The Differences Between Muscle Strength, Muscle Endurance & Muscle Fatigue

Man lifting up weights rear view

In laymen’s terms, strength refers to the amount of power you have, endurance lets you perform physical activity over time and fatigue refers to the point at which your physical abilities begin to diminish. Understanding their roles during a workout will help you maximize your physical condition.


Muscle strength is your ability to exert your muscles against resistance. The resistance might be a weight or exercise bands, an opposing athlete or an object at your workplace that you need to lift. To build strength, create resistance against your muscle to the point that you cause small tears in the fibers. As your muscles repair these tears, they grow larger, giving you more strength. Bodybuilders often create workouts using their maximum strength to create loads for sets. For example, if you can lift a barbell with 200 pounds of weight one time before failure, that is your maximum weight. If you wanted to use 60 percent of your max to perform a warm-up or a circuit-training set, you’d put 120 pounds on the barbell.


Muscular endurance helps you use your muscles for longer periods of time. Strength helps you lift a heavy object with a single, powerful movement, while endurance helps you play football or tennis for several hours. Prolonged use of your muscles, rather than extreme resistance, helps you improve your endurance. You don’t need to use weights to improve endurance. Activities such as power walking, swimming, cycling, aerobic dancing, jogging, using a cardio machine or circuit training for extended periods create endurance workouts.


When your muscle can no longer perform the movements you want at maximum efficiency, they begin to fatigue. Failure occurs when they can no longer contract. This can be caused by factors such as an increase in lactic acid in your muscles, which occurs when you exert your muscle for long periods, or a lack of neural impulses sent to your muscles that occurs when they are overworked, even for a short period.

Relevance to Workouts

If your goal is building strength, your workouts will consist of heavy loads that fatigue you to failure within a short number of reps. Depending on the amount of weight you use to perform the exercise, this might be anywhere from three to 12 repetitions. If your goal is to build muscular endurance, you will decrease the amount of weight you use so that you can continue to perform repetitions over the course of a workout without failure, continuing to exercise for 30 minutes or more. You can move from exercise to exercise every 30 to 60 seconds to create endurance workouts, or perform one movement, such as jogging.