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Heart Rate and Exercise

Heart Rate and Exercise

Heart Rate and Exercise go hand-in-hand for proper training.  As athletes we are striving to be our best and understanding heart rate is key.  And from time to time we ask ourselves, “how hard should I be training?”  To become stronger we know that we need to push our body to make it stronger. The intensity level must be high enough to overload the cardiovascular system, but not so severe that it over taxes other systems in our body. This is where a knowledge of heart rate and exercise is important.

A heart rate and exercise general rule of thumb says that the intensity of our exercise should be in the range of 55% to 85% of our VO2max.  Here in lies the problem, not too many of us are able to get our VO2max tested.  And for people just starting out on an exercise program they may not be able to really judge the effort that they are exerting. This inability can lead to a lack of improvement, or the opposite; excessive exercise leading to injury.

With VO2max testing pretty much out of the question for most of us, what are our options for determining the correct heart rate and exercise training intensity?  The answer lies within using your Heart Rate, age, and your Maximum Heart Rate, to determine your Target Heart Rate (THR) for training.

Heart Rate and Exercise: Heart Rate

Simply stated, Heart Rate is the number of heartbeats per unit of time, typically expressed as beats per minute (bpm). Heart rate is a major factor that determines the health of your heart.  The conditioned heart beats more slowly because it is pumping more blood with each stroke.  On the other end, training also reduces the maximum heart rate; which is just as important (Int J Sports Med 2008).  At rest the heart is conserving energy by beating slowly and during activity it has built-in protections against beating too fast and resulting in strain or failure.  Exercise and training can help lower the maximum rate, and it also can strengthen the amount of time that you can hold your near-maximum heart rate before fatigue sets in.

In the medical field, doctors use heart rate as a tool to assist them in making diagnosis and to track medical conditions.  In the athletic field, athletes use heart rate and exercise goals as a tool to get the most gains from their training programs.  They do this by training at a particular percentage of their Maximum Heart Rate (MHR) to continually improve their strength and fitness.

Heart Rate and Exercise: Heart Rate: Maximum Heart Rate

What is “max” heart rate?  Max heart rate is the highest number of heart beats per minute when exercising at your all-out maximal potential.  This is the rate where you push your body to its limits.  In a clinical setting the definition sounds much safer as is as follows: MHR is the highest heart rate an individual can safely achieve through exercise stress, and depends on age.

Methods to Determine your Heart Rate and Exercise Intensity

Graded Exercise Test (GXT)

Taking a Graded Exercise Test (GXT)

Determining your Target Heart Rate can be used as a method to measure the intensity of your exercise.  Monitoring your heart rate during exercise is a very accurate account of the metabolic intensity of the exercise.  Heart rate values can be correlated in terms of values that are approximate to VO2max values.  One way to find this equivalent is to take a graded exercise test (GXT), better known as a stress test.  During the test your heart rate is plotted against your VO2max equivalents during each stage of the test.  From this relationship your can determine what your target heart rate is for a give percent of your VO2max.  While this method is very accurate, it is pretty much impractical for most people to have a GXT.  Since taking a GXT is nor a practicality, there are two formulas to determine your training intensity, they are: 1) The Standard Conventional Formula, and 2) The Karvonen Formula.

The Standard Conventional Formula

The standard conventional formula is taking the number 220 and subtracting your age to come up with your Max Heart Rate, and then multiplying that number time the percentage of exercise intensity.  It is based on observations that 70% and 85% of maximal heart rate is equal to approximately 60% and 80% of functional capacity VO2max.  THR range = maximal HR x .70 and .85, where maximal HR = 220 – age.

Karvonen Formula

The Karvonen Formula has been found to be more accurate than just subtracting your age from 220, and multiplying it by the level of intensity of your workout.  The Karvonen Formula takes into account your resting heart rate and uses it to determine your heart rate reserve.  Your Heart Rate Reserve is the difference between Resting Heart Rate and Maximum Heart Rate.  The formula takes into account that as you train, your resting heart rate will change and start to decrease over time.  As your resting heart rate goes down, your heart rate reserve will increase which is a direct reflection of the heart’s increased ability to pump blood.

