LAB V
ANAEROBIC METABOLISM
Reminder: In this lab, all healthy students who are able to do so, will be performing
high intensity exercise. If you, or your physician, feel that your health might be
compromised by performing high intensity exercise, then you should not serve as a subject.
We have now thoroughly covered aerobic metabolism and some of the general principles
of anaerobic metabolism. In this lab we will direct our attention principally to evaluating
anaerobic metabolism. The term anaerobic literally means without molecular oxygen or
occurring in the absence of molecular oxygen. Anaerobic metabolism is critical and necessary in
exercise when the body's energy demands exceed the body’s ability to produce ATP aerobically.
However, if a cell is using anaerobic metabolism, it does not necessarily mean that the cell is
lacking oxygen. Anaerobic metabolism simply means that ATP is being produced by nonaerobic processes. For example, red blood cells use exclusively anaerobic metabolism to
produce ATP, even though there is plenty of oxygen in the cell. The reason why red blood cells
are dependent on anaerobic metabolism is that they lack mitochondria, which are necessary for
the aerobic production of ATP. It is a common misconception students, that cells only use
anaerobic metabolism if they don’t have enough oxygen. It is true that anaerobic metabolism
can be used if the cell is lacking oxygen, but during exercise, a number of studies have
demonstrated that anaerobic metabolism occurs, even though there is sufficient oxygen for the
mitochondria to produce ATP aerobically. So, why do cells use anaerobic metabolism, which is
less efficient, if there is enough oxygen in the cells?
Cells use anaerobic metabolism when the ATP demands of the cell exceed the rate at
which aerobic metabolism is producing ATP. While anaerobic metabolism is less efficient at
ATP production than aerobic metabolism (e.g. you get fewer ATP per glucose molecule using
anaerobic glycolysis compared to aerobic glycolysis), both major anaerobic energy systems are
capable of producing ATP much faster than aerobic metabolism. During high intensity exercise
aerobic metabolism is simply not producing ATP fast enough to meet the cell's ATP demands.
That is why anaerobic metabolism is required during high intensity exercise. Anaerobic
metabolism is also necessary at the beginning of exercise (even if it is low intensity) when the
aerobic energy systems are not "up to full speed" yet.
As previously discussed, there are two major anaerobic energy systems that allow
skeletal muscle reveals to rapidly produce ATP; the ATP-PC and Lactic Acid systems. You will
recall that the ATP-PC system provides ATP very rapidly but can only do so for short periods of
time (5 to 10 seconds) due to the limited amount of stored ATP and PC. The Lactic Acid system
(anaerobic glycolysis) also provides ATP rapidly but is limited to around 90 seconds due to the
accumulation of lactate in the muscle and blood.
While the study of aerobic metabolism is made fairly easy by assessing oxygen
consumption, the study of the anaerobic energy systems is considerably more difficult. Some
invasive and non-invasive evaluation techniques have been utilized, but there is a question of
accuracy of measurement for all of them. Invasive techniques of obtaining venous blood
samples and muscle biopsies provide the most direct means of assessing the amount of anaerobic
energy during exercise. For example, the amount of PC used during an anaerobic exercise bout
can be determined from muscle samples (biopsies) obtained immediately following exercise.
However, since the rate of PC replenishment is so rapid the accuracy of this method has been
questioned. Recent studies using nuclear magnetic resonance spectroscopy show promise as a
non invasive method of determining muscle ATP-PC levels and use, but more research is
needed. For these reasons, many of the methods used to assess anaerobic energy production are
Lab V - 1
imperfect and are based on indirect measurements that require us to make assumption that may
or may not always be 100% correct. Today we will be studying several classic measurements
related to anaerobic metabolism that are widely used. We will be assessing blood lactates during
and following exercise and evaluating the "anaerobic threshold". We will also perform a few
tests that are routinely used to asses anaerobic power and capacity. Read and review appendix
pages 55 to 62 while reading and completing this lab.
Blood Lactate
At rest, most of our body’s energy needs are met via aerobic metabolic pathways.
However, there is always some amount of anaerobic metabolism occurring. Much of this is via
anaerobic glycolysis and, is therefore associated with the production of lactic acid. Thus, we
regularly produce some amount of lactic acid; even at rest. Under most physiological conditions,
lactic acid, like other acids readily dissociates from its hydrogen ions and is more commonly
found as the salt of lactic acid; lactate. Resting blood lactate concentrations are typically on the
order of 0.8-1mM concentrations (mM = millimoles/liter or mmol•liter-1). If we are regularly
producing some lactate, why don’t blood lactates climb above this level?
Well, it is important to remember that lactate is not just a by-product of anaerobic
glycolysis. Lactate has several potential uses to us. As covered in previous labs, the liver plays
an important role in glucose homeostasis. Students may, for example, recall the Cori Cycle.
Glucose is used in the muscle, forming lactate, which enters the circulation, is taken up by the
liver, which converts it back to glucose, which can enter the circulation, and be taken back up by
the muscle.
There are several potential fates of lactate after it has been produced, including: oxidation
(and thus production of ATP) in very aerobic tissues like slow twitch fibers and the heart,
gluconeogenesis (and thus production of glucose) in tissues like the liver, and perhaps even to
replenish glycogen stores. Blood lactate is dependent, then, not just on the rate at which it is
being produced, but also the rate at which it is being cleared, or removed, from the circulation.
Mathematically you can think of it like this:
[blood lactate] = lactate produced – lactate cleared.
