5 Levels of Fitness

HIIT Class doing box jumps

This article is part of our 9-part series on Health for Busy People. In it we introduce the Three by Five Framework. The 3×5 Framework consists of 5 Levels of Mastery within 3 Components of Health: Nutrition, Exercise, and Psychology. If you haven’t read it yet, begin with our Three by Five Framework Introduction. Or, start from scratch with Part 1, Health Beginnings: Your WHY.

This article is about the 5 Levels of Fitness (Exercise). Let’s dive in!

Level 1: Sedentary, Little Daily Movement

Watching tv and being a couch potato

Just like with Nutrition, the bottom level of Fitness is not doing much of anything. If you are at this level, you are not formally exercising at all – and you haven’t been for at least 6 months to a year. The amount you move your body is just whatever you do during the course of the day, which can vary greatly from person to person.

One person may spend 95% of their day being completely sedentary: They sit during meals, sit during driving, sit during their job, and sit in front of the TV in the evening. Their only form of movement may be walking in between home, car, and office desk.

Other people may have jobs that have them up and about a lot, such as being a school teacher, working retail or in a factory, etc.

Anything that you do that isn’t sitting or laying down, counts as “extra calorie burn” at this level – and that can add up, but usually over several hours. Things like walking your dog, shopping for Christmas presents at the mall, housework, chasing kids around, etc, is considered “day to day movement”.

If you are at this level, you would likely not be able to maintain a very brisk, consistent walking pace for much longer than 5 or 10 minutes before becoming winded. (You would also be like one third of all Americans!)

If you’re at this level and ready to dive into the world of fitness and exercise, where do you begin? First, don’t try to do it all at once. Follow the levels below. Don’t try to skip ahead. Don’t try to go out for a 3 mile run or do a bunch of burpees if you can’t yet walk briskly for 30 minutes.

The secret to success is in moving up the pyramid, one level at a time. Master each level before adding in another layer.

Here are the remaining Levels, briefly:

Levels 2 and 3 – LISS and Strength Training form the basis of Foundational Exercise. You should plan to do them lifelong with no finish line – or, as long as your body lets you.

Levels 4 and 5 – Moderate and High Intensity workouts are more advanced. While they have many benefits, feel free to consider them Supplemental Exercise – particularly for people who live chronic high-stress lives.

Getting Started

Let’s chat about some basic gear first: There are just three things that I recommend, that you’ll end up using every day, for every workout:

  1. An easy-access, large-capacity water bottle (I use one by Contigo that I love. It carries enough water, easy to fill, easy to carry, easy to open one-handed, and locks watertight for shaking ingredients or throwing in your gym bag)
  2. Some water electrolyte tabs (I use Nuun Hydration, caffeinated and non-caffeinated). These not only help replace lost vitamins and minerals, but they make water taste better and therefore you’re likely to drink more of it!
  3. A heart rate monitor. Although I use an Apple Watch, you do not have to invest in something that expensive if you can’t afford it. A basic, accurate heart rate monitor wristband is just fine.

I have put together this “Get Started” pack with my favorites, if you’re looking to save time and just want to use what works great for me.

But yeah, that’s about it for “absolutely essential” fitness gear. Other than some comfortable clothes and shoes, everything else in the workout world is truly optional. Even though places like Nike and Under Armour make expensive training shoes and workout clothes, I see serious weightlifters in the gym all the time wearing cheap Converse shoes, some sweatpants and an old ratty t-shirt. You don’t have to be rich to start exercising. NOR do you (or should you) think you need to look like a fitness model before you begin a workout. You’re there to roll up your sleeves and sweat, not look pretty. Don’t let Instagram and the Supplement companies tell you any differently!! 😄

Level 2: Mastering LISS

walking LISS

At this level, you will master THE foundational exercise for people just beginning to train their bodies: Low Intensity Steady State (LISS) Cardio.

LISS is a form of cardiovascular exercise that raises your heart rate and gets your blood pumping, but because it remains low to easy-medium intensity, it is stress relieving rather than stress inducing. It is enjoyable. It teaches people who don’t currently exercise that moving your body feels GOOD.

