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As your exercise intensity increases (such as in a race), you
begin to use more and more of your anaerobic energy system,
which produces energy without using oxygen (glycolysis). As a
byproduct, you also produce lactic acid. Though your body can
clear some of this acid, as you produce more and more, it
begins to spill from the muscles into the blood at a faster and
faster rate. The point at which this spilling begins to occur
faster than it can be cleared is known as the Lactate Threshold.
Graphically, this is defined differently by different authors. In
our lab, we use a common definition of the intensity of exercise
that causes a sustained rise in blood lactate of 1 mmol/L above
baseline measurements. Some labs use a set point of 2
mmmol/L, but we feel that this does not account for different
athlete's baseline measurements.
What's the difference between Lactate Threshold and
Anaerobic Threshold?
It is a serious problem in athletic literature that people use the
terms Lactate Threshold and Anaerobic Threshold
interchangably, and often use other words to describe the same
phenomena. We have chosen to use the terms to mean two
different points on the lactate curve. Whereas Lactate
Threshold is the point when lactate is just beginning to
accumulate, Anaerobic threshold (also termed maximal lactate
at steady state and onset of blood lactate accumulation) refers
to the highest intensity exercise for which blood lactate levels
rise more than 1 mmol/L after the initial increase from baseline.
In other words, even though lactate has already started to
accumulate, at Anaerobic Threshold, it will start to accumulate at
a very fast rate if any more intensity is added. Usually this
occurs at about 4 mmol/L of lactate, but it is highly variable
between athletes (2.5-5.5), so we choose to individualize this
result as well. If there is no clear point graphically, then we,
too, will choose the point equal to 4 on the curve. For those of
you who have used the popular Conconi test for defining fitness,
the Anaerobic Threshold corresponds to the "deflection point."
To help you think more clearly about Anaerobic Threshold, it is
an intensity of exercise that can be sustained for up to an hour
in highly trained athletes (but much less in most of us). A 5k
race would often be run even slightly faster than the Anaerobic
threshold, while a marathon would be run ~5% slower than the
Anaerobic Threshold (in elite athletes). Because of these
relationships, it is felt that the Anaerobic threshold is in many
cases even more predictive of performance than Lactate
Threshold. Again, be very careful when looking at training plans
to find out whether the workouts are calling for true Lactate
Threshold vs. Anaerobic Threshold. Most are referring to
Anaerobic Threshold (L4)
Why are thresholds important?
Switching from your aerobic energy system to glycolysis seems
like a great thing to do - after all, you can't burn enough oxygen
to keep up, so why not use some other means? The problem is
that anaerobic metabolism isn't sustainable for long periods of
time. The buildup of Lactic Acid (and other byproducts)
contributes to fatigue and discomfort during intense exercise,
causing you to have to slow down. It's easy to imagine, then,
that the faster you can run or the harder you can pedal without
over-using your anaerobic energy system (or reaching your
lactate and anaerobic thresholds), the longer you could sustain
the activity. In other words, by increasing your lactate threshold,
you will be able to race faster for longer periods of time. In fact,
Lactate Threshold and Anaerobic Threshold have been shown
to be the best predictors of endurance performance in both
cyclists, runners, and rowers.
Also, by knowing your lactate levels at various exercise
intensities, you will be able to better know how hard your training
should be, and you'll work the right energy systems at the right
times. For instance, during recovery, your lactate level should
stay below Lactate Threshold. During long endurance runs, you
should be right around Lactate Threshold. During shorter
endurance runs, or tempo runs, you will stay between anaerobic
and lactate threshold. Moving into intervals, you'll be at the
anaerobic transition for longer intervals but above anaerobic
threshold for shorter intervals.
How do I increase my Anaerobic Threshold?
Typically, heartrate at Anaerobic Threshold may go up 6-10
beats during the year (and even more over time). More
importantly, your speed at LTHR will improve throughout the
year. Here are a few ways to accomplish these changes:
-Spending enough time right at Anaerobic Threshold intensity
will allow your energy systems to adapt to this level of intensity.
-Interval training is another key to reducing lactic acid buildup.
Your training program should include interval training each week
(include high intensity periods alternating with moderate
intensity periods). Your body will learn how to buffer lactic acid
that is created during these high intensity workouts and allow
your body to adapt to the stresses of acidosis. This adaptation
will gradually allow you to continue at a higher intensity for a
longer time without feeling the burn of the lactic acid build up.
-REST! You must include times of rest to allow your body to
adapt to the stresses you have put it through.
Why do I need to get my Lactate Threshold Tested? Can't
I just use my estimated maximum heart rate?
There are three main reasons to measure Lactate Threshold:
1. Measure your fitness level - The work that an athlete can do
at lactate threshold is highly predictive of performance across
most, if not all endurance types of sports, including cycling,
running, swimming, and rowing. Of all the tests this is probably
the most valuable for endurance athletes, no matter what the
discipline.
