Published online Sep 18, 2014. doi: 10.5312/wjo.v5.i4.469
Revised: March 12, 2014
Accepted: April 17, 2014
Published online: September 18, 2014
Although injury and neuromuscular activation patterns may be common for all individuals, there are certain factors which differentiate neuromuscular activity responses between children, adults and elderly. The purpose of this study is to review recent evidence on age differences in neural activation and muscle balances around the knee when performing single joint movements. Particularly, current evidence indicates that there are some interesting similarities in the neuromuscular mechanisms by which children or the elderly differ compared with adults. Both children and elderly display a lower absolute muscle strength capacity than adults which cannot fully be explained by differences in muscle mass. Quadriceps activation failure is a common symptom of all knee injuries, irrespective of age but it is likely that its effect is more evident in children or adults. While one might expect that antagonist co-activation would differ between age categories, it appears that this is not the case. Although hamstring: quadriceps ratio levels are altered after knee injury, it is not clear whether this is an age specific response. Finally, evidence suggests that both children and the elderly display less stiffness of the quadriceps muscle-tendon unit than adults which affects their knee joint function.
Core tip: Children and elderly display a lower absolute muscle strength capacity than young adults. This may be due to a higher quadriceps activation failure as well as a more compliant quadriceps muscle-tendon in children (probably due to maturation) and elderly (due to age effects on neuromuscular system) than adults which, in turn, leads to an altered strength capacity. In contrast, age differences in muscle co-activation are not age dependent. Current evidence precludes any conclusions on whether muscle strength balance ratios are age specific.