title: Right-left digit ratio (2D:4D) predicts free testosterone levels associated with a physical challenge.
abstract: There is evidence that the digit ratio (2D:4D) is a negative correlate of prenatal levels of testosterone, but there is no association between 2D:4D and the circulating levels of both total and free testosterone. Sports provide a physical challenge and participants often show increased levels of free testosterone immediately preceding and during competition. We tested this hypothesis of a link between 2D:4D and testosterone under challenge in 79 professional rugby players using the following procedures; (i) 25 players were physically challenged using a repeated sprint agility test, and saliva samples were assayed for testosterone immediately preceding the repeated sprint agility test (time 1) and 5 minutes (time 2) and 20 minutes after completion of the repeated sprint ability (time 3); (ii) 54 players were also tested for salivary testosterone in an unchallenged condition. We found that right-left 2D:4D was significantly and negatively related to testosterone concentrations at times 1, 2 and 3 following the repeated sprint agility test (P < 0.05) and there was no association between the 2D:4D and basal testosterone levels in the unchallenged group. We suggest that low right-left 2D:4D is a predictive marker of free testosterone responsiveness when trained men are physically challenged, and that this association is programmed by the action of prenatal testosterone.
authors.affiliation: Swansea University, Sports Science, Talbot Building, Singleton Park, Swansea, UK. l.kilduff@swansea.ac.uk
authors.forename: Liam
authors.initials: L
authors.lastname: Kilduff
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Cook
authors.forename: Mark
authors.initials: M
authors.lastname: Bennett
authors.forename: Blair
authors.initials: B
authors.lastname: Crewther
authors.forename: Richard Michael
authors.initials: RM
authors.lastname: Bracken
authors.forename: John
authors.initials: J
authors.lastname: Manning
mesh_terms: D054874:Athletic Performance; D003163:Competitive Behavior; D005385:Fingers; D005538:Football; D007839:Functional Laterality; D006801:Humans; D008297:Male; D012420:Running; D012463:Saliva / Q000378:metabolism; D012727:Sex Characteristics; D013739:Testosterone / Q000097:blood / Q000378:metabolism*
chemical_list: D013739:Testosterone