The purpose of the present study was to compare the peak impact force-reducing abilities of point-elastic and area-elastic sports floors in series with shoes. A secondary purpose was to design, construct and validate a modified version of the Berlin Artificial Athlete method (MBAA). Three different floors: A concrete, a hard court and a wooden floor were tested by measuring impact forces alone and in series with shoes when dropping the MBAA onto each floor-shoe combination. The impact force reduction was then calculated and compared with concrete, which is considered a non-absorbent floor. Peak impact forces on hard court (point-elastic) and wooden floor (area-elastic) were found to be 6731±141 N (102 % of concrete) and 3023±178 N (54 % of concrete), respectively, thus verifying that the wooden floor is the more force-reducing. When testing three different shoes and floors in series, the shoes additionally reduced force by 25-34, 27-35 and 16-19 percent points on concrete, hard court and wooden floor, respectively. In addition, the shoe type was more influential on the concrete and hard court floors than on wooden floor. This is expressed by a larger difference between the force-reducing abilities between the shoes, 9 and 2 percentage points for hard court and wooden floor, respectively. This indicates that area-elastic floors have significant influence on impact force reduction in sports. The MBAA is lighter and less costly to produce compared with the unmodified version. The standard deviations were found to be sufficiently small to assume that the MBAA was a reliable method for testing impact forces on floors with and without shoes in series. In addition, the peak impact forces found by the MBAA were within the 250 N range of the theoretical maximum impact force described in the European standard for “Surfaces for sports areas”, thus making it valid a method for testing peak impact forces on sports floors.

1. Impact force-reducing abilities of
floor-shoe cominations examined with a
modified Berlin Artificial Athlete
Søren ter Beek, Adam Frank, Rasmus Hagen,
Rasmus Kokholm, Jonas Møll & Mathias Sonsby
Aalborg University, Faculty of Medicine and Health, Sports Technology.
Abstract
The purpose of the present study was to compare the peak impact force-reducing abilities of point-elastic and
area-elastic sports floors in series with shoes. A secondary purpose was to design, construct and validate a
modified version of the Berlin Artificial Athlete method (MBAA).
Three different floors: A concrete, a hard court and a wooden floor were tested by measuring impact forces
alone and in series with shoes when dropping the MBAA onto each floor-shoe combination. The impact force
reduction was then calculated and compared with concrete, which is considered a non-absorbent floor. Peak
impact forces on hard court (point-elastic) and wooden floor (area-elastic) were found to be 6731±141 N (102
% of concrete) and 3023±178 N (54 % of concrete), respectively, thus verifying that the wooden floor is the
more force-reducing. When testing three different shoes and floors in series, the shoes additionally reduced
force by 25-34, 27-35 and 16-19 percent points on concrete, hard court and wooden floor, respectively. In
addition, the shoe type was more influential on the concrete and hard court floors than on wooden floor. This
is expressed by a larger difference between the force-reducing abilities between the shoes, 9 and 2 percentage
points for hard court and wooden floor, respectively. This indicates that area-elastic floors have significant
influence on impact force reduction in sports.
The MBAA is lighter and less costly to produce compared with the unmodified version. The standard
deviations were found to be sufficiently small to assume that the MBAA was a reliable method for testing
impact forces on floors with and without shoes in series. In addition, the peak impact forces found by the
MBAA were within the 250 N range of the theoretical maximum impact force described in the European
standard for “Surfaces for sports areas”, thus making it valid a method for testing peak impact forces on
sports floors.
Keywords: Floor | Shoe | Berlin Artificial Athlete | Force reduction
Introduction
During sports, the impact forces experienced
by athletes at heel strike have been suggested
to lead to overuse injuries, such as shin splints,
stress fractures, damage to articular cartilage and
bone injuries (Nigg et. al., 1995; James et al., 1978;
Andréasson et al., 1986). Two parameters that
are assumed to play major roles in reducing the
impact forces are the shoe and floor (Chiu, 2001).
Two other components that have been shown to
influence the impact forces are the stiffness of the
leg and the heel pad (Derrick, 2000; Rome, 1998).
1

