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Early Hum Dev. 2016 Sep; 100:21-5

https://www.sciencedirect.com/science/article/pii/S0378378216300123

Epub 2016 Jul 6

 

Digit ratio (2D:4D), testosterone, cortisol, aggression, personality and hand-grip strength: Evidence for prenatal effects on strength.

Ribeiro E Jr, Neave N, Morais RN, Kilduff L, Taylor SR, Butovskaya M, Fink B, Manning JT

 

Abstract

 

BACKGROUND:

Digit ratio (2D:4D) is a putative marker for prenatal testosterone and is correlated with performance in many sports. Low 2D:4D has been linked to strength but the evidence is mixed and strength is also influenced by mass, testosterone, and behavioural factors. It has been hypothesised that the 2D:4D-strength correlation may be strongest in challenge conditions when short-term changes occur in steroid hormones.

 

AIMS:

We tested this suggestion in men.

 

STUDY DESIGN:

We used a cross-over study design with a challenge (an aggressive video of rugby tackles) and control (a blank screen) condition.

 

SUBJECTS:

89 healthy men.

 

OUTCOME MEASURES:

Finger lengths (2nd and 4th for both hands), hand-grip strength (HGS), testosterone (T), cortisol (C), aggression (Buss-Perry Aggression Questionnaire) and personality type (Ten Item Personality Measure). In both conditions participants provided saliva samples (for hormone assays).

 

RESULTS:

In the challenge condition there was a highly significant increase in HGS, and modest changes in T, physical aggression and emotional stability. HGS correlated negatively with left hand 2D:4D. In a multiple regression, left hand 2D:4D was negatively related to HGS and emotional stability was positively related to HGS. In the control condition HGS was not correlated with 2D:4D. In a multiple regression, BMI, physical aggression, and emotional stability were significantly related to HGS.

 

CONCLUSIONS:

2D:4D is a negative correlate of strength in challenge situations. This finding may in part explain associations between 2D:4D and sports performance.

 

Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

 

KEYWORDS:

Aggression; Digit ratio; Hand-grip strength; Testosterone

 

PMID: 27393866

DOI: 10.1016/j.earlhumdev.2016.04.003

 

 

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