We can now answer the previous question; the reason why we do not continuously
increase blood lactate is that at rest, and also during low intensity exercise, we clear lactate from
the circulation as fast as it is being produced. However, as exercise intensity increases, skeletal
muscle increases it’s reliance on anaerobic metabolism, especially anaerobic glycolysis, to help
meet the ATP demands of the cell. Put another way, aerobic metabolism alone is not producing
ATP fast enough to meet the cellular ATP demands, and thus must supplement aerobic ATP
production with anaerobic ATP production. It is also important to note that the above formula
assumes that the lactate, once produced in the working muscles, will enter the blood.
Once lactate is produced in the muscles, there is a time lag before it enters the circulation.
For this reason, studies that have taken simultaneous measurements of blood lactate and muscle
lactate have found that muscle lactate usually exceeds blood lactate by some margin. For this
reason, if we want to take a single blood lactate sample to reflect the contribution of anaerobic
glycolysis to the activity, we usually take the sample 2-5 minutes post exercise; it has been found
that blood lactates usually peak in this time frame after cessation of activity. While there is a
time lag, and muscle lactates are usually higher than blood lactate, there is certainly a
relationship between muscle lactate and blood lactate. An average from several studies suggest,
for example that muscle lactate could be expected to be around 1.5 times greater than levels in
Lab V - 2
the blood (e.g. when blood LA = 5mM, muscle LA  7.5 mM and if blood = 10 mM, muscle LA
heart 15 mM.
By the time post exercise blood lactate peaks, some lactate has already been cleared. This
is especially true if an active recovery is used after the exercise bout. Thus, blood lactates alone
can not help us completely account for the contribution of anaerobic glycolysis to an exercise
bout. It is also difficult to directly assess the contribution of the phosphocreatine system to an
exercise bout. We therefore require other methods to evaluate the contribution of anaerobic
metabolism to an exercise bout. For example, we can evaluate one’s ability to perform work
under conditions (high intensity, short duration exercise) that should maximize the use of
anaerobic metabolic pathways (such as in the Wingate test that we will perform in today’s lab).
We can also determine one’s oxygen requirement for a very high intensity bout (above VO2max)
and see how great a deficit there is between the oxygen required for the activity and the actual
amount of oxygen consumed (such as in our accumulated oxygen deficit test that we will do
today). Please note that both of these methods will only indirectly reflect the anaerobic
contribution to exercise.
Elite rowing, cycling, running, and cross-country skiing athletes can produce maximal
lactate values during exercise in excess of 20 mM. Subjects who are not accustomed to high
intensity exercise may even fail to achieve maximal values of 8-10 mmol•liter-1. Again, resting
blood lactates are on the order of 1 mM. So what happens to blood lactate between resting and
maximal exercise values?
Anaerobic Threshold
There has been continuous debate about whether or not an anaerobic threshold actually
exists since at least 1985 (See articles in Medicine and Science in Sports and Exercise in 1985 by
Brooks and Davis). While many physiologists argue that an anaerobic threshold does occur, it is
complex phenomena and remains somewhat controversial. It can also be difficult to measure
objectively. Much of the early controversy centered on a few common themes. For example, it
was commonly thought that the increased reliance on anaerobic metabolism was due to a lack of
sufficient oxygen (which now appears to be untrue for most during exercise). It was also
commonly thought that increases in blood lactate reflected this increased reliance on anaerobic
metabolism. However, it now appears that much of the increase in lactate beyond this point is
due to a reduced ability to clear lactate. Another point of contention was the use of the term
“threshold”. Physiologists traditionally reserve this term when something does not happen
below some point and all of a sudden does happen (or visa versa); that is for all or none events.
For example, if membrane potential is brought to threshold, an action potential occurs (if not, no
action potential occurs). There were also controversies around the methods used to evaluate the
anaerobic threshold.
Some have described the anaerobic threshold as the intensity where an unfit subject must
cease and where the fit subject may find it necessary to slow down if they desire to prolong their
exercise bout. It has also been described as the intensity beyond which physically active
individuals would have a tough time keeping a conversation going. For our purposes, we will
use a definition which is still somewhat vague and difficult to objectively define: the anaerobic
threshold (AT)is the intensity beyond which our body increases its reliance on anaerobic
metabolism to meet the body’s energy demands. Aerobic metabolism is still occurring and the
cells, in a living subject, still have access to oxygen. The need to supplement aerobic ATP
production with anaerobic ATP production is due to the fact that aerobic ATP production is not
occurring fast enough to meet the cell’s energy demands.
Lab V - 3
VE/VO2, VE/VCO2, and [LA] vs. Power
VE/VCO2
26.0
16.00
Lactate &
Ventilatory
Thresholds
LA
24.0
VE/VO2 & VE/VCO2
18.00
VE/VO2
14.00
22.0
12.00
20.0
10.00
18.0
8.00
16.0
[LA] (mmol/L)
28.0
6.00
14.0
4.00
12.0
2.00
10.0
8.0
0.00
50
75
100
120
150
180
210
245
280
315
350
Power (Watts)
VE, VO2, VCO2, and RER vs. Power
7.00
90
VO2 (L/min)
VCO2
80
RER
6.00
70
5.00
60
4.00
50
3.00
40
VE (L/min)
VO2 & VCO2 (L/min) & RER
VE (stpd)
30
2.00
20
1.00
10
0.00
0
50
75
100
120
150
180
210
245
280
315
350
Power (Watts)
Figure 1. Lactate and Ventilatory Thresholds
Because of some of the controversy around the term “anaerobic threshold” it is common to
name this nebulous term based on how it was determined. In this lab we will use a few different
indicators of the AT: lactate threshold (LT) , onset blood lactic acid (OBLA), and the ventilatory
threshold (VT). Regardless of any controversy regarding these indicators of the AT, all of them
Lab V - 4
have been useful in identifying the intensity, velocity, power output, or metabolic rate that can be
maintained for prolonged periods of time. In fact, many studies have found that the % of
VO2max at the lactate threshold (or OBLA, or VT) is a better predictor of endurance
performance than VO2max itself. This intensity has sometimes been referred to as the maximum
sustainable intensity (or sustainable velocity).
