Updated: 20 September 2008
Cardio-respiratory or aerobic fitness refers to the ability of the heart-lung system to deliver O2 to and remove CO2 from the working skeletal muscles during prolonged exercise activities. The greater this ability, the higher the cardio-respiratory fitness level. A low level of cardio-respiratory fitness is directly related to lack of exercise. Regular exercise is a significant factor in reducing the severity of cardiovascular disease. A regular exercise program leads to adaptive changes in the system to yield a higher cardio-respiratory fitness level. To obtain an adaptive response of the cardio-respiratory system, demands must be made on the system that exceed those normally encountered.
Most experts recommend consideration of four factors to achieve beneficial results from exercise:
A number of methods have been developed to determine the appropriate intensity level. The heart rate reserve or Karvonen method of calculating your target heart rate or training zone is based on your maximal heart rate (MaxHR) and resting pulse (RHR) and considered relatively accurate. Easier calculated but less accurate is the method using only the age specific maximal heart rate. Other methods include the Borg Scale of Perceived Exertion. This method relies purely on your subjective feeling of how hard you think you are working. This is especially helpful when the other methods cant be used, e.g., when the exerciser has a condition that affects heart rate, e.g., takes certain medication or fights a disease causing agent. With a little bit of practice it is surprising how much this scale can correlate with the actual HR computed using one of the other methods. For heart rate calculation during Exercise in the Water, subtract 13% or 17 beats per minute from the Target Heart Rate Zone calculated by above methods, as water temperature, gravity, compression, partial pressure and the dive reflex affect (reduce) heart rate.
- The Type of Exercise - in order for exercise to provide for improvement of the cardio-respiratory system, it must involve large muscle groups, be rhythmical and continuous while providing an adequate but not too great intensity. It must also be enjoyable for adherence (would you rather engage in something you enjoy, or an unpleasant activity?). Examples are walking/jogging, running, bicycling, cross country skiing, swimming, rope skipping, or aerobic movement to music, like Nia, Nia, Nia.....
- Frequency of Exercise - 3 times per week is the minimum required for improvement, 4 to 6 times per week will provide greater improvement.
- Duration of each Exercise Session - is the amount of time during each exercise session that the appropriate intensity is continuously maintained. Minimum is 20 minutes per exercise session. Duration and intensity are dependent upon each other in order to achieve improvement. Duration needs to be increased if lower end intensity levels are chosen within the appropriate range.
- Intensity of the Exercise - is the degree of difficulty. Intensity is the most critical component of the exercise prescription. Choose your desired intensity level according to the five Heart Rate Zones:
- Zone 1 the Healthy Heart Zone: 50 to 60% of Maximum Heart Rate,
appropriate for beginners, for recovery sessions for fitter people, for after lay-off or injury, or when "not really feeling well".
Exercise example: easy walk, easy Nia
- Zone 2 the Temperate Zone: 60 to 70% of Maximum Heart Rate,
moderate, comfortable exercise that burns a high percentage of fat, leads to gain of muscle mass and increase in resting metabolism. Also leads to cardiovascular improvements such as increased size and number of blood vessels and increased size and strength of the heart, which results in higher blood volume pumped with each heartbeat, and an increased ability to deliver oxygen to the muscles. Endorphins ("Pleasure Hormones") are released, resulting in a euphoric feeling of after-exercise bliss.
Exercise example: brisk walk, easy jog, Nia (more mellow, lyrical moves, slower music or smaller range of motion)
- Zone 3 the Aerobic Zone: 70 to 80 % of Maximum Heart Rate,
more intense, less comfortable exercise that requires more effort than above. Continues to burn a high percentage of fat, leads to gain of muscle mass and increase in resting metabolism. Also leads to cardiovascular improvements such as increased size and number of blood vessels and increased size and strength of the heart, which results in higher blood volume pumped with each heartbeat, and an increased ability to deliver oxygen to the muscles. Endorphins ("Pleasure Hormones") are released, resulting in a euphoric feeling of after-exercise bliss.
Exercise example: Step aerobics class, Nia (more energetic, power moves, faster music or larger range of motion)
- Zone 4 the Anaerobic Zone: 80 to 90% of Maximum Heart Rate,
short spurts of very hard, vigorous exercise, improves tolerance to lactic acid and is beneficial for high performance training. However, during anaerobic exercise, the muscles being exercised have insufficient oxygen to meet the demands of the activity, and thus must also use alternate, non-oxygen-dependent and thus non-fat-burning processes to produce energy. Anaerobic exercise uses the phosphagen energy system (can provide maximal muscle power for 8 to 10 seconds) and the glycogen lactic acid system (can, under optimal conditions, provide 1.3 to 1.6 minutes of maximal muscle activity in addition to those 8 to 10 seconds provided by the phosphagen system).
Exercise example: race pace, time trials
- Zone 5 the Redline Zone: 90 to 100% of Maximum Heart Rate,
no health benefits. Near max, near total exhaustion, for the extreme athlete who wishes for a near-death experience.
Exercise example: Sprints to finish line in a race
To figure out your target training zone, determine your true resting heartrate: Three mornings in a row, just after waking up (preferrably without startling alarm), before sitting up or standing up, take your resting pulse for one full minute. When counting beats, start with the first beat as zero: ie., 0-1-2-3-4.... Add all of them together, and divide by 3, to get the average. For most healthy people it should be somewhere around 60 beats per minute.
|Then apply the formula for the Karvonen method:
||so, for example I calculate for myself J thus:|
|(220) - (your age) = MaxHR||220 - 25 = 195 (MaxHR)|
|(MaxHR) - (resting heart rate) = HRReserve||195 - 60 = 135 (HRReserve)|
|(HRR) x (60% to 80%) = recommended training range %
||135 x .6 = 81 (60% training percentage)|
135 x .8 = 108 (80% training percentage)
|(training range %) + (resting heart rate) = (your target training zone)
||81 + 60 = 141 (low end target training zone, in beats per minute)|
108 + 60 = 168 (high target training zone, in beats per minute)
So, my target training zone in beats per minute is between 141 and 168.  Of course, heart rate slows down immediately after cessation of vigorous exercise, so to get a more accurate count, take your pulse only for 6 (or 10) seconds, then multiply by 10 (or 6) to get your heart rate per minute. Remember to start with the first beat as zero: ie. 0-1-2-3-4....
Another way of determining how hard you are working is the Borg Scale of Perceived Exertion. Using your own subjective Rate of Perceived Exertion (RPE) on a scale of 6-20 or a scale of 0-10, you determine how hard you *feel* you are working.
|Original Scale ||Revised Scale|
|6 ||0 - Nothing at all |
|7- Very, very light||0.5 - Very, very weak|
|8 ||1 - Very weak|
|9 - Very light ||2 - Weak|
|10 ||3 - Moderate|
|11 - Fairly light ||4 - Somewhat strong|
|12 ||5 - Strong|
|13 - Somewhat hard ||6|
|14 ||7 - Very strong|
|15 - Hard ||8|
|16 ||9 - Very, very strong|
|17 - Very hard ||10 - * Maximal|
|18 || |
|19 - Very, very hard|| |
|20 || |
Consider that the recommendation is to work out in your aerobic zone, which is, you should not work out too hard (in your anaerobic system). For more detail to this see Chapter: Energy Systems.
Go to the next chapter: The Energy Systems of the Body
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