One of the differential characteristics in the production of sex cells between men and women is that, while the female sex is born with a certain number of cells that are depleted over the years, males produce spermatozoa daily from puberty onwards. This, together with the fact that the male reproductive organs are located outside the pelvis, determines the factors that can affect the quality of a semen sample.
On the one hand, the location of the testicles outside the body means that their temperature is below the temperature of the rest of the body, and this decrease is a determining factor in sperm production and sperm motility.
Those factors that can increase testicular temperature, such as the presence of varicose veins at this level, obesity, the use of very tight underwear, a professional activity that involves spending a lot of time sitting or even certain sports, such as cycling, will have a negative impact on seminal quality.
On the other hand, there is the daily production of sperm cells and implies that external factors that may affect the male at a given moment will interfere in the maturation process of the spermatozoa at a given stage. This is the reason why a single seminal study is not enough to establish the diagnosis of a male factor, since it must be confirmed with a second study that should take between a month and a half and two months.
Exposure to environmental pollutants (pesticides, fertilizers, solvents among others), consumption of toxins or even stress can have a negative effect on seminal quality.