2. Leg stiffness and heel pad
Floor properties have been shown to affect
changes in joint angles and muscle activity in the
lower extremities (Dixon et al., 2000). A study by
McNitt-Gray et al. (1993) tested the peak impa-
ct force when landing on gymnastic mats that
had distinctly different cushioning abilities and
found that the peak impact force did not differ
significantly between mats. This is believed to
be due to a mechanism that protects the joints
by reducing the stiffness of the limb by muscle
relaxation, and thereby enabling faster joint fle-
xion, thus reducing impact forces (van der Krogt
et al., 2009; Reeve et al., 2013; Hopper et al., 2014).
The function of the heel pad is to reduce and
absorb shock and protect from excessive local
stress, by decelerating the mass of the body (Ro-
me, 1998). Normally the heel pad cannot be chan-
ged but differs between subjects (Rome, 1998).
Noe et al., (1993) examined the heel pad’s abili-
ty to absorb shock with and without shoes and
found that the heel pad alone could attenuate
peak accelerations by 80 percent. The shoe alo-
ne attenuated accelerations by up to 93 percent.
However, when shoes and cadaveric heel pads
were tested in series, the shoes added as little
as 18 percent extra shock absorption. This could
indicate an importance in the interaction between
the shoe material and the foot. This is also sup-
ported by Clercq et al. (1994), who found that the
heel pad deforms 9 mm in barefoot running and
approximately 5.3 mm when wearing shoes. Even
though the research is somewhat contradictive, it
shows the importance of the interaction between
the heel pad and the shoe.
Shoes and floors
Shoe cushioning has been suggested to be the
most important factor of footwear for athletes, as
the cushioning properties have been connected
with overuse injuries (Bates, 1985; Snel et al., 1985;
Hennig et al. 1996). Different shoe cushioning
has shown to provide different properties for
impact force reduction (Chiu & Shiang, 2007).
The cushioning properties of the shoes can be
altered by increasing the material thickness of
the mid-sole, using another material composition
or changing the design (Frederick et al., 1984).
When the cushioning is loaded repeatedly, the
properties are altered. The shock absorbing abili-
ties of some shoes have been shown to decrease
by 25 percent compared to their initial shock
absorption, after being used for running 50 miles
(Cook et al., 1985). Therefore, when testing shoes,
attention should be given to the condition of the
shoe.
Sport floors can be categorized based on their
basic structure, with the two most common types
being the area-elastic floor and the point-elastic
floor. The area-elastic floor is almost synonymous
with a wooden floor system, where the suppor-
ting structure has gaps (Figure 1), whereas the
point-elastic floor consists of a resilient materi-
al like vinyl or rubber on top of concrete (tar-
kettsportsindoor.com). The difference between
point-elastic and area-elastic floors is that the
relative area of deflection is smaller on a point-
elastic floor when a downward force is applied
(Figure 1), making the area-elastic floors disperse
the force on a wider area (Sudol & Policinska-
Serwa, 2011). The point-elastic floors are usually
less force-reducing which means that the impa-
ct force is higher than on area-elastic floors (EN
14904).
2

3. Figure 1: Area-elastic (top) and point-elastic (bottom) systems.
(Floors for indoor sports, 2007)
Dixon & Stiles (2003) tested the relative role of
surface and shoe to provide cushioning. Five dif-
ferent surfaces commonly used for tennis and two
shoe models were tested. The impact absorbing
ability of surface and shoe in series were tested
with in-shoe pressure insoles and with a force pla-
te placed below the different surfaces. The impact
absorbing abilities of the floors and shoes were
also tested using two mechanical drop tests, the
Berlin Artificial Athlete (BAA) and ASTM F1976.
The floors tested by the BAA varied from 9.6-33
percent in impact force reduction. When testing
the floors in series with shoes, using the ASTM
F1976, no significant differences were found be-
tween surfaces. There was, however, a significant
difference between the two shoes, when tested
in series with the floors. They conclude that for
shoe-surface combinations, the shoe has more
potential to influence impact loading. The study,
however, focused only on point-elastic floors.
Purpose
Demker (2009) tested two test procedures, the
BAA and the Stuttgart Artificial Athlete, and fo-
und that these were applicable for quantifying
force reduction and vertical deflection of floors.
Using these tests give a relative measure of the
impact forces in the lower extremities on different
floors.
In the present study, a modified version of the
BAA (MBAA) will be designed to measure the
force reduction of different floors. Furthermore
the purpose is to construct a lighter and less cost-
ly version of the original BAA. The MBAA will
be constructed with the possibility to test a shoe
in series with the floor.
As several components can alter the impact forces
in the lower extremities, it is relevant to establish
the importance of each component. When testing
the heel pad in series with the shoe and the floor,
it adds a third unknown variable to the system,
making it difficult to determine each component’s
force-reducing ability. For this reason, the heel
pad was not considered in the present study. For
the same reason and because the MBAA cannot
simulate the joint protection mechanism, the leg
stiffness was disregarded.
To the authors’ knowledge, research focusing
on the shoe-floor interaction has only been con-
ducted on point-elastic floors (Chiu et al., 2001;
Dixon & Styles, 2003; Stiles & Dixon, 2006; Drakos
et al., 2010). The main purpose of this study was
to find the difference in force-reducing properties
between an area-elastic and a point-elastic floor.
In addition, the point-elastic and area-elastic flo-
ors were also tested in series with shoes to exa-
mine the difference in properties between shoes
on different floors. The secondary purpose of
the present study was to design, construct and
validate the MBAA.
3

