Write Yourself a Prescription for Threshold Therapy

The race season is upon us, and everyone is looking for an extra edge to help them perform their best on race day. One of the most potent forms of training you can utilize to get yourself into shape is threshold training.

What is threshold training? Called lactate threshold (LT) by some and anaerobic threshold by others, an athlete reaches his or her LT when exercise intensity increases and blood levels of lactic acid begin to rise in an exponential fashion. In untrained athletes, this can occur at 50 to 60 percent of VO2 max, but it occurs at higher intensities (up to 88 to 95 percent of VO2 max in some cases) in well-trained individuals.

Although there is some disagreement on the exact point and even the definition, it is generally agreed that the sudden rise in lactic acid and ventilation during exercise represents an increasing dependence on anaerobic metabolism (producing energy without oxygen)—and it is this point that is generally referred to as the LT.

As long as your heart and lungs provide enough blood flow to your muscles, your muscles can operate aerobically, but as your level of exertion increases, your muscles require more oxygen than the body can provide and metabolism becomes anaerobic.

Your anaerobic threshold occurs when you are no longer taking in enough oxygen to supply to your body's requirements. During anaerobic metabolism, lactic acid accumulates in the muscles, and the muscles become fatigued and sore.

Being able to work close to your maximal oxygen consumption without suffering from a debilitating accumulation of lactic acid in the blood is what we want to accomplish, and through training our bodies become more efficient at clearing lactic acid out of the working muscles.

Pacing Yourself

There are several ways to determine your LT pace. The easiest way is to conduct a field test. Simply put, your threshold pace should be 25 to 30 seconds slower per mile than your 5K PR. So, if your PR for 5K breaks down to a 6:10 per mile pace, then your threshold pace would equate to a 6:35 to 6:40 per mile effort.

Another, more accurate, way of determining your threshold pace is to have a blood-lactate test performed. Using portable lactate analyzers, blood is drawn from a finger-pricked sample at various intervals during a controlled training session. When blood-lactate levels reach of 4.0 millimoles of lactic acid per liter of blood (BLa), the testers record the corresponding heart rate and pace, which equates to LT intensity—approximately an effort one can maintain for about an hour in a race situation.

However, it has been shown that there are significant variations around this 4.0 BLa value. Specifically, one athlete might have an LT that occurs at 6.9 BLa while another goes anaerobic at a BLa of 2.6. Therefore, a coach and athlete must be very careful if they are attempting to use BLa as a threshold definition.

Why Train Your LT?

Threshold training serves several important purposes. It will improve your endurance and your ability to maintain a pace close to your max effort. However, to get the most out of these sessions, it's critical to perform the workouts at the correct pace.

Pacing too slowly will not put the proper amount of lactate into your muscles while going too quickly will put too much lactate into your system and may prevent you from completing the workout. Thus, it's critical that you develop a sense of your LT before forging ahead with any LT training.

There are two basic forms of threshold training. One involves completing one or more repeats of steady-state threshold efforts, each of which can last up to 20 minutes. After a good 15- to 20-minute warm-up (regardless of the sport), move straight into 20 minutes at your threshold effort/pace followed by a 15- to 20-minute cool-down.

Most people feel they are going too easy during steady-state threshold training, but it is crucial to maintain disciplined pacing during these interval sessions. Afterward, you should feel as though you've worked hard, but you should not be completely wasted.
The other type of threshold training involves cruise intervals, which were made popular by exercise physiologist Dr. Jack Daniels in the 1980s.

Cruise intervals, or tempo intervals, are done at the same pace and effort as steady-state threshold runs but with extremely short rest periods in between the efforts: often one minute or less. Distances of each work interval can range anywhere from 1,000 up to 3,200 meters, with the total work-interval distance in one session totaling between four and eight miles.

For example, a typical cruise-interval workout includes:

  • A 10- to 15-minute warm-up
  • 6 x 1 mile with 1-minute recoveries, or 6 x 1,200 meters with 1-minute recoveries
  • 4 x 1,000 meters with 1-minute recoveries
  • A 10- to 15-minute cool-down

Steady-state threshold workouts are fantastic for building concentration and focus at race efforts, while cruise intervals, because rest is built in throughout the set, allow you to get in a greater volume of threshold work in a single training session. However, each effort has its place as you build your fitness, and both workouts can have you toeing the line in your next race feeling sharp, fast and ready to go hard.


Jason Goldberg is the director of performance enhancement for Functionally Innovative Training, a full-service functional-strength and cardiovascular-training company. Goldberg works with many levels of triathletes, from age groupers to pros. For more info, go to www.fitcenter.net.

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