High-Intensity Interval Training — better known as HIIT — is one of the most effective ways to burn a large number of calories in a short amount of time. A HIIT workout alternates between bursts of high effort and periods of lower intensity, making it efficient and adaptable to different fitness levels.
How a HIIT Workout Works
The core principle of HIIT is simple: push hard, then recover. During the high-intensity interval, you exert yourself at around 90% of your perceived effort — think an all-out sprint. During the low-intensity interval, you slow down to between 0–50% effort, such as walking, standing, or a slow jog.
High-intensity intervals typically last 30 seconds or less. Low-intensity intervals can be shorter, equal, or longer than your work period — depending on your fitness level.
One of the biggest benefits of a HIIT workout is that you don’t need any equipment. If you have access to cardio machines, they can help you track distance, calories, and exertion — but they’re not required.
The EPOC Effect: Burn Fat for Up to 36 Hours
Here’s something remarkable about HIIT: your body continues to burn fat for up to 36 hours after your workout ends.
This happens because of a physiological effect called EPOC — Excess Post-Exercise Oxygen Consumption, also known as the “afterburn effect.” According to the American College of Sports Medicine, HIIT significantly elevates post-exercise oxygen consumption compared to steady-state cardio. After an intense session, your body uses more oxygen than before the workout. The more oxygen it consumes, the more fat it burns. This includes the energy needed to repair muscle tissue, regulate hormones, and return your body to its resting state.
The harder you push during your session, the greater the afterburn effect.
HIIT Ratios: Finding the Right Intensity for You
Your work-to-rest ratio depends on your current fitness level:
1:2 ratio (beginner): 30 seconds of high intensity followed by 60 seconds of low intensity. This gives your body extra time to recover between efforts.
1:1 ratio (intermediate): 30 seconds of high intensity followed by 30 seconds of low intensity.
2:1 ratio (advanced): 30 seconds of high intensity followed by only 15 seconds of rest. This is a significant challenge and should only be attempted by those with a solid fitness base.
When Should You Do HIIT?
Doing HIIT at the end of your workout is recommended for two reasons:
You’re already warmed up. Your body is primed and ready to perform at high intensity.
Your glycogen stores are already depleted. When your body runs low on stored carbohydrates, it turns to fat as fuel — which means more fat burned during your HIIT session.
If you plan to do HIIT on its own without weight training beforehand, warm up for 5–8 minutes and stretch before starting. HIIT places significant stress on your muscles, joints, and blood vessels. A proper warm-up reduces your risk of injury — especially if you’ve been sedentary or inactive recently.
Tracking Your Effort: Why a Heart Rate Monitor Helps
During a HIIT workout, it can be difficult to gauge how hard you’re truly working. A heart rate monitor gives you accurate data on your exertion level and the calories burned. It also helps ensure you’re actually reaching the intensity needed to get results.
Is HIIT Right for You?
HIIT is not for everyone — especially those just starting to exercise. If you’re brand new to working out or returning after a long break, spend one to two weeks conditioning your heart, muscles, and joints with lower-intensity exercise first. Building that foundation will help you get more from HIIT and significantly reduce your risk of injury.
Watch this video for a visual breakdown of how HIIT works: HIIT Workout Explained
(link: https://www.youtube.com/watch?v=z02A5QLQ4S0&t=26s)
Disclaimer: Before beginning any exercise routine, consult with your physician first. The tips and exercises in this post are intended for educational purposes only.