What are the 3 levels of exercise intensity?

The Australian government recommends at least 150 minutes per week of moderate-intensity exercise, or at least 75 minutes per week of high-intensity exercise.

Which is great on paper — but what do those intensities actually mean in the real world?

Physical activity can broadly be split into three categories: low-intensity, moderate-intensity, and high intensity. (And zero intensity, if you count "browsing Netflix with the remote control in one hand while reaching for more popcorn with the other" as physical activity.)

Here's the easy way to tell which intensity you're moving at.

RELATED: How much physical activity do I need?

Low-intensity activity

Examples include a casual walk, a stretch session, a beginners' yoga class or tai chi, bike riding or using a cross trainer (aka an elliptical) at an easy pace. Incidental exercise — everyday movements like bringing in the shopping, walking upstairs or doing housework, which burns a surprising number of calories  — also counts as low-intensity activity.

To understand exercise intensity it's helpful to know your maximum heart rate (MHR), which you can estimate by subtracting your age from 220 — so a 35-year-old has a MHR of about 185 beats per minute, for example.

Low-intensity activity is that which gets you to about 40 to 50 percent of your MHR.

A heart-rate monitor is obviously the best way to monitor your heart rate: a fitness band on your wrist will give you a decent estimate, though a chest strap is most accurate. You can get an idea of your heart rate without any equipment by taking your pulse for 15 seconds, counting the number of beats, then multiplying that number by four.

Of course, measuring your heart rate is pretty technical — and not really that practical to do while you're exercising. So the easiest on-the-go way to check your exercise intensity is the talk test: if you can talk and sing while exercising without running out of breath, you're exercising at a low intensity.

While it's true that low-intensity exercise like walking isn't the most effective way to lose weight in the long term, that definitely doesn't mean it's a waste of time: incidental movement is linked to improved overall physical fitness and health.

Studies have also linked movement — any kind of movement — to a boost in mental health, which doubles if you move outside in nature.

RELATED: Walking burns more calories than you think

Moderate-intensity activity

Moderate intensity is what most of us would think of as a proper workout. Many of the low-intensity exercises listed above can easily become moderate-intensity exercises by upping your pace: brisk walking or walking uphill, or a strenuous yoga session, for example.

Moderate-intensity exercise can also include weight training, or endurance exercise — things like jogging, cycling, or lap swimming. If you have older (and therefore heavier) children, carrying them around also falls in the moderate intensity category.

During moderate-intensity exercise, you're at 50 to 70 percent of your MHR. To go by the talk test, you can comfortably chat, but you can't sing any more than a few words without running out of breath.

Ideally, you want to accumulate 150 minutes of moderate-intensity exercise every week.

If moderate-intensity exercise is all you can tolerate but you worry it's not going to have maximum impact, never fear: recent research indicates moderate intensity can deliver the same health benefits as high-intensity workouts. (The only downside is that you have to work out at a moderate pace longer.)

RELATED: No time to work out during the week? Exercising only on weekends could deliver the same benefits

High-intensity activity

Examples include circuit training, vigorous forms of weight training, and moderate-intensity exercises at a heart-pounding pace — sprints in the park or up the length of the pool, for example. 

Your MHR during a high-intensity (aka vigorous-intensity) workout is 70 to 85 percent, and to go by the talk test, you can’t say any more than a few words without having to pause to breathe. (Emotionally, you might be praying for a swift and merciful death.)

Note that just because you're dripping with sweat doesn't necessarily mean you're exercising at high intensity — a bunch of other factors can influence sweating, including your workout environment, your fitness level, and your gender.

Seventy-five minutes of high-intensity training is recommended per week.

High-intensity exercise is super popular right now in the form of high-intensity interval training (aka HIIT), where you work out at a high intensity for a set period of time, take a short break to get your heart rate back down a little, then repeat. HIIT is particularly effective for weight loss and increasing cardiovascular fitness.

The big advantage of high-intensity exercise is that you get big health benefits from less time spent exercising — even though you have to put in more effort, it's over faster. And while that increased effort is notorious for bringing on that "I wish I was dead" feeling, studies suggest that many fitness beginners actually prefer HIIT workouts.

RELATED: Why you should incorporate high-intensity activity into your exercise regime

Exercise intensity is one of the important components of your workout program. It's the "I" in the F.I.T.T. (Frequency, Intensity, Time, Type) Principle, a set of guidelines that can help you set up a workout routine. Measuring your workout intensity and using that information to plan your future workouts can help you reach your fitness goals.

Intensity is probably the most important element of your workout. When you work out at a sufficient intensity, your body grows stronger and you'll see changes in your weight, body fat percentage, endurance, and strength. Exercise intensity is usually described as low, moderate, or vigorous.

