The 5 Components of Physical Fitness, Explained (With Home Tests)

“Fit” is not one thing. A marathon runner who cannot touch their toes, a powerlifter who is winded on a flight of stairs, and a yoga teacher who has never lifted anything heavy are each fit in one way and unfit in another. Exercise science handles that by splitting fitness into five measurable parts, the five components of health-related physical fitness, and the split is useful for a simple reason: each one is tested differently, trained differently, and protects your health differently.

This guide names the five, defines each one, gives a test you can do at home for each, and says what the research links each one to. It ends with the six skill-related components that often get mixed into the list, and a table you can use to find the one you are neglecting.

Quick Answer

The five components of physical fitness are cardiorespiratory endurance, muscular strength, muscular endurance, flexibility, and body composition. The first four are abilities: how long your heart and lungs can sustain effort, how much force a muscle can produce once, how many times it can repeat a sub-maximal effort, and how far a joint can move. The fifth is a measurement: how much of your body is fat versus lean tissue. Together they describe health-related fitness. Agility, balance, coordination, power, speed and reaction time are the separate skill-related components.

In this guide:

• The Five Components, Defined
• Where the List Comes From
• 1. Cardiorespiratory Endurance
• 2. Muscular Strength
• 3. Muscular Endurance
• 4. Flexibility
• 5. Body Composition
• The Six Skill-Related Components
• Test All Five at Home in Twenty Minutes
• How to Train Each One
• Which Component Matters Most
• The Verdict

The Five Components, Defined

Two things about the list that trip people up. First, strength and endurance are separate components even though they both involve muscle: strength is one maximal effort, endurance is many sub-maximal ones, and a person can be high in one and low in the other. Second, body composition is on the list although it is not something you can “do”. It is there because it is a health outcome that the other four influence, and because it changes disease risk independently of them.

Where the List Comes From

The split between health-related and skill-related fitness was formalised in a 1985 paper in Public Health Reports by Caspersen, Powell and Christenson, written to give researchers shared definitions. It defined physical fitness as a set of attributes people have or achieve, separated the attributes that relate to health (the five above) from those that relate to athletic skill, and drew the line that still holds: physical activity is any bodily movement that uses energy, exercise is the planned, structured subset of it done to improve fitness, and fitness is the result. The American College of Sports Medicine uses the same five health-related components in its testing guidelines, and its exercise prescription framework, the FITT principle, is organised around training them.

You will see slightly different lists elsewhere. Some school curricula fold strength and endurance into one and add “balance” or “skill fitness” as the fifth. That is a simplification for teaching, not the standard. The five on this page are the ones in the research and the ACSM manuals.

1. Cardiorespiratory Endurance

Also called aerobic fitness or cardiovascular endurance. It is the component with the strongest evidence behind it, by a distance. A 2024 overview in the British Journal of Sports Medicine pooled 26 systematic reviews covering more than 20 million observations from 199 cohort studies and found that higher cardiorespiratory fitness was consistently associated with lower all-cause mortality, lower cardiovascular disease, lower cancer mortality and lower incidence of type 2 diabetes. A 2009 meta-analysis in JAMA put a number on it: each 1-MET increase in fitness, roughly the difference between a slow walk and a brisk one, was associated with a 13 per cent lower risk of death from any cause and 15 per cent lower risk of cardiovascular events.

• What it measures: how much oxygen your body can take in, deliver and use per minute, and how long you can sustain work that depends on it.
• Home test: time a 1-mile walk on flat ground as fast as you can without running. Under 15 minutes is a reasonable baseline for most adults under 60; under 13 is good. Alternatively, note how far you can cover in 12 minutes at any pace. Retest every 6 to 8 weeks; the number moving is what matters, not the number itself.
• Trained by: any activity that keeps a large amount of muscle working continuously: walking, running, cycling, swimming, rowing, dance. The guideline floor is 150 to 300 minutes a week of moderate work, or 75 to 150 vigorous. The steps to miles calculator is a quick way to see how much of that a normal day already covers.
• Why it matters beyond the numbers: it is the component that decides whether daily life feels easy. Stairs, a late dash for a train, a long day on your feet: all cardiorespiratory.

2. Muscular Strength

Strength is the most force a muscle can produce once. It was the component most often left out of general health advice until the last decade, and the evidence has since caught up. A 2018 meta-analysis in Archives of Physical Medicine and Rehabilitation, covering roughly two million adults, found that people in the highest third for muscular strength had a 31 per cent lower risk of death from any cause than those in the lowest third, and the association held after accounting for aerobic fitness. Grip strength, the simplest strength measure there is, tracked the effect on its own.

