NASM essentials of sports performance training
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NASM essentials of sports performance training

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of capacity) are often displayed on various
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pieces of exercise equipment. While the intent is educational, the application is somewhat
These zones were derived from the respiratory quotient (RQ). The RQ is simply the amount
of carbon dioxide (CO2) expired divided by the amount of oxygen (O2) consumed, measured
during rest or at steady state of exercise using a metabolic analyzer. When VO2 and VCO2 are
measured and the RQ calculated during steady state exercise, the relative contribution of fats and
carbohydrates as fuel sources can be determined. RQ is not used as a statement of fuel usage dur-
ing progressive tasks like a VO2 max test. In exhaustive, progressive tests, the RQ is used as con-
firmation of effort. An RQ of 1.1 or better is generally accepted as one factor in verifying an ex-
haustive effort.
As Table 5.3 illustrates, the body is able to derive the highest percentage of its energy from
fat when it has an RQ of 0.71 (1,2). The so-called \u201cfat burning\u201d zone is achieved through low
intensity aerobic exercise, when the body mainly uses fat as fuel. At this low intensity, the activated
muscle fibers, mostly slow twitch fibers, are able to get a large percentage of their energy from the
aerobic metabolism of stored fats.
Logic might suggest that in order to burn the most calories from fat, an athlete should exer-
cise at an intensity that allows for a low RQ, nearing 0.71. However, the only time the body is
truly at an RQ of 0.71 is when it is at a state of complete, fasted rest. It is rare for anyone to be able
to run at an RQ of 0.71. Therefore, although it is possible for a person to be in the \u201cfat burning
zone,\u201d it is unlikely that most people will be running at an RQ of 0.71. During low intensity
exercise, a higher percentage of fat may be used, but the overall caloric expenditure for the same
duration exercise will also be low. An increase in intensity will increase the overall caloric expen-
diture as well as the total amount of energy from fat as a fuel. 
As the intensity of exercise increases, the RQ will rise. During moderate exercise (e.g., about
65% of maximum heart rate), such as a fast walk or a light jog, the RQ will rise to 0.80\u20130.90
(1,2). The mixture of carbohydrates and fat as a fuel is close to equal at an RQ of 0.85; above
that, carbohydrates are the predominant energy source while below that, fats are the predomi-
nant energy source. The calories per minute (intensity) is greater and the total caloric expendi-
ture is greater if the duration of exercise remains the same. Thus, although the percentage of
calories that are coming from fat has decreased with increasing intensity, the total caloric ex-
penditure has increased, so the total fat calories burned will be the same (or perhaps even
greater) than when the exercise was done at a lower intensity. There are simple methods in the
The amount of CO2 expired
divided by the amount of O2
consumed, measured during rest
or at steady state of exercise.
RER and Percentage of Calories from Fats and Carbohydrates
Percentage of Calories Derived Percentage of Calories
RER from Carbohydrates Derived from Fats
0.71 0.0 100.0
0.75 15.6 84.4
0.80 33.4 66.6
0.85 50.7 49.3
0.90 67.5 32.5
0.95 84.0 16.0
1.00 100.0 0.0
RQ versus RER
Although respiratory quotient (RQ) and respiratory exchange ratio (RER) are often used interchange-
ably, they are different. RQ is the ratio of CO2 produced to O2 consumed as measured across the
lungs.The RER is the same calculation measured at the cellular level. The assumption is that what
is measured at the lungs is representative of the exchange across the cell. Although this is a
reasonable assumption for most steady state conditions, in some situations there is a disconnect.
While most people use these terms synonymously, realize there is a difference.
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laboratory that use the RQ and oxygen consumption to determine the actual calories per minute
and the proportion of calories that come from fat and carbohydrates. 
An RQ of 0.80\u20130.90 is a great zone to work within (verified by the athlete using prescribed
heart rate monitors provided by the consulting Sports Performance Professional). This RQ range
can be used for a beginning or deconditioned athlete to improve the blood\u2019s capability of deliv-
ering oxygen and removing waste. With regular training, the heart increases its cardiac output,
blood volume increases, and total peripheral resistance to blood flow decreases allowing blood a
less restricted path to the cells. The result is a greater flow of oxygen to a greater number of cells
throughout the body, which helps the muscle cells and the cardiorespiratory system work more
From this point on, this chapter will refer to an RQ of 0.80\u20130.90 (or, approximately 65\u201375% of
maximum heart rate) as \u201cZone 1\u201d although many people know this as the so-called \u201cfat burning
zone.\u201d Some may also refer to this as a \u201ccardio base zone\u201d or \u201crecovery zone\u201d (the intensity used
between interval work bouts).
Athletes that train in this zone without variation will initially improve their oxygen con-
sumption, but in the absence of further overload will quickly plateau in their training. When this
occurs, weight loss is slowed (or sometimes ceases). If Zone 1 is maintained, the only solution to
end the plateau is to keep increasing the training duration, frequency, or both. Increasing inten-
sity will place a new stress to the cardiorespiratory system to adapt to (enhancement in car-
diorespiratory efficiency, increases in caloric expenditure) without adding more time or fre-
quency to the program.
Exercise at an intensity that results in an RQ of 0.9\u20131.0 would be considered Zone 2, which cor-
responds to about 80\u201385% of maximum heart rate. Some athletes may mistakenly think that per-
forming higher intensity (or, \u201ccardio zone,\u201d not to be confused with the \u201ccardio base zone\u201d of
Zone 1 above) workouts every time is preferred.
Zone 2 is close to the anaerobic threshold (which some say occurs when the RQ is around
1.0 during steady state exercise). In this zone, the body can no longer produce enough energy
for the working muscles solely through aerobic metabolism, so the fraction of energy pro-
duction from anaerobic metabolism increases. The higher the intensity the body can train at
while remaining aerobic, the greater the number of calories burned from fat and the less lac-
tic acid is produced. Thus, one of the outcomes of cardiorespiratory training is an increased
anaerobic threshold and greater reliance on fat as a fuel at progressively higher percentages of
the maximum.
For weight loss, the bottom line is to burn more calories than are consumed. By referring
back to Table 5.3, it is easy to see that at higher intensities of exercise, such as at RQ values ap-
proaching 1.0, the body is using predominantly carbohydrates for fuel and the caloric expendi-
ture per minute is high. Because total caloric expenditure is the most important issue, this ap-
proach is an effective one for weight loss if that is the athlete\u2019s goal.
As with Zone 1, staying in Zone 2 will also lead to a plateau for most athletes. Remember, to
improve the athlete\u2019s fitness level, the body needs to be progressively overloaded. 
A true \u201chigh intensity\u201d workout would be considered going to an RQ \ufffd 1.0 (approximately 90%
of maximum heart rate), which could consist of several short 30\u201360 second sprints. This overload
requires training close to, or at, peak exertion, which would be in Zone 3. 
Most athletes may exercise in Zone