Cardiorespiratory endurance: what it is and how to build it by walking while you lose weight

Cardiorespiratory endurance: the short answer

Cardiorespiratory endurance is your body’s ability to keep going during longer, rhythmic activity, such as a brisk walk, a bike ride or a swim. It depends on how much oxygen your heart and lungs can deliver and how well your muscles can use it.

Scientists measure it as VO2max, the most oxygen your body can take up per minute, or in METs. One MET is the oxygen you use sitting quietly, about 3.5 millilitres per kilo of body weight per minute. A fitness of 8 METs means your body can work at eight times that resting level.

Low fitness predicts early death about as strongly as smoking or diabetes. A large meta-analysis in JAMA found that every extra MET of fitness went with a 13 % lower risk of dying from any cause and a 15 % lower risk of heart disease events.

A newer overview of 26 systematic reviews, covering more than 20.9 million observations from 199 cohort studies, found an 11 % to 17 % lower risk of death per extra MET. People in the highest fitness group had roughly half the risk of the least fit.

The good news: endurance responds to training at any weight. Regular brisk walking raises it within a few months. Talk to your doctor first before you start a new exercise plan or try one of the walk tests below.

What cardiorespiratory endurance means, with everyday examples

In simple words, cardiorespiratory endurance is stamina for your heart and lungs. It is what lets you walk to the shops, climb a hill or play with grandchildren without needing to stop and catch your breath.

Three systems work together. Your lungs take in oxygen, your heart and blood vessels carry it, and your muscles burn it to make energy. If one link is weak, you tire sooner.

The word “cardiorespiratory” means heart plus breathing. “Cardiovascular” refers to the heart and blood vessels only, so cardiovascular fitness is a slightly narrower term for almost the same idea.

Activities build this kind of endurance when they use large muscles, keep going for several minutes and raise your breathing. A single heavy effort, like lifting a box once, trains strength instead.

If your main question is which kind of exercise burns the most body fat, see our guide on steady versus interval cardio. This page is about fitness itself: what it is, how to measure it and how to raise it.

Why fitness matters as much as the number on the scale

Your fitness level tells doctors a lot about your future health, separately from your weight. People who are fit tend to live longer, whatever they weigh, and people who are unfit carry extra risk even at a lower weight.

A meta-analysis of 10 studies compared people by both their fitness and their weight group. Unfit people had about twice the risk of death of fit people with a lower weight, whatever their weight group. Fit people with overweight or obesity had risks similar to those of fit people at a lower weight.

These were observational studies. They show a strong link, not proof that fitness alone explains it, and fit people may differ in other ways too.

A very large hospital study points the same way. Among 122,007 adults who did a treadmill test, being just below average for fitness, rather than just above, carried about the same extra risk of death as smoking or diabetes. The fittest group had about one fifth of the risk of the least fit.

For this reason the American Heart Association has called fitness a clinical vital sign, worth checking as routinely as blood pressure. Its experts argue that doctors should estimate fitness routinely, because it may predict death better than several classic risk factors.

Fitness and weight loss: not a choice

None of this means weight does not matter. Losing weight lowers blood pressure, blood sugar and strain on your joints, and it makes moving easier, which in turn makes it easier to get fitter.

So think of fitness and weight loss as partners. Good food helps the scale, regular walking helps your heart and lungs, and each makes the other easier. If you want to know whether you are losing fat or just water, our page on fat loss vs weight loss shows simple ways to tell.

Why your fitness score improves as you lose weight

Most fitness scores are given per kilo of body weight, so the same heart and lungs give a higher score when you weigh less. That is why your number can rise while you lose weight, even before your training changes much.

Doctors and researchers often use two versions of VO2max. Absolute VO2max is the total oxygen your body can use, in litres per minute. Relative VO2max divides that by your weight, in millilitres per kilo per minute, and this is the number most charts and tests report.

A heavier body needs more oxygen to move, so a relative score fairly reflects how hard everyday activity feels. It also explains why a hill feels easier after you lose 10 or 20 kilos, even at the same pace.

This is a simplified example to show the arithmetic, not a prediction for you. In real life, training raises your absolute oxygen uptake too, while losing muscle can lower it.

That is why keeping your leg muscles strong matters while you lose weight. Two short sessions of strength training a week, plus enough protein, help you keep the muscle that does the work on every walk.

In the JAMA meta-analysis, people below about 7.9 METs counted as the low-fitness group. In the example above, losing weight alone moves the score up by two METs, and regular walking can add more on top.

How to test your cardiorespiratory endurance with a walk

You can estimate your fitness at home with a timed walk: either the one-mile walk test, also called the Rockport walk test, or the 6-minute walk. Both are used in research and clinics, and both need only a flat, measured route and a timer.

