HIIT (short for high-intensity interval training) is popular for a reason. It’s one of the most time-efficient exercise formats, but what does this mean, exactly? And how does HIIT get so much done so quickly?
It’s worth understanding why it can be so effective within relatively short sessions. This guide covers the real, evidence-backed benefits of HIIT, who it’s best suited for, how it compares to steady-state cardio, and how to get started safely.
What Is HIIT, Exactly?
HIIT is a type of workout that alternates between short bursts of intense exercise and intervals of rest or easier, low-intensity movement. The short bursts of harder exercise should generally be near-maximal effort, typically 20 seconds to two minutes each. The rest periods or low-intensity intervals can be anywhere from 10 seconds to 90 seconds.
HIIT vs. “Hard Workouts”
A general “hard workout” can involve continuous intense effort with little to no breaks. What sets a HIIT workout apart from other challenging workouts is its structure. HIIT alternates short periods of high-intensity effort with planned recovery periods, allowing you to repeatedly push your intensity throughout the workout.
What Are the Proven Benefits of HIIT?
Maybe you’ve heard about HIIT and want to find out whether it lives up to the hype. Perhaps you’re a regular gym-goer considering adding a more challenging workout to your routine. Or maybe you’re just looking into new training styles to mix things up. In any case, we’ll go over all the research-backed benefits of HIIT ahead.
Does HIIT Burn More Calories Than Steady-State Cardio?
Studies have shown that HIIT might generate a higher calorie burn per minute than moderate-intensity, steady-state cardio. This may be even more true for HIIT with speed intervals than circuit-based HIIT. Even with periods of rest, the intensity of the work intervals requires substantial energy expenditure.
Some research points to the “afterburn effect” of HIIT. Known as excess post-exercise oxygen consumption (EPOC), this essentially means you keep burning calories at a slightly higher rate in the hours after a HIIT session.
Other research has suggested that HIIT may be more effective than moderate-intensity continuous training (MICT) for supporting weight loss. On the other hand, while regular continuous-intensity and MICT sessions can both support better health outcomes, steady-state sessions might be more suitable for older adults and others with mobility issues who want to lower the risk of injury during exercise.
Variety can be beneficial when creating a workout schedule. More research is needed, but a mix of HIIT and lower-intensity work might maximize your energy expenditure more than doing just one or the other.
Is HIIT Good for Heart Health?
High-intensity interval training has been shown to improve aerobic capacity (how much oxygen your body can use for energy during intense exercise) and VO2 max (maximal oxygen uptake). A higher VO2 max is associated with heart health. Some consider it one of the strongest predictors of cardiovascular health and longevity.
Some studies suggest that HIIT improves cardiovascular markers as effectively as longer-duration moderate exercise in less total time. Keep in mind, though, these benefits come from regular training, with consistent effort and proper execution.
Can HIIT Help Build or Maintain Muscle?
HIIT circuit training that incorporates resistance-based intervals (kettlebell swings, weighted squats, push-ups, etc.) may help you maintain muscle mass. It might also support modest strength gains, especially for beginners.
Pure cardio-based HIIT (think sprints or bike intervals) builds muscular endurance and power. But this type of exercise is less effective for muscle hypertrophy (building muscle mass in response to training) than dedicated resistance workouts. So, cardio-only HIIT should be seen as a complement to, not a replacement for, strength training.
Is HIIT More Time-Efficient Than Other Workouts?
Many view HIIT as one of the most time-efficient workouts. A meaningful HIIT session can be completed in 15 to 30 minutes, including a warm-up and cool-down. This makes it a practical option for people with limited time who still want cardiovascular and metabolic benefits. Including strength moves with a circuit-based routine can also offer modest muscle-building benefits in limited time.
Does HIIT Improve Metabolic Health?
Yes, doing regular HIIT sessions seems to help improve metabolic health. Research has linked this form of exercise to improved insulin sensitivity and blood sugar regulation. There’s even some evidence that high-intensity interval training might help improve these and other metabolic health markers (cholesterol levels, blood pressure, etc.) independent of weight loss.
