Cardiovascular exercise is a vital component of fitness training, and running is a great form of cardiovascular exercise. Plus, it requires relatively little equipment and can be performed almost anywhere.

The drawback? Traditional long distance running is incredibly time consuming and doesn’t typically involve higher intensity sprints.

Fortunately, interval running offers a solution for busy individuals who are looking for large improvements in fitness but don’t have the time for longer runs.

Interval running also appeals to those who prefer greater intensity in their workouts than the typical long, slow jog.

This article breaks down interval running as an aerobic training method and prepares you to create your own interval training program to meet your fitness and lifestyle needs.

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Interval running is a method of structuring your running workouts to allow increased intensity and greater aerobic improvement with less total time spent per workout.

Regardless of your age or specific health goals, the Centers for Disease Control (CDC) and American College of Sports Medicine (ACSM) recommend that healthy adults age 18–65 years participate in moderate aerobic exercise for 30 minutes 5 days per week.

Alternatively, you can perform vigorous aerobic activity for at least 20 minutes 3 days per week to meet this recommendation (1).

Interval running is an efficient way to maximize aerobic improvement while minimizing the overall time spent per workout. It also fits well into the ACSM guidelines of getting at least 20 minutes of vigorous aerobic exercise 3 times per week.

With interval running, you’ll perform a few minutes of light jogging to warm up. Afterward, the bulk of the workout revolves around brief periods of high intensity running, followed by periods of lower intensity jogging, walking, or even rest.

The high intensity pace for interval running exercise exceeds what you could physically sustain for 30 minutes, and the lower intensity pace allows you a brief recovery for the next high intensity pace.

Each interval period lasts 10–60 seconds at the high intensity pace, and 10–60 seconds at the lower intensity pace. In coaches’ terms, these are known as “duty cycles.”

The specific duration of each duty cycle, including the ratio of high intensity to low intensity time in each cycle, varies based on your specific fitness goals, conditioning level, and time available for working out.

This ratio of high intensity to low intensity is called the work-rest ratio, and it’s a key variable in designing interval running programs.

Overall, the structure of interval running programs allows far more time spent at higher intensities compared to a traditional running program.

The higher intensity results in greater improvements in your maximum aerobic capacity and works more muscle fibers overall compared to longer, slower jogs.

Summary

Interval running involves periods of high intensity running alternated with low intensity running, walking, or rest. These cycles allow greater intensities within the workout but reduce the overall total training time.

Planning the specific time spent in each interval, number of intervals, and weekly frequency are the most important factors in designing an appropriate interval running program.

Designing the right program depends on your specific training goals and baseline fitness level.

Aerobic versus anaerobic training

Interval running allows you to target different energy systems in your body depending on your specific goals.

The main sources of energy used in interval running are the aerobic and anaerobic systems. Both systems always contribute some energy, but the relative contribution of each depends on the specific interval used.

Aerobic improvements include increased endurance and improved efficiency in the cardiovascular system.

Anaerobic improvements include greater maximal speed, increased muscle growth, and improved maximal power.

You should focus each 4-week workout plan on either aerobic or anaerobic improvements for the duration of the program.

Start with at least one period focused on aerobic improvements to build a strong base and prepare your muscles and joints for the intensity of anaerobic training.

General workout structure and tracking improvement

Always warm up with 5–10 minutes of light jogging before an interval training session.

Beginners should start with just a few duty cycles per workout twice per week and add additional cycles each week as their fitness improves to avoid overuse injuries.

Avoid doing maximal intensity intervals until you build up a baseline fitness level with aerobic intervals.

Without having to wear a heart rate monitor or perform calculations, the best way to track improvements is by tracking the distance you cover during each high intensity interval.

Even a rough estimate from running around a track can show clear signs of improvement.

For a more precise method of tracking progress, you must wear a heart rate monitor or manually take your pulse and compare it with the distance traveled and your perceived exertion.

This can be tedious to do during intense training without a coach or workout partner.

Tracking your resting heart rate as soon as you wake up in the morning is an easier way to measure cardiovascular improvement for non-athletes targeting aerobic benefits.

