Female gymnasts have an incidence of spondylolysis which is four times higher than in non-sporting females of a similar age. It is thought that sex hormones during puberty can have an adverse effect on bone health. Obviously, these changes can affect young female footballers as well. Alterations to bone quality can be further accentuated by eating disorders, over-training and disturbances to the normal menstrual cycle. This puts the female sportsperson at greater risk of osteoporosis and stress fractures.
Genetics
Researchers have demonstrated a familial incidence of 31% through x-ray screening of families in which one member has spondylolysis. This suggests that some people have a genetic weakness in the pars, which predisposes them to spondylolysis. However, pars defects due to participation in sport show that the stresses and strains to which the body is subjected during sporting activity play as much of a role as genetics.
Nutrition
Calcium compounds make up more than half of bones mass, and are therefore essential in the diet to maintain bone mineral content. Without this, bones are less stiff and are therefore prone to fracture. Vitamin D can affect calcium absorption, and body stores of this are dependent on exposure to sunlight. Dietary protein, phosphorous, fibre, fats and sugars can all have an affect on calcium absorption and therefore bone health. Eating disorders and calorie-restricted diets in young athletes leave them susceptible to reduced bone mineral content and thus a greater risk of sponylolysis.
Age
At around 13 years of age for girls, and 14 years for boys, the ‘growth spurt’ usually occurs. This is where the adolescent enters a period of rapid growth, reaching more or less their full height, due to growth in the long bones. Approximately one year after this growth spurt there is a peak gain in bone mineral content – thus for the year after the growth spurt the bones have a relatively low bone mineral content and are prone to fractures