Sex differences in grip strength from birth to age 16

In 1985, Thomas and French published results of a meta-analysis that examined sex differences in grip strength in children 5 years of age and older. Their analysis included results from only four studies, and no attempt has been made to update it. The purpose of the current study was to use meta-analysis to examine sex differences in grip strength from birth to age 16. The analysis included 791 effects from 164 studies. Studies were published between 1961– 2023. The total sample was 351,559 (177,469 boys, 174,090 girls). From birth to 16 years of age, grip strength was consistently greater in boys than girls. Between 3-10 years old, the effect size was small-to-moderate, with female grip strength equaling about 90% of male grip strength (Hedges g = 0.33-0.45). At age 11, the effect size decreased, likely due to girls reaching puberty before boys (g = 0.28; 95% confidence intervals (CI) = 0.21, 0.35). At age 13, the effect size increased markedly due to male puberty (g = 0.63; CIs = 0.55, 0.70). By age 16, the sex difference in grip strength was substantial, with female grip strength 65% of male grip strength (g = 2.07; CIs = 1.86, 2.27). Secondary analyses revealed that the sex difference in grip strength is broadly similar between countries and has been mostly stable since the 1960s, except for a narrowing of the difference among 5-10-year-olds in the 2010s. Biological factors likely explain why, on average, boys are stronger than girls from birth onward.