A lower resting heart rate is a sign that your aerobic system is becoming more efficient.

To avoid overtraining, perform two 20-minute light jogging sessions in the week following your completion of each phase of the program before continuing.

This beginner program will get you going on your aerobic interval training. After performing your 5-minute light jogging warmup, increase your intensity to roughly 75% of your maximal effort for 30 seconds.

After the intense interval, jog slowly for another 30 seconds and repeat 3 times. Perform twice per week for 4 weeks.

Add a duty cycle each week. In week 4, you should be performing 6 total intervals per workout, twice per week. Combined with your warmup, the total workout duration should be roughly 11 minutes by week 4.

Beginner interval running workout:

  1. Complete 5 minutes of a light jogging warmup
  2. Run 30 seconds at 75% intensity followed by 30 seconds at 25% intensity
  3. Repeat for 3 cycles on week 1
  4. Perform the workout twice per week, adding a cycle every week for 4 weeks

Once you’ve performed the 4-week beginner program, you should be ready to add a training session. The intermediate program involves three sessions per week and adds cycles each week.

For this program, you’ll begin by performing 3 cycles, followed by a full 1-minute rest, then repeat the cluster 2 more times.

Perform each workout 3 times per week for 4 weeks. Each week add a cycle to each cluster.

By week 4, you’ll be performing 3 clusters of 6 intervals. This results in a total of 18 intervals and roughly 25 minutes of total workout time.

Intermediate interval running program:

  1. Complete 5 minutes of a light jogging warmup
  2. Run for 30 seconds at 75% intensity followed by 30 seconds at 25% intensity
  3. Repeat for 3 cycles followed by a 1-minute rest — this is 1 cluster
  4. Perform 2 additional clusters per workout in week 1. Over the course of the week, there will be a total of 9 cycles broken into 3 clusters.
  5. Perform the workout 3 times per week, adding an interval cycle to each cluster per week.

By the time you get through the beginner and intermediate training programs, you will have 8 weeks of interval running training under your belt.

At this point, you can opt to continue to push your aerobic capacity with the advanced aerobic training program, maintain your fitness with the intermediate program, or begin the anaerobic training program.

For the advanced program, you will begin with 3 clusters of 4 cycles using a 30-second interval.

Each week, you will perform an additional cluster per workout. By week 4, you will be performing 6 clusters of 4 cycles for roughly 30 minutes of total workout time, including the warmup.

The overall workout volume will be substantial by the end of week 4.

Advanced interval running workout:

  1. Complete 5 minutes of a light jogging warmup.
  2. Run for 30 seconds at 75% intensity followed by 30 seconds at 25% intensity.
  3. Repeat for 4 cycles followed by a 1-minute rest.
  4. Perform 3 full clusters in week 1. Week 1 workouts will have a total of 12 cycles broken into 3 clusters.
  5. Perform the workout 3 times per week, adding a cluster to each workout per week.

Customizing your interval training plan

As mentioned, interval running can be used for both aerobic and anaerobic training.

The interval used in the programs above is a 1-to-1 work-rest ratio and will primarily target the aerobic system. However, you can adapt your program for anaerobic training or a heavier aerobic focus by manipulating the ratio.

Generally, higher intensities are sustainable for a shorter period and require more rest.

To target anaerobic improvements, a work-rest ratio of 1-to-5 is better than 1-to-1. In this case, an all-out sprint for 10 seconds followed by a 50-second rest would maximally target anaerobic improvements.

Understand that aerobic and anaerobic training is a spectrum rather than a hard-and-fast number cutoff. Every activity involves some contribution from both systems, with each playing a greater role depending on the interval.

The shorter the work interval and the longer the rest, the more your body will rely on anaerobic energy, provided you’re proportionally increasing the intensity.

With this in mind, it’s best to stick with one work-rest ratio for a 4-week duration to optimize the specific adaptation.

Summary

Interval running should be performed as part of a structured, planned program. Begin with just a few aerobic intervals before progressing to more intense anaerobic training or a high number of interval cycles.

