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Cardio 3. Calculation of the optimal heart rate for cardio training

Once again, we note that this series of articles is designed for people of middle and old age, with an average and low level of fitness, who want to improve their health through physical cardio training.

Previously, we discussed the importance of cardio training for maintaining overall health and highlighted the significance of monitoring heart rate (HR) to effectively control the level of physical activity. Additionally, it was emphasized that the level of physical activity should be carefully measured and regulated.

As previously mentioned, the level of physical activity is directly correlated with HR. When the activity level increases, so does the HR.

This section will outline practical steps to determine the optimal HR range for effective cardio training.

Sports and scientific research have revealed that training at different HR levels elicits various physiological effects, such as strength development, endurance improvement, and fat burning for energy. To optimize these effects, specific HR intervals or zones have been identified where these outcomes are most pronounced.

In this article, we will adopt the method proposed by Finnish researcher Martti Karvonen to define these intervals.

For the initial calculation of HR intervals, two main parameters are needed:

  • Maximum heart rate – MHR (maximum heart rate)
  • Heart rate at rest – RHR (resting HR)

We will discuss each of these parameters in more detail below. Now we note that the HR intervals are percentages of MHR. Thus, we get a table

Please note that in many articles HR zones are indicated by different colors.

Upon reviewing the table, we can observe that the first and second zones are particularly suitable for warm-up exercises. On the other hand, the second and third zones are ideal for engaging in the main cardio training.

Let’s now analyze the main parameters we need to calculate HR zones.

Calculation of the maximum heart rate – MHR

The first parameter to consider is the maximum heart rate (MHR). This represents the maximum frequency at which the heart functions normally during intense physical exertion. It is important to note that attempting to verify this statement oneself can be dangerous, so it is advised not to do so.

Although the maximum heart rate (MHR) is a somewhat approximate value, it can still be utilized in calculations as it closely approximates the actual values obtained from experimental findings.

There are two main ways to calculate MHR

  1. Calculation by formulas. It’s simple and fast, but less accurate because it’s too average.
  2. Determination in the laboratory on special tests. It is expensive and requires a visit to a special laboratory. It is impossible to do this at home.

The simplest formula for calculating MHR is 220 minus your age. There are some other formulas, but for our purposes, this is good enough.

Finding heart rate at rest – RHR

The second parameter to consider is the resting heart rate (RHR). This represents the number of heartbeats when the body is in a completely relaxed state.

To measure the resting heart rate, it is recommended to do so immediately after waking up, without making significant movements. The most accurate method is to use a chest strap sensor. If the sensor is already in place prior to measurement, it is advisable to lie down and relax for a brief period before taking the reading.

For optimal results, it is recommended to wear the HR sensor prior to going to bed and activate the recording feature. Upon awakening, you can then analyze the recorded data and determine the desired parameter, such as the resting heart rate.

Calculation of HR intervals (zones)

Once we have determined the maximum and resting HR (MHR and RHR), we can proceed to calculate the HR intervals. There are various methods available, and for our purposes, we will utilize the Karvonen method.

One convenient approach is to make use of dedicated calculators. I have created a calculator specifically for this purpose.

Let’s illustrate the calculation process using an example of a 52-year-old man:

  • Calculate the maximum HR (MHR): Subtract the age from 220. In this case, it would be 220 – 52 = 168 beats per minute.
  • Measure the HR at rest (RHR): Take the pulse when the body is completely relaxed. Let’s assume it is 72 beats per minute.
  • Input the obtained data, MHR and RHR, into the calculator I have provided. This calculator will generate the HR values for different zones based on the Karvonen method.

Additional calculations.

While the results obtained thus far can be used, it is worth considering a few additional steps. It should be noted that the first parameter, the maximum HR (MHR), may appear too generalized or averaged in nature.

To illustrate the potential limitations of using a generalized MHR value, let’s imagine a lineup of individuals who are all 52 years old. At one end of this imaginary row, we have a tall and well-trained athlete, while at the other end, we have an overweight individual with posture disorders and possible hypertension, who leads a sedentary lifestyle sitting in an office all day. Surprisingly, according to the MHR calculations, the same value of 168 is assigned to the entire lineup. It is indeed difficult to believe.