There are MANY ways of evaluating the “Anaerobic Threshold” and determining the
maximum sustainable intensity. One of the oldest, and still most traditional way, of evaluating
the AT is by determining the Lactate Threshold (LT). In this lab we will objectively define the
lactate threshold during a GXT as the intensity beyond which there is an increase of greater than
1 mM with an increase in intensity. For example, in Figure 1, blood LA is going up prior to 245
Watts, however, it fails to increase by greater than 1mM with each increase in intensity prior to
this point. But beyond 245 Watts blood LA increased from around 2 mM to around 4 mM; an
increase of greater than 1 mM with an increase in intensity. Thus, the LT for this subject is at
245 Watts. Students should note that there are several commonly used criteria for determining
the LT. These different criteria are of varying objectivity and validity.
The terminology of Onset of Blood Lactate Accumulation (OBLA) has recently become
widely used because it can account for a point in time when lactate levels increase due to
increased rates of production or reduced rates of removal or both without using the term
“threshold”. Different labs have used different blood lactate levels to denote OBLA. For our
purposes, a blood lactate of 4 mM will be used to define the intensity at OBLA. Can you identify
at what intensity OBLA occurs using the data in figure 1? Some have referred to OBLA as LT2
(to differentiate it from LT1, which occurs as above, or at about a blood lactate of around
2.5mM). For the average individual the LT and OBLA occur at around 50-60% of VO2 max but
it usually occurs at higher percentages of maximum for trained individuals; especially endurance
athletes.
One possible mechanistic explanation for why the intensity at the LT (sustainable
intensity) is such a good predictor of endurance performance is that at this intensity the subject is
clearing lactate as fast as they are producing it. Therefore, they could theoretically maintain this
intensity for prolonged periods of time without accumulating lactate in the blood or muscle. This
may be partly true, as a decrease in pH can potentially cause fatigue by several different
mechanisms. However, students should keep in mind that there are many mechanisms that
contribute to fatigue and if this mechanistic explanation is true, it is likely only partly true. It is
also possible that the resulting large increases in ventilation (at the VT) could ultimately result in
the sensation of dyspnea, and thus result in fatigue.
What are the major contributors to the increase in blood lactate at the LT (or OBLA)?
Let’s partition our answer to this question into two parts: factors related to increased rate of LA
production and factors related to reduced LA clearance. The rate of lactate production increases
as a function of exercise intensity for several reasons. First, the ATP demand of the muscle cells
increases as a function of intensity. In order to meet this increased demand, several metabolic
pathways are stimulated, including anaerobic glylcolysis. Remember PFK is stimulated by an
increase in ADP and by a decrease in ATP. Second, as the intensity of exercise increases, there
is an increased rate of glycogenolysis, which increases the formation of pyruvate. If all of the
pyruvate dehydrogenase (PDH, a multisubunit enzyme located in inner mitochondrial
membrane) is already being used (is saturated), then instead of accumulating pyruvate will be
shuttled towards formation of lactate via lactate dehydrogenase (LDH, a glycolytic enzyme).
Students should also be reminded that the rate of glycogenolysis is regulated by both hormonal
(e.g. increase in epinephrine) and intracellular (e.g. increase in ADP, calcium) mechanisms.
Third, there is an increase in the recruitment of glycolytic muscle fibers (IIA and IIX). As you
learned in prior physiology courses, at low intensities we mostly recruit the smallest motor units;
Lab V - 5
those with type I fibers, which specialize in aerobic metabolism. As the intensity increases, we
recruit MU with type IIA fibers, which can use aerobic metabolism and anaerobic glycolytic
metabolism. Finally, if the intensity is very great, we will recruit the largest MU; those with IIX
fibers, which specialize in glycolytic metabolism (and thus production of lactate). Finally, during
exercise, the liver and other tissues can clear lactate from the circulation and make glucose via
gluconeogensesis. A large amount of lactate can be taken up by the liver, kidney, and gut
(mostly liver) to perform gluconeogenesis. However, blood flow to these regions decreases as a
function of intensity, and thus less lactate is being cleared as a function of intensity. A smart
student would make a list that explains why blood lactate goes up at the lactate threshold and
partition it into production-related and clearance-related aspects.
It is worth noting that with exercise training the mitochondrial volume, oxidative enzymes,
and muscle capillarity all increase. These will tend to increase the muscle cell’s ability to rely on
aerobic metabolism (there is more PDH, for example) and thus less reliance on anaerobic
glycolysis. This also allows the trained muscle fiber to rely more heavily on fats than untrained.