Ask your doctor before doing any walk test if you have a heart or lung condition, high blood pressure, diabetes treated with insulin, or symptoms such as chest pain, fainting or unusual breathlessness. Skip walk tests if you had a heart attack or unstable chest pain in the past month.

Ask first, too, if your resting pulse is above 120 or your blood pressure above 180/100. Stop at once if you feel chest pain, dizziness, severe breathlessness, leg cramps, unsteadiness, or if you turn pale or sweat heavily, and get medical help if it does not settle quickly with rest.

The one-mile (Rockport) walk test

This test asks you to walk one mile, which is about 1.6 kilometres, as briskly as you safely can without running. It suits people who can already walk that far without stopping.

Researchers developed it in 343 healthy adults aged 30 to 69, comparing the walk with a full treadmill test. An equation using walking time, heart rate at the end, age, weight and sex matched the lab results closely, with correlations of 0.92 to 0.93.

1. Choose a flat, measured route, such as a 400-metre running track (four laps is close to a mile) or a mapped path.
2. Warm up with five minutes of easy walking.
3. Walk the mile as fast as feels safe and steady for you. Note the time in minutes and seconds.
4. Straight after you finish, count your pulse for 15 seconds and multiply by four, or read your heart rate from a monitor.
5. Cool down with a few minutes of slow walking.

The published formula, as reported in later research, is: VO2max = 132.853 − (0.0769 × weight in pounds) − (0.3877 × age) + (6.315 × sex, 1 for men and 0 for women) − (3.2649 × time in minutes) − (0.1565 × heart rate).

To get pounds, multiply your weight in kilos by 2.2, and write the time as a decimal (15 minutes 30 seconds is 15.5).

Treat the result as an estimate. The formula comes from healthy adults of an average fitness level, so for you its main value is comparing today’s walk with your own walk six or twelve weeks from now.

The 6-minute walk test: the gentler option

The 6-minute walk measures how far you can walk in six minutes at your own pace. You may slow down, stop and rest during the test; the clock keeps running. That makes it a better choice if a mile is still too far.

The American Thoracic Society wrote the original guidelines for clinics, where the test is done on a flat, straight corridor with marked turning points, ideally 30 metres long. Staff give the same few words of encouragement each minute, because extra cheering changes the result.

A later European and American standard asks for two tests, because the result is sensitive to small changes in how the test is done. At home, do one practice walk on a different day and count the better of the two as your starting point.

At home, a simple version works well for tracking your own progress. Mark out a flat stretch, walk back and forth for six minutes, count the laps and write down the distance. Your distance cannot be compared with clinic norms, but it shows clearly whether you are improving.

Repeat your chosen test every four to six weeks, at a similar time of day, in similar weather, with the same shoes. A shorter time, a longer distance or a lower heart rate for the same walk all mean your endurance is growing.

Smartwatch “cardio fitness” and VO2max estimates: how much to trust them

A smartwatch or fitness band can give you a rough fitness estimate, but for one person on one day it can be several points off. Use it to follow a trend over months, not as a diagnosis.

A meta-analysis of 14 validation studies compared wearable estimates with lab tests. Devices that worked from resting data overestimated VO2max by about 2 ml/kg/min on average, and individual readings could be wrong by much more in either direction.

Devices that used data from a walk or run were close on average, but the error for a single person was still large. The authors concluded that these estimates are reasonable for groups of people, yet need improvement before anyone relies on them for sport or medical decisions.

So if your device labels your fitness as “low”, do not panic. That label is often based on charts for the general population, and a heavier body starts lower because the score is divided by your weight.

What matters is the direction over time. A score that creeps up, a lower resting pulse and easier walks all point the right way. To set your walking effort without any device, the talk test works well.

How to improve cardiorespiratory endurance by walking

Walk briskly on most days, add a few minutes every week or two, and keep it up for at least two to three months. Fitness responds to regular practice more than to hard single sessions.

A meta-analysis of 24 randomised trials found that brisk walking programmes raised VO2max in people who had been inactive. Weight, BMI, body fat and the lower blood pressure number went down as well.

How much walking is enough?

Even a small amount helps. In a trial of 464 inactive women after menopause with overweight or obesity, about 72 minutes a week of moderate exercise for six months raised fitness by about 4 % compared with no exercise.

About 136 minutes a week raised it by 6 %, and about 192 minutes by 8 %. More minutes brought more fitness, but every amount counted.

The intensity in that trial was moderate, about half of each woman’s peak capacity. In practice that feels like a brisk walk where you can still talk in full sentences.

