Sprint Interval Training: How to Burn Fat and Increase Speed

SIT is an advanced workout with two components — short bursts of activity performed at maximal effort followed by a long rest period.

More specifically, SIT is characterized by repeated, brief intermittent bursts of all-out exercise, typically 4–6 intervals of up to 30 seconds each, interspersed with periods of active or passive recovery, generally around 4–5 minutes (1, 2).

While the work-to-rest ratio varies, it is often set around 1:8. For comparison, the HIIT ratio is often set at 1:1, 1:2, or 1:3.

Summary

Sprint interval training (SIT) is an advanced training method that involves a brief maximal work period followed by a longer rest period.

SIT is an excellent workout to add to an advanced fitness routine. It allows you to put in maximal effort in a minimum amount of time, and it’s a great way to improve athletic performance and aerobic and anaerobic fitness (2).

“Anaerobic fitness” refers to activities that are generally of short length and high intensity. During this type of activity, your body breaks down glucose, or sugar, for energy without using oxygen. SIT is an anaerobic activity.

Meanwhile, “aerobic fitness” refers to activities that raise your heart rate and breathing for a sustained period of time, such as walking and jogging.

In a 2016 study in previously inactive participants, 14 people ages 40–50 and 14 people ages 20–30 performed 4–6 30-second all-out sprints with 4 minutes of active recovery in between (3).

After completing this workout 3 times per week for 4 weeks, both age groups had improved anaerobic and aerobic fitness (3).

SIT also improves running performance in trained athletes.

In a 2018 study, 16 trained trail runners completed 4–7 bouts of 30 seconds of maximal intensity sprinting, interspersed with 4 minutes of recovery (4).

After doing this just 3 times a week for 2 weeks, they had improvements in running performance metrics like endurance, strength, and power (4).

Summary

SIT can improve athletic performance, cardiorespiratory fitness, and anaerobic fitness.

HIIT often tops the list of popular fitness trends. While this exercise method provides many benefits, including a high calorie burn, it’s not the only way to burn calories in a short amount of time.

SIT also burns calories and promotes similar gains in cardiorespiratory fitness (5).

Plus, a 2019 review and meta-analysis found that interval training — both HIIT and SIT — resulted in 28.5% greater reductions in total absolute fat mass compared with moderate-intensity continuous training (6).

When it comes to fat loss differences between HIIT and SIT, SIT may have an advantage.

Results from a 2018 trial in active women ages 24–36 found that an 8-week SIT protocol induced greater reductions in the sum of skinfolds, body weight, and BMI than a HIIT protocol did (7).

Summary

Both HIIT and SIT burn calories, but some research points to greater fat reduction with SIT.

SIT is considered vigorous physical activity.

Although the highest calorie burn comes from the sprint intervals, you’re also burning calories during the rest periods. This holds especially true if you’re performing active rest such as walking as compared with passive rest such as sitting or standing still.

Using a physical activity calorie counter can help you pinpoint how many calories you’ve burned based on your body weight, movement duration, and activity.

If you’re interested, you can look online for free sites and apps that can help you determine the number of calories burned during a specific activity.

Additionally, smartwatches and some heart rate monitors can give you an estimate based on your heart rate during an activity.

Because SIT requires intense work periods followed by rest periods, it may be difficult to estimate your calorie burn based on pre-designed charts.

Summary

Determining the exact calorie burn from a session of SIT depends on your body weight, activity duration, and overall intensity. Because of the rest periods, finding an exact calorie number can be difficult.

Like any other form of exercise, SIT has some disadvantages.

Overall, it’s incredibly demanding and taxing on your body. Some people should not do this type of workout unless they receive approval from a doctor or another healthcare professional.

Because you use nearly maximal effort during the work period, SIT requires a baseline fitness level. If you’re new to exercise or just getting back to it, it’s best to take some time to build up your cardiovascular fitness and muscular strength before attempting SIT.

A healthcare professional may recommend that you avoid SIT if you have any ankle, knee, hip, or other lower body injuries or chronic pain. In these cases, sprinting could do more harm than good.

This also applies to heart conditions, high blood pressure, and other medical issues that may require a modified exercise program or supervision from a doctor or physical therapist.

That’s why it’s always best to check with a healthcare professional before starting to exercise or adding a new activity to your fitness program.