4. Method and materials
Creating the MBAA
Figure 2: System of the BAA and a free body diagram of the force
acting on the BAA.
For the present study, a MBAA was used in-
stead of the original BAA. The principle of the
BAA, as described in the EN 14809 standard, is
to drop a mass and spring system onto a floor
while measuring accelerations. The standard sta-
tes that the stiffness of the spring should be 2000
N/mm, the drop height should be 55 mm and
the mass should be 20 kg. A spring with a stiff-
ness of 2000 N/mm is not commercially available
and has to be custom made. Therefore, a 749
N/mm spring was used in the present study. In
order to achieve the same characteristics of the
impact as with the standard method, the drop
height and mass had to be altered. To model the
BAA, the following assumptions were made: The
floor, shoe and BAA were considered a system
of springs in series. In addition, it was assumed
that the acceleration would be constant within a
small time step. Calculations of the acceleration,
velocity and displacement were needed to be
able to simulate the impact force. In order to
calculate the acceleration, the forces acting on
the BAA, which are gravitational pull and spring
force, must be known (Figure 2). Known factors
were the spring stiffness, gravity constant, the
weight of the mass dropped and the distance
from the mass to the floor. When these factors
are known it is possible to calculate acceleration,
velocity, displacement and in the end force, from
the dynamic equilibrium equation:
1 Fs − mg = ma ↔ −kx − mg = ma
Where Fs is the spring force, m is the mass
dropped, g is the gravity, a is the acceleration, k
is the spring constant and x is the displacement.
Because acceleration is the second derivative of
displacement (x), the equation can be rewritten
and the acceleration can be isolated:
2 −kx(t) − mg = m ¨x ↔ ¨x(t) = −kx(t)−mg
m
From an assumption of constant acceleration in
a small time interval, ∆t, follows linear velocity
(v), which is the first derivative of displacement
and can be calculated with the following formula:
3 v(t) = v0 + a∆t
Where v0 is the velocity ∆t earlier and t is
the time. From linear velocity follows quadratic
displacement, which can be calculated with the
following:
4 x(t) = x0 + v∆t + 1
2 a∆t2
Where x0 is the displacement ∆t earlier. When
the spring constant and displacements are known,
the force (F) can be calculated as:
5 F(t) = -kx(t)
To determine the force for each time step, nu-
4

5. Figure 3: Difference in impact force between the BAA model and the MBAA model.
merical solution was applied by setting the above
equations in series. For the calibration of the BAA
model, the concrete floor was assumed infinitely
stiff and heavy. The spring constant in the BAA
model was changed to 749 N/mm corresponding
to the commercially available spring, thereby
creating the MBAA model. To determine the new
drop height and weight, an optimization study
was conducted, minimizing the integral differen-
ce in impact force (∆F) between the BAA model
and the MBAA model, altering drop height and
mass of the adapted model.
6 ∆F =
t
∑
i=1
(F(t)BAAModel − F(t)MBAAModel)2
Where t is the number of time steps for the
impact.
The impact force of the MBAA model was con-
sidered applicable as a difference of 4 percent
between the two models was found (Figure 3).
The drop height of the MBAA model was 425
mm and the weight was 7.31 kg.
Validation test
The stiffness of the spring was found to be 749
N/mm through a compression test. The accuracy
of the accelerometer was tested in a centrifuge;
no noteworthy error was found. The MBAA was
validated by performing 15 consecutive trials on
concrete. The mean of the trials was 6754±212
N, which was within 250 N of the BAA standard
value for concrete of 6760 N, as prescribed by the
standard (EN 14904).
Test protocol
Three different floors were tested: A concrete,
a point-elastic and an area-elastic floor. The area-
5

