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GaitMaturationDatabase
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<B> Previous:</B> <A NAME="tex2html111" HREF="node11.html">Relationship of Stride Dynamics </A>





  
  

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<BR> <P>





  
  

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<H1><A NAME="SECTION00050000000000000000">Discussion</A></H1>





  
  

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<P>





  
  

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This quantitative study of stride variability and dynamics reveals





  
  

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several interesting new findings: 1) Stride to stride variations in gait cycle





  
  

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duration are significantly larger in healthy 3 and 4 year old





  
  

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children compared to 6 and 7 year old children and in 6 and 7 year old





  
  

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children compared to children ages 11 to 14. 2) The temporal structure





  
  

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of gait fluctuations is not fully developed in 7 year old





  
  

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children, while in  older children (11 to 14 year olds), stride dynamics





  
  

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approach the values observed in adults. 3) Different features of stride





  
  

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dynamics do not develop at the same time (Table 4).  Thus, while





  
  

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visual observation might suggest that the stride dynamics of 





  
  

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children are not different from that of adults, quantitative





  
  

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measurement of gait dynamics indicates that stride-to-stride control





  
  

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of walking is not fully mature even in 7 year olds.





  
  

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<P>





  
  

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A number of similarities have been reported in the gait pattern of children and elderly adults  (5,6,23). This finding may reflect a





  
  

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reappearance of primitive reflexes or simply diminished control of





  
  

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balance  (23). The present study 





  
  

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demonstrates that parallels also exist with respect to stride dynamics. 





  
  

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In older adults and persons with neurological





  
  

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impairment, alterations of stride dynamics have been observed  (3,4,7,8,10,14). 





  
  

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However, 





  
  

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while the stride dynamics of young children share some characteristics





  
  

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of the unstable dynamics of older persons  and those with





  
  

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neurological impairment, there appear to be important differences as





  
  

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well. For example, the present findings suggest  that the fractal scaling





  
  

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index changes monotonically throughout the lifespan (highest in





  
  

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children, lower in adults and lowest in the elderly and persons with





  
  

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neurological disease). In contrast, stride variability likely changes in a





  
  

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U-shaped fashion (high in children, lower in adults, and higher with





  
  

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disease and perhaps also in very advanced age). Thus, from the 





  
  

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perspective of stride time dynamics,  the changes





  
  

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in gait of older persons do not simply reflect a return to 





  
  

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an immature gait pattern.





  
  

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<P>





  
  

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The alterations of the dynamics of the stride time in the younger





  
  

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children may be due to a number of factors.  The increased variability





  
  

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may in part be related to decreased walking velocity and decreased





  
  

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postural stability at lower speeds  (23).  However, while adjustment





  
  

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for height minimized the effects of age on velocity, the age-related





  
  

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differences in both the magnitude of the variability and in the





  
  

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dynamics persisted after controlling for height.  A number of factors





  
  

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also suggest that the observed age-related changes in the temporal





  
  

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organization of stride dynamics are most likely not simply





  
  

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attributable to reduced height, gait speed, change in concentration





  
  

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during the walk, or increased stride-to-stride variability





  
  

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(unsteadiness). For example, fractal scaling indices were similar in





  
  

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the 3 and 4 year old children compared with the 6 and 7 years old





  
  

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children, despite significant differences in stride-to-stride





  
  

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variability, velocity,  and height.  Age-related differences in stride dynamics were evident





  
  

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in dynamical measures even after detrending to minimize the effects of





  
  

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changes in speed or local average stride time. Moreover, an age-related effect





  
  

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was observed in the ratio of spectral balance, a measure that was derived





  
  

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independently of stride to stride variability and very low frequency





  
  

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changes likely to be associated with change of speed or loss of concentration.





  
  

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<P>





  
  

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Future study of children walking at different speeds may help





  
  

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elucidate the role of velocity on stride dynamics in children. 





  
  

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In addition, studies that include assessment of 





  
  

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motor control and balance as well as other aspects of the locomotor 





  
  

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control system





  
  

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may also help clarify the  role of 





  
  

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potential contributing factors to the development of mature





  
  

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gait dynamics. Perhaps, differences in motor control development





  
  

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account for some of the observed heterogeneity in stride dynamics





  
  

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within each age group (e.g., Figure 1). 





  
  

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An intriguing possibility is that these dynamical measures 





  
  

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may provide a means of quantifying the stage of maturational development.





  
  

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In any case, it seems  that 1) stride time





  
  

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dynamics most likely depend on some aspect of the neuromuscular control system





  
  

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that is not merely related to walking velocity or gait variability,





  
  

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and 2) the immature gait dynamics in children may reflect the subtle





  
  

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ongoing development of more than one component of motor control.





  
  

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The dynamical action theory of motor





  
  

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control postulates  that locomotor function can be viewed as 





  
  

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 a complex system with multiple degrees of freedom whose





  
  

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 collective behavior is governed in part by the principle of





  
  

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self-organization  (13,23,27). Therefore, perhaps mature locomotion dynamics





  
  

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emerge only once all of the interacting individual components are





  
  

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fully developed. The change in scaling exponents with age, 





  
  

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a measure  associated with a non-equilibrium dynamical





  
  

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system with multiple-degrees-of-freedom  (1,22), may reflect





  
  

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this emergent behavior. Candidate elements that could affect 





  
  

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stride dynamics include 





  
  

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biomechanical and  neural properties that are





  
  

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known to mature only in older children (e.g., electromyogram recruitment patterns





  
  

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are more variable in children under 7 years of age)  (15,23). 





  
  

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Additional studies will be needed to explain these complex age-related





  
  

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 changes  in the magnitude and temporal





  
  

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structure of stride dynamics. Nonetheless, the present findings have 





  
  

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potentially 





  
  

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important implications for the understanding and modeling of the





  
  

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integrative control of locomotor function and neural development. Further, 





  
  

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the results suggest the possibility that quantitative measures





  
  

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of stride dynamics may be useful in augmenting the early detection





  
  

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and classification of gait disorders in children.





  
  

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<P>





  
  

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