LISS has so many health benefits, it’s unfortunate that some folks dismiss it as “not real exercise”. It absolutely is! It gets your blood flowing, improves circulation, flushes out toxins, helps alleviate water retention and digestion, and clears your mind. Its also helps prevent heart disease and diabetes. It stimulates your immune system. And finally, it is great for the adrenal system. It is proven to lower adrenaline and cortisol (stress) levels in the body, which also favors a reduction in belly fat and bloated midsection.

Although LISS does technically burn fewer calories per minute than a more intense form of exercise, it’s more effective at burning specifically FAT. The 60-70% Max Heart Rate that you are targeting ensures that your body will be burning only excess blood sugar and fat stores rather than muscle. When you work out too intensely, your body can panic and switch over to burning lean muscle (a more efficient fuel storage than fat). That is why it’s super important to support Level 4 and 5 higher-intensity activities with proper nutrition before and after.

It’s a lot harder to mess up LISS – in fact, its impossible. If you can move your body, you can learn to LISS. Just go out for a brisk walk, hike, elliptical, row, etc and you’ll get all the benefits! No special diet or supplement needed.

In Summary: If you cannot sustain any form of exercise currently beyond a 5-10 minute walk, mastering LISS first is where you should start.

Your goal to master this level is to get your heart rate into a 60-70% Max Heart Rate (MHR) range, and KEEP IT there for 45 minutes.

This is why I HIGHLY recommend a heart rate monitor – for accuracy in heart training and clearer visual signs of improvement.

My “perceived level of effort” deceives me all the time, and I’ve been working out for years. There will be times I’m walking very briskly and thinking I’m getting a decent LISS workout in, but when I look down at my Apple Watch, my heart rate will be barely above non-exercising, like 95 to 105 Beats Per Minute (BPM). That isn’t where I need it to be to be conditioning my heart! So I’ll purposefully speed up to boost myself to where I need to be. And there have been other times I’ll be cruising away on a run, thinking I’m getting a moderate workout in, but my heart rate monitor says I’m up in the 160’s. That’s too much for a jog, that’s entering High Intensity territory! I adjust my activity up or down to keep myself in the target heart zone that I want.

I know a lot of people feel that a heart rate monitor is a frivolous extra, and its true that you don’t NEED one to just go start walking – but if you truly want to measure your fitness level accurately, I consider it an essential. When you monitor your heart during a workout, you guarantee yourself being in the range you want during the full workout.

Speaking of hearts, let’s talk about Max Heart Rate for a minute. Max Heart Rate, or MHR, is theoretically how many times per minute your heart can beat without beating any faster. And while it’s not a precise science due to individual differences, you should start by calculating your Max Heart Rate as 220 minus your age.

It’s crucial to understand the relationship between heart rate and fitness level. The measurement of how hard your heart has to work to pump blood to the body is indicative of both your fitness level and your level of effort.

A “Low Intensity” exercise would keep your heart at 60-70% of your MHR.

A “Medium Intensity” exercise would keep your heart at 70-80%.

A “High Intensity” workout would push your heart to 80-90%, or even touching 95-100% for Maximum Intensity (which should only be done carefully, and in very short intervals).

Here’s what a LISS target range looks like for different age exercisers:

In Your 20’s: MHR 200-ish, LISS should be 120-140 BPM for the duration of the exercise.
In Your 30’s: MHR 190-ish, LISS should be 115-135 BPM.
In Your 40’s: MHR 180-ish, LISS should be 110-130 BPM.
In Your 50’s: MRH 170-ish, LISS should be 105-125 BPM.
In Your 60’s: MHR 160-ish, LISS should be 100-120 BPM.

The MHR calculation is not an exact science and you SHOULD listen to your body particularly if you are just starting to exercise and feel like your heart is beating harder than it should be. Always, please stop exercising immediately if you feel symptoms like nausea, sudden headache, dizziness or light-headedness, chest tightness or sudden shoulder pain, your throat closing up, or any physical injury like a muscle or ligament strain or joint pain.

LISS, especially, should NEVER be grueling, or even a big challenge. You are training your mind to enjoy exercise at this point. If you’re just walking but still huffing and puffing, slow down! It’s OK. You’ll be making progress in no time but for now, you need to be enjoying your workouts if you’re going to make them a habit.

