Muscular endurance is the ability of a muscle or muscle groups to contract repeatedly or exert force over time while resisting fatigue. It involves the muscle's capacity to remove waste products and prevent acidity buildup, and various theories have explored the mechanisms behind muscle fatigue.

Muscular endurance is measured by the number of repetitions performed with a specific weight or the duration that a force can be maintained against a load. Common tests include repetitions of squats or bench presses at 50% of 1-repetition maximum and holding positions like planks or wall sits.

Muscular endurance can be improved through dynamic exercises, such as isotonic movements with high repetitions at submaximal resistance or static exercises like isometric holds. The American College of Sports Medicine recommends isotonic resistance training at low-to-moderate intensity for 2 sets of 15 to 25 repetitions, performed 2 to 3 times per week.

Caffeine, creatine monohydrate, and beta-alanine have been studied and shown to improve muscular endurance through various mechanisms, such as enhancing energy production and reducing fatigue. Other supplements like nitrates, sodium bicarbonate, and citrulline show potential but lack consistent evidence for effectiveness.

A higher-carbohydrate diet, comprising approximately 60% of energy intake, enhances muscular endurance and reduces fatigue during high-volume training, and carbohydrate mouth rinses can also be beneficial. Additionally, a protein intake of 1.4 to 2.0 grams per kilogram of body weight supports muscle maintenance; higher intakes may help retain muscle during fat loss, and spreading protein consumption throughout the day may aid recovery.

Sleep is a crucial factor that affects muscular endurance, and short-term sleep loss reduces strength endurance by 10%. Additionally, muscular endurance declines with age and varies by sex, though training can help mitigate these effects.