What Is Muscle Endurance?

Muscle endurance refers to the ability of your muscles to contract for extended periods of time, or perform a higher number of contractions. Greater muscle endurance enhances your quality of life, because it provides a critical component of functional fitness. For example, muscles that support a healthy posture must have endurance to reduce your risk for developing abnormal lengthening or shortening, which limits your range of motion. Muscle endurance also enhances your performance in multiple sports.

Contractions

Muscle endurance supports activities that require continuous muscular tension. Extreme examples of continuous muscular tension include mountain climbing and tug-of-war. Keeping an upright posture is an example of everyday muscular tension. Activities that require repetitive dynamic contractions also rely on muscle endurance. Repetitive dynamic contractions occur during running, swimming and cycling.

Mitochondria

Your muscles contain myofibrils and mitochondria. Myofibrils are the contractile components of your muscle tissues, and mitochondria are located all along the myofibrils. Mitochondria are responsible for producing energy that drives muscle contractions. Therefore, myofibrils with higher concentrations of mitochondria have greater muscle endurance, because they have the energy production capacity to sustain contractions for extended periods of time.

Twitch Fibers

Each of your muscle groups contains varying proportions of different twitch fibers. Fast twitch fibers are responsible for exerting short-term contractile strength, and contain more myofibrils. Slow twitch fibers are responsible for muscle endurance and maintaining extended contractions, because they contain higher concentrations of mitochondria. You may target slow twitch fibers and increase their numbers of mitochondria by performing high repetition weightlifting sets with lighter resistance. Performing weightlifting sets with 20 to 25 repetitions to failure can increase the endurance of slow twitch fibers. This type of training depletes your muscle energy, and your muscles respond by increasing the number of mitochondria in slow twitch fibers. You can gauge the effectiveness of your workout by the way your muscles feel, because energy depletion generally corresponds with a burning sensation in your muscles.

Sports

Muscle endurance is a critical component of performance for multiple sports. Endurance athletes, such as marathon runners and triathletes, require muscle endurance to complete those sporting events. Soccer and basketball players require muscle endurance to sustain muscle contractions throughout the game, and make long drives across the field or court. Wide receivers in football must have muscle endurance to moving quickly across further distances. Swimmers, particularly distance swimmers, must have a high degree of muscle endurance to sustain continuous muscle contractions simultaneously throughout their upper and lower body.