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. 2009 Apr;106(4):1227-33.
doi: 10.1152/japplphysiol.90555.2008. Epub 2009 Jan 22.

Complexity of force output during static exercise in individuals with Down syndrome

Kevin S Heffernan  1 , Jacob J Sosnoff, Edward Ofori, Sae Young Jae, Tracy Baynard, Scott R Collier, Stella Goulopoulou, Arturo Figueroa, Jeffrey A Woods, Kenneth H Pitetti, Bo Fernhall
Affiliations

Complexity of force output during static exercise in individuals with Down syndrome

Kevin S Heffernan et al. J Appl Physiol (1985). 2009 Apr.

Abstract

Force variability is greater in individuals with Down syndrome (DS) compared with persons without DS and is similar to that seen with normal aging. The purpose of this study was to examine the structure (in both time and frequency domains) of force output variability in persons with DS to determine whether deficits in force control are similar between individuals with DS and older adults. An isometric handgrip task at a constant force (30% of maximal voluntary contraction) was completed by individuals with DS (n = 29, age 26 yr), and healthy young (n = 26, age 27 yr) and older (n = 33, age 70 yr) individuals. Mean, standard deviation (SD), and coefficient of variation (CV) were used to analyze the magnitude of force output variability. Spectral analysis and approximate entropy (ApEn) were used to analyze the structure of force output variability. Mean force output for DS was lower than in young controls (P < 0.05) but no different from old controls. Individuals with DS had greater SD and CV than young and old controls (P < 0.05). The DS group had a significantly greater proportion of spectral power within the 0-to 4-Hz bandwidth than the young and older controls (P < 0.05). The DS group had significantly lower ApEn values than the young controls (P < 0.05), but there were no differences in ApEn between the DS group and the old controls (P > 0.05). In conclusion, young persons with DS demonstrate enhanced temporal structure and greater amplitude of low-frequency oscillations in the force output signal than age-matched non-DS peers. Interestingly, young persons with DS and older persons without DS have similar time-dependent structure of force output variability. This would suggest a possible link between premature aging and less complex force output in persons with DS.

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Figures

Fig. 1.
Fig. 1.
Subject grasping force transducer.
Fig. 2.
Fig. 2.
Representative force output for young control and Down syndrome (DS) subject.
Fig. 3.
Fig. 3.
Mean force output in young, old, and DS subjects. SD, standard deviation; CV, coefficient of variation. #Significantly different from young, P < 0.05.
Fig. 4.
Fig. 4.
A: SD of force output in young, old, and DS subjects. B: CV of force output in young, old, and DS subjects.*Significantly different from young and old, P < 0.05.
Fig. 5.
Fig. 5.
A: proportion of spectral power of force output in young, old, and DS subjects. B: approximate entropy of force (ApEn) output in young, old, and DS subjects. *Significantly different from young and old, P < 0.05. #Significantly different from young, P < 0.05.
See this image and copyright information in PMC

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