Baxter-Jones, A. D. (1995). Growth and development of young athletes. Sports Medicine, 20, 59-64.

This review primarily considers the chronological versus maturational age debate in competitive sports. It does highlight some of the general principles concerning age-group sports.

Growth refers to size increases in the body or its parts and development refers to the timing or stage of progress toward the mature adult state. An individual's maturation status is referred to as their biological age. Using chronological age (CA) to categorize competitive levels does not take maturational age (MA) into account. This is particularly important during puberty when maturity-related differences in strength, speed, and endurance are evident among children of the same CA.

In talent identification and development programs, there has been a "catch them young" philosophy, driven by the belief that to achieve performance success at the senior level, training and competition must begin early, and more often, the earlier the better. This belief is not corroborated by research. Physical educators and medical professionals have advised consistently against sport in the young. It has been proposed and shown that participation should be the aim in pre-pubertal children.

Two major concerns arise from age-related competitions: the possible decrease in sports participation, and the use of performance results to identify talent. Talent identification "success" is often defined in terms of success in CA-grouped competitions. The research that exists strongly supports size and physique as being very important determinants of CA competitive success.

Biological maturity and physical performance. Many of the physiological components used to determine exercise-performance change with growth. Biological maturity should be considered when evaluating performance capacities and levels. Skeletal age has been found to be a better predictor of athletic performance than CA. Advanced maturation positively influences aerobic power, muscular strength, and muscular endurance as well as motor proficiency and intelligence. Children differ not only in physical maturity but also psychological maturity.

In sports where weight, height, strength, and power are required, the early maturer is at a distinct biological advantage over others even though the CAs are equivalent.

Sexual maturity and performance. Elite adult athletes have basic body structures which favor their specific sport. Height is the most important characteristic ("sport for the tall"), in both age-group and adult performers in the majority of sports (exceptions are gymnastics, diving, etc.). Since height influences selection into a sport, then the further training that results from emphasizing that sport produces an even further increase in performance.

One has to always ponder whether age-group selections and talent identification reward maturational growth rather than skill development, a factor which differentiates most sports at the highest level.

Seasonal birth distribution. Not only does CA-grouped competition give advantages to the early maturer but it also is of advantage to those born during the earliest part of the selection year. Sports that are favored by size (e.g. tennis, soccer, swimming) show a strong tendency to select children whose birthdays are early in the year. In sports where size is not an advantage, the birth dates of selected athletes are distributed more evenly throughout the year.

Implications. Children and adolescents are not miniature adults. Since the components of physical fitness change as a function of growth and maturation, it is not appropriate to use adult-validated physical characteristics as selection or identification criteria in young children.

Physical education and sports need to devise experiences which provide and reward success (e.g., skill dominated activities) and do not discriminate against late developers.

Young athletes who experience success primarily because of their size and early maturation often give up top-level sport participation later on when they encounter those who have trained hard but developed more slowly.

Rather than asking whether competition levels should be age-related, it would be more applicable to ask at what age should youth competitions take on adult forms and rules.

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