6. Figure 4: Unfiltered and filtered data of one trial.
elastic floor was a wooden floor laid out on top
of dowels. The point-elastic floor consisted of a
blend of latex, rubber and plastic with an acrylic
top layer, laid out on concrete. The MBAA was
dropped directly on the floor three consecutive
times, with a distance of 425 mm between the
floor and the foot of the MBAA. This was repe-
ated at five different locations, separated by at
least 100 mm and at least 100 mm from the walls.
This was done for all floors. The same procedure
was then repeated with three different shoes, by
attaching the heel region of the shoes to the foot
of the MBAA, for each floor, with a distance of
425 mm between floor and shoe. The sides of the
shoes were removed to stop them from interfe-
ring with the impact. In addition the shoes were
tested without insoles. The three shoes were all
unused badminton shoes from different brands
(Table 1).
Table 1: Brand, model and shoe size for Shoe1-3.
Brand Model Size (EU)
Shoe1 Victor SH-LYD-G 40
Shoe2 Forza Leander 40
Shoe3 Asics Gel Blade 4 40.5
As suggested by Harrison (1999), a ninth or-
der Butterworth filter with a low pass cutoff
frequency of 220 Hz was applied, instead of the
2nd order filter prescribed in EN 14809. Figure
4 shows unfiltered and filtered data for one trial
on wooden floor.
The peak impact force (Fmax) for each floor
was calculated by inserting the peak acceleration
(Amax) in formula 7.
7 Fmax = m(Amax+g)
Formula 8 is used to calculate the percenta-
gewise force reduction (FR) compared to concrete,
as concrete is considered a non-absorbent floor.
8 FR = (1 − Fmax
6597N ) ∗ 100
Where 6597 N is the mean maximum impact
force on concrete found in the present study.
6

7. Statistics
IBM SPSS 22 was used for statistical analysis.
Analysis of variances (ANOVA) was used to in-
vestigate if there were any significant differences
between the three floors, the three shoes on each
floor and the five different locations on each floor.
If a difference was found, the independent t-test
was used to find the floors that differed. The pai-
red sample t-test was used to examine, which of
the five different locations differed on each floor.
In addition, the paired sample t-test was used to
find differences between the shoes in series with
floors. The level of significance was set at p≤0.05.
Results
Table 2 shows the mean peak impact force for
the five different locations on each floor. No sig-
nificant difference was found between the five
points tested on concrete and hard court (p=0.64
and p=0.30). For the wooden floor, location 1 was
significantly different from location 2-5 (p<0.05).
No difference was found between locations 2-5
(p>0.065).
Table 2: Mean peak force of three trials, on each of the five
locations, on the three floors, without shoes.
Location Concrete Hard-
Court
Wooden
1 6676 N 6726 N 3320 N *
2 6843 N 6713 N 3062 N
3 6330 N 6885 N 2870 N
4 6596 N 6649 N 2938 N
5 6542 N 6680 N 2926 N
* = Statistical significance between locations
(p < 0.05)
The mean force of each floor-shoe combination
is shown on Figure 5. It shows that the impact
force on the concrete and hard court are greater
than on the wooden floor (p<0.001).
Figure 6 shows a difference in impact force be-
Figure 5: The mean force±SD of the 15 trials for each floor-shoe combination. On the x-axis C=concrete, H=hard court, W=wooden
floor, S1=Shoe1, S2=Shoe2 and S3=Shoe3.
7