Interval running offers many benefits. These include the standard benefits of aerobic exercise, such as a lower heart rate and reduced blood pressure levels. However, interval running causes additional adaptations due to the intensity level you reach during the hard intervals.

The studies on interval running show many overall health benefits, such as the following (2, 3, 4,):

  • improved capacity to utilize oxygen, including in older adults
  • a decreased resting heart rate
  • a decreased resting blood pressure
  • decreased risk factors for cardiovascular disease

These benefits are similar to those associated with traditional longer duration running at slower paces.

However, research suggests that interval running offers additional benefits over traditional running, including (5, 6):

  • reduced workout durations for similar results
  • improved performance during sprinting with anaerobic intervals
  • increased use of fat for energy
  • increased insulin sensitivity
  • increased muscle mass growth when using anaerobic intervals

Calories burned from interval running

The number of calories you burn in an interval running session depends upon many factors, including your current weight and fitness level, the intensity of each work interval, and the total number of intervals used.

A 20-minute session of aerobic exercise like interval running burns anywhere from 150–400 calories.

However, the increased intensity from the intervals increases your metabolism over the following 24–48 hours, burning more calories at rest. This is advantageous given the shorter amount of time needed for interval running workouts (7).

When combined with a proper nutrition plan, interval running is a good way to support weight loss programs.

Muscles used in interval running

Interval running activates most of the larger muscle groups of the lower body. Research using electrical measurements of muscle activation found the following muscle groups are involved in interval running (8):

  • quadriceps (front thigh muscles)
  • gluteus maximus and medius (hip muscles)
  • gastrocnemius and soleus (calf muscles)
  • adductors (inner thigh muscles)
  • anterior tibialis (shin muscles)
  • hamstrings (back thigh muscles)

These muscles are essentially the same as those worked during traditional running. However, due to the increased time spent at higher intensities, interval running will offer greater stimulus to these muscle fibers.

Summary

Interval running offers many health and performance benefits and burns calories during and after the workout. Interval running targets many of the large muscle groups in the lower body.

Overall, interval running is a safe way to improve cardiovascular health via shorter duration workouts, compared with traditional running.

Nevertheless, there are a few potential risks with interval running. These largely stem from the increased intensity and impact that occurs during the faster-paced intervals.

The impact on the ankles, knees, and hips is greater during faster running.

You’ll probably feel especially sore after your first couple of interval workouts. While muscles can adapt fairly rapidly, it takes more time for your joints and bones to adapt to this stress.

To mitigate the potential for injury, start slowly when you begin interval running. If you’re new to running altogether, do 10-minute jogs with a brief sprint at the end twice a week for 4 weeks to begin adapting to running.

If you have experience running but not with intervals, start with the beginner program and consider doing a single cluster for the first few weeks, with at least 2 full days between sessions.

Your body will adapt better to the stress if you don’t overload it too quickly and ensure adequate recovery.

If you have not exercised in a long time, a brisk walk may be enough intensity for the high intensity interval, and a slow walk for the low intensity interval.

If possible, you should avoid hard surfaces like concrete or asphalt to reduce the impact. Rubberized track, grass, or other softer surfaces are your best bet for interval running.

Finally, always take an active rest week in between 4-week sessions. A few brief jogs or walks will maintain your fitness while allowing your body to recover for the next phase of training.

Summary

To avoid risks of injury or overtraining, add intervals slowly and take active rest weeks between each 4-week program.

The simplest way to time your intervals is with a standard stopwatch.

However, due to the intensity of interval running, you may be out of breath and fumbling around trying to track your intervals manually.

As such, it may be helpful to have an interval timer app that tells you when to rest and when to go.

The following are just a few apps that offer interval timing:

Interval running is an efficient and effective way to improve your aerobic and anaerobic fitness, as well as your cardiovascular health.

Generally, interval workouts require less total time than traditional distance running and allow greater intensities during the workout itself.

Depending on your specific goals, you can adjust your intervals to target different energy systems in your body.

The most important thing is to start slow and ease into interval training, particularly if you’re newer to running.

If you’re looking for a method of adding intense aerobic and anaerobic exercise without long traditional workouts, interval running offers an excellent solution.