2. Establish training zones - We are all familiar with using
Heart-Rate Training Zones to guide our training. As we said
above, by spending time training at the correct intensity level,
we are training our body to adapt to that level of intensity.
Unfortunately, predicted maximum heart rate can be 20-30
beats away from true maximum heart rate, which could make
your attempts to train at a certain intensity quite inaccurate. An
alternative is to actually measure maximum heart rate instead of
estimating. However, in establishing your training zones, using
lactate threshold has been found repeatedly to be more
effective than heart rate. The reason behind this is that Lactate
Threshold changes as your fitness level changes, while
maximum heart rate remains relatively constant. Therefore, as
you become more fit, your body will be able to sustain a higher
heart rate for a longer period of time, and your training plan
should reflect this. In other words, as your energy systems
adapt to your training, you need to adjust your exercise
intensities to continue to push your limits. Retesting your
Lactate Threshold 3-5 times through your season would allow
you to do this.
3. Monitor training effectiveness across the course of the
season - Because Lactate Threshold can change rapidly over
the course of weeks, it is often used to measure progress during
training. By standardizing testing, we are able to compare tests
done at different points in the season to help you evaluate your
training program.
What are the training zones?
These are some guidelines, but you will find many different
guidelines from many different coaches. The Anaerobic
Threshold percentages are often called Lactate Threshold, but
in most cases, the zones refer to your intensity at around a
Lactate Level of 4
Zone 1: Recovery
Also known as: Overdistance
Intensity: Very Low - Below Lactate Threshold (keep lactate
level less than 1.5)
% Anaerobic Threshold: 65%-85
% VO2 Max: 55%-65%
% Max Heart Rate: 60%-70%
RPE Scale: 6-9
Used for: These are the easiest workouts, used to promote
recovery after harder workouts. It is also generally the intensity
level used during the recovery period of interval work and long
slow distance (LSD) runs.
-In this zone you are burning primarily body fat for energy. You
should be in this zone for recovery rides, for warm-ups and
cool-downs and also for the easy portion of long rides. Training
in this zone helps to build your endurance for tours and ultra
races.
Zone 2: Endurance
Also known as: Extensive Endurance
Intensity: Moderate (lactate level between 1.5 to 2.5 - hovering
around your Lactate Threshold)
% Anaerobic Threshold: 85%-91%
% VO2 Max: 66%-75%
% Max Heart Rate: 71%-75%
RPE Scale: 10-12
Used for: Used for long, endurance workouts and easy speed
workout; builds and maintains aerobic endurance.
-In this zone you are burning a mix of fat and glycogen (carbs)
for energy. Training in this zone will improve your ability to
transport oxygen. You should be in this zone much of the time
during rides over three or four hours, except for climbs in zone 3.
Zone 3: Threshold
Also known as: Intensive Endurance (Lactate between Lactate
and Anaerobic thresholds (2.5-3.5)
Intensity: Moderate Plus
% Anaerobic Threshold: 92%-95%
% VO2 Max: 76%-80%
% Max Heart Rate: 76%-80%
RPE Scale: 13-14
Used for: Used for Tempo workouts, training in Zone 3 is usually
done in the preparation and base phases. Generally, in the later
phases you want to bump up to Zone 4.
-In this zone you are burning primarily glycogen for energy.
Training here will improve your efficiency burning
carbohydrates. You should be in this zone most of the time
when climbing. You will have better endurance if you can climb
in zone 3 and ride the flats and rollers in zone 2, instead of
climbing at a higher heart rate and then taking a long time to
recover in zone 1.
Zone 4: VO2 Max Intervals
Also known as: Anaerobic Threshold, Race/Pace, Extensive
Intervals
Intensity: Race-Pace (keep lactate right around anaerobic
threshold.
% Anaerobic Threshold: 96%-100%
% VO2 Max: 81%-90%
% Max Heart Rate: 81%-90%
RPE Scale: 15-16
Used for: Intervals, hill work, and tempo work. Intervals in this
zone generally have work-to-rest ratio of 3:1 or 4:1. Training at
or slightly below your Lactate Threshold (a.k.a. Anaerobic
Threshold) helps your body lean to "recycle" the lactic acid
during high intensity work.
-In this zone you are burning glycogen for energy, but without
enough oxygen, so you are going anaerobic. Training in this
zone builds speed and your tolerance for lactate acid and over
time raises your lactate threshold. This training is hard on your
body and it takes a day or two to recover.
Zone 5a: Threshold Endurance
Also known as: Superthreshold, Intensive Intervalse
% Anaerobic: 100%-102%
% VO2 Max: 91%-93%
% Max Heart Rate: 91%-93%
RPE Scale: 17
Used for: Intervals, hill work, and tempo work; typically used
after some Zone 4 time has already been done. Zone 5
workouts are very short because it is difficult to maintain this
level for any length of time.
