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Endurance means a lot of different things to different people. To runners, it means being able to run for a long time, covering many miles. To weightlifters, it might mean being able to lift heavy weight for a lot of reps. To athletes, it can mean getting through an entire practice or game without needing to rest.

No matter the setting, endurance refers to your ability to carry out any given physical task for an extended period of time. Two parts of your body -- your heart and your muscles -- both contribute to giving you endurance. While they are both important in helping your body go the distance, knowing the difference between cardio and muscular endurance is key to reaching your fitness goals.

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What is cardiovascular endurance?

Cardiovascular or cardiorespiratory endurance is what most people mean when they refer to endurance in general. Defined, cardiovascular endurance is the ability of your cardiorespiratory system (heart and blood vessels; lungs and airways) to keep your body active for a long period of time.

Most people mean "aerobic fitness" when they talk about endurance. During aerobic exercise, your body uses oxygen to supply your working muscles with energy, and this is the type of exercise that can be performed for hours on end, depending on how conditioned you are.

People often picture marathon runners and Olympic swimmers when they think of people who have good endurance, because those activities require a high level of aerobic conditioning. But, elite athletes also have great muscular endurance, however -- a lesser known, but equally as important, part of fitness.

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What is muscular endurance?

The true definition of muscular endurance is "the ability of a muscle or muscle group to perform repeated contractions against a load for an extended period of time."

In plain speak, that means the number of reps you can perform of any given exercise without failing or breaking form. Common tests of muscular endurance include doing as many push-ups, squats and pull-ups that you can, before being physically unable to continue, but muscular endurance is also important for activities like hiking, running, swimming and high-volume weightlifting.

Which one is better?

Surprise: neither is better than the other. Cardio endurance and muscular endurance intertwine to promote an optimal level of health and fitness.

Take running, for example: You definitely need good cardio endurance so that your heart and lungs can continue working efficiently and make sure your muscles get enough oxygen throughout your run. You also need muscular endurance to complement cardiovascular endurance to ensure that your legs don't give out on you, especially when running on rough or hilly terrain.

You also use both types of endurance during everyday activities, like walking up a few flights of stairs.

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How to build cardio endurance

When it comes to cardio, there's nothing to it but to do it. You can't weasel your way out of building cardiovascular endurance: You have to put in the work. This means going running, biking and hiking; climbing stairs and sprinting intervals; doing things that make you sweat heavy and breathe hard.

Steady-state cardio and interval-based cardio both help to build cardio endurance, and it's best to incorporate both into your training plan. Slow, long-distance training is the most common form of endurance training, and it's what marathon runners primarily use to stay in shape for their races.

You can also build cardio endurance with tempo training, Fartlek training and sprint workouts.

Read more: How to make running on the treadmill more fun

Track it

Cardio exercise is by far the easiest form of exercise to track because it's primarily distance or time-based. The wealth of activity trackers and exercise-logging apps make it so easy to keep track of cardiovascular endurance.

For running, walking, biking and hiking, you can use your fitness watch or virtually any distance-based activity app.

You can also use perceived exertion to measure cardio endurance. Pick a workout -- for the sake of an example let's use a 5 km run -- and complete it with an all-out effort. If you log your first test as "5 km run, 30 minutes, felt very hard" and your second test, three months later, as "5 km, 27 minutes, felt very hard," you know you improved.

Even though both tests were rated as very hard, your time lets you know that your all-out effort for a 5 km is now faster.

Another way to test and track your cardio endurance is with your VO2 max.

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How to build muscular endurance

You build muscular endurance primarily through resistance training. You can effectively build muscular endurance through bodyweight training, weightlifting and the use of resistance cables and bands -- anything that involves contracting your muscles against resistance will improve the endurance of your muscles.

The key thing to remember is that training for muscular endurance is different than training for muscular strength. To train for endurance, you should lift lighter loads for more reps; to train for strength, lift heavier loads for fewer reps.

Track it

Keeping tabs on your muscular endurance is, naturally, more difficult than keeping track of cardiovascular endurance. You can't measure muscular endurance explicitly in terms of distance, speed or time, though those metrics can certainly help.

Tracking muscular endurance is more segmented by body part and often based on effort. For example, you can test the muscular endurance of your lower body by performing as many bodyweight squats as possible before breaking form (breaking form during squats can mean your knees cave in, your heels come off the ground, or you can no longer reach parallel).

You can test the muscular endurance of your upper body by performing as many push-ups as possible before your form breaks (your core collapses, shoulders start protracting) or you fail a rep.

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Retest these movements periodically, such as every three to six months, to see if you improve.

If you're more advanced, you can do a weighted test for muscular endurance. For example, consider your baseline test a set of 20 barbell back squats (bar resting on your shoulders) at 100 pounds. Perform the 20 reps at an all-out effort and note these metrics:

How long the 20 squats took

How many reps were completed with perfect form

How you felt during and after the set (use ratings of perceived exertion

Let's say I did this test and it took me 60 seconds to complete all 20 reps, and by the eighth rep, my form was dwindling. If I retest in three months and it takes 50 seconds, and all 20 reps are perfect, then my muscular endurance has clearly improved.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.