By Dr. Guy Thibault
Guy Thibault, PhD, is an Associate Professor in the Kinesiology Department at the University of Montreal and a scientific advisor to the Canadian Cycling Association and the government of Quebec in Canada. His work, published mainly for French-speaking audiences, is dedicated to the interpretation of scientific knowledge for coaches, particularly those involved in individual sports. He can be reached at: guy.thibault@mels.gouv.qc.ca.
Training & Conditioning, 16.3, April 2006, http://www.momentummedia.com/articles/tc/tc1603/aheadofpack.htm
Many myths and misconceptions surround endurance training. Popular
magazines provide advice that is not always backed by science. And
coaches who have “always done it” a certain way may not keep up with
the latest
research.
Anyone who trains athletes needing
endurance does them a disservice by not knowing the latest research. In
this article, I’ll explore three important topics in endurance training
that are often misunderstood.
LACTIC ACID
When an athlete
fatigues, lactic acid is often blamed. For years, we have told athletes
the reason they can’t push anymore is that lactic acid has built up in
their muscles. But this is false, and there is much evidence disproving
it.
Let’s start with a fact: at high intensity, muscles produce
lactic acid, which enters the blood in the form of a salt called
lactate. From this truth, many have reasoned that the more lactic acid
accumulates, the more the muscle fatigues. However, if we examine the
way energy is produced in the muscle during efforts of varying
intensities, we find that lactate is not as detrimental as once
thought.
The most convincing evidence for this conclusion is
that it’s possible to observe muscle fatigue while the lactic acid
concentration in the muscle remains low. Conversely, there can be an
absence of fatigue when the lactic acid concentration in the muscle is
high.
For example, at the end of a demanding bike ride of
several hours in the mountains, the athlete’s fatigue level is quite
high, but his or her blood lactate concentration is not much higher
than in a resting state. Another example is found in people who suffer
from McArdle’s Disease, which makes them incapable of producing (and
thus accumulating) lactic acid. These individuals are very prone to
suffering from muscular fatigue, even though there is no lactic acid
accumulating in their muscles.
Now, let’s look at the opposite
scenario. If an athlete performs an exhausting isometric effort with
the quadriceps (for example, one study had athletes perform a chair
exercise, with their backs leaning against a wall), fatigue will tend
to reduce strength temporarily. The athlete gets to the point where he
or she can’t continue the exercise and needs to rest. Two minutes after
completion of the exercise, fatigue in the muscle is gone, and the
athlete can once again produce his or her initial force.
However, during the recuperation period, the degree of acidity
in the muscles lowers to normal rather slowly. At the two-minute mark,
the degree of acidity remains very high. Thus, it is difficult to
embrace the idea that an increase in lactic acid in the muscle causes
fatigue, since a high degree of acidity without fatigue can be
observed.
An athlete’s overall level of fatigue depends on a
mixture of causes, which vary with different types of effort. Lactic
acid or lactate is not the sole cause, nor even one of the major causes
of muscular fatigue.
In fact, lactic acid build-up may be a
positive. For an average sprinter, blood lactate concentration, which
is about 1 mmol/l in a resting state, increases to about 18 mmol/l at
the end of a 400-meter race. But, for an elite sprinter, it rises to 23
mmol/l. The extra lactic acid produced by the elite runner supplies his
muscles with a greater amount of anaerobic energy, which means a better
performance. Thus, in short efforts (under 10 minutes), higher blood
lactate concentration helps to make elite runners elite.
It is
wrong to believe that athletes training in anaerobic events learn to
“tolerate” more lactic acid. Instead, they learn how to produce more,
which means they develop a greater supply of energy.
Related to
the lactic acid myth is the anaerobic threshold misconception. It says
that among the vast range of exercise intensities, there is a threshold
at which you start producing lactic acid at a much higher rate and
cannot increase exercise intensity anymore. This seems to make sense:
During a prolonged high-intensity run, you sometimes feel that it would
be very difficult to increase your speed by even the smallest amount.
In addition, popular fitness magazines frequently cite anaerobic
threshold as if its existence is generally agreed upon.
However, current scientific knowledge refutes the anaerobic
threshold theory. Studies have found that there is no power threshold
below or above which the muscle does not produce lactate. Muscles
constantly produce lactate, from the lowest work level to the highest.
During a ramp test, in which an athlete must exercise at an
intensity that keeps increasing until exhaustion, blood lactate
concentration never appears as a threshold. In fact, a curve comparing
intensity level to lactate concentration shows no
deflection.
The take-home message is this: There is no reason to
consider lactic acid build-up or anaerobic threshold when designing
your strength and endurance programs. Lactic acid and lactate—the
scapegoats for the pain athletes experience—are not responsible for all
the ills they are blamed for. They are not the cause of fatigue,
cramps, or soreness. The anaerobic threshold is just as meaningless,
and its importance has been vastly overstated.