8. Figure 6: Force-reducing ability in percent for floors and floors in series with shoes on the different floors compared to concrete.
tween wooden floor and concrete of 54 percent
(p<0.001), with wooden floor having the lowest
impact force. Although not significant (p=0.21),
a 2 percent difference was found between hard
court and concrete, hard court having the hig-
her impact force. Comparing the impact force re-
duction in percent of the three shoes on the three
different floors, shows that the force reduction be-
tween shoes varies more on the concrete and hard
court (25-34 % & 25-34 %) than on the wooden
floor (61-63 %)(Figure 6). A significant difference
between all shoes on all floors was found (p<0.01).
Shoe2 has the best force-reducing ability on all
floors, where Shoe1 has the worst.
Table 3 shows that the floor-shoe combinations
add 24.9-33.9, 26.6-35.4 and 15.6-19.0 percent to
the force reduction when compared to concrete,
hard court and wooden floor alone, respectively.
The table also shows that the shoes add more for-
ce reduction on the concrete and the hard court
floors compared to the wooden floor, and the per-
8

9. centage difference between the shoes gets smaller
on the wooden floor.
The peak impact force and impact time for the dif-
ferent floor-shoe combinations are similar (r=0.88)
on the concrete and hard court floors, as seen on
Table 4. The peak impact force on the wooden
floor is lower, while the impact time is higher
compared to the concrete and hard court floors.
Table 3: Mean peak force of three trials, on each of the five
locations, on the three floors, without shoes.
Floor Shoe1 Shoe2 Shoe3
Concrete 24.6 % 33.9 % 27.6 %
Hard Court 26.6 % 35.4 % 29.9 %
Wooden 15.6 % 19.0 % 17.6 %
Discussion
The impact forces on Figure 5 show that bo-
th the shoe and the floor influence the force
reduction. This is shown by the average peak
impact forces, where the peak for wooden floor
(3023 N), was significantly lower (p<0.05) than
for concrete (6597 N) and hard court (6731 N).The
influence of the shoes can be seen in Figure 6 and
Table 3, where it is shown that Shoe1, 2 and 3
attenuate 24.9, 33.9 and 27.6 percent of the force
compared to concrete, respectively.
It is remarkable that the peak forces on hard
court and concrete in series with shoes were gre-
ater than on the wooden floor alone. This shows
that the wooden floor has greater influence on
force reduction than the three shoe models tested.
The shoes in series with all three floors reduce
the force further (Table 3), but the reduction is
greater for the concrete and hard court floor. In
series, both the shoe and the floor must reduce
force, as force reduction on wooden floor in series
with the shoes is higher than the force reduction
Table 4: Mean peak force of three trials, on each of the five locations, on the three floors, without shoes.
Floor-shoe combination Peak impact force ± SD (N) Impact time ± SD (ms)
Concrete 6597 ± 383 8.1 ± 1.1
Concrete+Shoe1 4957 ± 132 11.1 ± 0.3
Concrete+Shoe2 4358 ± 105 12.8 ± 0.5
Concrete+Shoe3 4774 ± 70 12.2 ± 0.3
Hard Court 6731 ± 141 8.5 ± 0.5
Hard Court+Shoe1 4939 ± 36 10.9 ± 0.3
Hard Court+Shoe2 4345 ± 54 12.5 ± 0.1
Hard Court+Shoe3 4717 ± 43 11.2 ± 0.2
Wooden 3023 ± 178 11.2 ± 0.2
Wooden+Shoe1 2551 ± 129 16.1 ± 0.1
Wooden+Shoe2 2448 ± 110 17.5 ± 0.1
Wooden+Shoe3 2489 ± 96 17.8 ± 0.6
9

