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INTRODUCTION

My coach said I ran like a girl, I said if he could run a little faster he could too.

Mia Hamm, American soccer icon, Olympic gold medallist and FIFA Women’s World Cup champion

The 2016 Summer Olympic Games marked the highest level of participation by female athletes in Olympic history, with women accounting for 45% of Olympians.1 In this chapter, we discuss many of the ways in which females differ from males, and the implications for sport. Early physiology studies primarily enrolled male participants and thus differences observed in females were viewed as ‘female specific’. As the sporting status of women equilibrates with men, it is important to view the following discussion not as concerning female-specific qualities but rather as sex differences relating to athletics.

PHYSICAL DIFFERENCES HEAD TO TOE

Bony growth in girls and boys occurs at similar rates until girls hit their (earlier) adolescent growth spurt. Peak height velocity occurs soon after the development of breast buds, which typically occurs between ages 10 and 12 years. A comparison of timing of height velocity in boys and girls can be seen in Figure 29.1. Population studies in the USA and Europe suggest a trend towards earlier breast development and height spurt, possibly correlated to environmental factors and/or increased adiposity. Conversely, pubertal delay is seen in girls who are physically very active.2 The rate of vertical growth typically decelerates with menarche (beginning of menstruation), at an average age of 12.8 years in the USA.2

Figure 29.1

American boys (solid line) reach peak height velocity (cm/year) later than girls (dashed line). The number 50 indicates that this is the 50th centile line

ADAPTED FROM THE JOURNAL OF PEDIATRICS, 107(3), TANNER JM, DAVIES PS. CLINICAL LONGITUDINAL STANDARDS FOR HEIGHT AND HEIGHT VELOCITY FOR NORTH AMERICAN CHILDREN, 317–29, 1985, WITH PERMISSION FROM ELSEVIER3

https://www.sciencedirect.com. Due to rights and permissions restrictions, this content cannot be reproduced in a digital format. The content is available in the print edition at page 403.

When fully developed, women have less lean body mass compared to men, reflecting relatively higher body fat composition and lower muscle mass. The average female body fat composition is 28.4%, versus the male equivalent of 15.2%.4 From an evolutionary perspective, the greater percentage of body fat in females compared with males was necessary to support ovulation, gestation and lactation.5 Oestrogen, the predominant sex hormone in females, maintains the body fat percentage, while the influence of androgens typically promotes muscle mass accumulation.6

The external reproductive organs are one of the obvious physiological differences between the sexes. Female breast development is the first visible stage of puberty, beginning between ages 9.0 and 13.4 years.7 Breast size and shape is largely determined by genetic predisposition but may be affected by general weight loss or weight gain.

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