INTERVAL TRAINING
MODEL
Interval training is frequently chosen over continuous
training because it enables an athlete to perform a greater amount of
work at elevated intensity. And that is the key to boosting important
physiological performance factors, such as anaerobic capacity, maximal
aerobic power (MAP or power output when VO2max is reached), and
endurance capability.
One key to effective interval training is
planning the correct amount of work at the correct intensity. However,
no model for determining the ideal duration, frequency, and intervals
for this type of training existed.
In response, I designed one
that relates the elements of an infinite number of interval training
sessions, all of which are of the same level of difficulty. In fact,
they are all very difficult, which means after doing any of these
workouts, an athlete needs one or two days of easy training to recover
before taking on another session.
My interval training model is
represented by a graph (PDF). Each of the six curves corresponds to a relative intensity,
from 85 to 110 percent of MAP in five-percent increments. The duration
of each work interval is represented on the x-axis, and the number of
repetitions on the y-axis. Each point on the curves of
the graph represents an interval training session. The squares
represent sessions in which work intervals are multiples of 30 seconds.
The varying colors on the chart indicate the number of sets that should
be used based on the number of repetitions chosen. The box in the upper
right-hand corner provides the duration of active recovery between work
intervals and between sets. It is assumed that recovery occurs at
around 50 percent of MAP, a relatively low intensity.
For
example, the session represented by point A on the graph consists of
four sets of seven to eight repetitions (for a total of 30), each
consisting of 1:30 minutes of work at 85 percent of MAP. One minute of
active recovery is allowed between repetitions and three minutes
between sets. The session represented by point B on the graph consists
of one set of four repetitions, each consisting of six minutes of work
at 85 percent of MAP, this time with five minutes of active recovery
between repetitions. The session represented by point C on the graph
consists of two sets of five repetitions (for a total of 10), with each
consisting of 1:30 minutes of work intervals at 100 percent of MAP.
Three minutes of active recovery is allowed between repetitions and 10
minutes between sets.
Coaches and athletes can also use this
model to plan interval training sessions that are not as difficult. A
session in which an athlete completes less than the number of
repetitions called for by the model has a level of difficulty below the
“maximum” level. For example, completing only five work intervals
instead of 10 as prescribed by the model corresponds to a 50 percent
level of difficulty.
The beauty of the model is that it helps
coaches plan sessions and develop training programs for any sport in
which anaerobic capacity, MAP, and endurance capability are performance
factors. Feedback from coaches and athletes who use the model indicates
that it has useful pedagogical and practical applications in organizing
sessions and developing long-term training plans. It may also lead
coaches to consider unexplored forms of interval training, thus
enabling them to develop innovative workouts.
Athletes
performing one to three interval training sessions every week based on
this model improve their MAP by a margin almost impossible to achieve
with a regular training program. I have often seen MAP improvements of
more than two watts per hard interval training session. It truly takes
the guesswork out of planning interval training.
To use this
model, you must first answer some questions about your training goals.
For instance, what is the physical quality you want to improve? If it
is anaerobic capacity, then target intensity should be 105 or 110
percent of MAP. If you want to train MAP, then the target intensity
should be 95 or 100 or 105 percent of MAP. For endurance, target
intensity should be 85, 90, or 95 percent of MAP.
Also, do you
want to put the emphasis on quantity or quality? If the answer is
quantity, choose a session with more than 20 repetitions. If the answer
is quality, choose a session with less than 10
repetitions.
Let’s say I want to improve MAP in “quantity” at a
75-percent difficulty level. Therefore I’ll train at 95 percent MAP
(100 or 105 would also be okay), with each session consisting of 24
repetitions of one minute. Using three sets at a 100-percent difficulty
level, I would do eight repetitions with two minutes of active rest
between repetitions and five minutes between sets (see point D on the
graph). But instead of doing all 24 repetitions, I’ll do only 75
percent of the 24, or 18 repetitions. That would translate into six
reps in each set.
If I have a device that provides feedback on
the actual intensity at which I exercise (such as a CompuTrainer), I
can set the intensity if I know my MAP, which can be assessed with a
progressive maximal test. If I do not have such a device, I have to
pace myself as if I’d be doing 24 exhaustive repetitions even though
I’m stopping at 18. In the latter case, even if I’m not exactly at the
targeted intensity (95 percent MAP), I should be close enough to
achieve my goal, in this case increasing MAP.
LUNG
POWER
Exercise physiologists used to believe that it was not
possible to improve performance through training the respiratory
muscles. But now, a technique to strength train respiratory muscles
(the diaphragm and intercostals) has been developed, and it shows great
promise.