10. measured for the wooden floor.
It was assumed that it would be possible to detect
differences in force reduction on different areas
of the wooden floor, cf. Table 2, and this was
indeed the case. A significant difference between
points on the wooden floor indicates that diffe-
rent structural properties were tested.
The difference in force-reducing abilities of dif-
ferent shoes, which is clear on hard court and
concrete, is not as clear on the wooden floor. Be-
tween shoe models, the range of force reduction
varies more for concrete (25-34 %) and hard court
(25-34 %), than for the wooden (61-63 %). This
suggests that different shoe models have less
influence on force reduction on compliant floors,
compared to hard floors (Figure 6).
It was uncertain if a specific shoe would add for-
ce reductions with equal relative amounts when
tested on different floors. The results show a
tendency of the shoes adding less force reduction,
when in series with a compliant floor (Table 3).
These results suggest that the floor-shoe inter-
action plays a role on force reduction, because
none of the shoes add the same amount of force
reduction, neither relatively or absolute, on each
floor.
In the present study, the shoes were tested wit-
hout insoles, as this was considered a separate
part that could easily be replaced by an insole
with different cushioning properties. It is likely
that insoles further reduce the impact forces.
There is a strong correlation between peak
impact force values and impact time (r=0.88). For
the concrete and hard court floor, which had the
highest peak force values, the impact times were
8.1 ± 1.1 ms and 8.5 ± 0.5 ms respectively. For
the wooden floor, the impact time was 11.2 ± 0.2
ms. The tendency can also be seen with shoes in
series (Table 4). This is consistent with the trans-
fer of momentum interpreted as the time integral
of force, i.e. a given amount of momentum will
require higher forces if transferred over a shorter
time interval.
The hard court was assumed to be more force-
reducing than concrete, as it is designed with a
blend of latex, rubber and plastic with an acrylic
top layer, laid on top of concrete. However, the
mean force on hard court turned out to be grea-
ter than on concrete, although not significantly
(p=0.21). This is also contradictive to the fact
that impact time for measurements on concrete
were shorter than those for hard court, which
indicates that impact force should have been hig-
hest on concrete. Demker (2009) concluded that
the BAA was unsuitable to distinguish between
floor types with force-reducing abilities lower
than 4 percent. This, in combination with the
MBAA (4000 Hz) having a lower sampling rate
than the BAA (9600 Hz), could be the reason
behind the counterintuitive impact-time/peak-
force relationship. However, it is not believed
to influence the validity of the present study, as
standard deviations were relatively low for all
floors: Concrete 6597 ± 383 N, hard court 6731 ±
141 N, and the significantly different locations on
the wooden floor, location 1 3319 ± 105 N and
location 2-5 2949 ± 92 N.
The drop height and mass used in the present
study differed from other studies. Chiu et al.
(2001) also tested shoe-surface interaction, using
drop heights varying between 5-8 cm, and impact
weights varying from 6.5-8.5 kg. Dixon & Stiles
(2003), whom also tested shoe-surface interaction,
used a mass of 7.8 kg and a drop height of 5 cm.
As a result of using the MBAA method, the peak
impact forces in the present study are higher.
Dixon & Stiles (2003) measured running at 3.83
m/s with pressure insoles. They found that im-
10

11. pact forces vary from 1280.5-1367.5 N depending
on shoe model and surface. However, they only
measured impact forces ranging from 590-975
N, when conducting the ASTM F1976 drop test,
which is lower than the impact forces from their
biomechanical test, suggesting too low impact
values in the mechanical test. In the present study,
the impact forces ranged from 2447.9-4957.3 N,
when testing in series with shoes, making the
impact forces higher than what was measured in
the biomechanical test by Dixon & Stiles. This me-
ans that the impact forces created by the MBAA
are higher than what is typically seen in running.
When testing the maximum impacts of jumping
from heights between 0.32-1.28 m, McNitt-Gray
(1993) found that impacts varied from 3.9-11.0
times bodyweight. When testing impacts in run-
ning in regards to bodyweight, Munro et al.
(1987) found that maximum impacts varied from
1.57-2.32 times bodyweight, when running at
speeds between 3-5 m/s. This shows that impact
forces are higher when jumping compared to
running. As jumps often occur in sports like bad-
minton and basketball, the method used in this
present study might better simulate the impacts
occurring in these sports compared with running.
Shoe1 differed in cushioning characteristics
as it had a soft pad embedded in the sole, this
lead to the assumption, that Shoe1 would reduce
the peak impact force the most. However, Shoe1
turned out to be least force-reducing on all floors.
Furthermore, Shoe2, which was believed to be
the least force-reducing, as it felt harder than
the other two shoes, turned out to be the most
absorbing shoe on all floors. This could suggest
that the force applied to Shoe1 deforms the heel
region fully, making it lose its force-reducing
abilities, before the MBAA is decelerated comple-
tely. This could be a result of the impact forces
applied in the present study being too high for
testing shoes.
The shoes in the present study were examined
by taping the shoe sole inferiorly to the MBAA,
and releasing it towards the floor. The taping
proved an effective way to attach the sole on to
the MBAA and ensuring it hit the same spot
on the sole every time. This is supported by the
results in Table 4, where the standard deviations
with shoes in series are small compared to the
trials directly on floor, suggesting that the MBAA
with shoe attached impacted correctly.
The sides of the shoes had to be cut away to
ensure that the MBAA impacted directly on the
sole where the heel pad would usually impact.
This was necessary, as the diameter of the foot of
the MBAA was too wide to fit onto the heel part
of the sole, without creating friction on the sides
of the shoe. The altered structure of the shoes
could result in different results, as the structure
could contribute to the force reduction. Each
shoe was cut to avoid compromising seemingly
important structures, allowing for comparability
between shoes. It was estimated in the present
study, that the shoes maintained most of their
structure, as over half of the sole length was left.
Furthermore, it was unlikely that removing the
sides of the shoes would influence the cushioning
characteristics of the sole. For future research, it
would be preferable to avoid cutting the shoes,
either by getting bigger shoe sizes or by changing
the diameter of the MBAA foot.
Previous studies have been able to measure
differences between floors by mechanical drop
tests (Dixon & Stiles, 2003; Dixon et al., 2000;
Nigg, 1990). However, no difference between the
floors was detectable in terms of peak impact
force measured with force plates when running
on the floors. This may, as previously mentioned,
11

