Just two to three weekly HIIT workouts can improve health and performance. Here’s how to build a workout and recovery routine that’s actually effective.
High-intensity interval training (aka HIIT) is exactly what it sounds like: a workout that alternates between periods of vigorous work and bouts of full-fledged rest or active recovery.
Actually incorporating HIIT workouts into your routine isn’t as straightforward. There’s a science to building a regimen that’s both effective and safe.
How Many HIIT Sessions Per Week Is Best?
Two to three HIIT workouts a week is generally the sweet spot.
Research suggests that performing just two HIIT sessions a week is tied to greater increases in maximum heart rate than doing moderate-intensity continuous training or training that combines the two modalities. Among inactive adults, a twice-weekly HIIT routine has been found to promote quality of life and cardiometabolic health.
Plus, in a recent exploratory study, recreationally active participants had the largest improvements in specific performance and health markers when they did two to three HIIT workouts a week. Importantly, there wasn’t a clear, additional benefit of doing three weekly sessions. This suggests a twice-a-week routine is efficient enough to improve cardiorespiratory health.
The Benefits of Regular HIIT
By alternating between high-intensity bursts and recovery moments, you’re able to spend more time overall training at a vigorous intensity. That allows you to more efficiently hit the recommended 75 minutes of vigorous aerobic activity per week, set in the Physical Activity Guidelines for Americans, to support health. (The alternative: 150 minutes of moderate-intensity aerobic activity or a combo of the two.)
Cardiovascular health aside, HIIT can improve performance markers such as time to exhaustion and VO2max — the maximum amount of oxygen your body can use during exercise, which is the best indicator of aerobic fitness. The VO2max benefit is likely due to adaptations such as increased stroke volume (the amount of blood pumped per beat) and improved heart contractions that support oxygen delivery to working muscles. The fitness format may also reduce body fat percentage, though the exact mechanisms still need to be determined, research suggests.
The Problems with Overdoing HIIT
Like any other workout, HIIT can cause exercise-induced muscle damage, particularly if you’re performing new or strenuous exercises. But due to the high-intensity nature of the format, it also runs the risk of compromising muscle fibers, thus contributing to injuries, research shows. Sprint interval workouts (SIT, a style of HIIT) have been found to trigger greater damage and muscle pain than longer, sub-max intervals.
Do HIIT too often, and you might experience injury.
How to Program Your Own HIIT Workouts
Your workout doesn’t have to follow one specific protocol to be considered HIIT. Your intensity, interval time, number of sets, recovery time, and exercises performed can vary in each workout.
During your working periods, the goal is:
To increase your heart rate to at least 77 percent of your maximum heart rate (HR max)
To elevate your rating of perceived exertion to feel like a 7 out of 10, at minimum
Those work bouts may last 15 seconds to four minutes, depending on your intensity; a 7 out of 10 effort might be 90 seconds, while an all-out effort might last 20. All in, your HIIT workout might have just 15 minutes of active work — and that’s enough to improve cardiometabolic health and cardiovascular endurance, research suggests. If you’re a beginner, your rest periods are generally equal to or slightly longer than your work periods (except for Tabata). You might do active recovery movements that keep your heart rate slightly elevated or passive rest, focusing on deep breathing before the next set.
What Work-Rest Ratio Should You Use?
Your HIIT workout’s work-rest ratio should reflect your fitness level and goal.
To Build Baseline Fitness: Beginners might start with a 1-2 or 1-3 ratio, like 30 seconds of work followed by 60 or 90 seconds of recovery. Give yourself enough recovery time to let your heart rate fall and your breathing pattern return to normal. As you progress, gradually dial down your recovery to reach a 1-1 work-rest ratio.
To Enhance Athleticism: Program short work intervals and long rest periods (e.g., a 1-5 ratio) if you’re doing demanding, explosive movements, like squat jumps, thrusters, or all-out sprints — essentially, work that gets your heart rate soaring close to your max and tests your power.
To Improve Cardiovascular Fitness: Try a HIIT workout with a 1-1 ratio, like the HIIT-30S, to improve cardiorespiratory endurance and muscular strength. The longer work and rest intervals may enhance neuromuscular adaptations, research suggests.
If you’re not able to maintain roughly the same output during your work intervals, you need a longer recovery period. If you don’t feel like you need that recovery period, you might not be working hard enough.
HIIT Workouts to Try
Here are some common HIIT formats to try:
The 4x4 HIIT workout: 4 minutes of work (85 to 95 percent HR max), followed by 3 minutes of active recovery (70 percent HR max). Repeat 4 times.
The 10x1 HIIT workout: 1 minute of work (90 percent HR max), followed by 1 minute of rest. Repeat 10 times.
The HIIT-30S workout: 30 seconds of work (85 percent HR max), followed by 30 seconds of rest. Repeat 4 times.
Tabata: 20 seconds of work (90 percent HR max), followed by 10 seconds of rest. Repeat 8 times.
How to Add HIIT Workouts to Your Routine
To unlock the benefits of HIIT without burning out, follow these three tips.
