Gait Analysis: Effect of an unstable shoe construction
Introduction
Linear and angular kinematics during walking have been widely analysed whilst waking barefoot
and in shoes (Lythgo et al. 2009) in order to establish a ‘normal’ model and identify any factors
that may lead to injury. ‘Unstable shoe constructions’ were originally used clinically to help
treat conditions such as plantar fasciitis, diabetes mellitus and the rehabilitation of ankle joint
injuries (Hutchins et al. 2009). However they are now increasingly popular with ordinary
consumers who purchase them in the belief that they will reduce stress on lower body joints and
increase lower limb muscle activation thus helping to tone the lower body (Pocari et al.; Romkes
et al. 2006).
The gait cycle consists of a stance and swing phase of which the shoe affects mainly the stance
phase. The stance phase is again split into two phases: the braking phase and the propulsive
phase.
Aim
The aim of this study is to look at the effect of three unstable shoes on gait kinematics during the
stance phase of walking.
Method
Video data was collected for the three shoes and a barefoot trial for nine subjects. The subjects
performed six walks in each of the shoes.
Data Acquisition



Subjects filmed side on using Casio FH25 camera at 210 frames/sec and a shutter speed
of 1/1000
Reflective markers placed at hip, knee, ankle and metatarsophalangeal (MTP) joints.
Hedler lamp used to ensure markers were clearly visible
Data Analysis




Markers used to identify heel strike and toe off
Videos calibrated and digitised in Quintic Biomechanics Software (9.03 v17) – 10 frames
prior heel strike and 10 frames after toe off (figure 1)
Linear and angular data exported to excel where means were calculated
Multi image capture used to create photo sequence of the gait cycle
Figure 1: Video with digitisation trace
Results – Linear joint velocities
Figure 3 shows the average linear velocity of the four joints during the stance phase. Hip
velocity is relatively constant throughout with a range of 0.91m/s whereas the other 3 joints
display a far greater range of velocities starting around 1.30m/s then dropping to below 0.50m/s
before increasing to over 2.00 m/s. Knee, ankle and MTP velocity all follow a very similar
pattern: sharp decrease after heel strike, then a period of low constant velocity before a rapid and
sustained increase in velocity up to toe off. The hip joint also follows this pattern but with far
less severe changes in velocity.
3.00
Heel Strike
Toe Off
2.50
Velocity (m/s)
Braking Phase
Propulsive Phase
2.00
Hip
Knee
1.50
Ankle
1.00
MTP
0.50
0.00
-10
10
30
50
70
90
Figure 2: Overall mean velocities during the stance phase of the gait cycle
110
130
Figures 3, 4, 5 & 6 show that the barefoot condition resulted in the lowest linear joint velocities
at all four joints but otherwise there is very little variation in linear velocity between the different
shoes.
2.00
Mean Hip Linear Velocities
Velocity (m/s)
1.80
Shoe 1
1.60
Shoe 2
1.40
Shoe 3
Barefoot
1.20
1.00
-10
10
30
50
70
90
110
130
Figure 3: Mean Hip Linear Velocities for all shoes
3.00
Mean Knee Linear Velocity
Velocity (m/s)
2.50
2.00
Shoe 1
1.50
Shoe 2
Shoe 3
1.00
Barefoot
0.50
0.00
-10
10
30
50
70
90
110
130
Figure 4: Mean Knee Linear Velocities for all shoes
3.00
Mean Ankle Linear Velocity
Velocity (m/s)
2.50
2.00
Shoe 1
1.50
Shoe 2
1.00
Shoe 3
Barefoot
0.50
0.00
1
21
41
61
81
Figure 5: Mean Ankle Linear Velocities for all shoes
101
121
141
2.50
Mean MTP Linear Velocity
Velocity (m/s)
2.00
Shoe 1
1.50
Shoe 2
1.00
Shoe 3
Barefoot
0.50
-10
-4
2
8
14
20
26
32
38
44
50
56
62
68
74
80
86
92
98
104
110
116
122
128
134
0.00
Figure 6: Mean MTP Linear Velocities for all shoes
Results – Joint angles
All shoe conditions displayed very similar knee angles throughout the stance phase (figure 7).