12. be due to a protective mechanism that shields the
joints by lowering the muscle activity. The MBAA
used in the present study might provide a more
objective measure of shoe-floor combinations
because it contains no human in the loop. This
is supported by the registered significant diffe-
rences that were found between all floor-shoe
combinations (p<0.01)(Figure 6).
The study by Dixon & Stiles (2003), who also
used a mechanical drop test to investigate shoe-
floor combinations, contrary to this study did
not report any significant differences between
surfaces when testing with a shoe in series. The
floors in the study by Dixon & Stiles (2003) varied
from 0-33.5 percent in force reduction between
surfaces, measured with the BAA, whereas the
floors in the present study varied between -2-54
percent (Figure 6). As the force-reducing abilities
between floors measured in the present study are
higher, this might have been the reason for the
significant differences between the floors with a
shoe in series. However, the impact forces measu-
red in the mechanical tests are also higher in the
present study (2448-6731 N)(Table 4) compared
to those measured by Dixon & Stiles (2003)(605-
1057 N). The higher impact forces might also
have contributed to the findings of significant
differences between the floor-shoe combinations.
The amount of contribution is unknown, but it
indicates that higher impact forces are better sui-
ted to detect differences between floors in series
with shoes.
The BAA method is generally accepted as a
valid method for testing floors, as this is the pur-
pose of the method. The MBAA was considered a
valid method as the values measured on concrete
were within the range stated in the BAA stan-
dard. The MBAA was also considered a reliable
method for measuring floors and shoes, as values
were consistent.
Conclusion
The present study found the wooden floor to
be more absorbent than the hard court floor. No
significant difference in force reduction betwe-
en the concrete and hard court floor was found
(p=0.21). The difference in force reduction betwe-
en the concrete and wooden floor amounted to
54 percent and was significant (p<0.001). Further-
more, differences between all shoes were found
(p<0.05), when in series with the floors. The small
variations between the shoes on the wooden floor
(61-63 %) compared to concrete and hard court
(25-34 % and 25-34 %, respectively), suggests that
the shoe model is of less importance, when doing
sports on a compliant floor. The wooden floor
reduced the impact more than the shoes in seri-
es with concrete and hard court, suggesting that
the floor plays an important role in reducing the
impact force. However, the shoes in series with
the wooden floor added to the force reduction,
suggesting that the shoes play a role as well, even
on a compliant floor.
The MBAA was considered a reliable method for
measuring impact forces on floors, as it measured
consistently, making it able to detect differences
between floor types and locations on the wooden
floor. The MBAA was considered valid becau-
se it measured within the range stated by BAA
standard.
Acknowledgments
The authors would like to thank Active
Sporswear Int A/S for supplying the shoes used
in this study. Furthermore, we would like to
thank Inter Ice-pump ApS for sponsoring and
manufacturing the MBAA.
12

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