Lower Extremity Support during Toddler Gait

1
Lower Extremity Support during Toddler
Gait S.Potoczny1, D.G.E. Robertson1 H.
Sveistrup1,2 1School of Human Kinetics and
2School of Rehabilitation Sciences ,University of
Ottawa
Hypothesis Toddler support moments, net moments
and powers will differ from adults and will
develop to more adult like patterns over the
first year of walking.
Purpose To examine whether toddler lower
extremity support moments, net moments of force
and their powers differ from that of adults and
to determine if and when these kinetic patterns
develop within the first year of walking.
Conclusion Toddler support moments, net moments
and powers all differ from that of adults.
Toddler joint kinetics also develop over the
first year of walking. There is a general trend
in the lower limb joint kinetics to develop
patterns closer to that of ?normal adult-like
joint kinetics from ankle to hip?.
Results
Support Moments
Introduction Walking is one of the most
purposeful and fundamental movement patterns for
humans. The first two years of life are
characterized by some of the greatest physical
development and motor ability changes in a child
including the acquisition of gait, yet there is
little research available on the kinetic gait
patterns of toddlers. Brenière Bril (1988)
proposed that children within their first few
months of independent walking actually walk
while falling, whereas adults fall while
walking. The purpose of this study was to
determine whether this transition was consistent
with developmental changes resulting in
increasingly adult-like support moments as well
as net moments and powers.
Moment Powers
Figure 4. Does the progression observed in the
toddler joint moments show similar progression in
the moment power production? Is development of
gait characterized by a sequential development of
moment power production? Hip, knee, and ankle
powers (mean /-sd) for three toddlers (one, five
and eleven month autonomous walkers) and adult
slow walking (mean /-sd data from Winter 1991).
All moments were normalized to body mass and to
percent of stride. Note the different scalings of
the adult slow ankle powers. The vertical dotted
line represents the foot strike of the right foot
and the beginning of stance phase. Despite the
differences in toddler and adult ankle moment
power amplitudes, a very similar pattern of power
production occurs at the ankle throughout the
first year of walking. This was evident in both
the ankle moment powers as well as the
correlation ranges of 0.37 to 0.87, 0.57 to 0.93
and 0.18 to 0.88 for the one, five and eleven
month walkers respectively. The knee power
production correlation ranges of -0.35 to 0.36,
-0.24 to 0.44 and -0.016 to 0.55 show that the
increases in power production by the fifth month
corresponds to a development into a more
adult-like pattern. By the fifth month the hip
also begins to exhibit a more adult like pattern
as seen in the average correlations of 0.25,
0.496 and 0.45 for the one, five and eleven month
walkers, respectively, but begins to exhibit more
adult-like power production amplitudes by the
first year of walking as seen by the hip powers.
Moment / Body Mass (N.m/kg)
Stance
Figure 2. Is falling while walking reflected in
the toddler support moments? Do toddler support
moments show increasingly greater control
becoming more adult-like over the first year of
walking? Support moment curves of individual
steps for a one, two, four, five, nine and eleven
month autonomous walker are plotted. Also plotted
are adult (mean /-sd data from Winter, 1980)
support moment curves for both natural and slow
walking cadences. Note the different scalings for
the adult support moments. Toddler support
moments are approximately two-fold smaller than
adults in relative amplitude. Also, the first
twenty percent of stride for both the one and two
month walker show negative support moments in
approximately 50 of the trials indicating a
controlled fall during the initial part of stance
period. The number of steps with negative support
moments then diminish for the four and five month
walkers, while the nine and eleven month walkers
support moments show minimal to no negative
values. The amplitudes of the support moments
increase over the first year of walking
indicating greater contributions by the moments
of force during stance.
Figure 1. Illustration of a toddler with
digitized segments and force signature overlaid
for that trial.
IFS
IFS
Methodology
Power / Body Mass (Watts/kg)
Participants Thirteen healthy toddlers
autonomously walking for less than a year
participated in this study. Procedure Ground
reaction forces were recorded (240 Hz) and video
images (3 cameras 60 Hz) as toddlers walked
toddlers walked unsupported across two AMTI force
platforms. Eight reflective surface markers were
placed over the anterior superior iliac spine,
sacrum, greater trochanter, knee, tibial
tuberosity, ankle, heel and fifth
metatarsophalangeal joint. Toddler body segment
parameters (BSP) were recorded according to
Schneider and Zernicke (1992) and were used in
inverse dynamics calculations. Steps were
included for analysis if all surface markers were
visible in at least two cameras, if the right
foot only was in full contact with a single
plate, and if the toddler was not running or toe
walking. Between six and fifteen steps were
analyzed for each toddler. All calculations were
done using the Biomech software (Robertson, 2002).
Net and Support Moments
Table 1. Subject Characteristics and Body Segment
Parameters
Moment / Body Mass (N.m/kg)
Stance
Figure 3. Is the transition observed in the
support moments reflected by a parallel
transition in joint moments? Is the development
of gait characterized by a sequential development
of joint moments? Support, hip, knee, and ankle
moments (mean /-sd) for three toddlers (one,
five and eleven months autonomously walking) and
adult slow walking (mean /-sd data from Winter,
1980) are plotted. All moments were normalized to
body mass and percent of stance. Extensor moments
are plotted as positive values and flexor moments
plotted as negative values. Note the different
range on the y axis of the adult slow graphs.
Pearson product-moment correlation ranges were
also obtained for each toddler by comparing adult
slow walking mean curves with each toddler
walking step to obtain the range of correlations.
Correlation averages were obtained by dividing
the sum of the range correlation values by the
number of steps (between 6 and 15) analyzed for
that toddler. Although the amplitude of the
joint moments remain approximately two-fold lower
than that of adults, the pattern of joint flexor
and extensor moments approaches that of the adult
pattern over the first year. This transition in
the pattern of extensor and flexor moments is
characterized by a sequential development over
the first year of walking beginning with the
ankle, proceeding to the knee and then the hip.
The pattern of ankle joint moment is adult-like
after as little as one month of walking and
remains consistent over the first year of walking
as indicated by both the shape of the moment
curves and the correlation ranges and (averages)
of 0.78 to 0.95 (0.87), 0.68 to 0.98 (0.86) and
0.78 to 0.98 (0.89) for the one, five and eleven
month autonomous walkers respectively. The
patterns of knee moments develop over this first
year as seen by the increase in the range and
(average) correlation values from -0.35 to 0.36
(0.04), -0.36 to 0.47 (0.18) and 0.1 to
0.84(0.49) and the change in shape of the joint
moment curve. Even with this development of the
knee moment by 11 months, the knee has an
inconsistent flexor moment that spans less of the
stance phase then adults and is only present in
approximately half of the trials. The hip also
develops over this first year of independent
walking as indicated by the correlation ranges
and (averages) of -0.47 to 0.74 (0.29), -0.03 to
0.85 (0.61) and 0.09 to 0.84 (0.43) for the one,
five and eleven month walkers, but even by the
first year of walking the hip continues to remain
in extension longer and lacks the shift to a
flexor moment around midstance. These data
suggest that joint moment development occurs from
distal to proximal. It is hypothesized that this
order of developmental occurs as a function of
the increased resources utilized for posture
control by toddlers with less walking experience.

Table 2. Gait Characteristics
IFS
IFS
Stride