If you’re just starting out, you should test walking at different speeds for 5 minutes at a time, to see what feels best for you. Peek at your heart rate monitor frequently to see how you’re doing. Settle on a speed that feels brisk but good – clearing your lungs, sinuses, pores, blood, and mind. Again – it shouldn’t feel heavy or too hard.

There are two levers you can adjust with this exercise:

  1. Speed and Incline will adjust your heart rate
  2. Length of time will adjust your heart, muscular and mental endurance

Start with a baseline 10 minute walk at 3.5 mph(ish). See if you can maintain that. If not, work up toward it. Even starting at 5 minutes is better than nothing! And if the 10-minute baseline walk is easy for you, establish what your baseline IS. Can you walk fast enough to get your heart rate into the 60-70% range for 20 minutes straight? 30 minutes straight?

Remember, your goal is to have your heart rate at 60-70% MHR for 45 minutes solid. You might be tired at the end of 45 minutes, but you shouldn’t be wiped out.

If you are less fit, then your heart will start thumping more quickly with even lighter exercises like brisk walking. You will perceive this as greater effort. Once you start becoming more fit, your heart becomes stronger. You are probably losing weight so there is less physical mass to move during workouts. Exercise also helps clean sludge from your arteries. So each heart pump is more effective. This makes it have to work less hard when you exercise.

Eventually, you’ll find that you’re barely breathing heavily during a brisk walk, and that it is challenging to walk fast enough (at least on a level surface) to break a sweat or get your heart rate much above 50-60% MHR.

When this happens, it is time for two things:

  1. Continue doing LISS as a foundational exercise, but make it more challenging. One way to do this is by starting to walk up hills rather than on a flat surface. I personally do my LISS on a treadmill set anywhere from 7% to 10% incline, depending how energetic I’m feeling, and a speed between 3.2 and 3.5 mph.
  2. You can now move up to Level 3, Strength Training. You are ready to begin incorporating Strength (Skeletal/Muscular) training into your fitness regimen.

PS – Before we move on, be aware that there are a million and one types of LISS out there. I’ve used walking here as a baseline LISS activity that almost all people can do. However, anything that gets your heart rate consistently, counts.

Cardio-based yoga or pilates, light dance classes or lightly dancing out with friends, skipping around the playground with your toddler, going for a nice long hike, playing frisbee on the beach, etc.

The point is that it can’t just be walking your dog or strolling around the mall. You need to get your heart rate consistently over the 60% threshold for the clock to start on on a proper LISS. Even though its low-intensity, you should aim to set aside dedicated time for it – even if its going for a brisk walk with headphones during your lunch hour.

Level 3: Strength Training

Woman doing a basic bench press strengh training move

As mentioned, you’ll want to keep doing LISS 3-5 times a week. But now you’re ready to start working out your muscles once a week. Because this initial new exercise is likely to leave you VERY sore the first few times, we will start you with one and gradually work our way up to three times a week.

Strength Training is the 2nd Foundational Exercise. While LISS trains your heart and cardiovascular system, Strength trains your skeletal and muscular systems. Both of them train your mind and help you feel more confident.

I consider Levels 2 and 3 to be Essentials from a Fitness perspective. People of all ages can and should be doing low-intensity cardio and moderate strength training.

I consider Levels 4 and 5 to be Supplemental Exercises. Sort of like an extra-credit for people who are interested in upping their fitness game or achieving specific goals, whether it be a specific body fat percentage or running a marathon.

It is true that once you get to a certain BMI or body fat percentage, it is tough to shave off more and get super lean without delving into the more advanced workouts. But 95% of Americans do not need to worry about that yet. That is why I try to focus on getting people going with the basics first. We can’t run until we can walk – quite literally! 🙂

A full Strength Training regimen is beyond the scope of this article, but I will break it down for you a little into a framework that you can follow. You can check out our articles on Gym Workouts and Non-Gym Workouts to get you started on effective, efficient strength workouts.

You can also utilize sites like,, Youtube how-to videos, or your favorite workout app like NTC or SWEAT to help you learn what moves are called, and find ones you like.

When you first begin to Strength Train, your muscles are likely to be very weak. The new movement is going to cause them to become inflamed and sore. This is called Delayed Onset Muscle Soreness (DOMS) and it can be pretty miserable. You can expect the soreness to peak at 2 days post-workout. You should not be sore more than 5 days after your workout. If you are, you over-trained, or injured yourself.