With training there will tend to be less of a decrease in insulin (which inhibits glycogenolysis)
and less of an increase in glycogenolysis-promoting hormones (such as epinephrine) for any
given intensity. This means that there will be less stimulation of glycogenolysis and thus slower
rate of pyruvate formation, and thus slower rate of lactate formation. With training cardiac
outputs are higher and thus maintaining blood pressure is easier at any given intensity, thus blood
flow to the liver (and other lactate-clearing organs) will decrease less; increasing the ability of
the liver to clear lactate. For these reasons, lactate threshold increases (to a higher intensity) with
training.
The relationship of lactic acid accumulation, blood pH, and respiratory mechanisms for
buffering blood pH has also been used to determine “anaerobic threshold”. By use of the
bicarbonate buffering system, the respiratory system has the ability to buffer the blood pH by
blowing off CO2. When expired CO2 increases, the RER also increases. Some have used this
change as a marker of AT, although some have found the increase in RER to not be a very good
objective marker of the AT.
CO2 + H2O

H2CO3

HCO3- + H+
An increase in lactic acid accumulation results in an increase in hydrogen ion
concentration and thus an increase in circulating CO2. Both an increase in hydrogen ions and
CO2 in the blood stimulate an increase in ventilation (VE). Recall from human physiology that
an increase in CO2 in the circulation only weakly stimulates peripheral chemoreceptors in the
aorta and carotid arteries. But, an increase in CO2 in the circulation also increases CO2 in the
cerebrospinal fluid. This, in turn increases the amount of hydrogen ions in the cerebrospinal
fluid (CSF). The major chemical stimulus for increasing ventilation is the concentration of
hydrogen ions in the CSF (via central chemoreceptors). Thus, during high intensity exercise,
both an increase in hydrogen ions and an increase in CO2 in the blood stimulated ventilation.
This increase in ventilation allows the subject to blow off more CO2 (resulting in an increase in
VCO2). Thus, during a graded exercise test, the intensity where VCO2 and VE begin to increase
at a higher rate has been used to indicate the “AT” without needing to take blood lactate samples.
This method of identification of anaerobic threshold is referred to as the ventilatory threshold
(VT, also called T-vent, ventilatory breakpoint). See appendix pages 45-46 and 56-57 (as well as
your textbook) for figures related to the “anaerobic threshold”.
It has been demonstrated that using the ventilatory equivalent ratios for oxygen and carbon
dioxide provide a more reliable way of identifying AT. The ventilatory equivalent ratios for
oxygen (VE/VO2) and carbon dioxide (VE/VCO2) are the ratios of air breathed to the amount of
Lab V - 6
O2 consumed and CO2 produced, respectively. AT is represented by the point beyond which
there is a continuous rise in VE/VO2 without a concomitant increase in VE/VCO2.
Ventilatory threshold results are not always consistent with the LT and OBLA
determinations of AT. Some researchers question the validity of using ventilatory variables for
determining the AT. One reason for this skepticism is the presence of a ventilatory threshold in
McArdles Syndrome patients. Due to a gene mutation, McArdles patients produce a
nonfunctional version of the enzyme phosphorylase, and thus are unable to break down glycogen
and are unable to accumulate lactate. Interestingly, while they have no lactate threshold, they
still exhibit a ventilatory threshold. These findings have caused many to question the
relationship between the blood and respiratory responses used to assess the anaerobic threshold.
Anaerobic Threshold, Endurance Performance, and Diseases that influence Exercise Tolerance
Even though many question the relationship between the blood lactate and respiratory
responses to exercise, strong correlations have usually been found between the lactate and
ventilatory thresholds. All three of these methods (LT, OBLA, and VT) of studying the AT are
used by physiologists on a regular basis and all of these methods can be found in current research
literature. Regardless of the method used to study the AT, all correlate very well with endurance
performance. In fact, the intensity at the anaerobic threshold has a stronger correlation to
endurance performance than VO2max or mechanical efficiency. The reason for this strong
correlation is that the intensity at the AT corresponds to the intensity that the subject can
maintain without accumulating a lot of lactic acid and hydrogen ions. If the subject can run at
this intensity, or just below it, they should be able to maintain this intensity for a long period of
time while avoiding fatigue (see the fatigue section of muscle labs for a more complete
description of fatigue and how lactate and hydrogen ions relate to fatigue). For example, whereas
most subjects reach the AT at 50-60% of maximum, elite marathoners may not reach it until over
90% of VO2max. Because these elite marathoners also have very high VO2max values, this
combination allows them to race at very high intensities (over 90% VO2max) for the duration of
a marathon (elite marathon pace may be faster than 5 minutes per mile for 26.2 miles!).
VO2max, the % of VO2max at the AT (LT, VT, OBLA), and mechanical efficiency (or
running economy) are all major contributors to the intensity that can be maintained for long
distance races (sustainable pace). The role of the AT is noteworthy. First, while VO2max can
increase up to 10-20% with training for untrained individuals, individuals who are already
trained see limited, if any, increases in VO2max with further training. If increasing VO2max
were the only way to improve endurance performance, these individuals would be unable to
improve. Fortunately, the % of VO2max at the AT is very trainable. In fact, increase in % of
VO2max at the AT can more than double for some subjects. Many also feel that the % of
VO2max at the AT is also a good reference point in providing exercise prescription.
