High-Intensity Physical Exercise and the Menstrual Cycle

With the increase of sports practice in the population, individual and personalised intervention in athletes becomes essential for more appropriate responses, in terms of physical performance as well as recovery and associated health conditions. The female body has particularities that must be taken into account, such as hormonal changes, which throughout the menstrual cycle may impact on muscle development and intense physical exercise.

The menstrual cycle is the period of time between two menstrual periods, going through different phases with different hormone levels.

1 – Menstrual phase – Decrease in estrogen and progesterone levels;
2 – Proliferative phase – Exponential increase of estrogen;
3 – Secretory phase – Increase in hormone levels, being higher in progesterone.

Estrogen is responsible for altering cholesterol levels, with a decrease in low-density lipoproteins (LDL) and an increase in high-density lipoproteins (HDL). It is also responsible for storing glycogen in the liver and muscle, increasing lipid synthesis and promoting greater use of fatty acids.

Progesterone is associated with an increase in basal temperature and an effect in thermoregulation, as well as an increase in water and sodium excretion by the kidneys.

These hormones also have an influence in several parameters, such as cardiovascular, respiratory and metabolic parameters, with implications in the aerobic and anaerobic performance in female athletes.

Training and intense physical exercise promote changes in weight, body composition, eating habits and endocrine system. Some mesntrual dysfunctions may be a negative consequence of intense training in competitive athletes, being considered a physiological adaptation when training is done in a proper way.

Although menstrual dysfunctions can have a multifactorial origin, the main factors associated with female athletes are genetic predisposition, food deprivation, marked reduction in fat percentage, phychological stress and intense training routines.

The most common menstrual dysfunctions are:
– Delayed puberty – It occurs mainly in girls who start practising intense physical exercise before puberty and consequently the menarche appears at a later age.
– Anovulatory cycles – These occur due to a decrease in estrogen production, preventing ovulation. They are usually associated with menstrual irregularities or amenorrhoea.
– Amenorrhoea – This is the most severe dysfunction and it is characterised by the absence of bleeding. It may occur with the delay of the menarche until the age of 16 or by the absence of menstruation in a consecutive period of three or more menstrual cycles after the menarche.

Given that these conditions may be caused by the intensity of physical exercise typical in female athletes, as well as the restricted food volume and consequent changes in body composition, the individualised monitoring from the beginning of the sports practice in this population group becomes fundamental. Only in this ways it is possible to ensure that the athlete includes in her diet all the essential nutrients instead of overly restrictive and insufficient food routines.

Nutritionist, Jacinta Mendes
3341N