Vary your training intensity to achieve greater fitness

The most important element you can vary in your training is intensity
Of the three stress elements you can vary in your training to produce greater fitness -- frequency, intensity and duration -- the most important is intensity. It is even more important than volume, which is the combination of duration and frequency.

This does not mean that volume is unimportant but rather that when it comes to determining training emphasis, proper intensity should be the core of your program. This is even more important if you have a limited amount of time to train, as most of us do. The professional athlete training 30, 40 or more hours per week will get adequate stress to create high fitness just from the volume. The experienced 10-hour-per-week athlete will not see a similar volume benefit.

Even though of lesser significance than intensity, volume is what endurance athletes most commonly refer to when asked about their training ("I'm training 15 hours per week"). Part of the reason for this is that intensity is more difficult to quantify. With the growing popularity of power meters this is slowly changing for cycling.

What is intensity?

For the endurance athlete intensity may be defined in two ways: absolute and race-specific:

  • Absolute is the greatest output one can produce in a given period of time or for a given distance, especially short time durations or distances that take about six minutes or less to complete. These intensities will be equal to VO2 max intensity or greater.
  • Race-specific is the intensity at which the athlete intends to race -- the goal-oriented output.

Either type of output may best be measured using power for cycling or pace for running, swimming, cross-country skiing or other such endurance events. Heart rate is not as effective a metric since it really tells you nothing about output. It is an input measurement and not always reliable even in that arena since environmental factors such as stress, diet, heat and humidity affect it. Heart rate is best used at low absolute intensities done in a steady-state manner.

Absolute intensity

Absolute intensity training is most beneficial for short events such as bicycle criterium races and sprint-distance triathlons since this level of power or pace is close to what the race demands. In other words, for short events absolute and race-specific intensities are practically the same thing. But absolute intensity also has benefits for longer races. More on this later.

The benefits of absolute intensity training include increases in muscle force production, muscle size and muscle contraction rate. The nervous system also becomes more effective at recruiting muscles in efficient patterns. This last point means your economy (how much energy a given output takes) improves -- you need less energy with improving economy. And the anaerobic metabolic pathways become better at clearing acid and utilizing lactate as a fuel. There is even a considerable body of research showing that very high intensity training -- even in excess of velocity at VO2 max -- improves aerobic fitness more effectively than does greater amounts of low-intensity, high-volume training.

Despite the benefits, you need to be cautious with absolute intensity training. Most self-coached athletes abuse this form of training. By this I mean they put themselves at risk for injury, illness and overtraining caused by excessive use of absolute intensity. Every type of workout for a given athlete has an associated "risk-reward curve." As the high-intensity workout progresses the benefits increase up to a certain point in the workout before beginning to taper off and ultimately plateau.

At the same time the risk associated with the workout is low initially but increases more rapidly as the workout progresses. This means that at some point in the workout risk exceeds reward. Many athletes reach this high-risk, low-reward point frequently in training. Smart athletes know when to stop the session.

Absolute intensity workouts also have a long recovery requirement. If you try to put them too close together too many times the risk is greatly magnified. How much is enough recovery? That depends on the nature of the workout and your personal capacity for work and ability to recover. The fitter and younger you are the less recovery required.

Race-specific intensity

Generally, race-specific intensity is of lower magnitude than short duration absolute intensity, but not always. Obviously, when the endurance event is short (for example, the cycling kilometer or an 800-meter running race) absolute and race-specific may be quite close or even the same.

But let's approach this aspect of training from the perspective of an event that takes an hour or more to complete. In this case, short-duration, absolute intensity will greatly exceed the demands of the event -- race-specific intensity.

Here's an important point to remember: The intensity at which you most frequently train is the intensity at which you will become most economical. So for example, if you are a runner and do nearly all of your running at an eight-minute pace you will become most economical at an eight-minute pace. Should you race at six minutes per mile you will waste a great deal of energy and perhaps find it difficult to hold that pace for the entire race.

Therefore, race-specific pace/power training is always valuable. It's hard to go wrong by doing much of your training at your intended goal intensity.

This brings up an interesting old wives tale about three-zone heart rate training. There is a myth that one should never train in the three zone -- the middle heart rate zone. The argument is that it is too easy to produce fitness but too hard thus requiring a long recovery. Sounds good, huh? But what if your goal intensity involves racing at a three-zone intensity? Never do it? Does that make sense? As with all such "rules," there are exceptions.

Periodization of intensity

So given these two types of intensity -- absolute and race-specific -- when should you include them in your training? The answer is, as with most such questions in training: It depends. Primarily, it depends on the A-priority race for which you are training and periodization.

The key point to remember about periodization is that the closer you get to your A race, the more race specific training should become. For short races, on the order of an hour or less, the more absolute-intensity training you will do in the build period. With few exceptions, the longer the race the less absolute training one will do in the build period and the more emphasis will be placed on race-specific training, usually referred to as "pace" or "tempo" training. A notable exception is long bicycle road races, which still place absolute power demands on the riders in various situations such as hills, covering breaks and sprinting.

But note that this key point then implies that training in the base period is less specific. So if less specific in terms of intensity, this means that an athlete training for a very short event would not do much absolute intensity in base. On the other hand it means that athletes training for very long events may do absolute-intensity training in base. In fact, I have done this with some advanced athletes training for Ironman-distance and other such long races. It's not for everyone, however.

When I've trained Ironman or other long-distance racers with absolute intensity it has been near the end of the base period -- typically in the last three weeks. The purpose of this has been to reap all of the benefits described above -- muscular fitness to help resist injury, nervous system changes to boost economy and aerobic system benefits.

Example workout
An example of a high-level, absolute intensity workout I've used in base is "30-30s." Following a warm up, the athlete completes a 30-second work interval at velocity or power at VO2 max or a slightly higher intensity. This is the power or pace the athlete can maintain for about six minutes of all-out effort. Then he or she recovers for 30 seconds with a power or pace approximately twice as easy as the work interval. Twelve to 24 of these 30-30s are completed in a session depending on the athlete's capacity for work and ability to recover keeping the risk-reward curve in mind.

Before embarking on absolute-intensity training be sure that your endurance, force and speed skills are well established. If that is not the case, this sort of training will not be very effective.

On the other hand, race-specific intensity training is always appropriate in the build, peak and race periods.

Understanding intensity training means first understanding pace and/or power. You can read more about these topics in previous e-Tips articles archived here. Do a search on either of these words to find previous articles.

Copyright 2005 by Joe Friel

Joe Friel is the author of the Training Bible series and other books on training and racing for various endurance sports. For more information on coaching he may be contacted at

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