Effect of the physical fitness on the 2D:4D ratio
Faculty of health, medicine, and life sciences
Maastricht university
Course BBS1021
, 1. Introduction
There are a lot of differences between men and women, the traits which are different
between males and females are called sexually dimorphic. Characteristic dimorphic
differences between male and female are for example the secondary sex organs, differences
in muscle mass, the height and the weight of a person. A bit less obvious sexually dimorphic
trait is the length difference between the index finger and the ring finger, or the 2D:4D ratio.
The difference in this ratio is observable by two years of age but this might change later in
life. [1]
Digit ratio (or 2D:4D) is the relative lengths of the second digit (the index finger) and the
fourth digit (the ring finger), measured from the midpoint of the bottom crease to the top of
the finger. It is a fact that 2D:4D varies according to sex, such that males tend to have longer
fourth digits relative to second digits. [2] This ratio is an explanation of the balance between
testosterone (T) and estrogen (E) in a narrow window of early ontogeny [3]. In fact, a low
2D:4D ratio linked to a low fetal testosterone relative to fetal estradiol, while a high 2D:4D
ratio is linked to a low fetal testosterone relative to fetal estradiol. [3]
Prenatal exposure to sex hormones influences the 2D:4D ratio, as studies show us, which
means that phenotypical factors possibly influence the 2D:4D ratio. But it remains to be
investigated that also genotypic factors play a role in the 2D:4D ratio as well. As genes are
passed on from generation to generation, it could be expected that there is a relationship
between the 2D:4D ratio of the parents and their offspring. [4,5]
The purpose of this study is to investigate whether a correlation can be found between the
2D:4D ratio of parents and their offspring of a sample of 334 students (119 Males) and what
is wanted to find out is the influence of your physical fitness on this 2D:4D ratio.
2. Methods and materials
2.1 Participants
The study population consisted of 334 first year biomedical sciences students from
Maastricht university, 119 of them were male and 215 were female. The study recruited
participants in 2022.
2.2 Measurements
The participants measured their second and fourth digit. The lengths of the digits were all
measured with a ruler while the hand was fully straightened. The fingers were measured
from de mid of the crease the closest to the base of the finger to the top of the finger, this all
was done once for the right hand. the 2D:4D ratio was calculated by dividing the 2D length
by the 4D length, all participants had to do this by themselves. Other data such as the first
covid infection, country of birth, age, date of birth, hemisphere of birth and physical fitness
Faculty of health, medicine, and life sciences
Maastricht university
Course BBS1021
, 1. Introduction
There are a lot of differences between men and women, the traits which are different
between males and females are called sexually dimorphic. Characteristic dimorphic
differences between male and female are for example the secondary sex organs, differences
in muscle mass, the height and the weight of a person. A bit less obvious sexually dimorphic
trait is the length difference between the index finger and the ring finger, or the 2D:4D ratio.
The difference in this ratio is observable by two years of age but this might change later in
life. [1]
Digit ratio (or 2D:4D) is the relative lengths of the second digit (the index finger) and the
fourth digit (the ring finger), measured from the midpoint of the bottom crease to the top of
the finger. It is a fact that 2D:4D varies according to sex, such that males tend to have longer
fourth digits relative to second digits. [2] This ratio is an explanation of the balance between
testosterone (T) and estrogen (E) in a narrow window of early ontogeny [3]. In fact, a low
2D:4D ratio linked to a low fetal testosterone relative to fetal estradiol, while a high 2D:4D
ratio is linked to a low fetal testosterone relative to fetal estradiol. [3]
Prenatal exposure to sex hormones influences the 2D:4D ratio, as studies show us, which
means that phenotypical factors possibly influence the 2D:4D ratio. But it remains to be
investigated that also genotypic factors play a role in the 2D:4D ratio as well. As genes are
passed on from generation to generation, it could be expected that there is a relationship
between the 2D:4D ratio of the parents and their offspring. [4,5]
The purpose of this study is to investigate whether a correlation can be found between the
2D:4D ratio of parents and their offspring of a sample of 334 students (119 Males) and what
is wanted to find out is the influence of your physical fitness on this 2D:4D ratio.
2. Methods and materials
2.1 Participants
The study population consisted of 334 first year biomedical sciences students from
Maastricht university, 119 of them were male and 215 were female. The study recruited
participants in 2022.
2.2 Measurements
The participants measured their second and fourth digit. The lengths of the digits were all
measured with a ruler while the hand was fully straightened. The fingers were measured
from de mid of the crease the closest to the base of the finger to the top of the finger, this all
was done once for the right hand. the 2D:4D ratio was calculated by dividing the 2D length
by the 4D length, all participants had to do this by themselves. Other data such as the first
covid infection, country of birth, age, date of birth, hemisphere of birth and physical fitness