A Canadian trial in 300 adults with abdominal obesity tested different amounts and intensities over 24 weeks. All exercise groups lost more from their waist, by about 4 to 5 cm, than people who did not exercise, whether they trained gently or harder.

The WHO advises adults to aim for 150 to 300 minutes a week of moderate activity. That is a destination, not a starting point; the plan further down builds towards it gently.

Frequency, time and effort in plain words

• How often: five days a week works well for most people. Rest days are part of the plan, especially for sore feet and knees.
• How long: start where you are, then add two to five minutes per walk every week or two. Two shorter walks in a day count too.
• How hard: breathing faster, feeling warm, still able to speak in full sentences. Later, short faster stretches can push your fitness further.
• How long until you notice: the trials above measured clear gains after about six months. Many people feel their usual route getting easier well before that, and a walk test every six weeks shows your own pace of change.

If you only have a few minutes at a time, short bursts of stair climbing or brisk walking still count. Our page on exercise snacks shows how to fit them into a busy day.

Endurance options for a heavier body

Walking is the easiest place to start, but any rhythmic activity that you enjoy and that does not hurt can build endurance. Choosing what is kind to your joints helps you keep going for months.

Each option has its own guide. See Japanese walking for the 3-minute intervals, Nordic walking for weight loss for poles, and swimming for weight loss for the pool.

For wheels and music, there are guides to cycling for weight loss and dancing for weight loss. Mixing two activities across the week spreads the load on your joints.

If your knees complain, choose the bike or the pool more often, and keep walking days short until they settle.

Food that supports fitness while you lose weight

To get fitter while you lose weight, eat a little less than you use, but not so little that you run out of energy for your walks. A modest shortfall works better than a crash diet, which leaves you tired and weak.

Our calorie deficit calculator shows a realistic daily range for your body. Most people do well with a steady, gentle loss rather than big swings.

Protein at each meal helps you keep the leg muscle that powers every step. Eggs, yoghurt, beans, lentils, fish and chicken all count; our list of high-protein meals has simple ideas that fill you up for fewer calories.

Before a longer walk, a small meal or snack with some carbohydrate, such as fruit, oats or wholegrain bread, gives your muscles easy fuel. On short walks, an ordinary meal earlier in the day is enough.

Drink water before and after you walk, and take some with you on warm days. You do not need special drinks, energy gels or so-called stamina supplements; ordinary food and water do the job.

A 12-week plan to build cardiorespiratory endurance by walking

Talk to your doctor first before starting this plan. It is meant for people who can already walk about 10 minutes without stopping and builds up to about 150 minutes a week, with walk tests in weeks 1, 6 and 12.

If 10 minutes is still too much, begin with our 12-week beginner walking plan first and come back here afterwards. The effort column uses the talk test: “easy” means you could chat, “brisk” means full sentences but no singing.

Write down each test result together with the date, the weather and how you felt. Seeing the distance grow or the time fall is often more motivating than the scale.

Repeat any week that felt too hard. Aching muscles that settle by the next morning are normal; pain that lingers or swelling means you should step back a week and rest your joints.

After week 12, keep two walks a week brisk and longer, and try a new activity from the options table on another day. If you want more structure for your effort, the talk test and zone guide mentioned above can help.

Safety: breathlessness, chest pain and when to stop

Breathing faster, feeling warm and having tired legs are normal signs of effort. Chest pain, dizziness, fainting, or breathlessness that is severe or does not settle with rest are not, and they mean you stop at once.

Sit down and rest if you notice any of those warning signs. If chest pain or pressure does not settle within a few minutes, call your local emergency number.

Getting out of breath quickly is common when you start, and it usually improves as you get fitter. Our guide to shortness of breath and obesity explains when breathlessness is expected and when it needs a doctor.

If you live with heart disease, your heart team should set your walking pace. Ask about a supervised programme; our page on a cardiac diet for weight loss explains how cardiac rehab combines walking and food.

Diabetes treated with insulin or certain tablets, uncontrolled high blood pressure and lung conditions also need a doctor’s advice on pace and timing before you increase your walking.

Free help to lose weight with good food and walking

At Obesity Foundation we help people lose weight and get healthier with good food, suitable exercise and walking. Getting fitter is part of that, and all our help is free.

• Your own eating plan, with filling, protein-rich meals that give you energy to walk. Ask for your free eating plan.
• Exercise videos at the Start, Build and Strong levels, for stronger legs and a fitter heart. Get the free workout videos.
• A free video meeting (in English) to plan your walks and walk tests around your health. Book a free video meeting.
• A Club account to log your walks, test results and progress at no cost. Join the Obesity Foundation Club.

Once your doctor agrees, your first step can be a calm 6-minute walk this week. Write down the distance; in six weeks you can see how far you have come.