=.2in
Note that unlike variability measures, temporal structure measures
are sensitive to the order of the data points in the time series.
Table 2: Stride Time Variability | ||||
3 & 4 Year Olds | 6 & 7 Year Olds | 11--14 Year Olds | ||
SD (msec) | Original Time Series | 55 ![]() ![]() | 31 ![]() | 23 ![]() ![]() |
After Detrending | 48 ![]() ![]() | 28 ![]() | 22 ![]() ![]() ![]() | |
1st 30 Strides | 47 ![]() ![]() | 25 ![]() | 17 ![]() ![]() ![]() | |
CV (%) | Original Time Series | 6.1 ![]() ![]() | 3.3 ![]() | 2.1 ![]() ![]() ![]() |
Lowest 30 stride segment | 3.1 ![]() ![]() | 1.8 ![]() | 1.2 ![]() ![]() ![]() | |
1st 30 Strides | 5.1 ![]() ![]() | 2.6 ![]() | 1.6 ![]() ![]() ![]() |
SD: standard deviation; CV: coefficient of variation. and
denote p < .005 and p < .0001, respectively,
compared to the 6 and 7 year olds.
denotes p < .0001
comparing the oldest and youngest groups.
Kruskal-Wallis tests detected
significant differences among the three groups for all measures (p <
.0001).
Table 3: Spectral Analysis | |||
3 & 4 Year Olds | 6 & 7 Year Olds | 11--14 Year Olds | |
% High Frequency Power (0.25--0.5 stride![]() | 0.054 ![]() | 0.064 ![]() | 0.100 ![]() |
Low/High Ratio | 6.8 ![]() | 4.1 ![]() | 2.3 ![]() ![]() |
Low/High Ratio after Detrending | 0.30 ![]() ![]() | 0.20 ![]() | 0.15 ![]() ![]() |
% High Frequency Power (0.3--0.4 stride![]() | 0.022 ![]() | 0.023 ![]() | 0.038 ![]() |
Low/High Ratio | 6.8 ![]() | 4.5 ![]() | 2.3 ![]() ![]() |
Low/High Ratio after Detrending | 0.41 ![]() | 0.29 ![]() | 0.18 ![]() ![]() |
denotes p < .05
compared to the 6 and 7 year olds.
denotes p < .005
comparing the oldest and youngest groups.
Kruskal-Wallis tests detected
significant differences among the three groups for all measures except high frequency power.
Table 4: Effects of Age on Stride Time Dynamics![]() | |||
3 & 4 Year Olds | 6 & 7 Year Olds | 11--14 Year Olds | |
Variability | ![]() ![]() | ![]() | -- |
Low/High Frequency Power | ![]() ![]() | ![]() | -- |
Autocorrelation Decay Time | ![]() | -- | -- |
Fractal Scaling Exponent | ![]() | ![]() | -- |
Compared to the oldest children in whom stride time dynamics
are the most adult-like.
Note how different aspects of
the temporal structure of the stride dynamics tend to mature at
different ages. (The low/high ratio was not statistically different in the two youngest groups,
however, this representation reflects the observed trend toward a decreased ratio
in the 6 and 7 years olds compared to the 3 and 4 year olds.)