Anaerobic threshold

To address this issue, I suggest introducing an additional parameter of HR called the anaerobic threshold (AHRT). The anaerobic threshold represents the point at which there is a shift from aerobic metabolism to anaerobic metabolism during physical exertion.

By referring to Table 1, we can observe that the anaerobic threshold is situated around the transition to zone 4. Considering the calculations we made earlier (as shown in Table 2), we can determine that the individual’s anaerobic threshold HR is approximately 149 beats per minute.

Considering the significant increase in breathing and the difficulty in maintaining long audible speech during the transition to anaerobic metabolism, we can use this observation as a means to experimentally determine the threshold. To do so, follow these steps:

  1. Begin by sitting on a bicycle or going for a walk, gradually increasing your HR to zone 3, approximately reaching an HR of 139 (as indicated in Table 2). At this point, prepare a specific phrase in advance that you will pronounce aloud, clearly, and distinctly. For example…
    But it’s been no bed of roses
    No pleasure cruise
    I consider it a challenge before the whole human race
    And I ain’t gonna lose 
  2. Record your breathing and HR while pronouncing the prepared phrase. If you are able to calmly and clearly articulate the phrase without any interference to your breathing, it indicates that you are still within the aerobic zone. Continue moving, slightly raising your HR, and repeat the phrase once more.
  3. Keep going until you reach a point where the increased breathing starts to interfere with the pronunciation of the phrase. This indicates that you have surpassed the anaerobic threshold and entered the 4th anaerobic zone. Take note of your HR at this point.

As a result of this process, you will have a range of HR values and can identify the point at which interference in pronunciation begins. Step back slightly, reducing the HR by 3-5 beats, and you will obtain the desired value – the Anaerobic Threshold. To validate this determination, repeat the steps outlined above to ensure accuracy.

Let’s assume that as a result of the experiments described above, we obtained a threshold value of 132 beats per minute.

Now, enter the value we just obtained in the ‘Your Anaerobic HR threshold’ field of my calculator (LINK), and it will generate a new table of values (Table 3)..

  • Calculated maximum HR (MHR) –  168 bpm
  • Corrected MHR –  147 bpm
  • HR at rest (RHR) – 72 bpm

Our table has now changed. A third column of corrected HR values will appear in it. It will look like this:

As we observe in the new (right) column, the values have slightly decreased compared to the previous calculations. The modified Maximum HR (MHR) has also changed accordingly. The anaerobic threshold we determined during the experiment now aligns with the transition from zone 3 to zone 4. These adjusted values in the right column now better correspond to the individual training level of a specific person.

Use of obtained data

The data presented in Table 3 are valuable for analyzing and assessing one’s fitness level. They provide a basis for experimentation and offer great opportunities for personal growth. The key aspect is having clear and comprehensive information to guide your training endeavors.

By comparing the data in the two right columns, it becomes evident that the values tend to align more closely as the individual’s fitness level increases. This observation highlights the positive correlation between fitness level and the corresponding HR values.

Determining your fitness level

If the data in the right column is significantly lower than the calculated values, it indicates a lower fitness level. In such cases, it is important to approach cardio training with caution and gradually increase physical activity levels.

If the HR values in the right column are higher than expected, it is advisable to reevaluate the determination of the anaerobic threshold. Double-check if the phrase is being pronounced comfortably and without any signs of strain or breathing difficulties. It is possible that there was an error in the previous assessment. Alternatively, if the HR values remain consistently higher, it could indicate that you are exceptionally well-trained and above average in terms of fitness level. In such cases, the provided guidelines and information may not be as applicable to your specific situation.

Do Not Rush!

Take your time and avoid rushing into intense training. It’s important not to force yourself but rather start at level two, which is the beginning of zone three according to the values in the right column. Gradually progress toward the end of the third zone, keeping your HR within that range. Avoid pushing yourself into the fourth zone, and if you find that happening, reduce the intensity of your workout to bring your HR back to the middle of the third zone.

Keep in mind that as you continue training, your HR indicators, including the anaerobic threshold, may change. It’s recommended to recalculate the data periodically to stay updated. Occasionally, check yourself by pronouncing the phrase as described earlier, and take note of the HR at which you can comfortably say the phrase. Aim to keep your HR slightly below that value for optimal training.

Remember, gradual progression and monitoring of your HR are key to safe and effective cardio training.

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