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INDEPENDENTLY
TESTED
BY
CENTRE
FOR
ALLIED
HEALTH
EVIDENCE
University
of
South
Australia
Project
Directors: Associated Professors
Karen Grimmer & Mr.
Steve Milanese |
Aims |
This
study
provides
evidence
regarding
the
usefulness
of
the
Drag
Bag
in
protecting
spinal
health. The
research
questions
were:
- How
much
difference
is
there
between
the
spinal
posture
of
the
completely
unloaded
body,
and
carrying
the
Drag
Bag?
- How
does
the
Drag
Bag
compare
ergonomically
with
other
backpacks,
using
the
same
weights?
- What
is
the
general
perception
of
users
of
the
Drag
Bag
with
respect
to
useability,
time
spent
carrying
compared
with
dragging
etc
?
- How
does
the
Drag
Bag
compare
ergonomically
with
other
trolley
bags
on
the
market,
using
the
same
weights?
|
Method |
Testing
comprised
three
phases:
laboratory
assessment,
ergonomic
assessment
and
a
field
study.
- The
laboratory
assessment
tested
the
effect
of
carrying
the
Drag
Bag
on
spinal
posture. The
laboratory
sample
consisted
of
21
consenting
individuals
(age
range
9
years
to
53
years). Weights
of
5%,
10%
and
15%
of
body
weight
were
carried
in
the
Drag
Bag,
and
in
the
PhysioPak
V2
(the
comparison
bag). Previous
testing
has
identified
the
percentage
difference
in
measures
of
net
spinal
posture
(from
unloaded)
when
using
PhysioPak
and
off-the-shelf
school
backpacks
with
these
same
weights. PhysioPak
V2
was
identified
as
being
the
best
available
backpack
(at
the
time)
in
minimising
net
postural
deviation
from ‘unloaded’.
Side-view
photographs
were
taken
of
body
posture,
using
usual
marker
positions. From
the
x,y
coordinates
digitised
from
these
pictures,
postural
change
in
the
horizontal
direction
was
measured
between
different
carrying
conditions
and
backpacks,
and
within-subject
comparisons
made.
- A
comparison
of
the
effects
on
posture
was
made
of
5%,
10%
and
15%
body
weight
carried
in
main
space
in
the
bag. The
effect
of
5%
of
body
weight
was
also
tested
in
the
computer
pocket
of
both
backpacks
(which
is
situated
in
the
anterior
aspect
of
the
PhysioPak
V
2
and
in
the
posterior
aspect
of
the
Drag
Bag). Two ‘unloaded’ photographs
(without
any
backpack)
were
also
taken
for
comparison.
- Subjects
were
questioned
at
the
end
of
the
laboratory
session
to
assess
the
levels
of
comfort
and
ease
of
use
of
the
bag
in
relation
to
the
PhyioPak
V2
and
elicit
opinions
on
the
Drag
Bag.
- A
small
number
of
volunteers
from
the
laboratory
study
sample
trialed
the
Drag
Bag
for
one
week
each
in
their
usual
study
/
work
environments. They
reported
in
free
text
at
the
end
of
the
week
on
predetermined
topics:
the
useability
of
the
bag
in
their
own
environment,
including
the
things
that
they
liked
and
didn’t
like
about
the
bag’s
design
and
features,
the
nature
and
weight
of
loads
they
carried in
the
bag,
and
how
they
preferred
to
use
it
(on
the
back
or
pulling
along). They
were
asked
to
compare
their
experiences
of
the
Drag
Bag
with
those
of
using
their
usual
method
of
load
transportation.
|
Results
from
Laboratory
Study |
21
subjects
participated
in
the
laboratory
study:
- 11
young
people
(8
boys,
3
girls,
aged
between
9
and
18
years)
- 10
adults
(5
males,
5
females,
aged
between
19
and
53
years)
|
Under
backpack
carrying
conditions,
compared
with ‘unloaded’ |
There
were
consistent
findings
for
all
but
one
of
the
children,
and
for
six
of
the
adults,
in
the
way
they
responded
to
the
Drag
Bag,
compared
with ‘unloaded’ posture.
There
was
a
linear
response
of
increasing
net
postural
deviation
from ‘unloaded’ for
loads
of
the
empty
bag,
5%
and
10%
of
body
weight. However,
the
Drag
Bag
seems
to
perform
better
with
higher
loads
in
it,
as
it
produces
the
same
amount
of
postural
deviation
at
higher
loads
as
it
does
at
lower
loads. There
seems
to
be
a
threshold
effect
at
about
10%
body
weight,
where
the
true
value
of
the
bag
becomes
obvious
under
its
backpack
carrying
performance. Carrying
a
weight
in
the
computer
pocket
seems
also
to
be
more
posturally
efficient
than
carrying
the
same
weight
in
the
body
of
the
backpack
.
