Abstract
Optimal feedback control theory suggests that control of movement is focused on movement dimensions that are important for the task's success. The current study tested the hypotheses that age effects would emerge in the control of only specific movement components and that these components would be linked to the task relevance. Fifty healthy volunteers, 25 young and 25 older adults, performed a 80s-tandem stance while their postural movements were recorded using a standard motion capture system. The postural movements were decomposed by a principal component analysis into one-dimensional movement components, PMk, whose control was assessed through two variables, Nk and σk, which characterized the tightness and the regularity of the neuro-muscular control, respectively. The older volunteers showed less tight and more irregular control in PM2 (N2: −9.2%, p = 0.007; σ2: +14.3.0%, p = 0.017) but tighter control in PM8 and PM9 (N8: +4.7%, p = 0.020; N9: +2.5%, p = 0.043; σ9: −8.8%, p = 0.025). These results suggest that aging effects alter the postural control system not as a whole, but emerge in specific, task relevant components. The findings of the current study thus support the hypothesis that the minimal intervention principle, as described in the context of optimal feedback control (OFC), may be relevant when assessing aging effects on postural control.
Highlights
In the USA around 20% of people aged 65 and over are diagnosed with only fair or poor health and long-term care services alone require between 210 and 317 billion USD annually (Rothwell, 2016)
The purpose of the current study was to investigate age effects in the postural movements observed in healthy volunteers standing in a tandem stance
The aspects of postural control that each PM resembled are listed in Table 1 and visualized in Figure 3 and the videos submitted as Supplementary Materials
Summary
In the USA around 20% of people aged 65 and over are diagnosed with only fair or poor health and long-term care services alone require between 210 and 317 billion USD annually (Rothwell, 2016). Age Effects in Postural Control hand, deterioration in balance function accelerates after reaching the approximate age of 60 (Era et al, 2006) and, on the other hand, this age group is usually still active and a suitable target for preventive programs. In this context gender effects or interactions between gender and aging on postural control are interesting, because literature is somewhat incoherent on this issue: there is evidence that the two genders are unequally influenced by aging (Evans and Hurley, 1995) and postural control may be affected differently (Wolfson et al, 1994). Other authors found that some of the gender effects on balance performance disappear when normalizing, for example, to body height (Bryant et al, 2005)
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