Once you have worked out the same muscle group for 3 or 4 times you should (by and large) stop getting DOMS. Remember that muscle soreness is not an indicator of workout effectiveness, only that you worked out a muscle that isn’t accustomed to being worked.

The real indicator of workout effective is whether you are progressively stronger with each workout.

You’ll be amazed at how quickly your body gets stronger. When I started doing pushups, I couldn’t even do one properly. Within 5 sessions of training my arms I could do 10 pushups in a row. That’s quick progress!

So don’t get discouraged thinking it takes years to become strong. It might take years to look like a bodybuilder, but that’s not where we’re trying to get you. You most likely just want to get started, and end up just looking like a normal fit person. If you want to take off and become specialized after that, there are far better fitness teachers out there than me who can take you.

For now, we’ll take this Strength Training (Level 3) in 3 phases – from once a week to twice a week to 3x a week strength workouts.

Woman using bodyweight to perform plank position

First Phase

I recommend you start Strength Training once a week. I recommend one of the two following methods:

#1: Full Body Strength Training using your own Body weight. These can be incredibly effective!! There are some incredible programs out there like Nike’s NTC (Nike Train Club) app that is free. Aim for a 30 minute workout of complex body moves, going at your own pace that is a little challenging but not grueling. These are some of my favorite combo moves. Perform 10-15 repetitions of one move from each of the 3 categories. Repeat this cycle 3 times, for 3 “sets”. Then pick a 2nd move and do the same thing – 10-15 repetitions, 3 different exercises, 3 sets.

  • Lower Body: Squats (basic or single-leg), Lunges (Step Forward, Step Back, Side to Side), Step Ups, Jumps
  • Upper Body: Pushup Variations (Incline, Standard, Decline, Wide or Narrow Stance), Commandos, Tricep Dip, Pull-up
  • Core: Pushups, Planks (Regular and Side), Sit-ups, Crunches, Flutters, Ab Bikes
  • Workout-intensity Yoga or Pilates are also great Bodyweight programs that tone both heart and muscles

#2: Full Body Strength Training using 3 Complex Weighted Moves:

  • Squats
  • Deadlifts
  • Bench Press
  • (We should add in Planks here as well for additional Core strength for desk-sitters)

Second Phase

squatting using bodyweight

Once you’ve had a taste of strength training and your body is getting stronger, you should increase these sessions to twice a week. You still want to focus on large muscle groups rather than small targeted ones.

It is your choice if you want to continue doing full body, or to split up into upper body and lower body at this point. Regardless, you should aim to work multiple muscle groups in a workout.

I love this strategy because I can go work one group (ie abs) while another group (ie shoulders) is resting. This makes my workouts super efficient, lowers time in the gym so I can get on with my day, keeps my heart rate moderately up for a good cardio workout, and minimizes “rest” time which can make me feel like I didn’t get a good workout in.

If you continue to do Full Body, do one of each of the above workouts each time, ie do the Bodyweight Workout once a week, and the Weighted Workout once time a week if you can.

If you choose to break up Upper Body and Lower Body, just choose for each whether you’d like to do a Bodyweight based workout, or a Weights based workout. They’re both exceptional ways to teach your body to become stronger, so feel free to rotate and don’t always do the same thing.

Also, feel free to ignore the gender stereotypes around strength training: Ie, its OK for women to use heavy weights, and its OK for men to do bodyweight training. A well-rounded curriculum is ideal for a well-rounded body. Muscles are muscles, no matter your gender.

As you become stronger, you will increase repetitions, choose harder moves, and in the case of weights, start lifting heavier.

It’s really important that you stay safe by never choosing a move or weight load that you have to struggle to even do one or two repetitions. So don’t try to use weights that are too heavy for you, and modify bodyweight movements if you need to. (It’s OK to do pushups on your knees before you can do them from your toes! It’s OK to do crunches instead of full situps!)

Also, make it a practice to use lighter weights or easier moves for your first 2 sets, as a warm up. This will prevent injury when you are doing harder stuff later in the workout. Focus on good form and slow, controlled movements over jerking the weights around or trying to speed-rush through. Poor form almost always results on pressure to the spine (we arch our backs to try and lift things too heavy for us, for example) and can result in spinal injuries such as strained ligaments, lumbar compression, etc.