This
finding
is
of
particular
interest,
when
considering
the
variability
in ‘unloaded’ posture
in
the
children
in
the
study. Thus
it
seems
that
wearing
Drag
Bag
on
the
back
corrects
posture
of
young
people. |
Under
backpack
carrying
conditions,
compared
with
PhysioPak
V2 |
For
children,
there
were
real
similarities,
with
no
statistically
significant
differences,
in
the
way
that
Drag
Bag
performed
at
the
same
weights,
compared
with
PhysioPak
V2. As
PhysioPak
V2
is
the
best
backpack
we
have
tested
to
date,
in
terms
of
minimising
postural
deviations
when
carrying
loads,
this
means
that
Drag
Bag
can
claim
similar
good
performance. |
Feedback
after
laboratory
study |
All
but
one
participant
liked
the
Drag
Bag
design,
including
the
fabric,
strap
width
and
positioning,
compartment
design
and
features
(such
as
lunchbox,
rain
cover
etc).
Preliminary
testing
of
trolley
bag
version
of
the
Drag
Bag
around
the
laboratory
and
the
immediate
university
environment
(up
and
down
stairs,
in
and
out
of
lifts,
on
carpet,
tiles,
gravel,
concrete)
brought
favourable
reactions
from
everyone,
with
the
friction-free
wheel
design
bringing
most
approval .
All
subjects
commented
on
the
comfort
of
the
Drag
Bag
when
worn
as
a
backpack,
saying
that
the
strap
width
suited
their
body
shape,
the
backpack
sat
comfortably
on
their
backs
(and
in
some
instances
subjects
noted
that
they
seemed
to
stand
better
with
the
backpack
on). They
didn’t
notice
any
increase
in
discomfort
when
increasing
weights
were
placed
into
the
backpack
during
testing. |
Recommendations
from
Laboratory
Study |
Drag
Bag
performs
well
under
laboratory
conditions
for
most
body
types,
and
for
both
genders
over
a
range
of
ages. When
it
is
unloaded,
it
significantly
changes ‘unloaded’ posture,
but
then
so
have
every
bag
that
we
have
tested. It
seems
to
perform
better
under
heavier
weights,
when
carried
in
the
body
of
the
backpack,
and
in
the
computer
pocket. It
seems
that
carrying
Drag Bag
on
the
back,
as
in
a
conventional
backpack
arrangement,
does
not
put
the
spine
under
abnormal
horizontal
perturbations,
and
thus
it
can
be
deemed
to
be
posturally
safe
for
adult
and
child
wearers.
The
Drag
Bag
offers
a
well
designed
piece
of
equipment
which
works
well
as
a
backpack
and
as
a
trolley
bag
under
usual
conditions. It
seems
to
handle
heavier
weights
well
in
its
backpack
version,
and
its
ease
of
locomotion
as
a
trolley
bag
suggests
that
this
is
also
an
efficient
way
of
transporting
heavy
loads . |
Field
Trial |
Drag
Bag
was
tested
for
one
week
under
usual
load
carrying
and
transport
conditions
by
six
subjects
(three
children
and
three
adults)
(representing
6
weeks
total
of
testing). The
good
things
about
the
bag
were
commonly
identified
as
being:
- Its
versatility
(being
able
to
be
carried
on
the
back
when
appropriate,
and
dragged
along
the
ground
when
appropriate)
- Its
comfort
when
being
carried
- Its
smart
looks
and
features,
including
the
lunchbox
features
and
rain
cover
- Its
wheel
and
handle
design,
which
allowed
for
easy
locomotion
along
streets,
over
gutters,
up
and
down
stairs
etc
- Its
fabric
and
the
sturdy
zips
- Its
different
compartments,
making
it
easy
to
keep
track
of
items
All
subjects
liked
the
trolley-bag
feature
of
the
Drag
Bag – the
trolley
handle
seemed
to
be
at
an
appropriate
height
for
all
subjects
(irrespective
of
their
physical
size),
the
wheels
travelled
over
all
required
terrain,
it
was
very
energy
efficient
to
drag
heavy
loads
and
easy
to
manoeuvre
the
trolley
bag
in
all
situations. |
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