Intervals for Cardio


How to Design Cardio Intervals

You will find many interval training programs on the internet but I still urge you to be creative and make your own programs.  Experiment by adjusting the length and intensity of the work interval along with the length of the rest interval.  The work interval or rest interval length can be longer or shorter than the other, or equal to each other.  For example, you can create intervals that are 30 second work intervals by 15 second rest intervals, 15s work intervals by 30s rest intervals, or 30s work intervals by 30s rest intervals.  Also, experiment by increasing or decreasing the number of sets within an interval workout.

Work Interval Tips

The shorter the work intervals are the more intense you should make them.  For example, lets compare intervals of 20 seconds and 60 seconds.  You can push yourself much harder in 20 seconds than you can in 60 seconds because you'll have to pace yourself more with 60 seconds.  It's like the difference between running a 200 meter and a 400 meter dash.

Short work intervals from 15 to 20 seconds are for speed and strength
Medium work intervals from 30 to 45 seconds are for overall fitness
Long work intervals from 60 to 90 seconds or more are for endurance

Rest Interval Tips

The shorter the rest intervals are the more intense the interval workout will be.  So interval workouts with longer rest intervals are easier to perform.  Beginners should start interval training with rest intervals that are longer than the work intervals.


Increasing the number of interval sets makes the workout more difficult to complete and it can lead to pacing rather than pushing yourself.  Decreasing the amount of sets will make the interval workout easier.

Interval Intensity

Although high intensity interval training (HIIT) is very popular, intervals can be designed for medium or even low intensities.  Some people prefer exercising at lower intensities simply because they feel more comfortable training there or because of health issues.  So there is no "best" interval training program and the intensity level that you choose for your intervals will depend on your personal fitness goals.  The top guideline is safety, beginners should train at lower intensities and gradually work up to higher intensities as fitness improves.

 Exercise Intensity alongside the Target Heart Rate Zone:

 Target Zones  Percentage of Max HR  Exercise Intensity
 Healthy Heart Zone  50% - 60%  Very light to light
 Temperate Zone  60% - 70%  Light to moderate
 Aerobic Zone  70% - 80%  Moderately hard
 Anaerobic Zone  80% - 90%  Hard
 Red Line Zone  90% - 100%  Very hard