Ankle muscle activity modulation during single-leg stance differs between children, young adults and seniors.
PURPOSE
Incomplete maturation and aging-induced declines of the neuromuscular system affect postural control both in children and older adults and lead to high fall rates. Age-specific comparisons of the modulation of ankle muscle activation and behavioral center of pressure (COP) indices during upright stance have been rarely conducted. The objective of the present study was to quantify aging effects on a neuromuscular level. Thus, surface electromyography (SEMG) modulation and co-activity of ankle muscles during single-leg standing was compared in healthy children, young adults and seniors.


METHODS
Postural steadiness (velocity and mean sway frequency of COP), relative muscle activation (SEMG modulation) and co-activation of two ankle muscles (tibialis anterior, TA; soleus, SO) were examined during single-leg stance in 19 children [age, 9.7 (SD 0.5) years], 30 adults [23.3 (1.5) years] and 29 seniors [62.7 (6.1) years].


RESULTS
Velocity of COP in medio-lateral and anterior-posterior directions, mean sway frequency in anterior-posterior direction, relative muscle activation (TA and SO) and co-activation revealed large age effects (P < 0.003, η p2 > 0.14). Post-hoc comparisons indicated higher COP velocities, anterior-posterior frequencies, relative SO activation and co-activation in children and seniors when compared with adults. Relative TA activation was higher in children and adults compared with seniors (P < 0.001).


CONCLUSIONS
Increased postural sway in children and seniors seems to be counteracted with higher TA/SO co-activity and SO modulation. However, TA modulation is higher in children and adults, whereas seniors' TA modulation capacity is diminished. An aging-induced decline of TA motor units might account for deteriorations of TA modulation in seniors.
['Kurz|Eduard|E|http://orcid.org/0000-0001-6931-5615', 'Faude|Oliver|O|', 'Roth|Ralf|R|', 'Zahner|Lukas|L|', 'Donath|Lars|L|']
D000328:Adult D000368:Aged D000375:Aging D000842:Ankle D002648:Child D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D009119:Muscle Contraction D018482:Muscle, Skeletal D004856:Postural Balance
Muscle activation Co-activation Postural sway Balance Elderly Risk of falling