High Intensity Interval Training (HIIT) is often promoted as the ultimate form of cardio. It provides a time-efficient way to improve fitness, burn fat, and reshape your body. Many headlines claim it delivers faster and better results compared to traditional steady-state cardio. But does HIIT really live up to the hype?
In this article, we break down what HIIT actually is, how it compares to other forms of cardio, and how you can include it safely and effectively in your program.
What is HIIT?
High intensity interval training (HIIT) refers to repeated bouts of relatively hard exercise, alternating with rest periods. It is typically contrasted with Moderate Intensity Continuous Training (MICT), where a person exercises at a longer, moderate intensity without breaks or rest periods. High intensity interval training generally involves heart rate targets above 80 percent of maximum heart rate. This is sometimes referred to as exercise in zones 3, 4, and 5 in the “5 zone” model of exercise, where each zone reflects an increasing intensity. Another form of HIIT is Sprint Interval Training (SIT), which has an even higher intensity rate, 90 percent of maximum, and zone 5 or greater. VO2max describes a person’s maximum ability to take in, transport, and use oxygen during physical exertion. This is sometimes known as a person’s maximum “aerobic capacity”.
Here are a few simple examples of HIIT workouts:
- 3 to 6 Running: 30 seconds on at 600 to 800 m running pace
- 4 to 5 Exercises (e.g., High Knees, Squats, Mountain Climbers, Push ups) for 30 seconds
- 4 rounds 250 meters rowing (time based)
- Tabata intervals (20 sec ON / 10 sec OFF) on an Airbike
What Are The Health Benefits of Interval Training?
HIIT dramatically boosts VO2max, insulin sensitivity, and fat loss in far less time than traditional cardio, while preserving muscle mass and improving cardiovascular health (Milanović et al., 2015; Gibala et al., 2012). Just 15–20 minutes of HIIT can match or surpass the aerobic and metabolic gains of 45–60 minutes of moderate steady state training.
That said, both HIIT and moderate intensity continuous training (MICT) improve VO2max similarly when total work is matched; longer intervals (>2 minutes) are especially effective for aerobic gains. Every incremental rise in cardiorespiratory fitness lowers all cause mortality risk, making either approach a powerful tool for health and longevity.
FFor body composition, exercise alone—including HIIT—has minimal direct impact on weight loss, with no significant fat loss edge over MICT (Wewege et al., 2017). But HIIT shines indirectly: it enhances appetite regulation, builds and preserves muscle during fat loss, and combats metabolic slowdown (Wilson et al., 2012).
Safety Considerations
HIIT doesn’t mean going “all out” every time. True maximal efforts are not sustainable and may increase injury risk and fatigue, especially for beginners.
Instead, think of HIIT as “hard but repeatable” — challenging without completely exhausting you.
Here’s a safe progression for those new to high-intensity work:
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Always begin with a proper warm-up
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Start at a low to moderate intensity, focusing on mastering good form before adding speed or power.
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Keep workouts short initially (e.g., 15-20 minutes), gradually increasing their length as your fitness improves.
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Limit sessions to one HIIT workout per week, slowly building up to a maximum of two or three as your body adapts.
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Avoid heavy lifts or explosive movements at first; especially beginners as it’s fast-paced and can compromise your form.
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Listen to your body and prioritize recovery
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Track your progress in a journal or fitness app to stay motivated and monitor improvements.
Conclusion
In summary, HIIT is safe and effective for improving aerobic capacity, VO2max, and improving health, but should not be the only form of cardio training a person uses. The intensity and volume should be programmed specifically for individual goals and current fitness levels rather than always pursuing maximum effort.
For example, short-duration HIIT (15 minutes including warm-up) performed 3 times weekly for 6 weeks can meaningfully improve cardiorespiratory fitness. In contrast, elite endurance athletes typically perform very high weekly training volumes, and distribute a high proportion of moderate-intensity exercise, with a much lower proportion of high-intensity work.
Finally, remember that consistent, long-term progress depends not just on your effort, but on prioritizing adequate recovery and gradual progression to prevent burnout and injury.
Resources
📝Milanović et al. (2015)Effectiveness of HIIT vs. MICT on VO2max
📝Gibala et al. (2012)“10 x 1-min” HIIT protocol → Matches 50 min of MICT.