Try Equinox Group Fitness HIIT Classes
Instead of programming your own HIIT workout, let Equinox do the work for you. All Clubs offer a variety of HIIT Group Fitness Classes, including favorites like:
MetCon3: This metabolic conditioning workout taxes all three energy systems for optimal results. Three rounds of exercises designed to leave you fit, energized, and ready for more. An Equinox exclusive.
Stacked: Maximize your workout by “stacking” targeted exercises to increase endurance, strength, and power. Each set is an opportunity to uplevel and achieve all-out effort. An Equinox exclusive.
Tabata Max: Max out your training in this science-based HIIT class. Push your strength and cardio limits with intervals where your rest is always shorter than your work. Challenge the possibilities of what you can accomplish in just 20 seconds as you meet or beat your goals in this Equinox exclusive class.
Whipped!: Whip yourself into shape in this circuit class that will push your limits. Build power and endurance using battle ropes, high-intensity strength, and cardio drills. An Equinox exclusive.
Check out your Club’s schedule for specific offerings and book your spot on the EQX+ app.
RELATED: I Tried: One-to-One Stretching
Prioritize Recovery After Your HIIT Workout
Recovery can’t be neglected when doing HIIT. Spread your workouts out throughout the week, with one to three days between sessions that work the same muscle groups.
Immediately after your workout, practice active recovery. HIIT generally triggers high blood lactate levels, which cause fatigue. Active recovery (like cycling, swimming, or jogging) can speed up the removal of blood lactate so your levels return to their resting state quicker than pure rest, research suggests. That means you’ll be back in the Club and ready for your next workout sooner than if you were to skip your cool-down.
Plus, active recovery may actually enhance the benefits of HIIT; one study found that people who did a HIIT program with active recovery after each workout had significantly higher anaerobic lactate thresholds than people who did the HIIT program with passive recovery. (The anaerobic lactate threshold is the point at which small increases in workload lead to large increases in blood lactate concentration. The higher the threshold, the more you can work before getting fatigued.)
Recovery also requires fueling properly. Stay on top of your carbohydrate and protein intake.
“We really want to get the protein and the carbs dialed in first, because those [respectively] support protein muscle synthesis and glycogen replenishment once carbohydrate sources are used,” Cassandra Padula Burke, M.F.S., R.D.N., L.D., C.P.T., a registered dietitian, certified triathlon and endurance coach, and owner of Catalyst Nutrition & Performance in Maryland, previously told EQX+.
Watch for the Signs of Overtraining from HIIT
When your training consistently outpaces your recovery, you’re at risk of overtraining syndrome.
Your physical performance might decline (even if you’re increasing or maintaining your training volume), and your heart rate may be higher than usual at lower exercise intensities or lower than normal during max-effort periods. Symptoms like elevated resting heart rate, persistent fatigue, sleep problems, mood disturbances, and immune system dysregulation are common. To top it off, overtraining syndrome is linked with an increased injury risk.
To help prevent overtraining, prioritize rest, eat enough carbs and protein, and pair your HIIT workouts with active recovery days to promote blood flow and tissue repair, such as stretching and other low-intensity exercise methods, research suggests. If you notice signs of overtraining, meet with an Equinox Coach to decide a plan forward, which may include taking a break from fitness entirely.
RELATED: Why You Should Be Periodizing Your Training
FAQs
Can I do HIIT every day if I keep the intensity a little lower?
You can, but your workout won’t be true HIIT. Instead, you’ll be doing moderate- or low-intensity intervals; they’ll still support your fitness, but don’t expect to see the same benefits as genuine HIIT. When using authentic training protocols, doing HIIT daily can increase your risk of overtraining.
Should HIIT come before or after strength training on the same day?
Both HIIT and strength training are demanding workouts and should be performed on different days. Otherwise, your performance will suffer. Start with HIIT, and you may not be able to lift as heavy. Begin your day with a strength session, and you might not be able to run as fast or move as explosively in your HIIT workout later.
Is a 20-minute HIIT class enough, or do I need a full hour?
Yes, a HIIT workout with 20 minutes of vigorous work (excluding recovery periods) can be beneficial. Research shows that you can improve cardiometabolic health and cardiovascular endurance with just 15 minutes of high-intensity work.
Can I still do HIIT while training for an endurance event like a marathon?
Yes, HIIT — especially sprint interval training (SIT) — can be valuable cross-training for marathon runners. Research on trail runners has shown that doing max-effort shuttle run sprints, followed by recovery periods, three times a week improves endurance and power performance. For specific guidance, talk with a Precision Run Coach.
Does age change how much HIIT I should be doing per week?
Maybe. Older adults tend to need more recovery time after workouts, particularly after introducing new exercises, due to age-related changes in the extracellular matrix (the proteins and molecules that support and give structure to cells and tissues), mitochondria, satellite cells, and more. Start with one to two HIIT workouts a week, with plenty of recovery in between sessions, and adjust your frequency as you progress.
Ready to incorporate HIIT into your fitness routine? Book an in-person HIIT class at your Equinox Club or press play on a digital class, available on the EQX+ app.