Introduction movements are scaled to the subjects body

Introduction

In Germany were the study was conducted
obesity is a growing problem, 1 in 6 children are overweight or obese and 4 out
of 5 of obese teenagers will remain obese into adulthood. Obesity may cause
orthopedic problems not only during childhood but may also have long-term
implications for musculoskeletal health during adolescence and into adulthood. A
higher body mass, has been identified as an important factor for the
development and progression of foot deformities, varus and valgus angular
deformities of the knee, slipped capital femoral epiphysis and has long term
implications for developing osteoarthritis. However, few studies have been done
to investigate the relation of these factors during dynamic activities.

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Obese adults make changes in their
movements such as slower walking velocities, longer double support phases,
wider stance widths, and an all in all have more tentative walking
characteristics. However there has only been a few studies conducted and while
greater absolute movements for obese subjects were found at the hip, knee and
ankle sagittal and transverse planes. The findings are inconsistent when the
movements are scaled to the subjects body weight. Similarly, while there is
information on the functional joint loading during level walking no to date
information on other daily activities such as stair-walking. The purpose of the
article was to examine if lower extremity joint moment normalized to body mass
in obese children are greater than those in normal weight children during stair
walking. 

Methods

The subjects for this study consisted of
35 children 18 of which were considered obese and the remaining 17 children
were of healthy weight. The obese children were those who had a body mass index
(BMI) at or above the 95th percentile and the healthy weight children’s BMI
were between the 15th and the 85th percentile. There were 18 children in the
obese group, this group had an average age of 10.5 with a standard deviation of
1.5 years. This groups

The staircase used in this experiment
consisted of six steps with no handrail.

The
step dimensions were 17 cm (riser) and 28 cm (tread) with a stair slope of 31
deg.

Kinematic
and kinetic recordings were collected by using a ten camera, three-dimensional
motion analysis system (VICON, MX Camera System, Oxford Metrics Ltd., UK) and
two force platforms (AMTI, Model BP600900, Advanced Mechanical Technology,
Watertown, MA) positioned as the 3rd and 4th stair step. Kinematic data were
sampled at 200 Hz, and ground reaction forces were collected at a rate of 1000
Hz.

The subjects were to walk bare foot
wearing swimsuits to allow the attachment of reflective markers to the skin.
These markers were placed according to the Vicon Plug In Gait (PIG) full-body
marker seta and by taking anthropometric measurements. All subjects ascended
and descended the stairs placing only one foot on each step with a cadence of
110 steps per minute. No subjects were given instruction on how to position
their arms while walking. During testing each subject performed one static
standing trial and as many ascending and descending trials, until they could
perform three valid trials for each condition. A trial would be considered
valid when the set cadence (110 steps per minute) was achieved and there were
no visible alterations in the subjects’ stride characteristics. Each subject
was given long periods of rest between each trial to avoid fatigue.

            Data analysis of the three-dimensional
coordinates of the reflective markers were collected during the locomotion
task. Relative angles were calculated using the Vicon Nexusa PIG analysis package.
According to the Vicon (PIG) definitions, the local x-, y- and z-axes related
to flexion–extension, abduction–adduction and rotation at the hip and at the
knee. When analyzing ground force the low cut-off frequency also eliminated
impact forces meaning only active forces were analyzed. The gait cycle was
analyzed as the initial foot contacted with the embedded force platform on the
3rd and 4th steps. An average of three trials were
calculated for the angular displacements and moment at each percent of gait
cycle.

Results

 

In table 2 Spatio-temporal gait cycle
parameters for stair ascent and descent for both groups are presented. Obese
children spent less time in single support during stair ascent, and more time
in double support (p = 0.014) with a delayed foot-off (p = 0.008) during stair
descent compared to normal-weight children. Table 2 also summarizes peak angles
observed at the thorax, pelvis, hip, knee and ankle joint, respectively, and
foot progression angle during stair ascent and descent for both groups. The
MANOVA revealed overall significances between groups in pelvis and knee angles
(p = 0.035 and p = 0.003, respectively) during stair ascent and in hip angles
during stair descent (p = 0.038). While ascending stairs, obese children walked
with a slightly more anteriorly tilted pelvis (+3.98; p = 0.041) and with the
knee in a more pronounced valgus position (+6.28; p = 0.005) than normal-weight
children.

Normalized ground reaction forces were
similar for obese and normal-weight children during stair ascent and descent.
Mean peak ground reaction forces in anterior–posterior, medio-lateral and
vertical direction and peak moments at the hip, knee and ankle in the sagittal
and frontal planes are given in Table 2. For stair ascent, overall differences
were found at the hip (p = 0.006) and the knee (p = 0.030). Obese subjects had
a 23% greater hip abduction moment (p = 0.001) and a 22% greater knee extension
moment (p = 0.008). All other moments during stair ascent were similar for both
groups. For stair descent, overall differences in hip moments (p = 0.027) and
in ankle moments (p = 0.030) were found. Obese children shifted from hip
extension moment into hip flexion moment at 10% of stance, while in
normal-weight children this shift occurred at approximately 50% of stance.
Hence, obese children had smaller hip extension moments (“53%; p = 0.031),
greater hip flexion moments (+26%; p = 0.016) and greater knee extension
moments (15%; p = 0.008) compared to normal-weight children. No statistical
difference in any other joint moment was observed.

Conclusion

 

The goal of this study was to provide
initial data on differences in stair-walking biomechanics between obese and
normal-weight children. Greater hip abduction and knee extension during stair
ascent and greater hip and knee flexion during stair ascent was observed in
obese children this may contribute to a cumulative overloading of the joints
until adulthood and to a greater risk of knee and hip osteoarthritis.

Even
with the results showing that obese children should reorganize their walking
pattern, this study does not support clear conclusions in regard to systematic
effects of obesity on gait pattern and joint movements. Further research should
be conducted to obtain more clear conclusions

 

 

Critique

 

This study had a limited number of
participants, with only 35 children acting as the subjects. The number of
subjects could have been more to offer a wider variance of the data collected. Along
with the limited number of subjects the article offered no information about
the subjects individually. Only the obese and healthy weight group’s average
age, weight, and height were given. It would have been helpful to have a chart
with the individual subject’s specific age, weight, and height to give more
background information on the subjects. Measurements could have also been added
for the length of their legs. This would have added more information to take
into consideration for the final results data.

The article also did not state the
genders of the children who participated. This is a problem because girls reach
puberty sooner than boys. Since girls being puberty younger than boys they are heavier
as well as taller than their male counter parts. The girls being heavier would
make it more likely that they are considered obese. While being taller may also
throw off the angle calculations in relation to the other children. The
unspecified gender problems were indirectly addressed by the article stating
they were using BMI by age, which is a comparison between people of the same
height and age. However, it was never clarified throughout the article which
the problems remain valid while reading the article.

There was an issue with the data analysis
of this article as well. It is stated that since no anthropometric data set for
obese children is available, the standard values for adults was used. This seems
to cause issue because the children who are the subjects are prepubescent or
have just began puberty, therefore their anthropometric data could not be
comparable enough to use during this study.

            There was difficulty understanding two of the three
charts, there was no information in the article that helped clarify the confusion.
These charts were in the article pages away from where the section it was
covering was placed. This made for an awkward time trying to figure out what
the charts were supposed to be showing since they both seemed incomplete as
well.  

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