Transcript Effect of an Unstable Shoe Construction on Lower

Effect of an Unstable
Shoe Construction on
Lower Extremity Gait
Characteristics
Nigg , Benno M.
Ferber , Reed
Gormley Tim
Human Performance Laboratory
University of Calgary
Calgary Canada
Theoretical Concept
Strengthening muscles close to
the movement axis
substantially reduces joint
loading
Reduced joint loading reduces
lower extremity pain
Methods
8 subjects (5 male ,3 female)
Age 28 + 3.6 years
Mass 70.1 + 7.5kg
Height 169.5 + 6.4 cm
All free from lower extremity
injury or pain
None had used MBT previously
Testing Procedure Test
1
Three trials of 30 seconds
each to determine the centre
of pressure and the
corresponding muscle activation
during quiet standing
In the control shoe ( Adidas
Supernova) mass 358g and the
black casual MBT mass 650g
Test 2
10 walking trials on a treadmill
initially in the Adidas then in the
MBT
Walking speed 5 + 0.5 km/h
Measured parameters were ;lower
leg kinematics and kinetics ,selected
soft tissue vibrations and selected
EMG data (tibialis anterior ,medial
gastrocnemius ,biceps femoris
,vastus medialis and gluteus medius)
Test 2 B
Subjects then wore the MBTs for
9.5 + 2.1 hours per day for the
next two weeks and then had
Test 2 repeated , the same
parameters being measured.
Oxygen consumption testing
was also carried out at this
stage
Kinematic and Kinetic
Data
Kinematic data –8 high speed video
camera system (MAC)
Kinetic data collected
simultaneously using a Kistler force
plate
Peak joint angle,peak GRF values
and rotational impulse to each joint
determined for the first and second
half of the stance phase for each
condition and trial
EMG data
Bipolar surface electrodes placed midway
between motor end plate and the distal
myotendinous junction
Frequency bands set to correspond to slow
and fast motor unit activation
Total ,low and high intensities were
averaged over the 30 second quiet standing
period
Total , low and high intensities were
averaged over the pre-heel strike(100ms
before heel strike) and post-heel
strike(100ms after heel strike) interval in
the walking tests
Soft tissue vibration
Soft tissue vibrations were
measured from the muscle
bellies of the rectus femoris
,long head of biceps femoris
and lateral gastrocnemius.
Using skin mounted tri-axial
accelerometers
Oxygen consumption
Testing
After the 2 week accomodation period.
Treadmill @ same time of day
Walking speed 5.0km/h
Four 5 minute walks with a 3 minute rest
interval in between each walk to change
shoes
Repeated on day 2
2 protocols used U-C-C-U or C-U-U-C
Each participant followed both protocols
STUDY RESULTS
GO TO ADOBE DOCUMENT!
Discussion………….
Sample size WAS sufficient for this
study
Centre of pressure excursions larger
for the MBT than the Adidas in quiet
standing
Muscle activity to provide this
stability changed between Test1 and
Test2
In MBTs initially both an ankle and a
hip strategy were incorporated to
maintain quiet standing………………….
In the restest there was less
activation of gluteus medius and
more activation of medial
gastocnemius ,biceps femoris and
vastus medialis.
Indicating recruitment of other ankle
and knee stabilisers during quiet
standing.In effect the MBT CAN BE
EFFECTIVELY USED FOR STABILITY
TRAINING
If the skeleton has a preferred movement
path for a given movement task then it
follows that joint moments and or muscle
activity should be altered to maintain that
preferred movement path.
If a shoe attempts to produce a movement
that counteracts this preferred movement
path then muscle activity or joint moments
are increased.
If however the muscle activity or joint
moments are decreased then one can
assume that the shoe approaches the
preferred movement path of the joint more
closely
In the knee there was a decrease in all
three moments measured and in the hip
there was a decrease in two of the three
moments measured.
Thus it can be concluded that THE MBT
SHOE PRODUCED A MOVEMENT FOR THE
HIP AND KNEE JOINT WHICH WAS CLOSER
TO THE PREFFERED MOVEMENT PATH
THEN THE ADIDAS SHOE.
THIS CORRESPONDS TO A REDUCTION OF
HIP AND KNEE LOADING DURING WALKING
Nigg et al have proposed that
muscles are tuned to minimise soft
tissue vibrations. This is achieved by
keeping the vibration amplitude
constant and changing the vibration
frequency if necessary.
This was the case with MBT shoes
especially in the biceps femoris and
gastrocnemius muscle groups.
Walking in MBT footwear required a 2.5%
increase in oxygen consumption with an
unchanged heart rate.
In walking muscle activity did not change
significantly other than a reduction in the
tib. Ant and biceps femoris activity
The difference in oxygen consumption was
primarily thought to be due to the mass
difference of the shoes- 292 g.
Subjects using the MBT shoe will therefore
use more energy in their exercise
programmes