The anaerobic threshold may occur at very low intensities in many clinical conditions
including heart failure, pulmonary diseases, peripheral vascular disease, among others. It can
also be very low following prolonged periods of inactivity (e.g. bed rest) and muscle
deconditioning (e.g. spinal cord transaction, aging without exercising). Just as having an AT at a
high intensity enhances endurance performance, having an AT at a low intensity reduces
endurance performance. In some of these patients and conditions, exercise tolerance may be so
low that the ability to perform exercise may be measured by how many steps a person can take
down a halway without having to stop. It should be pointed out that the above clinical conditions
result in either a reduced ability to use aerobic metabolism or result in an increase in the number
of type IIX muscle fibers, which tend to be very glycolytic.
Anaerobic Capacity and Anaerobic Power
Lab V - 7
Anaerobic energy systems are capable of creating ATP at much higher rates than aerobic
energy systems. This is why humans have the ability to attain power outputs that are two to four
times higher than the power output that elicits VO2max (2). However, anaerobic energy systems
can only maintain these high rates of anaerobic energy production for limited periods of time.
We have discussed the use of VO2max as a means of evaluating athletes and their training
programs. We have also discussed the use of VO2max and the anaerobic threshold, and their
relationship to athletic performance. Do you think VO2max, or the VO2 at the anaerobic
threshold would be a very good indicator of performance for a sprinter, football player, or
baseball player? Sprinting, football, and baseball are more associated with high-intensity, short
term activities. Thus, performance in these activities are more dependent on how quickly (and in
some cases how long) the anaerobic energy systems can create ATP.
Whenever you are evaluating an athlete the type of testing done should be as specific as
possible to the needs or demands of the subject. Thus, if we want to monitor training or study
what factors affect anaerobic performance, we must have some way of evaluating an anaerobic
athlete’s ability to create ATP from anaerobic energy systems. We have already looked at a
number of tests that can tell us something about anaerobic performance. For example, the
Wingate test can tell us something about our ability to perform work anaerobically. The Wingate
test tells us the maximum power output on a cycle ergometer that a subject can perform (an
indirect indicator of how quickly the ATP-PC system can create ATP) and what amount of
power one can maintain (average) over the course of the 30 second test. However, this does not
necessarily indicate how much energy expended during the test was attributable to anaerobic
glycolysis and the ATP-PC system.
In the study of exercise physiology an energetic capacity refers to an amount of energy
created by a given energy system (or systems) that is available to perform work. On the other
hand, the maximum amount of energy production per unit time is referred to as the energetic
power of the system (or systems). Thus, Anaerobic Capacity refers to the maximal ability of a
subject to generate ATP from non-aerobic energy pathways. That is, the anaerobic capacity
reflects an amount of energy. Remember, for the Wingate test, we looked at the average power
over the 30 second period, which if multiplied by 30 seconds would tell you how many joules of
work were accomplished. We called this the absolute maximal anaerobic capacity. It should be
noted that this value is not the amount of energy created, but rather is related to the amount of
work accomplished. As we have previously discussed only 20-30% of the energy expended ends
up as work. If the measurement of anaerobic capacity is based on the average power output
during high intensity exercise, such as the Wingate test, then the Anaerobic capacity is
sometimes referred to as the mean anaerobic power. The term anaerobic capacity should not be
confused with the term anaerobic power, which refers to the maximum rate of energy production
by the anaerobic energy systems. In the Wingate test we calculated the absolute maximal
anaerobic power by taking the average of the highest five-second power outputs. Some refer to
the anaerobic power calculated during such tests as the peak anaerobic power.
It is, at best, difficult to determine the exact amount of energy produced from anaerobic
energy systems. The measurement of muscle metabolites (which requires a muscle biopsy) in
combination with measurements of lactic acid escaping from active muscle (which requires the
insertion of a catheter for accurate, repeated measures) are traditional methods for estimating
anaerobic energy production. However, many assumptions must be made. One of the
assumptions that must be made is that the amount of lactic acid in the muscle plus the amount
released into the blood accurately reflects the total amount of lactic acid produced. We now
know this assumption to be false; at least some of the lactic acid is oxidized before it escapes into
the blood, or before the muscle biopsy is taken. In addition other tissues such as the heart, liver,
Lab V - 8
kidney, and inactive muscle can take up some of the lactate from the blood for their own use,
thus decreasing the blood lactate concentration.
Some methods of determining anaerobic energy production make the assumption that
anaerobic energy production can be categorized temporally into two phases: the early phase
representing use of the ATP-PC system, and the later phase representing anaerobic glycolysis.
However, this is also incorrect, the reason is that at the onset of exercise, even though the ATPPC system is providing most of the energy, lactic acid is still being accumulated (i.e. anaerobic
glycolysis is still providing a significant amount of ATP). In addition, many of the tests that are
designed to determine anaerobic capacity or anaerobic power use a significant amount of ATP
derived from aerobic metabolism. For example during a maximal cycle test lasting about 30
seconds (similar to a Wingate cycle test) it was estimated that aerobic energy release accounted
for approximately 40% of the total energy release. Other studies have estimated that the aerobic
energy cost of the Wingate test is around 16-28% of the total energy cost. It is important then,
that we exercise caution in interpreting data from these tests if we are using them to estimate
anaerobic capacity and/or anaerobic power.
Many of the above stated tests to determine anaerobic energy costs involve invasive
techniques (muscle biopsies, arterial and venous catheters), and thus they are not practical for all
labs, researches, and coaches. Additionally, even if a coach did have access to these techniques,
they are time consuming, expensive, and it is likely that not all athletes would be willing to have
these measurements made. Because of these problems a number of performance-oriented tests
have been developed to indirectly assess the ability of an individual to use anaerobic energy
systems. Tests such as the Wingate anaerobic have been used for a long time. But, as previously
stated, even this test, which is a well accepted means of assessing anaerobic capacity is not
completely anaerobic.
