Purpose: This study examined hamstrings-to-quadriceps ratio (HTQ) and HTQ activation (HTQA) across the velocity spectrum in male and female children and adolescents.
Methods: Seventeen children (n = 9 females, n = 8 males) and 22 adolescents (n = 11 females, n = 11 males) participated. Ultrasound images quantified quadriceps and hamstrings muscle cross-sectional area (CSA). Peak torque (PT) was taken from maximal voluntary isometric contractions (MVICs) and isokinetic leg extensions and flexions from 60 to 300° s-1. HTQCSA was calculated by dividing hamstrings CSA by quadriceps CSA, and HTQPT was PT from leg flexion divided by leg extension for all contractions. HTQA was calculated as electromyographic (EMG) amplitude from leg flexion contraction divided by EMG amplitude from leg extension muscle action. A two-way factorial analysis of variance (ANOVA) examined differences in HTQCSA. Three-way mixed-factorial ANOVAs examined differences in HTQPT and HTQA.
Results: HTQCSA was greater for males than females (p = 0.003). For children, HTQ from MVIC was lower than 120-240° s-1 (p ≤ 0.023), and HTQ from 60° s-1 was lower than 240° s-1 (p = 0.047). For adolescents, HTQ from MVIC was lower than 60-180° s-1 (p ≤ 0.012). For HTQA, there were no significant differences (p ≥ 0.352).
Conclusions: Age group differences in HTQCSA with no age group differences in HTQPT or HTQA may speak to sex-based developmental differences in muscle hypertrophy accompanying growth and development.
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