• What it measures: maximal force, in one effort. Not how many times, not how long.
• Home test: without a grip dynamometer, use the heaviest object you can lift once from the floor to standing with a straight back, or the heaviest dumbbell you can press overhead once with control. Record it and retest in 8 weeks. Gyms often have a grip dynamometer at the desk; a reading around 40 kg for men and 25 kg for women in middle age is typical, and lower than that is worth acting on.
• Trained by: resistance work heavy enough that a set ends within a few repetitions of failure: free weights, machines, bands, or bodyweight movements made harder. The guideline floor is every major muscle group on 2 or more days a week.
• Why it matters beyond the numbers: strength is what stops a slip becoming a fall and a fall becoming a fracture, and it is the component that declines fastest with age if it is not trained. Muscle also anchors the lean side of body composition, which is component five.

3. Muscular Endurance

Muscular endurance is the ability of a muscle to keep going: to repeat a movement against a moderate load, or hold a position, without fatiguing. It sits between the first two components and borrows from both. It depends on the muscle’s own ability to resist fatigue and on local blood supply, which is why a strong person can still fail a plank at 40 seconds.

Its best-known piece of evidence is a 2019 study in JAMA Network Open that followed more than a thousand men for ten years. Those who could complete more than 40 push-ups at baseline had a 96 per cent lower rate of cardiovascular events than those who managed fewer than 10. The push-up count was a better predictor than a treadmill test. The authors were careful to say that push-ups are a marker, not a treatment, but the size of the gap is a good argument for knowing your own number.

• What it measures: repetitions or hold time at a sub-maximal effort.
• Home test: push-ups to failure with good form (chest to a fist’s height from the floor, straight body; knee push-ups are a legitimate version, just record which one you did). And a forearm plank held with the hips level; 60 seconds is a fair adult baseline, 2 minutes is good.
• Trained by: lighter loads for higher repetitions, 12 to 20 or more per set, and timed holds; circuit-style training; carrying things. Any strength program trains it as a side effect.
• Why it matters beyond the numbers: most of daily life is endurance, not strength. Nobody lifts their maximum on a Tuesday afternoon. Everyone carries, holds, stands and repeats.

4. Flexibility

Flexibility is the range of motion available at a joint, set by the length and stiffness of the muscles and connective tissue around it and by the shape of the joint itself. It is the component with the weakest link to mortality and the strongest link to function: whether you can reach, bend, turn and squat without pain decides more about how life feels at 70 than most people expect at 30. At the far end of the range, some people are naturally hypermobile, which is usually harmless; see what being double jointed means.

It is also the component where the honest answer to “how much do I need” is “enough”. Flexibility is joint-specific, so a tight hamstring says nothing about a stiff shoulder, and more is not better past the range you use; extreme flexibility without the strength to control it raises injury risk rather than lowering it. A 2025 meta-analysis in Sports Medicine on the dose of static stretching found that range of motion improved with total weekly stretching time and kept improving up to around 4 minutes per muscle per week, with a single session lasting about a minute per muscle being enough to make progress. That is a small investment.

• What it measures: range of motion at a specific joint.
• Home test: sit-and-reach for the hamstrings and lower back: sit with legs straight, reach toward the toes, note where the fingertips land relative to the toes. Shoulder reach: one hand over the shoulder, the other up the back; note the gap between the fingertips, each side. Both are pass/fail against your own previous result.
• Trained by: static stretching held 10 to 30 seconds after exercise, when muscles are warm; dynamic mobility work before; yoga; training through a full range of motion under load, which improves flexibility about as well as stretching does.
• Why it matters beyond the numbers: lost range of motion is the reason people stop doing things, and stopping is what shrinks the other four components.

5. Body Composition

Body composition is what your weight is made of: the proportion of fat mass to everything else, which is muscle, bone, organs and water together, called lean mass. It is on the list because the amount and location of body fat changes the risk of heart disease, type 2 diabetes and several cancers, and because it responds to the other four components. It is not an ability. You cannot “do” body composition on a Tuesday.

Two findings are worth holding onto. First, where fat sits matters more than how much you weigh. A 2012 systematic review in Obesity Reviews found that waist-to-height ratio predicted cardiometabolic risk better than either waist circumference or BMI, and a simple boundary works across sexes and ethnic groups: keep your waist under half your height. Second, fitness partly offsets fatness. A 2014 meta-analysis in Progress in Cardiovascular Diseases found that unfit people of normal weight had roughly twice the mortality risk of fit people of normal weight, while fit people who were overweight or obese had a risk similar to fit people of normal weight. Body composition is a component to improve, not a verdict.

• What it measures: fat versus lean, and increasingly, where the fat is.
• Home test: a tape measure. Waist at the navel, relaxed, and height; the waist-to-height ratio calculator does the arithmetic and shows the bands. Our lean body mass calculator estimates the other half of the equation from height, weight and sex. Bathroom scales that claim to read body fat are poor at the absolute number and fair at the trend; a DEXA scan is the accurate option and is not needed for most people.
• Trained by: nothing directly. It moves with total weekly activity, with strength training that preserves or builds lean mass, and with what and how much you eat. Of the five components it is the only one where exercise alone is usually not enough.
• Why it matters beyond the numbers: it is the component people chase first and measure worst. Weight on a scale is not body composition. A person who loses 10 lb of muscle through dieting has made their body composition worse.

