Influence of puberty on muscle development at the forearm.

Despite its fundamental importance for physical development, the growth of the muscle system has received relatively little consideration. In this study, we analyzed the relationship between cross-sectional area (CSA) of forearm muscles and maximal isometric grip force with age and pubertal stage. The study population comprised 366 children, adolescents, and young adults from 6 to 23 yr of age (185 female) and 107 adults (88 female) aged 29 to 40 yr. By use of peripheral quantitative computed tomography, muscle CSA was determined at the site of the forearm, whose distance to the ulnar styloid process corresponded to 65% of forearm length. Both muscle CSA and grip force were higher in prepubertal boys than in girls. The gender differences decreased until pubertal stage 3 and reincreased thereafter. In girls at pubertal stage 5, muscle CSA no longer increased with age (P > 0.4), whereas there was still some age-related increase in grip force (P = 0.02). In boys at pubertal stage 5, both muscle CSA and grip force continued to increase significantly with age (P < 0.005 each). Specific grip force (grip force per muscle CSA) adjusted for forearm length increased by almost one-half between 6 and 20 yr of age, with no difference between the genders. In conclusion, forearm muscle growth takes a gender-specific course during puberty, indicating that it is influenced by hormonal changes. However, the increase in specific grip force is similar in both genders and thus appears to be independent of sex hormones.