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Anaerobic Interval Training


I am a newly qualified personal trainer. I have been doing interval training for my cardio workouts for quite a while as I thought this was the best way to achieve and maintain a good level of non sports specific aerobic fitness. However, I read today that anaerobic training/interval training results in no real improvement in your cardiovascular level of aerobic fitness. So should I switch from this to gain and maintain a good level of aerobic fitness (i.e., do medium distance jogging for 3-5 miles)?


This is a great question, and the answer somewhat depends on your goals (be they more endurance or strength related) and whether or not you want to improve cardiovascular fitness or maintain it. That said, it is important to understand the energy system demands in relation to exercise.

The three energy systems include the ATP-PCr, Glycolysis and Aerobic pathways. All three contribute to the body's energy needs at the start of exercise but it depends on the person, the effort of the exercise or the rate at which energy is used. The graph below will help to illustrate this. Aerobic conditioning, such as jogging at lower intensities, certainly helps to improve the cardiovascular and pulmonary systems and is very beneficial to include in all exercise programs. The goals of the individual will dictate the aerobic proportion relative to the exercise session time. Anaerobic conditioning does have a place in cardiovascular health but must be periodized at the proper time of the year for the client based on his goals but, more importantly, on his physical adaptations to training. It is much better for any person to be well aerobically adapted prior to starting a high intensity anaerobic training circuit. With this in mind, there is one particular research study I found that supports the benefits of using anaerobic training to improve aerobic conditioning.

It is important to realize that some interval training can actually help maintain cardiovascular fitness. One particular research study looked at this and had some very interesting conclusions. There were two types of interval workouts done on different days. The first was a work session of 20 seconds with 10 seconds rest with an intensity of 170 percent VO2max. The second was a work session of 30 seconds with two minutes rest at an intensity of 200 percent VO2max. The researchers reported that the first interval taxed the anaerobic and aerobic energy systems more than the second interval. During each interval session, PCr is used, oxygen is consumed and lactate is produced from anaerobic glycolysis. During the second interval with the two minute rest period, oxygen stores can be replenished more so and the PCr stores that were used in the interval session can be significantly restored. In contrast because the rest period is shorter in the first interval session, PCr and oxygen recovery will be minimal, which causes faster accumulation of lactate.

In conclusion, the results of this one study clearly indicated that the two different interval sessions with different work to rest ratios have different energy demands. The authors stated that the first session with a lower rest interval placed more demand on the anaerobic and aerobic energy systems due to peak stress of both, whereas the second interval session with prolonged rest did not elicit a peak stress on either energy system. To develop anaerobic capacity, interval session one is preferred. However, a combination of both interval types would be beneficial for both energy systems.

Anaerobic interval training can have a place in a training program but should be properly injected into a well periodized yearly program based on the client’s needs and goals. At certain times of the year, both anaerobic and aerobic training would have benefits while during others, aerobic training alone would be the preferred method to prepare the body for future higher intensity training sessions. Even though this study did prove some aerobic energy system benefit from high intensity interval training, I would ensure that adequate low intensity aerobic training is implemented prior to and the use of interval training be significantly shorter than its counterpart for non athletes.


  1. Gastin, P.B. Energy system interaction and relative contribution during maximal exercise. Sports Medicine 31 (10) 725-41. 1991.
  2. Tabata, I. et al. Metabolic profile of high-intensity intermittent exercises. Med Sci Sports Exerc 29(3): 390-395. 1997.