Accumulated Oxygen Deficit
A technique to obtain an estimate of the anaerobic capacity of a subject non-invasively has
been developed, it is called the (maximal) accumulated oxygen deficit. This test utilizes an
exercise protocol that requires the subject to maintain a high intensity (usually performed at
intensities corresponding to 115 to 140% of VO2max) until fatigue. This test ideally lasts
between 2-5 minutes. This test does require the measurement of oxygen consumption, but it is
much more practical, not to mention more cost and time effective than laborious procedures that
require blood samples and muscle biopsies.
However, the determination of anaerobic capacity, using an indirect method, such, as the
accumulated oxygen deficit, should ideally be validated by comparing results to the direct
methods (such as those mentioned above). To directly determine the anaerobic energy system
contribution to whole body energy use, one must know or be able to estimate with some degree
of accuracy the amount of muscle mass involved. Due to some of the problems inherent to the
direct techniques, the validation of the accumulated O2 deficit has come from primarily a small
muscle mass model: the dynamic knee extensor model (5). The comparison of direct and
indirect methods is very good with this knee extensor model. However, it remains to be
determined if these results also apply to whole body exercise.
The accumulated O2 deficit does appear, however, to be sensitive enough a determinant of
anaerobic performance that it has been demonstrated to increase with sprint training and to
observe differences between endurance trained and sprint trained individuals (2).
Wingate Test
This test involves pedaling with the legs and/or cranking with the arms on a cycle
ergometer at maximal speed for 30 seconds against a resistance determined according to the
Lab V - 9
body weight of the subject. This test was developed by Dr. Bar-Or of Israel to assess anaerobic
power. The number of revolutions is monitored every 5 seconds so that mechanical power
output can be calculated for each 5 second period as well as for the whole 30 second test
duration.
Using a Monark 864 fixed weight ergometer, the proper resistance is placed on the
weight tray, and the tray is lifted up slightly to take the resistance off the flywheel. The subject
then begins (unloaded) pedaling as fast as they can (RPMs should exceed 120 RPM before the
weight is lowered). The weight is then lowered, and the subject is encouraged to pedal as fast as
they can for the 30 second duration, as any attempt to conserve energy will produce a
submaximal performance and poor results. The prescribed resistance by Dr. Bar-Or for this test
is determined by loading the cycle ergometer with 75 grams for every kilogram of body weight
of the subject for the leg test: e.g., if the subject weighs 50 kg, then the prescribed maximal
resistance will be 50 kg x 0.075kg = 3.75 kiloponds. For the arm Wingate, the recommended
resistance is 50 grams per kilogram of body weight. It has been found that in fit subjects that a
resistance greater than 00.075kg/kg may be required to achieve the highest possible anaerobic
power and capacity values.
For this lab the test will be performed using a computer automated system. However,
this test can be performed by counting pedal revolutions for each 5-second period over the 30
seconds test. The highest 5 second output reflects peak power generated by the muscle groups
involved in the test and is referred to as Absolute Maximal Anaerobic Power. If the Absolute
Maximal Anaerobic Power is divided by body weight in kilograms, the Relative Maximal
Anaerobic Power is determined. The overall power produced during the 30 second period is
termed Absolute Anaerobic Capacity and reflects the rate of glycolysis. Again, if body weight is
divided into Absolute Anaerobic Capacity, the Relative Anaerobic Capacity is calculated. The
ratio between the lowest and highest 5 second power output is called the Fatigue Index (the
computer calculates work fatigue: 1 - Fatigue index). In reference to this test the term Power
refers to the maximal ability produce power (highest 5 second period), whereas Capacity refers
to the ability to sustain anaerobic power (average for the entire 30 seconds).
Examination of power output during each 5 second period permits determination of when
subject first begins to show signs of fatigue and when the greatest decrease in power occurs. The
following worksheet shows how all the measurements provided on the computer printout were
derived. Compare your computer printout to the population norms found in your Appendix.
Lab V - 10
LABORATORY PROCEDURES
I. Effect of active and passive recover on post exercise blood lactate.
This first experiment will serve as a demonstration of the procedures for determining post
exercise blood lactate and will also be used to demonstrate the role of passive and active
recovery on blood lactate. This will require a subject to perform two 5-minute exercise
bouts. The exercise bout will be at a constant work load that is above anaerobic
threshold.
A. The first will be performed at the beginning of lab. The 5-minute recovery period
following this exercise bout will be non-active. At the end of the recovery period the
lactic acid measurement will be made (described above).
B. The second exercise bout will be performed near the end of lab to allow complete
recovery. This exercise bout will be identical to the first, except that during the 5minute recovery the subject will perform exercise at 40-50% of HR max. Following
the active recovery the blood lactate measurement will be repeated. This experiment
will allow the comparison of a non-active and active recovery period on lactic acid
values.
II. Assessment of anaerobic threshold (AT) using Lactate Threshold (LT), Onset of Blood
Lactate Accumulation (OBLA), and ventilatory threshold (VT)
A. Following set up of a metabolic cart the subject will be fitted with head gear, breathing
valve and a nose clip. A heart watch will also be used to determine heart data.
