on machines, and these can be a little misleading. Anything we do could be described as fat burning from sitting around doing nothing to sprinting. What the fat burning zone tends to mean is that at that particular intensity the primary energy source (once you have warmed up and fat has started to be metabolised, typically 15-20 minutes) comes from fat.

As the intensity increases, fat is still used but glycogen, the stored form of carbohydrates, is used in greater amounts to fuel the exercise, so the relative amounts of the different fuel sources changes from mainly fat to mainly glycogen. As intensity increases further, a greater amount of glycogen is used which decreases the relative amount of fat being burned (even though it may well be the same amount as was used in the fat burning zone). Other physiological factors are shown below at the different intensities.

MODERATE  55-70%

  • Increases utilisation of fat as a fuel
  • Increases number and size of mitochondria in muscles (these are the power houses of the cells taking in fuel and nutrients and producing energy)
  • Increases muscle capillary density

FITNESS  70-80%

  • Increases slow twitch fibre recruitment (slow twitch are the endurance muscles)
  • Improves oxygen transport
  • Increased efficiency of glycogen utilisation
  • Increases aerobic enzymes (these help to break down fuel for energy more efficiently)


  • Introduces fast twitch fibre recruitment (power or strength muscles used in sprinting etc.)
  • Increased efficiency of glycogen utilisation in the presence of little or no oxygen, this will increase the lactic acid tolerance of the body
  • Improved clearance of lactic acid from the muscles
  • Increased anaerobic threshold (this is the point at which the body can no longer remove the lactic acid from the working muscles quickly enough


  • Improved fast twitch fibre recruitment which should in turn increase the speed at which you can run etc.
  • Increased anaerobic enzymes
  • Increased VO2 Max (increased amount of oxygen taken up and available to use at maximum intensity)


So now you know the zones and the effects they have on the body you know where to train to achieve your goal whatever it may be. For more information talk to one of our trainers.


About John

John has been involved in fitness, one way or another for over 20 years and has a wide range of experience and knowledge in playing and coaching football, instructing clients in resistance training, preparing clients for endurance events and instructing a number of different classes including circuit training, spinning and his own personal favourite, high intensity interval training. He holds qualifications in personal training, nutrition advice, sports conditioning, supple strength, exercise for older adults and exercise referral, all gained through YMCA Fitness Industry Training, one of the UK’s leading training providers. Whether your goals are to lose weight, increase your level of fitness, get in shape for a special event or just to take the first steps towards a more active and healthy lifestyle, then John can help. Once we have established your goals, he will write a safe, effective and progressive programme that is designed specifically for you. Novice to athlete, inclusive of all abilities and ages John will inspire you to achieve your fitness goals.

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