The principle is that by forcing the respiratory
muscles to overcome mechanical resistance, they can be trained to work
at a higher stamina. There are already products on the market for
this—I have used POWERbreathe and PowerLung. The apparatus resembles a
pipe with a small valve, which is placed in the mouth. While inhaling
(inspiring), the athlete must create enough negative pressure to
overcome a threshold load. About 30 repetitions are recommended, either
all at once or in series of five to 10 breaths with a few seconds of
rest in between. Obviously, the difficulty depends on the choice of
resistance, which can be modified on most units.
The
manufacturers claim that positive performance results appear after
about six weeks of training. However, in general, two or three sessions
are enough for the athlete to find intense aerobic exercise less
constraining.
In one valuable study, 14 elite female rowers
participated in a series of tests before and after an 11-week daily
training program for the inspiratory muscles. Seven of the participants
performed 30 repetitions each day against a resistance that
corresponded to 50 percent of their maximum inspiratory pressure.
During this time, the other seven participants performed 60 repetitions
against a resistance too weak to significantly affect the inspiratory
muscles (only 15 percent of their maximum inspiratory pressure). At the
end of the 11 weeks, the two groups were tested on an indoor rowing
machine: one all-out six-minute test and one simulated 5,000-meter
race.
It was found that the experimental group improved its
performance in the 5,000-meter race by an average of 36 seconds (a
decrease of 3.1 percent), while the control group improved only by 11
seconds (0.9 percent). Analysis of the results delivered other
interesting data, in particular, less fatigue of the inspiratory
muscles at the end of the all-out test in the experimental group. (See
“Training the Lungs,” below.)
A thorough review of all available
research recently done by Alison McConnell, PhD, and Lee Romer, PhD, of
Brunel University (Middlesex, England) backed up the validity of this
study. After a critical analysis of all the available data, they
concluded that this training technique was effective, especially in
tests lasting between six and 60 minutes. Some data suggests this type
of training also reduces the time needed to recover between sprints,
which is good news for athletes and coaches in many sports.
One
question remains: Should the expiratory muscles be trained as well as
the inspiratory muscles? Obviously, different muscles are used to
inhale and exhale. Most of the equipment on the market provides
resistance while air enters the lungs, while the expiratory pathway is
left alone. The belief is that expiration is passive during exercise of
low and average intensity. Therefore, there would be no value in
strengthening the expiratory muscles. This is also the opinion of
McConnell and Romer.
However, I feel the training of expiratory
muscles should be examined further. One product (PowerLung) provides
resistance during both inspiration and expiration, and I asked athletes
and coaches who regularly use it for their opinions. They all prefer to
mix exercises for both expiration and inspiration instead of just the
latter.
Gregory Wells, PhD, in the Department of Lung Biology
at the Hospital for Sick Children in Toronto, is presently doing
studies with elite swimmers and cyclists. So far, his studies show that
the work performed by expiratory muscles increases proportionally to
exercise intensity and can become very intense in certain
circumstances. In a series of papers (submitted for publication), he
concludes that elite athletes should train all respiratory muscles,
both agonists and antagonists, just as they would for any other muscle
groups.
Why is this training successful? It is quite possible
that the ergogenic effect of respiratory muscle strength training can
be explained through: 1) decreased respiratory muscle fatigue, 2)
increased blood flow to the active muscles due to a lowered blood
volume needed by the respiratory muscles, and 3) a perceived decrease
in respiratory effort.
Here is a sample respiratory
muscle-training protocol if you want to try it yourself: Five days a
week, twice a day, do three sets of 10 repetitions, with one minute of
inactive rest between sets. Set the inspiratory and the expiratory
restriction to a level that will make it difficult, but possible, to
complete all three sets, inhaling and exhaling. Do not try for an
elevated rhythm, but exert a maximal force at each repetition, so that
the valve will be set open.
Some of the advice presented in this
article may surprise you, as it contradicts long-held beliefs in
endurance training. But by keeping our eyes open to the latest
information and taking notice of new research, we can best help
athletes improve their performance. Try the training suggestions I have
provided, and I believe the results will speak for themselves.
Table/Sidebar: Training the Lungs
A study of 14 elite
female rowers showed the positive effects of a training program for
respiratory muscles. The rowers were dived into two groups—one that
trained heavily with respiratory trainers (the experimental group) and
one that trained lightly (the control group). Here are the
results:
Variable . . . . . . . . Experimental group . . . . . .
. . Control group
Strength of
inspiratory muscles. . . . . . . .
.+45.3% . . . . . . . . . . . . . . +5.3%
Virtual distance
traveled in
maximal test of six minutes . . . .+3.5% . . . . . .
. . . . . . . +1.6%
Time to perform
5,000-meter test . . . .
. . . . . . . -3.1% . . . . . . . . . . . . . .-0.9%
Fatigue
index of
inspiratory muscles . . . . . . . . . .
-59.8% . . . . . . . . . . . . .-3.6%