Using the Karvonen Formula adjusts your Target Heart Rate in such a way that it is a close heart rate approximation of the specific percentage of VO2max that you want to train at.  So, if you want to calculate your Target Heart Rate at an intensity level at 65% of maximal heart rate, it is roughly the same as the heart rate corresponding to training at 65% of your VO2max.

The Karvonen Formula is:

  • 220 – age = Age Adjusted maximum heart rate (AAMHR)
  • AAMHR – Resting Heart Rate = Heart Rate Reserve (HRR)
  • HHR x exercise intensity level between 60-80% + Resting Heart Rate = Target Heart Rate

If you strictly use the standard conventional formula to determine your training heart rate, it will put you well below your capacity to work which will result in a less effective and less efficient workout.

The Standard Conventional Formula vs. Karvonen Formula

Using the data below from myself and my friends I calculated our Target Heart Rates using both methods at perceived levels of exercise intensity of 60%, 70%, and 80%.

Name Age Resting Heart Rate 60% Standard Formula 60% Karvonen Formula 70% Standard Formula 70% Karvonen Formula 80% Standard Formula 80% Karvonen Formula
Andy 43 60 106 130 124 142 142 154
Lina 46 63 104 130 122 141 139 152
Ray 45 65 105 131 123 142 140 153
Marc 40 65 108 134 126 146 144 157
Jane 66 74 92 122 108 130 123 138
Gloria 44 54 106 127 123 139 141 152

As you can see, the standard formula is well below the capacity using the Karvonen Formula.  The average capacity shortfall is as follows: at 60% – 19.5%, at 70% – 13.6%, and at 80% – 8.3%.

Ratings of Perceived Exertion (RPE)

Another way to determine your exercise intensity is by using the Ratings of Perceived Exertion (RPE).  Perceived exertion is based on how hard you feel like your body is working.  Some of the signs used to determine your perceived work are an increased breathing rate, sweating, heart rate, muscle fatigue, etc.  This method is total subjective, but allows you to personally measure your exercise intensity.  One of the most common methods to measure your RPE is using the Borg RPE Scale, developed by the Swedish psychologist Gunnar Borg.  It is based on a 15 point scale:

  • 6 – Very, very light (Rest)
  • 7 – Very, very light (Rest)
  • 8 – Very, very light (Rest)
  • 9 – Very light – gentle walking
  • 10 – Very light – gentle walking
  • 11 – Fairly light
  • 12 – Fairly light
  • 13- Somewhat hard – steady pace
  • 14- Somewhat hard – steady pace
  • 15- Hard
  • 16- Hard
  • 17- Very hard
  • 18- Very hard
  • 19 – Very, very hard
  • 20 – Exhaustion

A high correlation exists between a person’s perceived exertion rating times 10 and the actual heart rate during physical activity; so a person’s exertion rating may provide a fairly good estimate of the actual heart rate during activity (Borg, 1998).  So, if a person has a perceived exertion of 12, then take 12 x 10 = 120.  So, the approximate heart rate is 120 beat per minute.

Using RPE we can take the data above from my friends and myself and determine our RPE for the exercise intensity levels of 60%, 70%, and 80%.  For example

Name Age Resting Heart Rate 60% RPE 60% Karvonen Formula 70% RPE 70% Karvonen Formula 80% RPE 80% Karvonen Formula
Andy 43 60 13 130 14 142 15 154
Lina 46 63 13 130 14 141 15 152
Ray 45 65 13 131 14 142 15 153
Marc 40 65 13 134 15 146 16 157
Jane 66 74 12 122 13 130 14 138
Gloria 44 54 13 127 14 139 15 152

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