Low intensity exercise raises your heart rate mildly and then keeps it steady. It is fairly slow-paced. Examples of low intensity exercises include:

• Walking at a leisurely pace
• Riding a bike on flat ground
• Lifting light weights
• Using an elliptical machine at a slow pace

A moderate intensity workout raises your heart rate. You will be sweating, breathing heavier, and moving at a quicker pace. You may not be able to talk easily, and you will feel warm. Examples of moderate intensity exercises are:

• Hiking
• Brisk walking
• Biking at 10 miles per hour or less
• Water aerobics

Vigorous intensity exercise gets your heart pumping, elevates your heart rate, and leaves you breathing hard. When working out at more intense levels, you will likely not be able to talk for long stretches without needing to take a breath. Examples of vigorous intensity exercises include:

• Running
• Swimming
• Jumping rope
• Cycling faster than 10 miles per hour

Increasing the intensity of your workouts can have many benefits. Regular moderate to vigorous exercise offers health advantages.

• Improved mood: Studies have shown that increasing the intensity of a physical activity can have a positive impact on mood and lower symptoms of depression.
• Increased calorie burn and metabolic rate: A small study examined 10 male subjects and found that 45-minute vigorous exercise resulted in higher calorie burn and a post-workout energy expenditure that lasted for 14 hours.
• Lower mortality risk: A 2019 research review examined how vigorous and moderate exercise affected mortality risk and found that higher intensity workouts, in particular, lowered the risk of death.

How hard you work out during any fitness session depends on a variety of factors. Your current fitness level, any physical limitations, and your fitness goals all affect desired workout intensity. And it's also important to vary your workouts and intensity levels to decrease the risk of injury and burnout.

Adults should participate in both aerobic (cardio) and muscle-strengthening workouts every week to improve their health, according to the Centers for Disease Control (CDC). The CDC recommends at least 150 minutes of exercise per week (that's 30 minutes a day for five days, but you can schedule it any way that works for you).

If you begin to feel dizzy or nauseous, are experiencing any pain, have trouble breathing, or have sudden cramps, stop your workout. Rest momentarily and if your symptoms do not subside, contact a medical professional.

It's helpful to monitor your intensity while exercising to make sure you're getting an effective workout. Unfortunately, it's one of the harder elements of exercise to measure. There are several choices, but none of them are perfect. It often takes a combination of methods to really get a sense of how hard you're working.

Using a percentage of your maximum heart rate (MHR) is probably the most widely used method of tracking intensity. It's simple, as long as you have a heart rate monitor device. For this method, you use a formula such as the Karvonen Formula to determine your target heart rate zone—the heart rate zone you try to work within to get the most effective workout.

The drawbacks: Formulas used to calculate target heart rate are imperfect and can be off by as much as 12 beats per minute. And you'll need a heart-rate monitor (with chest strap, for greater accuracy) or fitness tracker, unless you want to take your pulse regularly and do some calculations.

This is a very easy test to figure out your intensity: Just pay attention to how breathless you are. If you can easily talk, you're working at a light intensity, which is fine for a warm-up. If you can talk, but it's a little harder, you're getting more into the moderate zone. If you can only speak in short sentences, that's right about where you want to be for a vigorous workout.

If you're doing high-intensity interval training, that may include some breathless or anaerobic intervals where talking is out of the question. This is the high end of the intensity spectrum.

Your rating of perceived exertion (RPE), refers to how hard an exercise feels. The standard scale is the Borg Scale of Perceived Exertion, which ranges from 6-20 and is designed to help you estimate your heart rate by multiplying the rating by 10. If you're at a 15 on the Borg scale, you're working pretty hard (say, running) and your heart rate is an estimated 150 beats per minute (15 x 10).

You could also use a 1-10 scale, which is a little simpler. The idea is to check in and ask yourself how hard you're working. If you're very comfortable, maybe you're at a level 3 or 4. If you feel like you're exercising, but are still just in your comfort zone, you may be at a level 5. If you're sweating and very breathless, you might be at a Level 8 or 9.

Increase the intensity of your workout by adding speed or difficulty. That could mean boosting your running speed, increasing the weight you're lifting, or walking or hiking at a steeper incline.

For quick bursts of energy, your muscles will pull from adenosine triphosphate (ATP) stores. Carbohydrates are most often converted into ATP for moderate and high intensity workouts.

You can monitor your exercise intensity by using any of the three main test methods: measuring your heart rate, doing the talk test, or checking your rating of perceived exertion.

Exercise intensity is just one important aspect of fitness. Understanding the benefits of increased intensity and how to measure it can help you get the most out of your workout and achieve your fitness goals more efficiently.