(1) Body shape index
It mainly includes height, weight, length and proportion of limbs, circumference of limbs, etc. There are many track and field events, and each specific event has its own characteristics and requirements for body shape. Being tall is good for most track and field events. Among all physical characteristics, height is the most important, because height is closely related to athletic ability.
Track and field athletes should not only have a certain height, but also have a longer lower limb length. This is because a longer lower limb length can form a higher trajectory of the body's center of gravity and a larger range of motion, create good biomechanical conditions for exercise, and help overcome the influence of its own weight, thus better exerting speed and saving energy. The length of lower limbs is mainly controlled by genetic genes, and the heritability is 77% for men and 92% for women. When selecting materials, the ratio index of lower limb length (A)× 100℅ can reflect the athlete's lower limb length and the height of the body center of gravity. Morphologically, when the index is 55%, it reflects that the upper and lower limbs are equal in length, 56% means that the lower limbs are longer, and 57% means that the lower limbs are obviously longer.
(2) Physical quality level
Physical qualities include strength, speed, endurance, flexibility, sensitivity and coordination. Different sports have different emphases. Testing and evaluating physical fitness level is the most important content of selecting materials.
(3) Physiological function index
Cardiopulmonary function, maximal oxygen uptake and recovery ability were mainly tested. Physiological function, especially the function of cardiovascular system, directly affects the size of athletes' exercise load. In terms of physiological functions, the most basic requirements are good growth and development, good health, coordinated development of various organs and systems, and no congenital defects. Therefore, strict physical examination must be carried out when selecting materials.
(D) Sports behavior factors
Sports behavior includes athletes' intelligence, psychology, sports consciousness, sports ability and their personality characteristics. It is directly related to the mastery of sports skills and the victory or defeat of the game. An athlete should not only have good physical fitness, but also have good sports behavior. At present, many coaches at home and abroad attach great importance to sports behavior factors when selecting materials.
(5) Genetic factors
Attention should be paid to the role of genetic factors in the development of morphology, function and quality, and the evaluation scale should be mastered reasonably. For those indicators that are greatly influenced by genetic factors (such as shape and speed), we should strictly master the standards at an early stage, while for those indicators that are less influenced by genetic factors (such as general strength and flexibility), we can have greater flexibility in selection and evaluation. When selecting materials, we should analyze the genetic correlation of different events and physical fitness. From the perspective of sports genetics, the factors with genetic influence were investigated and tested in detail. (6) Age factor
Age should be considered from three aspects, namely natural (calendar) age, biological age and sports age. The three are interrelated, but there are obvious differences. Natural age refers to the age from birth. Biological age refers to the actual age of human growth and development. Sports age refers to the age at which athletes begin to participate in training or special training. From the calendar age and biological age, we can see that a person grows and develops sooner or later (the younger the biological age, the better), and from the sports age, we can study the best age of sports quality, the age of participating in training and early specialization, the age of participating in competitions and achieving results, etc.