| Study | Subjects | Tasks | Measures | Findings | ||||
| Frost et al22 | Grouped by age, years: 7–8 (n = 10); 10–12 (n = 10); 15–16 (n = 10) | Treadmill walk, treadmill jog | EMG, VO2 | Co-contraction index higher at running speeds matched to same relative metabolic intensity in younger age subjects. VO2 higher for younger age at matched speeds | ||||
| Croce et al24 | Grouped by age, years: prepubescent girls (n = 15); prepubescent boys (n = 15); postpubescent women (n = 14) ; postpubescent men (n = 14) | Vertical jump landing (50% of maximum) | EMG, kinematics | Co-contraction ratio higher in postpubescent compared with prepubescent before landing. Co-contraction ratio lower in postpubescent compared with prepubescent after initial contact | ||||
| Hamstra-Wright et al6 | Prepubescent children: boys, high skill (n = 11); boys, low skill (n = 6); girls, high skill (n = 10); girls, low skill (n = 9) | Drop jump | EMG, leg stiffness | Low-skilled prepubescent children had greater preparatory co-contraction than high skilled children. No differences in vertical leg stiffness between gender or skill level | ||||
| da Fonseca et al21 | Male, athletic (n = 9); male, sedentary (n = 9); female, athletic (n = 9); female, sedentary (n = 9) | Walk, jump landing | EMG | Walking: sedentary females had higher co-contraction levels than athletic females. Landing: no differences between groups | ||||
| Sigward and Powers23 | Girls, experienced (n = 15); girls, novice (n = 15) | Side-step cut | EMG, inverse dynamics | Novice athletes had higher co-contraction during early deceleration than experienced athletes. Experience athletes had higher internal knee flexion moments than novice athletes | ||||
| Russell et al25 | Grouped by age, years. Children: girls (n = 14), boys (n = 14); adults: women (n = 14), men (n = 13) | Vertical jump landing (50% of maximum, normal and perturbed) | EMG, kinematics | Adults had higher co-contraction ratio during preparatory landing phase than did children. No co-contraction ratio differences between groups during reflexive or voluntary phase. No gender difference in co-contraction ratio |
EMG, electromyography; VO2. oxygen uptake.