Fitness has become an important topic around people, and teenagers are the most lively group. By evaluating their participation in aerobics exercise with scientific measurement methods, this paper discusses the influence of aerobics on teenagers. Key words: Aerobics, Fitness, Teenagers, Physical Fitness and Physical Beauty, Influence Foreword In this brand-new century, with the continuous improvement of people's living standards and the popularization and deepening of national fitness, people's voice for improving the quality of life is getting higher and higher. Aerobics, which is popular all over the world, has absorbed the strengths of many families, and can complete various actions such as running, jumping, turning, twisting and swinging with moderate intensity of aerobic energy with pleasant music, so that people can always maintain a happy mood and be full of energy during the whole exercise process, which has a good impact on human fitness. In order to quantitatively study the influence of aerobics exercise on teenagers' physique and physical beauty, we conducted a 20-week experiment on some students in Happiness No.2 Middle School, and measured their body shape, physiological function, body composition and sports quality, discussed the effect of teenagers' participation in aerobics exercise, and analyzed the influence of aerobics exercise on physique and physical beauty, aiming at providing scientific basis for the theory and practice of aerobics exercise. 1 The subjects were 68 students (including 8 obese students) who chose aerobics in extracurricular activities, with an average age of 16.3 years old. Before and after the experiment, all subjects were given a comprehensive physical examination. The test contents are as follows: (1) Physical fitness test: 1 min sit-ups, standing long jump, shot put, 50m run and 800m run. (2) General physical examination, including: height, weight, chest circumference, vital capacity and heart rate. (3) Measuring the thickness of skin folds: measure the thickness of skin folds of arms, abdomen and back with a domestic skin fold thickness gauge. Arm: the midpoint of the connecting line from acromion to olecranon is parallel to the long axis of upper limb; Abdomen: the horizontal skin fold at the intersection of umbilical horizontal line at the midpoint of clavicle; Back: The lower corner of the scapula is folded at a 45-degree angle with the trunk. According to the formula, calculate the bulk density: d =1.0931-0.00160× (skinfold thickness under scapula+skinfold thickness of arm). Body fat content = weight × body fat percentage (F %)= 4.57/ body density D-4. 142 fat-free body weight (LBW)= weight-body fat content fat-free body mass index = fat-free body weight (kg)/ height (cm)× 100 3 Preparation of teaching steps. Basic part: first do "youth aerobics" for 30 minutes, and then do "shape gymnastics" for 30 minutes; End: Do 20 minutes of physical exercises such as flexibility, speed, endurance and strength, and do relaxation exercises. All calisthenics are done in music under the guidance of teachers. In physical fitness, according to the age, psychological and physiological characteristics of teenagers, games, competitions and other teaching forms and methods are adopted. For 8 obese students, in addition to the same exercise methods, they are encouraged to do extracurricular exercise about 1h three times a week. 4 Research Results and Analysis Table 1 Influence of Aerobics Exercise on Teenagers' Body Shape, Skills and Physical Fitness Table 2 Changes in Body Composition of Obese Students after Aerobics Teaching Class Height, Weight and Vitality 50m Standing Long Jump Sit-ups 800m(cm)(kg)(ml)(m)(one/min)(s) Class Average15/. .921509.331.8546.5 after the standard value of 2 13, it is 0.7 7.2 750 0.5 0.30 8 28, and the growth value is 2.6-3 900-0.40.210./kloc-