Muscular endurance refers to the ability of a muscle or muscle groups to contract or exert force for many successive exertions or repetitions.[1][2] It can also be thought of as a muscle’s ability to resist fatigue. While there are different theories on what exactly produces fatigue in a muscle,[3][4] muscular endurance at least partially relies on the muscle’s ability to remove waste products[5] and prevent a buildup of acidity in the muscle.[6] Other models of fatigue that involve biomechanics, muscle recruitment, cellular mechanisms, and the brain have also been proposed.[3][4]