Sex Differences in Upper- and Lower-Limb Muscle Strength in Children and Adolescents: A Meta-Analysis

Abstract

On average, adult men are physically stronger than adult women. The magnitude of this difference depends on the muscle tested, with larger sex differences observed in upper- than lower-limb muscles. Whether body region-specific sex differences in strength exist in children is unclear. The purpose of the current meta-analysis was to determine whether sex differences in muscle strength in children and adolescents differ between upper- and lower-limb muscles. Data were extracted from studies of participants aged ≤ 17 years who completed tests of maximal isometric or isokinetic strength of upper-limb muscles (e.g., elbow flexors and elbow extensors) or lower-limb muscles (e.g., knee extensors and ankle dorsiflexors). Participants were partitioned into three age groups: 5–10 years old, 11–13 years old, and 14–17 years old. The analysis included 299 effects from 34 studies. The total sample was 6634 (3497 boys and 3137 girls). Effect sizes of sex differences in upper- and lower-limb strength were g = 0.65 (95% confidence intervals (CI) [0.46, 0.84]) and 0.34 (95% CI [0.19, 0.50]) in 5–10-year-olds; g = 0.73 (95% CI [0.56, 0.91]) and 0.43 (95% CI [0.27, 0.59]) in 11–13-year olds; and g = 1.84 (95% CI [1.64, 2.03]) and 1.18 (95% CI [1.00, 1.37]) in 14–17-year-olds. Upper- and lower-limb strength were 17% and 8% greater in boys than girls when 5–10 years old, 18% and 10% greater when 11–13 years old, and 50% and 30% greater when 14–17 years old. Thus, boys are stronger than girls on average. This sex difference exists before puberty, increases markedly with male puberty, and is more pronounced in upper- than lower-limb muscles throughout development.