Chapter 3 – Cardiorespiratory Fitness
Intensity may be the most important aspect of the FITT principle. Engaging in a “cardio” program that does not stress the CR system to the recommended levels will be ineffective. Engaging in a program that overstresses the system can lead to injury and pose unnecessary risks. So how do you know if you are in the right range?
Heart rate is one of the best ways to measure effort level. Walking and jogging increase a person’s heart rate. Based on the function of the heart, this is no surprise. The heart rate directly correlates with the amount of oxygen being taken in by the lungs. As activity increases in intensity, oxygen demands increase and so does heart rate.
Because of this relationship, heart rate can be used in the design of an effective walking and jogging program by creating target heart rate zones. Heart rate zones represent an intensity range—a low end heart rate and a high end rate—within which a person’s heart rate would fall during a walking or jogging session.
The first step in determining your target heart rate (THR), is to determine your maximum heart rate (MHR), both measured in beats per minute (bpm). Generally, MHR is estimated to be your age subtracted from 220 beats per minute. In other words, your heart rate should theoretically stop increasing once it reaches the calculated maximum. While helpful, it is not uncommon to see variances in the laboratory tested maximum heart rate versus the calculated method.
The next step in calculating THR is to calculate a specific percentage of your MHR. This is done using two different methods. Keep in mind, finding the THR is the objective in both methods, even though slightly different numbers are used.
The first method, called Max Heart Rate Method, is more commonly used.
Max Heart Rate Method
- Calculate MHR;
MHR = 220 – age. - Calculate high and low THR by plugging in a percentage range. In this example, 60 and 80% are being used.
MHR x .60 = THRLow
MHR x .80 =THRHigh - The resulting low and high THR numbers represent the range, or target intensity.
The target intensity signifies an optimal training zone for that particular walking or jogging session. By keeping the heart rate within that range, you will drive adaptation specific to that intensity. By using real, but random numbers, and plugging them into the above equation this becomes apparent.
Female, aged 20:
- MHR = 220 -20
MHR = 200 bpm; - THRlow = 200 x .60
THRlow = 120 bpm
THRhigh =200 x .80
THRhigh = 160 bpm - THR = 120 – 160 bpm
To achieve her self-established goals, the female in the example above will need to stay within the range of 120 and 160 bpm. If her efforts are intense enough that she begins to exceed 160 bpm during her session, or easy enough that her heart rate falls below 120 bpm, she would need to change her intensity mid-session to get the optimal results.
The Karvonen Formula or Heart Rate Reserve Method
- Calculate MHR; MHR = 220 – age.
- Determine your resting heart rate