It’s important to remember: YOU be in control of your strength training. Ignore everyone else in the gym or your class and stay hyper-locked on YOUR body. Listen to it – rest when you need to, stretch when you need to, take a water break when you need to. The keys to results in strength training are FOCUS and INTENSITY.

Third Phase

man doing a plank

Once you’re rocking these workouts twice a week and feeling good, you can up your Strength Training to three times a week. At this point, you should break out your Strength Training into more focused areas of the body:

  • Workout 1: Core (Abs and Back)
  • Workout 2: Upper Body (Arms, Shoulders – you’ll get some abs and upper back in this one also)
  • Workout 3: Lower Body (Glutes, Hamstrings, Quads – you’ll get some lower back and calves in this one also)

The specific workouts, again, are beyond the scope of this article, but there are a multitude of options out there for you. Remember to keep it simple, don’t try all kinds of new trick moves – focus on big sweeping moves that work multiple muscle groups at a time. My favorites (and most fitness coaches) remain Squats, Deadlifts, Flat or Incline Bench Presses, and Planks with all their variations. You can get lean, toned and muscular by only doing these 4 moves consistency.

Final reminder: ALWAYS ALWAYS remember to warm your muscles and ligaments with lighter weights first before moving straight to the heavy ones. Multiple low back injuries have taught me this the hard way.

If you would like to learn a few effective Gym-Based and At-Home Workouts for busy people, you can see our articles here.

Level 4: Moderate-Intensity Steady State Cardio

man cycling on his bike long distance

As a reminder, Level 2 and Level 3 are Essential Fitness Activities. Levels 4 and 5 are Supplemental Fitness Activities. They are for people who enjoy fitness as a hobby (like running, rowing, biking, etc) or who want to achieve specific body composition goals that require more precise and high-intensity activities.

It will make sense for some people to progress into Level 4 and 5 fitness, and other people to stay at Level 3. There are factors that will dictate this such as your age, body composition, past injuries, health goals, and the amount of time you have to dedicate to exercise.

MISS is one step up from LISS – it stands for Moderate-Intensity Steady State. The most obvious example of the difference here is brisk walking vs brisk jogging. Whereas in a LISS exercise session you would still be able to talk, during a MISS its going to be more difficult to chat with a friend and better to just focus on your activity.

We went over the relationship of target heart rate to various exercise intensities up above, in the Level 2: LISS section. As a reminder, MISS is going to put your heart rate target at 70-80% of its theoretical max rate. Here are the approx ranges for various age groups – keep in mind that many individual factors such as arterial and heart health, fitness level, etc, will influence the range you should be targeting.

  • In Your 20’s: MHR 200-ish, MISS should be 140-160 BPM for the duration of the exercise.
  • In Your 30’s: MHR 190-ish, LISS should be 135-155 BPM.
  • In Your 40’s: MHR 180-ish, LISS should be 125-145 BPM.
  • In Your 50’s: MRH 170-ish, LISS should be 120-135 BPM.
  • In Your 60’s: MHR 160-ish, LISS should be 110-130 BPM.

For my age range (I’m 39), I tend to target the upper end of the range because I eat healthy, am hydrated, and am pretty fit – my heart and body can handle a 45 minute run at 150 BPM heart rate even though I’m almost 40 and the chart above says to keep it below 145. Someone else who is 20 years old but untrained may be struggling to maintain 140 BPM which is the low end of their MISS chart.

This is why we have you master LISS and Strength Training before you move up into more intensive heart rate training.

A good way to start into a more intensive heart rate steady state cardio is to start with moderate-intensity intervals. A classic example of this is jog/walk combos. You might jog lightly until you sense that your heart rate is getting a little too high, and you start struggling to catch your breath. Then you slow back down to a walk until your heart rate is at low LISS levels again.

