Weight training offers so many health and fitness benefits. That’s why it’s not surprising that almost every health and fitness coach recommends it. We weight train primarily to build muscle strength and to hypertrophy muscles or make them larger. Doing so helps preserve the loss of muscle tissue that’s an inevitable part of aging. Preserving muscle helps us stay functional at all stages of life. In addition, having more muscle tissue and less fat is more favorable for metabolic health as resistance training improves insulin sensitivity. But, there’s another benefit that weight training offers – it helps build muscle endurance.
How Muscle Strength and Endurance Differ
Strength training using heavy resistance increases the ability of a muscle to generate force over a short time period. For example, when you first started weight training, you may have only been able to generate enough force to curl with a 10-pound weight in each hand. But, as you kept training, curling that weight became easier and you were able to work with a 12 pound and then a 15-pound weight in each hand instead as your biceps became stronger. Strength is the ability of a muscle to generate maximum force in a single contraction. The muscle likely also increased in size to make the muscle capable of handling heavier loads.
But, there’s another characteristic of healthy muscles and that’s muscle endurance. Muscle endurance is the ability of a muscle or group of muscles to contract against a sub-maximal resistance for a longer period of time. In contrast to muscle strength where the force generated is maximal, but short in duration, muscle endurance is a muscle’s ability to lift a lighter weight many times without fatiguing.
Why is Muscle Endurance Important?
You need muscle endurance to carry out the tasks you do every day. Yes, you need to be strong to lift boxes out of your car or move furniture, but you need muscle endurance for certain tasks as well, especially if you play a variety of sports. For example, muscle endurance comes in handy if you play tennis where you’re moving your arm repetitively and if you jog or run. Certain occupations also require muscle endurance. If you’re a massage therapist, a hair stylist, or a dog groomer who shampoos dogs for a living, you will appreciate having muscle endurance. With these occupations, your muscles are in motion for a large portion of the day. Although you don’t need exceptional strength to do these tasks, your muscles have to have “staying power,” the ability to keep contracting.
Strength training calls into play fast-twitch, or type 1 muscle fibers, fibers designed to generate maximal force. Unfortunately, these muscles also fatigue quickly. In contrast, activities that require muscle endurance mainly target slow-twitch, or type 2 muscle fibers, those optimized for sustained activity. The slow-twitch fibers don’t have as much capacity to generate force, but they don’t poop-out as fast as the fast-twitch fibers do. That’s why they’re optimal for tasks that require repeated muscle contractions.
Developing Muscle Endurance
The way you train your muscles to build strength is to lift heavy weights. Because the weights are heavy, you’ll only be able to complete a limited number of reps as the fast-twitch fibers fatigue quickly. Building strength is all about the force you can generate short-term. You measure it with the one-rep max test, a test that measures the heaviest weight you can lift only one time. Some fitness trainers use a 5-rep or 10-rep max test and use a table to extrapolate one-rep max from these test. The one-rep max test is harder on the muscles and connective tissue and carries a higher risk of injury.
How do you measure muscle endurance? The American College of Sports Medicine recommends the partial curl-up test for measuring endurance. You can find instructions on how to do this online, along with a chart with age and gender-specific norms. The goal is to see how many curl-ups or crunches you can complete in a set cadence without time restraints. You can also use a timed test where you do as many crunches as you can in one minute.
Another useful test for measuring muscle endurance in the upper body is the push-up test. However, there is a component of strength to doing push-ups as well. For the push-up test, you complete as many as you can before breaking form or you do as many as you can in one minute. Again, there are charts showing values by age and gender.
Improving Muscle Endurance
Training for endurance is a bit different than training for strength. For building endurance, you use a weight between 50 and 60% of your one-rep max and do a higher number of reps. Using this weight, you should be able to complete between 15 and 20 reps before your muscles are thoroughly fatigued. You’re training your muscles to go a little longer than they’re accustomed to. You also build muscle endurance by doing other exercises that involve repetitive muscle contractions such as running, riding a bike, or swimming. These activities primarily build endurance in your lower body.
Some bodyweight exercises can also help you build muscle endurance. Push-ups, bodyweight squats, planks, and calf raises are good examples. The key is to do them to the point of complete fatigue. Over time, you’ll be able to complete more reps using the same resistance and you’ll have greater muscle endurance.
The Bottom Line
Building strength is important but having more muscle endurance will serve you well too, especially if you run, cycle, or play sports that require your muscles to work at a sub-maximal load for long periods of time. One way to work strength, power, and endurance is to periodize your workouts, so that you’re working each component during different cycles. Doing this adds variety to your training and reduces the risk of injury. So, don’t be so focused on building strength that you neglect muscle endurance. It’s what gives your muscles staying power!
American College of Sports Medicine. “Getting a Professional Fitness Assessment”
Asian J Sports Med. 2012 Dec; 3(4): 267–273.