The body???s core, including muscles in the abdominals, gluteals and quadriceps, also are used.???One of the best things about the push-up is that it coordinates all the muscles,??? said Kristen Ugrob, fitness director of the Magdalena Ecke Family YMCA in Encinitas.The push-up is a strength-building exercise that can improve muscular endurance but also tones and defines muscles.