Types of Interval Workouts

The word "interval" is often used to describe 2 decidedly different workouts. Understanding the goals and results of the formats can help you select the right workout for your personal fitness program.

By simple definition, Interval is alternating bouts of high intensity work followed by lower intensity recovery or rest.

Circuit Interval Workouts

In fitness, the term "interval " is often used to define a workout that alternates cardio with strength, which somewhat fits the simple definition.

In 1991, Reebok University defined this format as a "circuit" workout and when it is performed with one cardio station, such as a step platform, alternating cardio with weights, it is specifically a "unison circuit".

But perhaps because this format is not performed at stations, which circuit tends to imply, or perhaps because the workout is performed in timed segments and cycles, it is quite common for instructors and fitness professionals to call this format an "interval" workout.

The format typically alternates timed segments of cardio aerobic activity (3 to 5 minutes), followed by a minute or so of strength anaerobic activity and cycles as such are performed repeatedly.

The relatively harder "work" effort is performed at the high end of the target heart rate or aerobic training zone - where you are working hard, but still with oxygen.

The lower intensity "recovery" is the strength segment - which is considered the anaerobic work. This portion of the cycle slows or stops the aerobic cardio activity to perform the strength movements. This generally allows the cardio vascular system to rest, as you focus on the strength (anaerobic) portion of the cycle.

Examples of this workout format are Gin's Reebok Circuit Challenge (now available on DVD) and her newer version of this format, Simply Circuit.

Interval Training Workouts

True interval training workouts, however, are pure cardio workouts which alternate bouts of high intensity anaerobic cardio work efforts with lower intensity aerobic cardio recovery periods.

In interval training for improved cardio-vascular fitness, the work effort or exertion phase is the "anaerobic" portion of the cycle where you push up to and beyond your aerobic threshold in an all-out cardio-vascular effort. The recovery phase returns you to the low end of your "aerobic" training zone where you allow your body to rest and recover.

The purpose or goal of "Interval Training" is to allow for the highest level of exertion in manageable bouts which will lead to improvements in Max Vo2 and lactate tolerance, resulting in an increased level of fitness and a greater overall caloric expenditure.

An example of this workout format is Gin's ultimate video for improving cardio-respiratory fitness, Reebok Intense Moves.

The Different Goals and Results

Circuit Interval Workouts are great for establishing a base level of fitness, by working both the cardio-vascular system and muscular strength in "manageable bouts".

Because the two components of fitness are performed in alternating specific timed cycles, it results in general overall improvement in fitness, but only up to a point. Eventually, one will adapt to the limited time of the cycles, and a plateau will be reached.

Although intensity can be increased within the timed cycles, for further improvements in cardio-vascular fitness, other variables must eventually change in order to impose a new demand, specifically time and duration.

With strength, variables must also change. While the load of the weight can be increased somewhat within the timed segments, eventually the muscles need to be worked in different ways for continued improvements and to avoid overuse injury.

This can be done by changing the actual exercise, changing the number of repetitions and varying the load appropriate to either increasing strength or muscle endurance, varying repetition speed to emphasize either the concentric or eccentric contraction, and eventually go from working the muscles in isolation into integration with other muscle groups, as the body is intended to work.

Nevertheless, after adaptation, this format can be an efficient way to maintain a good solid level of fitness, particularly for time-pressed individuals.

With Interval Training Workouts, the goal is specific to imposing a new demand on your cardio-respiratory system. Performing these manageable bouts of high intensity work followed by lower intensity recovery allows for significant gains in cardio-vascular fitness.

With interval training, there are several approaches or models which can be applied to any mode of cardio-vascular activities. This includes everything from swimming, walking, jogging and running, step training and floor aerobics, and other formats, like kick boxing and cycling, which typically utilize an interval of format.

Aerobic Fitness Intervals

With this type of interval training, the effort portion of the cycle works at or slightly above maximum steady state, and is followed by a recovery at the lower end of the aerobic training zone. Compared to a continuous steady state training at a vigorous level, the application of very hard work followed be easier recovery can allow for a longer duration of activity and greater caloric burn overall. Working up to and slightly beyond maximum challenges your heart and lungs to work just a little bit harder than it is accustomed to working, with an RPE (Rating of Perceived Exertion) of 7 (at) or 8 (slightly above).

Anaerobic Fitness Intervals

Going to the absolute maximum for anaerobic fitness intervals requires all out effort - a very, very hard sprint - which is above maximum steady state, or a corresponding RPE of 9 and even 10. A nine is working so hard that you are seriously "sucking wind" and a full ten is at a level of major discomfort that's beyond sucking wind.

With both approaches, the key to working at maximum capacity is in the recovery portion of the cycle. Without dropping to the low end of the aerobic training zone, it is difficult to muster the required energy to really push Max VO2.

Because true interval training can be very demanding physiologically, especially with anaerobic fitness intervals, it is equally important to allow the body to recover and adapt for a couple of days following such a high intensity workout. It is recommended that other modes of fitness training - strength, flexibility, or even low to moderate steady state cardio for endurance - should follow an all-out high intensity interval workout.

(Gin's instructor video, Intense Moves 2, explains and demonstrates these 2 different models of interval training, aerobic intervals and anaerobic intervals.)

Combining Circuit with Interval Training

Perhaps one of the most challenging of workout formats combines both Strength and Interval Training.

Within the cardio portion of the cycle (5-6 minutes), after a build in intensity (2 minutes), there is a sudden increase in work effort (1 minute) at or beyond max steady state, followed by recovery to the low end of the aerobic zone (2 minutes) to complete the cardio portion of the cycle. This interval portion of the cycle is then followed by a strength segment and then the cycles are repeated.

Because one of the by-products of true interval training is the release of lactate, the legs are most likely the first to begin to feel fatigued, therefore the strength movements focus primarily on the upper body.

(An example of this format is Gin's Reebok Extreme Step.)

Complexity or Simplicity?

With all-out intensity interval workouts, it is important to be able to focus on intensity, rather than pattern execution. Therefore, as intensity increases, complexity generally decreases. At the peak of the workout, high met expenditure movements that can be performed repetitiously will allow for the highest level of work. Because oxygen supply is being primarily sent to the hard working muscles, thinking can become quite difficult, therefore the "keep it simple" approach generally allows for the greatest degree of effort.