PT on the Net Research

Interval Training Benefits


What are the physiological benefits of interval training?


To avoid any confusion, I've drawn the following information directly from the references listed below. They are great basic level texts for any fitness professionals and are recommended readings.

Interval training (IT) involves the alternating of relatively more intense bouts of cardiovascular exercise with those that are relatively less intense. IT has useful applications for beginning exercisers as well a experienced and conditioned clients who wish to improve aerobic power.

IT is based on the concept that more work can be performed at higher exercise intensities with the same or less fatigue than in continuous training. The theoretical metabolic profile for exercise and rest intervals stressing aerobic metabolism, fast glycolysis and the phosphagen system is based on the knowledge of which energy system predominates during exercise and during the time of substrate recovery.

It appears that every athlete needs a basic level of cardiovascular endurance, which can be achieved using a wide variety of training modalities and programs. The traditional modality has been slow, long distance run. For the strength and power athlete, however, this may be irrelevant or even detrimental to power development. Adequate gains in aerobic fitness can be accomplished with IT when appropriate and needed. The old concept of an "aerobic base" for purposes of recovery in anaerobic sports is somewhat misunderstood: athletes can gain aerobic training adaptations without the use of long distance running because a variety of alternative training programs exist (e.g., IT with short rest periods). Some of these adaptations include reduced body fat, increased maximal oxygen uptake (VO2max), increased respiratory capacity, lower blood lactate concentrations, increased mitochondrial and capillary densities and improved enzyme activity.

There are generally considered to be two basic types of IT: aerobic and anaerobic. For either, the following four variables may be considered when designing an IT program:

  1. Intensity of the work interval (e.g., speed)
  2. Duration of the work interval (e.g., distance or time)
  3. Duration of rest/recovery interval
  4. Number of repetitions or repeat intervals

Aerobic IT is best suited for those beginning in the poor or low cardiorespiratory fitness classifications because it is less intense. Anaerobic IT is primarily reserved for those in the higher cardiorespiratory fitness classifications who desire to increase speed, lactate threshold and overall aerobic power.


  1. Baechle, TR; Earle, RW. (2000). Essentials of Strength Training and Conditioning. 2nd ed. (NSCA)
  2. Cotton, RL. (1997). Personal Trainer Manual. (ACE)