Zone 5b: Anaerobic Endurance
Also known as: Speed Endurance
% Anaerobic Threshold: 103%-105%
% VO2 Max: 94%-98%
% Max Heart Rate: 94%-98%
RPE Scale: 18-19
Used for: Intervals and hill work to improve anaerobic
endurance. Intervals in this zone generally have work-to-rest
ratio of 1:1, for example, a 20 second sprint followed by 20
seconds of easy recovery (Zone 1).
Zone 5c: Anaerobic Capacity
Also known as: Power (lactate level above 12 or near your max)
% Anaerobic Threshold: 106%+
% VO2 Max: 98%-100%
% Max Heart Rate: 98%-100%
RPE Scale: 20
Used for: Short-term Sprinting. Intervals in this zone have a work
to rest ratio of 1:2 or more.
References:
Training Plans for Multisport Athletes, by Gale Bernhardt
Serious Training for Endurance Athletes, by Rob Sleamaker and
Ray Browning
The Triathlete's Training Bible, by Joe Friel
Lactate Threshold Training, by Peter Janssen
But I usually just train based on how I feel (perceived
exertion). Why would I use a heart-rate monitor?
1. Prevent Over-Training: For many competitive runners, every
week's workout regimen is essentially a seven-day dance along
the fine line between optimal training and over-training. Using a
heart monitor to avoid stressing your body too much means that
you will maximize the efficiency of your training, while minimizing
the opportunity for injury. Injuries are much less likely to occur
when you are not over-taxing your body, and avoiding injuries is
tantamount to avoiding setbacks in your training. While opinions
differ on how much running is too much (we will discuss this
more later), once you determine the desired intensity of your
weekly workouts, you can use the monitor as a gauge. Are your
recovery days really allowing your body to recover? The
surprising answer, in many cases, is that runners' easy days are
simply not easy enough. Use your monitor to stay below a
certain ceiling, and you will avoid depleting your body's
glycogen stores, ensuring that you will have the energy to
perform your intense workouts with vigor and that you will not
have to take unexpected days off from fatigue.
2. Prevent Under-Training: Though perhaps less common than
over-training, some runners simply do not run hard enough,
often enough. In this case, the monitor can function as a sort of
coach, telling you when your body can handle more, and
consequently, when you should pick up the pace. Set a
minimum heart-rate goal for your run, and the monitor will sound
an alarm when you have dropped below your target, telling you
to work harder.
3. Pacing During Training: Perhaps the most obvious use for a
heart monitor is to pace your training runs. Sometimes your time
is not the best measure of how hard you are working. Different
terrain, different energy levels, inconsistent distance
measurements, and any number of factors can mislead you into
thinking that you have performed well or poorly when the
opposite may be true. Your cardiovascular performance is best
measured by the work-rate of your heart, so pacing your
training runs according to your heart rate is the best method of
targeting your cardiovascular fitness as you do your workout.
4. Pacing During A Race: Some runners not only train with a
heart monitor, but race with one as well. The monitor is a better
tool for gauging effort during a race than mile markers, as the
appropriate speed of each mile during a race can vary. Also, the
monitor is indifferent to the wind, the paces of the other runners,
the cheering of the crowds, the silence of lonely stretches that
occur towards the end of some races, and any hills and curves;
it is an objective observer than can help you maintain a
consistent work rate, both over varied terrain and in areas
where external factors affect your motivation and speed. Within
a racing context, a monitor is perhaps most useful in preventing
you from going out too fast or working too hard early in the race.
5. Enjoyment: While many runners enjoy their long runs, using
a heart monitor adds a twist to running, whether it is being worn
for a race or for training, for one mile or for twenty. Monitors can
give you an accurate and fun way to quantify your progress,
and if for no other reason, contribute some variety to the activity.
How do I use these training zones?
Setting up your training program is certainly beyond the scope
of what we do at Cove Family and Sports Medicine. However,
many coaches are available both online and now locally. We
can make some suggestions to you if you would like. A general
gameplan usually includes a base-building period during which
you stay mostly under lactate threshold, followed by a time
period that builds into some running just under anaerobic
threshold. Through the season, you would progress to include
interval training above anaerobic threshold, and finally some
repeats at maximal intensity. Ask us if you have more specific
questions, and we will try to answer. Additionally, we can
recommend a few books that might be helpful in setting up a
training program yourself. One we definitely recommend to all
of you who like the very technical aspects of training and racing
is "Lactate Threshold Training" by Peter Janssen. It is useful to
runners, cyclists, triathletes, and rowers. The important thing is
that you have a plan with clear goals in mind. Otherwise, you
might find yourself training more with less dramatic results.
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