PERFORMANCE PHYSIOLOGY

PHYSIOLOGICAL CHANGES OF THE YOUNG ATHLETE

AND THE EFFECTS ON SPORTS PERFORMANCE

By Prof Craig Williams, PhD

INTRODUCTION In most countries throughout the world, the organisation of youth sport has become increasingly professionalised. As a consequence, it is not uncommon for some young child athletes to have had five years of training and competition experience before the age of ten. This strategy is exemplified by the catch them young phi- losophy (1) and is an important one for those countries intent upon maximising their talent pool for future medal success, but also if funding resources are scarce and need to be prioritised. Over the last ten years there has been a movement in the UK to recognise that children are not mini adults and need a coaching system that is pertinent to them and not a hand-me-down from adult models. The recent implementa- tion of the Long Term Athlete Development (LTAD) plans by many UK sports associations is a positive move, which acknowledges the unique demands imposed on young athletes.

At present, paediatric scientists are a long way from understanding the long-term impact of training on children and compared to adults little is known about the trainability of young athletes. For

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example, adolescence is a period of accelerated growth in the cardiorespirato- ry, musculoskeletal and reproductive systems but scientists are still unable to truly differentiate the impact of the growth spurt from the improvements by training. These are complex issues and involve an understanding of the growth, maturation and the response to training of the different systems of the body. The purpose of this article is to discuss some of the issues that impact on the performance of young child athletes.

GROWTH AND MATURATION Currently there is no definition of what defines a trained or elite child athlete. Most youth sport is organised by chronological age (CA) categories and success within these respective categories is often used to determine future sporting potential. However, it has been demon- strated that CA categorised competitions gives an advantage to those individuals born in the earliest part of the selection year. The relative age affect was first shown in academic educational studies and has been substantiated in youth sports. For example, in the Football Associations School of Excellence, of the 106 boys selected over a six year period for the School, 67% were born in the first quarter

of the selection year and less than 2% in the last three months (2). Since then this observation has also been noted in other sports eg. tennis, swimming. An explanation of this is that older individuals who are bigger, stronger and faster than their younger counterparts are selected because of these attributes and receive more coaching leading to greater success. It is therefore important to understand the consequences of growth and maturation in the process of sporting competition.

Growth, maturation and development are often used interchangeably, however they should not be confused, as each identifies a separate domain of the child. Table 1 represents a glossary of terms, which will aid understanding of the important issues.

Growth Growth is a continuous process, which does not necessarily have specific end points, whereas maturation does, as all children will eventually reach the fully mature adult status.

As children grow, there is an increase in height, body mass, lean and fat mass and all organs increase in size. The greatest rate of height increase is within the first year after birth, where approximately

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