When I’m doing intervals like this, I might jog around my neighborhood track for 1 loop, during which time my heart rate increases steadily from the mid 130’s to the mid 150’s. Then I’ll spend another loop walking, and it will end up back down into the 120’s. Then I start jogging again for another loop, adjusting my speed to make sure my heart rate picks up – slowly and not too suddenly.

people running in a park

If you are interested in getting into “running” (jogging), by the way, this is a great way to do it. You’ll find your jog/walk intervals will start out mostly walking with short stints of jogging, but you’ll get winded fast. But keep at it and pretty quick, you’ll be jogging longer and longer without needing the heart-rate rest of walking – until you can jog for a mile straight at your target heart rate, and then two miles, and so on.

After you can jog 4 miles straight and keep your target heart rate steady, the sky is pretty much your limit. That’s because people who achieve this level of cardiovascular fitness generally can keep going. You can then work on increasing your distance, or improving your speed time, according to your running goals.

PS – Unless you are REALLY into an active hobby like running and it comes somewhat easily to you, OR you are training for a specific event like a race, I would aim for no more than 1-2 MISS sessions a week, and keep them to around 30-40 minutes for general purposes. When you expend large amounts of energy for longer than about 45 minutes, your body runs out of glycogen, and it will begin burning a combination of fat and muscle. You want to avoid burning muscle at every expense.

If you ARE training more frequently than that, hopefully you are eating a specialized diet that is meant to preserve your muscle tone, give you adequate carbs for your increased energy needs, and plenty of healthy fats to fight inflammation in the body from so much repetitive movement and impact. The cookbook Run Fast Eat Slow (available in our Cookbook Shop) is an excellent resource for runners and other endurance athletes.

Level 5: High-Intensity Interval Training

HIIT Class doing box jumps

Welcome to our final level of fitness (for the purposes of the 3×5 Framework) – HIIT!

HIIT is at the top of our fitness pyramid because it is sort of like the finishing touch of fitness. In the same way that at the top of the nutrition pyramid are desserts and treats to be used in moderation.

HIIT stands for High Intensity Interval Training. It means that you are spending brief periods of time at a very high intensity, reaching perhaps up to 90 or 95% of your max heart rate, followed by an interval of light recovery, such as walking slowly.

Because HIIT is extremely strenuous to your body, you should only start to perform it when you feel comfortable with the other levels. I would recommend that you be able to workout a minimum of 30 minutes at your Moderate Intensity heart rate (Level 4) before attempting a 10-15 minute HIIT session.

There are 3 ways that I perform HIIT. These are easy ideas for you to implement as well.

Option 1: Elliptical Machine
Turn elliptical machine settings to 10 ramp and 10 resistance. Perform 3-5 minutes of warm up with ever-increasing heart rate from resting heart rate up to a low-moderate heart rate (for me this is somewhere in the 120-130’s). To begin your interview, turn the resistance up to 14 or 15 and pedal all-out, as fast as you can, for somewhere between 10-20 seconds. Turn the resistance back down to 9 or 10 and barely pedal, allowing yourself to recover until your heart rate is back down into a moderate-high rate. Repeat for a total of 10 minutes, however much you can handle, then cool down for 2-3 minutes and stretch your hamstrings and quads well before leaving the gym. This is the best option for beginners because it’s no-impact, and it’s safe.

Option 2: Track Sprints
I am lucky to have a school track near my house. You can find anywhere that you won’t be interrupted by traffic, lights, or pedestrians. After a 5 minute light jog warm-up, I will sprint for the straight 100 meters of the track, putting anywhere from 70-100% of my effort into the sprint, depending on how my body and heart are feeling. Then I will slowly walk the curved 100 meters. I will frequently do one “lighter” sprint on one side, then one “all out” sprint on the other side. I end with a light walk back home and stretch my legs really well at home.

If you don’t have a track you can also do this well on a short hill, or some stairs (sprint up the stairs, walk slowly back down).

Option 3: Bodyweight Cardio Endurance
This is a world where people keep making up crazier and crazier moves, but there are some basics that you can stick with. The gold standard in the arena of bodyweight HIIT, are Burpees.

Burpees are this exercise that people love to hate, but there is zero question that they are effective at burning body fat. When I started doing them I couldn’t even do two in a row at a quick pace. Still today I struggle to make it past 10 in a row. LOL! But really, any move that requires explosive effort is going to ratchet up your heart rate in a nanosecond.