180.00
Mean Knee Angle
170.00
160.00
1
2
5
Degrees(º)
3
150.00
Shoe 1
4
140.00
Shoe 2
Shoe 3
130.00
Barefoot
6
120.00
110.00
100.00
-10
10
30
50
Figure 7: Mean knee angles during the stance phase
70
90
110
130
1
2
3
1
Heel
Strike
1
164º
157º
171º
4
5
161º
149º
6
124º
Toe Off
Figure 8: Mean knee angles for a subject at six points during the stance phase.
Figure 8 provides a visual representation of the knee angle during the stance phase.
10 frames prior to heel strike - knee is almost fully extended – between 171º-174º
Heel strike – knee starts to flex to absorb impact forces of heel strike
End of braking phase – Knee continues to flex
Midstance – knee reaches maximum degree of flexion
Propulsive phase – knee extends to support bodyweight and centre of gravity passes in
front of the mid foot
6. Toe off – weight transferred to opposite leg and knee flexes as it enters the swing phase
1.
2.
3.
4.
5.
The ankle angle through the stance phase followed the same pattern in all four trials but there
were differences in the absolute values (figure 9). Shoe 1 displayed the most acute angle (96º at
frame 90) and shoes 2 the least acute ankle angles throughout the stance phase.
140.00
Mean Ankle Angle
130.00
Degrees (º)
120.00
Shoe 1
110.00
Shoe 2
6
Shoe 3
100.00
3
1
Barefoot
2
4
90.00
5
80.00
-10
10
30
50
70
90
110
130
Figure 9: Mean ankle angles during the stance phase
1
2
Heel
Strike
3
1
1
95º
95º
4
97º
103º
5
95º
Toe Off
6
123º
Figure 10: Mean ankle angles for a subject at six points during the stance phase.
Again figure 10 displays the ankle position throughout the stance phase.
1.
2.
3.
4.
5.
6.
10 frames prior to heel strike – ankle in neutral position ~ 90º
Heel strike – ankle in neutral position ~ 90º
End of braking phase – ankle plantar-flexes
Midstance – ankle returns to neutral position
Propulsive phase – Slight dorsi-flexion
Toe off – Rapid plantar-flexion helps propel subject forwards
Discussion
The results from this study would indicate that there is a difference in linear velocity between
walking barefoot and with shoes on. This is probably because the shoes provide a cushioning
effect and so subjects can walk faster without risk of injury. However the type of shoe seems to
have little effect on the linear velocity of the four joints detailed in this study or the angular
displacement of the knee and this is consistent with findings from other studies (Hutchins et al.
2009; Nigg et al. 2006).
Interestingly there was a clear variation in the ankle kinematics of shoes 1, 2 & 3 despite the
similarity of their rocker soles. This difference is most likely due to differing midsole densities
which provide different levels of support during the stance phase and thus influence the level of
dorsi/plantar-flexion occurring.
From the results of this study it is feasible that lower leg muscles (gastrocnemius, tibialis
anterior, etc.) may be more active during the stance phase as different ankle kinematics will
require different muscle activation. However it seems that, above the ankle, shoe construction
has little impact on gait kinematics and so the EMG activity is unlikely to differ significantly.
Any further study should focus on the EMG activity of the lower limbs and further quantify the
effect of differing midsole densities on ankle kinematics.
References
Hutchins, S., Bowker, P., Geary, N. & Richards, J. (2009). The biomechanics and clinical
efficacy of footwear adapted with rocker profiles—Evidence in the literature. The Foot 19, 165170.
Lythgo, N., Wilson, C. & Galea, M. (2009). Basic gait and symmetry measures for primary
school-aged children and young adults whilst walking barefoot and with shoes. Gait & Posture,
30, 502-506.
Nigg, B., Hintzen, S. & Ferber, R. (2006). Effect of an unstable shoe construction on lower
extremity gait characteristics. Clinical Biomechanics, 21, 82-88.
Pocari, J., Greany, J., Tepper, S., Edmonson, B., Foster, C., & Anders, M. Will toning shoes
really give you a better body? American Council on Exercise – www.acefitness.org .
Romkes, J., Rudmann, C. & Brunner, R. (2006). Changes in gait and EMG when walking with
the Masai Barefoot Technique. Clinical Biomechanics, 21, 75-81.