How Does HIIT Compare to LISS Cardio?
Let’s look at the key differences between HIIT and LISS (low-intensity steady-state) cardio:
- HIIT – High-intensity interval training generally involves shorter sessions with near-maximum-effort intervals alternating with rest or lower-intensity intervals. Research suggests it might have a slightly greater EPOC (“afterburn”) effect, but recovery can be more demanding on the body.
- LISS – People typically do longer sessions of low-intensity steady-state cardio. This type of exercise tends to be gentler on the body, so it might be better for active-recovery days and building an aerobic base.
Research has suggested that some people find HIIT more enjoyable than low- or moderate-intensity continuous exercise, possibly because the intervals break up a monotonous feel.
That said, a well-rounded fitness routine often includes both. For example, you might do two HIIT sessions a week for time efficiency and metabolic benefits, plus two LISS sessions for endurance and recovery.
See our HIIT vs. LISS guide for a deeper comparison of these two popular training styles.
What Types of Exercise Can Be HIIT?
Almost any type of exercise can be incorporated into a HIIT workout, as long as you alternate short bursts of high-intensity effort with brief rest periods. For example:
- Running/walking – Alternating between sprinting and walking or speed-walking at an incline and slower walking.
- Cycling – Pedaling as fast as you can on a stationary bike, then slowing your pace for the rest intervals.
- Bodyweight circuits – Combining high-effort explosive movements (squat jumps, burpees, etc.) with lower-effort moves, such as crunches or slow sumo squats.
- Weighted circuits – Including moves with free weights, kettlebells, or other equipment for high-effort or active-recovery intervals.
- Tabata – Following the Tabata method with alternating periods of walking and sprinting or applying it to bodyweight moves.
Just starting out? Check out our HIIT workout for beginners.
Who Benefits Most from HIIT?
HIIT can be a solid option for:
- People with limited training time who want maximum return per session
- Intermediate and advanced exercisers looking to break through plateaus or add variety to their routine
- Anyone trying to improve cardiovascular fitness, metabolic health, blood sugar levels, or body composition alongside a strength program
However, high-intensity interval training isn’t the ideal choice for everyone. Those recovering from injury, people who’ve had recent surgery, and those with mobility issues may want to go with a lower-intensity format, like LISS.
Although an HIIT session can be modified for any fitness level, true beginners may want to build a base before participating in high-level group classes. On the flip side, HIIT could pose an overtraining risk for folks already training at peak intensity five or more days a week.
How Often Should You Do HIIT?
You don’t need to overdo it with HIIT. Even just two sessions a week can offer meaningful benefits and show fitness improvements over time. Many people do two to three weekly sessions.
One thing to note is that HIIT is demanding on the nervous system and joints. More isn’t necessarily better, and recovery between sessions matters. Consider balancing out your HIIT sessions with lower-intensity workouts, such as walking, cycling, yoga, or swimming. Extra points if you include a couple dedicated strength-training sessions each week.
How Can You Get Started With HIIT?
If you’re new to HIIT, start with simple intervals: 30 seconds of work, 60 seconds of rest, repeated six to eight times on a bike, rower, or treadmill. You can also do circuit-based sessions with bodyweight movements.
Doing intense exercise without a warm-up significantly increases the chances of injury. Warm up for five to 10 minutes before every HIIT session with walking or dynamic moves, like arm swings, walking lunges, or jogging in place.
Group fitness classes that follow a HIIT format provide built-in structure and coaching. This can reduce the guesswork for those new to this type of training.
Find HIIT Group Fitness Classes Near You
Factory Store Online offers instructor-led group fitness classes. This includes HIIT formats, like boot camp and circuit classes.
Members also have access to our state-of-the-art cardio machines (treadmills, rowers, bikes, ellipticals, etc.), turf areas, free weights, and other exercise equipment that support HIIT training at every level.
Find your nearest Factory Store Online location to get started.