Some more examples are box jumps, squat or lunge jumps, jumping rope, plank jumps or mountain climbers, deadball slams, etc. These are “training” type moves that work on the explosiveness of your muscle tissue, so they mimic HIIT perfectly. Try doing 30 seconds of an exercise as quickly as you can, and then completely rest for the next 30-60 seconds.

Your first HIIT shouldn’t be more than 10 minutes or 10 intervals. You can ease into these intervals also, with the first one being more conservative and throughout the workout get more assertive with your energy. Try to get at least one “all out” interval in each HIIT. After you’re doing good with a 10 minute HIIT, you can increase it to 15 minutes, and then 20 minutes. I do not recommend HIIT sessions lasting longer than 20 minutes. You risk injuring yourself and burning muscle for energy. You can add a 5 minute warm up and 5 minute cool down to make it a 30 minute workout, if you like.

Hiit doing side skaters

HIIT will deplete your glycogen stores (sugar stored in muscles for energy) very quickly. A lot of fitness experts believe that as many calories are burned AFTER a HIIT workout as during it, and that is where the real power of HIIT comes in. Much like strength training, your body is busy repairing itself after an intensive HIIT workout. So even though you’re all showered and dressed in normal clothes and moving on with your day, your body continues to work above and beyond to repair itself and prepare itself for a future HIIT. (Keep in mind that body repair is a form of stress – read more in our Workouts and Stress article.)

This is the complete opposite of the way calories are burned during LISS. During LISS your body is burning calories gently as you move, prioritizing fat stores. But as soon as you are done, the calorie burning pretty much stops. That is why it is important to try to get longer LISS sessions in. In a 45- minute LISS and a 15-minute HIIT, you can burn the same amount of calories – maybe 250 to 400 depending on your body weight, height and age. The difference is in how those calories are burned, where they are pulled from, and what happens in your body after the workout is complete.

There are many other options for HIIT as you get comfortable with them. You can play frisbee, soccer or football with friends, sprinting across the field after the ball.

If you’re comfortable with the treadmill you can try sprints on that – but be cautious of your safety. I recommend the type of treadmill where the fast/slow interval speeds can be pre-set and changed at the touch of the button. I also recommend if you are being aggressive with your sprint speed, to keep it short and to hop onto the sides of the treadmill at the end of each sprint. This rebalances your body and reduces your risk of tripping while waiting for the belt to slow down to walk speed.

You can also increase the incline on the treadmill slightly – like 2-3%. This will help prevent injury from over-striding during your sprint interval, and will allow you to get the same heart-pounding benefit without having to go quite as fast.

HIIT workout with track sprints

Workout Frequency

So there you have it! This is how we define an easy to understand, easy to implement 5 Levels of Fitness (our Exercise Component of Health). But how often should you do each of them? What is safe versus risky for each exercise type?

Here is what I recommend in terms of each type of exercise. Mix and match according to what Level you are at, what exercise you ENJOY the most, and other factors like your daily schedule and budget (ie access to a gym vs at-home training).

Level 2 LISS: As much as you like. You can do it all 7 days a week, if you like. If mixing in other exercise, I still recommend a minimum of 2-3 LISS per week. It is a foundational exercise that will offset stress from other more intensive exercises, and is easier to do during high life stress, illness, etc. Its one drawback is time length. Aim for a 45 minute session but even a 30 minute session is better than no exercise for the day.

Level 3 Strength: Start with 1 and work up to 3 times a week. Aim for 30-45 minute sessions that keep your body moving with moderately-high intensity. (Ie don’t work one muscle group and then rest for 3 minutes – move on to another muscle group, only resting when your heart rate needs to come down or you need water).

Level 4 MISS: Up to twice a week, if desired. (Up to 4 times a week if training for a race. Do not run every day. Alternate your run days with strength, stretching and rest.)

Level 5 HIIT: Once a week if desired. (If you are very physically fit and struggling to shave off those last couple of pounds, you can do HIIT twice a week. I do not recommend more than 3 weeks straight of this, and only if the rest of your life is stable and relatively stress-free.)

Stress Response During Exercise

Starting with Level 3 (Strength Training) and other Higher-Intensity Workouts, you need to be aware of Stress’s relationship with Workout Intensity. There is a direct correlation between workout intensity and stress response in the body. This can be less than ideal for people who are already under large amounts of stress. You can read more about this in our article Workouts & Stress.

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