The Difference Between Muscular Endurance and Muscular Strength, Explained

Fitness pros break down the definitions of muscular endurance and muscular strength and explain why it's important to consider both when creating a workout program.

woman working out outside, doing a lunge while also performing biceps curls
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When you're a somewhat-clueless newbie to resistance training, you might pick up the first set of dumbbells you see and mindlessly perform a handful of biceps curls or shoulder presses. But exactly how you're training your muscles matters. Lifting 3-pound weights while riding a stationary bike, for example, works your muscles differently than when you're busting out a single, super-heavy bench press.

The key distinction: One workout is training your muscular endurance, while the other is calling upon your muscular strength. Both, however, are essential to focus on in your workout routine.

Does this have you wondering, "what is muscular endurance, and how is it different from muscular strength?" Don't stress: Here, fitness experts explain the difference between muscular endurance and muscular strength and why they're equally important. Plus, they share exercise tips that will help you mix muscular endurance- and strength-building activities into your schedule.

What Is Muscular Endurance?

You know how, when you head to a spin class, there's usually an upper-body segment incorporated into the workout? It's typically near the end of class, and it lasts about five minutes. During that time, you rotate between various exercises — such as biceps curls, overhead presses, and triceps extensions — often without rest. That, in a nutshell, is building muscular endurance.

Specifically, the muscular endurance definition is "the ability for the body to work for an extended amount of time," says Dyan Tsiumis, C.P.T., an instructor at Openfit and Equinox. The longer you can perform that action — whether it's continuous biceps curls, riding a bike, or running — the more muscular endurance you have. Even something as simple as sitting up with good posture or walking home on your commute with good stamina is a test of muscular endurance, adds Corinne Croce, D.P.T., a co-founder of Body Evolved and in-house physical therapist for SoulCycle.

During activities that call on your muscular endurance, your slow-twitch muscle fibers (aka type I) are recruited, says Dariusz Stankiewicz, C.S.C.S., another co-founder of Body Evolved. When you do endurance activities that train slow-twitch fibers, you improve the ability of your muscles to use oxygen, which, in turn, helps you perform longer before feeling tired.

The Importance of Muscular Endurance

Now that you're no longer wondering, "what is muscular endurance," you might be itching to know why it's so important. Whether you're tackling day-to-day activities — such as playing with your kids or doing chores around the house — or you're in the midst of a workout, you need muscular endurance to push yourself to the finish line. When you have a lot of it, "fatigue will not set in as fast and you will be able to withstand more while using less energy," says Croce.

How to Improve Muscular Endurance

Cardio training is typically the go-to method to improve muscular endurance, but lifting lighter weights for a higher number of reps can also boost endurance. Be it a barre class, a stair-climbing session, or a few laps in the pool, choose an activity that challenges you and keeps you interested.

Just don't expect this type of training to make your muscles visibly bigger, explains Tsiumis. "There is little to no increase in the size or strength of the individual muscles themselves," she says. "Slowly over time, though [in typical studies, about 12 weeks], there is increased strength in individual muscles and a thickening of the muscles that occurs," she adds. So rather than focus on how you look, tune in to how your body feels. If you're able to run, say, a 10K (6.2 miles) in the amount of time it would normally take you to cover six miles flat, your endurance is headed in the right direction.

What Is Muscular Strength?

While endurance is all about how long a muscle can perform, muscular strength is how hard it can perform. In more scientific terms, the muscular strength definition is "a measure of the greatest amount of force that muscles produce during a single maximal effort," says Michael Piermarini, M.S., a NASM-certified personal trainer and the former director of fitness at Orangetheory Fitness. It's called on when you need to do activities such as lift a heavy box, put a suitcase in the overhead bin, or carry a child without getting injured, adds Stankiewicz.

Think of it like running, suggests Tsiumis. "Muscular strength is a sprint, and muscular endurance is a marathon," she says. The more endurance you have, the harder you'll be able to go for a longer distance. But the more strength you have, the more power and speed you'll be able to generate to complete an action.

During activities that require your muscular strength, your fast-twitch muscle fibers (aka type II) are recruited, says Stankiewicz. These muscle fibers use less or no oxygen, produce power much faster, and are more easily fatigued than slow-twitch fibers, Ian Elwood, A.T.C., C.S.C.S., the founder of Mission MVNT, previously told Shape.

The Importance of Muscular Strength

Muscular strength not only comes with serious health benefits, but it can also help you get more out of your workouts. Resistance training, by way of improving strength and muscle mass, can counter bone loss and help prevent injury, while strength-promoting exercise has been linked to a reduction in all-cause and cancer-related mortality, research shows. Plus, "the more muscles you have, the more calories your body burns at rest and over the course of a day," says Piermarini.

How to Improve Muscular Strength

To amp up your muscular strength, don't shy away from the heavier side of the weight rack, plain and simple. You can get the most bang for your buck, though, by focusing on functional movements that utilize your entire body, suggests Piermarini. "Functional exercises are those that we, as human beings, perform regularly in our daily lives," he says. These are movements you perform all day (sometimes without even thinking about it) such as squatting, lunging, pushing, pulling, rotating, and hinging. Exercises that translate well include squats, reverse and side lunges, push-ups, bench presses, Russian twists, and deadlifts, says Piermarini. "They'll all help make daily activities easier by improving strength, coordination, and balance," he adds.

While you're training, "don't get caught up in the mindset that more is always better," warns Piermarini. "Instead, focus on the quality of movement. A strength session could be done in anywhere from 15 to 45 minutes," he says. To gauge your muscular strength, look to your one-rep max, which involves lifting as much weight as you possibly can during a given exercise (the chest press and deadlift are popular choices) for one rep — and one rep only. Keep track of these stats to see how your muscular strength improves over time.

How to Add Muscular Endurance and Muscular Strength Training to Your Routine

How often you should train for muscular endurance or muscular strength depends on your goals and where your weaknesses lie. "We are often more adapted genetically to one versus another," says Stankiewicz. So if you're looking to feel more balanced, then adjust your schedule to favor your weak link.

Your best course of action? Incorporate both into your weekly routine. In general, the standard recommendation is three sessions a week for both muscular endurance and muscular strength (or two if you're new to training).

If you're ever confused about whether you're working on muscular endurance or strength, think about the amount of weight you're lifting and how many reps you're performing, as the relationship is inversely related, suggests Piermarini. Going for lighter weights and a bunch (meaning, 15 to 20) of reps? That's endurance. Lifting heavier weight and only a few (meaning, five to eight) reps? That's strength. Regardless of which one you're focusing on for the day, you're sure to have a killer workout.

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