B. Data will be collected during a rest period until a stable base line has been established,
including a finger stick blood sample to determine blood lactate levels.
C. A progressive exercise test will be performed with small increases in exercise intensity
every 1-2 min until subject reaches maximum power output. Data will be recorded
throughout the test and blood lactates will be determined every other test stage.
D. Computerized plotting of the data will be used to determine ventilatory and expired gas
responses and these data will be compared to those obtained from blood sampling.
E. Graph all data over time and intensity of exercise.
F. Determine at what power output AT occurs using LT, OBLA, and the VT.
1. Lactate Threshold. The LT is the intensity above which the blood lactate rises by 
1.0mmol/L.
2. OBLA. OBLA is the intensity that corresponds to a blood lactate of 4 mmol/L
3. Ventilatory Threshold. The best way to find the VT is by determining the intensity
beyond which there is a continuous rise in VE/VO2 without a concomitant increase
in VE/VCO2. Students should also try and identify the VT by determining the
intensity where VE, VCO2, and RER begin to increase at a higher rate.
4. After finding the intensity at LT, OBLA, and VT, compare each of these values and
determine if they appear to correlate well with each other. Also calculate the
subject's AT as a percent of their peak oxygen consumption.
Lab V - 11
III. Wingate procedures
A. Take time to set up seat height correctly
B. Set up the ergometer so that the resistance is set to 0.075 kg/kg body mass are.
Calculate the resistance to be used by multiplying body mass in kg by 0.075.
C. Enter subject information on the computer
D. Tester #1 runs the computer and tester #2 holds up the weight tray
E. Tester # 1 presses the key for “start test” and tells subject to start pedaling (as fast as
they can) and gives a count down to zero
F. At zero, tester #1 tells tester #2 to lower the weight tray
G. Subject maintains highest RPM possible for 30 seconds
H. At the end of the test, the subject’s data will be printed out
I. Subject calculates absolute and relative anaerobic capacity, absolute and relative
maximum anaerobic power, and fatigue index.
J. If asked to do so, students should provide their data for determination of class
averages
IV. Accumulated oxygen deficit procedures
The measurement of the maximal accumulated oxygen deficit requires that the
relationship between oxygen consumption and exercise intensity be made. Once this
relationship has been determined one can estimate the oxygen consumption that would be
required for an intensity that is above VO2max. Then the "supramaximal" test is
performed and the difference between the predicted and the actual oxygen consumption is
added up to calculate the maximal accumulated oxygen deficit.
It has been suggested that 10-20 exercise bouts be performed between 50 and
almost 100% of VO2max to determine the relationship between exercise intensity and
VO2 accurately. This would be very time consuming process, requiring the subject to
come to the lab on several occasions. Medbo et al., 1988, has suggested that using just
three intensities would yield results that are not statistically different from the value
determined using ~20 intensities, provided that those three intensities be as close to
VO2max as possible, and a Y-intercept of 5.1ml/kg/min be used for oxygen consumption.
For most individuals the maximal accumulated oxygen deficit is approximately 3060ml/kg. Reported accumulated oxygen deficit values for athletes and controls are as
follows (please note that these data were obtained using treadmill running):
Sprinters: ~80ml/kg
Middle distance runners ~75ml/kg
Distance runners ~50ml/kg
Control subjects ~47ml/kg
A. Do three bouts of exercise at approximately 60, 70, and 80% of VO2max, recording
the "steady state" VO2 from that bout, and the workload that was performed by the
subject.
B. Calculate the average slope of the line that defines the relationship between workload
in Watts (power) and VO2. For example, calculate the rise/run (slope) using the 60%
bout and 70% bout as shown below. Then do the same using the data from the 70%
and 80% bouts, and then average them.
VO2-70% - VO2-60% = rise (ml/kg/min)
Watts-70% - Watts-60% run (Watts)
Lab V - 12
C. The supra-maximal test should last between 2-5minutes. Usually, a workload
corresponding to 115-125% of VO2max should last this amount of time. Chose
workload that you predict will allow the subject to last 2-5 minutes. Then calculate
the predicted VO2 using the average slope of the VO2-workload line, and use a Yintercept of the absolute VO2 equivalent to 5.1ml/kg/min.
Predicted VO2 = Y-intercept + ( slope from above x supra-maximal power)
D. Have the subject perform the "supra-maximal" bout while recording VO2. This test is
very effort dependent, so the subject should be encouraged to maintain the desired
power output for as long as possible.
E. Subtract the VO2s that were recorded during the "supra-maximal" bout from the
predicted VO2 for each data point to calculate the "deficit for each time period. Add
up the oxygen deficits from each stage to calculate the accumulated oxygen deficit
(Depending on how often the computer is reading VO2, you may need to correct for
the fact that the computer will "read off" a VO2 per minute value, even if you making
recordings every 20 seconds. Thus, when you add these up you will overestimate both
oxygen consumption & the oxygen deficit.)
Lab V - 13
Data Sheet
I. Effect of active and passive recover on post exercise blood lactate.
Exercise Bout 1 (passive recovery) Ergometer: ____________
Ergometer Settings: __________________
Power
Watts
Blood Lactate (5 minutes post exercise)
mmol/L
Exercise Bout 2 (Same ergometer, power, and settings, but with active recovery)
Blood Lactate (5 minutes post exercise)
mmol/L
II. Assessment of anaerobic threshold (AT) using Lactate Threshold (LT), OBLA, and
ventilatory threshold. Draw a rough sketch of the response of the following variables during
the test.
