Table 3.

Genotyping frequency in the Spanish population and elite endurance athletes

Symbol	Gene	Polymorphism	Genotypes (2 or 1 = “optimal” endurance genotype)	Frequency in Spanish population (%) (*)	Frequency in Spanish elite endurance athletes (%)
CYP2D6	Cytochrome P450 family 2 subfamily D member 6	c.506-1G>A	0 = AA–1 = GA–2 = GG	4–27–69	1–14–85
GSTM1	Glutathione S-transferase mu	Functional(+)/null(−)	0 = −–1 = +	82–18	71–29
GSTP	Glutathione S-transferase pi	Ile(I)105Val(V)	0 = GG–1 = GA–2 = AA	41–45–14	6–31–63
GSTT	Glutathione S-transferase tetha	Functional(+)/null(−)	0 = −–1 = +	64–36	28–72