Key Takeaways

• The five components of physical fitness are cardiorespiratory endurance, muscular strength, muscular endurance, flexibility and body composition.
• Four are abilities and one is a measurement. Strength and endurance are separate components, not one.
• Cardiorespiratory fitness has the strongest link to living longer; strength is a close second and was underrated for decades.
• Each one has a home test: 1-mile walk time, heaviest single lift or grip, push-ups and plank, sit-and-reach, waist-to-height ratio.
• Agility, balance, coordination, power, speed and reaction time are skill-related components. Balance is the one worth training for health after 60.
• Most people train one or two. The component you skip is usually the one that limits you.

The Six Skill-Related Components

The 1985 definitions listed six more components that matter for sport and for some jobs but are not, in most people, tied to health outcomes. They are agility, balance, coordination, power, speed and reaction time. They get mixed into “the five components” often enough that it is worth being clear: they are a separate list.

One of the six has crossed the line into health. Balance predicts falls, and falls are a leading cause of injury death after 65. The Cochrane review of exercise for preventing falls in older people, updated in 2019, found that programs built around balance and functional training reduced the rate of falls by about a quarter. And a 2022 study in the British Journal of Sports Medicine of more than 1,700 adults aged 51 to 75 found that those who could not stand on one leg for 10 seconds had nearly double the risk of death over the following seven years, after adjusting for age, sex and existing disease. If you are over 50, balance is worth treating as a sixth component and testing alongside the other five.

Test All Five at Home in Twenty Minutes

None of these need equipment beyond a tape measure, a watch, and something heavy. Write the results down; the point is the retest in two months, not the score today.

1. Body composition, 2 minutes. Measure your waist at the navel, relaxed, and your height. Divide. Under 0.5 is the target. Do this first, before the tests warm you up.
2. Flexibility, 3 minutes. Sit-and-reach: legs straight, reach for the toes, note the distance short of or past them. Shoulder reach: note the gap between your hands behind your back, each side.
3. Balance, 1 minute. Stand on one leg, hands at your sides, eyes open, for 10 seconds. Then the other leg. Pass or fail.
4. Muscular endurance, 4 minutes. Push-ups to failure with good form, then rest two minutes, then a forearm plank to failure.
5. Muscular strength, 3 minutes. The heaviest object you can lift once from the floor with a straight back, or a grip dynamometer if you have access to one.
6. Cardiorespiratory endurance, 12 to 15 minutes. A timed 1-mile walk, as fast as you can without running, on flat ground. Or the distance you cover in 12 minutes.

The lowest score relative to your own expectations is your neglected component, and the next section says what to do about it.

How to Train Each One

Each component responds to a different kind of work, which is the reason the list exists. The settings below are the guideline floors, written as frequency, intensity, time and type. The full method for turning them into a program, and for progressing them, is in the FITT principle guide.

A program that touches the first two rows every week and the fourth row most weeks covers all five components, because endurance comes along with strength work and body composition follows the total. That is three kinds of session, not five, and it is what the guidelines describe. If fat loss is the goal, the exercise side of the equation is set out in the best exercise to lose weight.

Which Component Matters Most

For living longer, cardiorespiratory endurance first and muscular strength second, and the gap between them is smaller than it looked ten years ago. For living well, flexibility and balance decide more than people expect, because they are what keeps the other components in use past 60. Body composition matters, but it is downstream of the others and of diet, and it is the one that a scale measures worst.

The more useful question is which one you are neglecting. Runners are usually short on strength and flexibility. Lifters are usually short on cardiorespiratory endurance. People who mostly walk are short on strength. People who do none of it are short on all five, and for them the answer is not to pick one; it is to start with the two that carry the most weight, a few brisk walks and two short strength sessions a week, and let the rest follow. That is also why a person can be a normal weight and still unfit: the scale reports one component out of five, and the least informative one. Can you be skinny and still unfit? covers that case.

The Verdict

Fitness is five things, not one: how long your heart and lungs can sustain effort, how much force a muscle can produce, how long it can keep producing it, how far your joints can move, and what your body is made of. Each has a test you can do at home, each responds to a different kind of training, and each protects your health in a different way. The research is clearest on the first two, and the practical advice follows from it: walk briskly most days, lift something heavy twice a week, stretch what is tight, and measure your waist rather than your weight.

Then retest in two months and look at the one that did not move. That is the component your program is missing.

For how the components change across childhood and adolescence, and why the trends there are heading the wrong way, see physical fitness of children and adolescents. For the bigger picture of what fitness means and why it matters, start with what physical fitness actually means.