Muscular endurance is the ability of a muscle or group of muscles to sustain repeated contractions against a resistance for an extended period of time. Endurance is important for sports but is helpful in everyday life also. The ability to repeatedly work without muscle fatigue helps your overall body development.
Reps of 12-15 promotes improvement in muscle endurance and tone. This technique works best at about 55-65% of your max rep for the muscle group you are working.