Although SIT has several benefits, a 2014 review found that it’s unlikely to promote regular participation in physical activity in a largely sedentary population (1).

For starters, the strenuous nature of SIT may be a deterrent for those new to regular physical activity. People who are not used to exercising may avoid exercise if they find it aversive.

Also, because SIT is a relatively complex and structured routine that requires a high degree of self-regulation to produce results, it may not be the best activity for people new to exercise who are looking for simplicity and easy-to-follow routines.

Summary

SIT is not meant for beginners. It’s a demanding protocol best suited for advanced fitness levels. Further, because it requires near-maximal to maximal efforts, it may not be suitable for people with certain medical conditions, chronic pain, or injuries.

Incorporating SIT workouts into your overall fitness plan a few days a week can boost your overall cardiovascular health, increase your muscular strength and endurance, burn calories, and improve certain sports-specific skills. Plus, you don’t need any fancy equipment or a gym.

If you’re a runner, you can do SIT on a treadmill, an outdoor or indoor track, a trail, hills, or a road.

To start, aim for a lower number of intervals and a longer rest period. Then, as your body adjusts and you become fitter, you can add intervals and decrease the rest period.

Try to implement one change at a time. For example, add 1–2 intervals to the workout, but leave the rest period the same. Then, when you’re ready for another change, decrease the rest interval, but don’t adjust the intervals.

Sample beginner to intermediate program

Warm up for at least 3–5 minutes with light cardiovascular exercise such as jogging in place. Follow this with a few dynamic stretches such as leg swings, high knees, and walking lunges.

Then go ahead with the interval training:

1. Complete 3–4 intervals lasting 20–30 seconds at an intensity of 10 — your maximal effort.
2. Rest 4–5 minutes after each sprint. These rest periods can be complete recovery with no activity or low intensity exercise like walking. Keep the level around a 1–2.

Perform this routine 2–3 days a week for a few weeks before adding more exercise intervals or decreasing the rest periods.

Remember, these protocols are for well-conditioned, advanced exercisers. If you’re running only three times per week, completing all of these as SIT is too much intensity. Instead, start with one SIT workout per week and add more only if you tolerate it well and recover well.

If running is not your preferred mode of exercise, you can also use a SIT protocol when rowing, swimming, cycling, or using an exercise machine such as the elliptical. As long as the activity allows you to maximize your effort, you’re good to go.

Summary

You can add SIT to an overall fitness routine 2–3 days per week. Running, cycling, swimming, rowing, and using an exercise machine all work as modalities.

Ready to add SIT to your overall fitness routine?

Here are some safety tips, common mistakes to avoid, things to look out for, and ways to get the most out of the program:

• See a doctor. If you’re not already participating in an intermediate to advanced exercise program or if you have any medical conditions or injuries, consult a healthcare professional before adding SIT to your routine.
• Gear up. Although not essential, it can be helpful to invest in a high quality pair of running shoes that fit correctly and sweat-wicking clothing to keep you comfortable while working out.
• Start slowly and increase the intensity even more slowly. SIT is meant as an addition to an overall fitness routine. When starting out, do only two sessions each week.
• Focus on progressive overload. As your body adjusts and you feel ready to advance the workouts, make only one change at a time. For example, add one session to the week or increase the work interval or number of intervals every 2–3 weeks (8).
• Spread out your training. It’s best not to do back-to-back SIT workouts. It’s OK to exercise the day after a SIT session — just stick to lower intensity cardio workouts or strength training sessions to allow your body to recover.
• Work with an expert. If you need help incorporating SIT into your fitness routine, consider working with a running coach, personal trainer, or physical therapist if it’s an option for you.

Summary

Even if you’re at a higher fitness level, it’s critical to go slowly when starting out with SIT. Start by adding just two SIT workouts per week. It can be helpful to invest in the right gear, including a high quality pair of shoes.

Sprint interval training (SIT) is a time-efficient workout that combines periods of maximal effort with longer rest periods. Because of this, SIT is designed for people who have a solid fitness foundation.

It can improve your fitness and burn fat and calories, and it doesn’t require a gym.

Because the intervals are performed at maximal effort, it’s a good idea to get clearance from a healthcare professional before beginning a SIT protocol, especially if you have any preexisting health conditions or injuries.