VE, VO2,
VCO2, RER
Intensity
[LA],VE/VO2,
VE/VCO2
Intensity
Lab V - 14
When did the subject's AT occur using each method?
Time
Power
VO2
% of VO2peak
LT:
_______
_____
____
____________
OBLA:
_______
_____
____
____________
VT:
_______
_____
____
____________
How did each of these methods compare for determining AT?
What is the physiological connection between LT and VT?
What VO2 and what power output do you think this subject could maintain for a
prolonged period of time? Explain your answer.
What objective criteria did you use to determine LT? OBLA? VT?
Lab V - 15
III. Wingate Anaerobic Test
Subject Weight: ______________ kg
Reistance: ________kg
Average Absolute Power Output for each 5 second period (Watts):
________ 5s ________ 10 s ________ 15 s ________ 20 s ________ 25 s ________ 30 s
Power (W)
Time
Calculations:
Absolute Maximal Anaerobic Power - __________ Watts
Calculate the mean power output, in Watts, from the highest consecutive five seconds of
power output (usually the first five seconds)
Relative Maximal Anaerobic Power - _________ Watts
Absolute Maximal Anaerobic Power / Kg (body mass)
Absolute Anaerobic Capacity - __________ Watts
Calculate the mean power output maintained during the course of the entire test.
Relative Anaerobic Capacity - __________ Watts
Absolute Anaerobic Capacity / Kg (body mass)
Fatigue Index - __________ %
Calculate the (lowest 5 second power output / highest 5 second power output)
How do your values compare to population norms? (see appendix p 58, 59)
How did you feel during the first 10 seconds of the test in comp arison to the last ten seconds?
What can account for this difference? Does your power graph reflect this?
Class averages:
Male:
Rel An Power
__________
Rel An Capacity
__________
FI%
__________
Female:
__________
__________
__________
Untrained:
__________
__________
__________
Anaerobic/strength trained: __________
__________
__________
Endurance trained:
__________
__________
__________
Lab V - 16
IV. Accumulated Oxygen Deficit
Subject body weight ______________Kg
A. Oxygen consumption at three (3) submaximal power outputs. This subumaximal data will
be used to determine the relationship between VO2 and workload.
Power
Rest
0
1
2
3
VO2 (L/min)
Slope of VO2/power
____________
____________
Average slope: ____________
VO2
Power
B. Y intercept: subject body mass x 5.1 ml/kg.min, then convert to L/min. ________L/min
C. Ideally the subject reaches exhaustion in 2-5 minutes, this usually corresponds to exercise
intensities around 110-140% of VO2max. What range of intensities could be used for this
test? ___________to __________ Watts
D. Choose an intensity to use for this test: ___________________ Watts
E. Based on this graph determine the estimated required VO2 for your subjects workout.
Est. Required VO2: = Y-int VO2 + (slope x intensity)
_______________ = ___________ + (_________ x ___________)
F. Now it is time to do the accumulated oxygen deficit test.
VO2
Required VO2
Time
Oxygen
Lab V - 17
Time
(from above)
Actual VO2
deficit
:20
:40
1:00
1:20
1:40
2:00
2:20
2:40
3:00
3:20
3:40
4:00
4:20
4:40
5:00
Total
-------------------------accumulated oxygen deficit in L: ___________________
Total O2 deficit divided by 3: ______________________
(Because we took 3 measurements per minute)
D. Now calculate the accumulated oxygen deficit in ml/kg.
E. How does this compare to normal values?
Lab V - 18
Study questions
1. What is the difference between serum (plasma) lactate and whole blood lactate?
2. What is the difference between the LT and OBLA?
3. What is ventilatory threshold? How is it physiologically connected to LT? Write in the
formula for the bicarbonate buffering system and refer to it in your answer.
4. What is a ventilatory equivalent ratio? How are ventilatory equivalent ratios used to study
the anaerobic threshold?
5. Was there any relationship between ventilatory data obtained in lab and the lactate data
used to assess the AT?
6. What are the advantages and disadvantages of determining AT by the methods described
above ?
7. How can AT be used in training and can it be used to predict performance?
8. Is AT information more valuable to the elite aerobic athlete than VO2 max?
9. What is McArdle’s disease? How does the study of this disease relate to the study of the
“anaerobic threshold?
10. Can a cell or an organism use anaerobic metabolism if they have enough oxygen?
Explain your answer.
Lab V - 19
11. Describe the two anaerobic energy systems in terms of their rate of energy
production,performance duration and recovery time. Also, name at least one test that
could be used to test each.
12. The tests in this lab determine the amount of work or power that can be performed
usinganaerobic energy systems. Do these tests allow us to determine the amount of
energy provided by anaerobic pathways or their maximal energy producing capacities ?
Explain ?
13. Which of the tests best evaluates the ability to perform work by use of the lactic acid
energy system ? What type of athlete would you expect to perform well on this test ?
14. What types of applications do these tests have?
(i.e. what is their greatest utility for
an exercise physiologist?
15. Explain what tests that we performed today (and measurements/calculations that we
made today) could be used to study the ATP-PC system.
16. Explain what tests that we performed today (and measurements/calculations that we
made today) could be used to study the lactic acid system.
17. What are some differences between using the Wingate test and the accumulated oxygen
deficit to assess Anaerobic Capacity?
18. In your own words, describe the methods used to determine accumulated oxygen deficit.
Lab V - 20