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EQUINE VETERINARY JOURNAL
Equine vet. J. (2010) •• (••) ••-••
doi: 10.1111/j.2042-3306.2010.00202.x
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Ground reaction force and kinematic analysis of limb loading
on two different beach sand tracks in harness trotters
N. CREVIER-DENOIX, D. ROBIN, P. POURCELOT, S. FALALA, L. HOLDEN, P. ESTOUP, L. DESQUILBET*†, J.–M. DENOIX and
H. CHATEAU
USC INRA-ENVA 957 de Biomécanique et Pathologie Locomotrice du Cheval; and †USC ENVA-AFSSA EPIMAI, Ecole Nationale Vétérinaire
d’Alfort 7, avenue du Général de Gaulle - 94704 Maisons-Alfort, France
Keywords: horse; fetlock; forces; kinematics; sand; trot
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Summary
Introduction
Reasons for performing study: Although beach training is
commonly used in horses, limb loading on beach sand has
never been investigated. A dynamometric horseshoe (DHS) is
well adapted for this purpose.
Hypothesis or objectives: To compare Ground Reaction Force
(GRF) and fetlock kinematics measured in harness
trotters on 2 tracks of beach sand with different
water content.
Methods: Two linear sand tracks were compared: Firm Wet
Sand (FWS, 19% moisture) vs. Deep Wet Sand (DWS, 13.5%
moisture). Four French trotters (550 ! 22 kg) were used.
Their right forelimb was equipped with a DHS and skin
markers. Each track was tested 3 times at 7 m/s. Each trial
was filmed by a high-speed camera (600 Hz); DHS and speed
data acquisition was performed at 10 kHz on 10 consecutive
strides. All recordings were synchronised. The components Fx
(parallel to the hoof solar surface) and Fz (perpendicular)
of the GRF were considered. For 3 horses the fetlock angle
and forelimb axis-track angle at landing were measured.
Statistical differences were tested using the GLM procedure
(SAS; P<0.05).
Results: Stance duration was increased on DWS compared
to FWS. Fzmax and Fxmax (oriented, respectively,
downwards and forwards relatively to the solar surface) and
the corresponding loading rates, were decreased on DWS
and these force peaks occurred later. Fxmin (backwards)
was not significantly different between both surfaces; the
propulsive phase (Fx negative) was longer and the
corresponding impulse higher, on DWS compared to FWS.
The forelimb was more oblique to the track at landing
and maximal fetlock extension was less and delayed
on DWS.
Conclusions: This study confirms that trotting on deep sand
overall reduces maximal GRF and induces a more progressive
limb loading. However, it increases the propulsive effort
and likely superficial digital flexor tendon tension at the
end of stance, which should be taken into account in
beach training.
Beach training is often used in race and sport horses, either for
regular training or rehabilitation. Although horses are most
commonly exercised along the water edge, beaches offer surfaces
with a variety of dynamic responses according to their water
content. It is well known that ground surface material can modify
the load transfer from the ground to the hoof and therefore the
propagation of forces to limb bones, tendons and ligaments
(Cheney et al. 1973; Thomason and Peterson 2008; Crevier-Denoix
et al. 2009). Soft sand running has been recommended as a useful
rehabilitative exercise in man since impact forces are reduced in
compliant (soft) surfaces and muscle activation strategies to
provide stability are emphasised (McMahon and Greene 1979).
However, compliant surfaces have also been shown to result in
increased eccentric muscle activity in the propulsive muscles,
generating shin pain (Richie et al. 1993).
In spite of their potential interest for training or rehabilitation,
the dynamic effects of beach sand surfaces on the equine locomotor
system, such as the forces and loading rates applied to the limbs,
have not been studied to date. Indeed, measuring the ground
reaction force (GRF) in a horse moving at training speed under
outdoors conditions is a technological challenge. Force platforms,
that have to be sealed in the ground in a rigid frame, are not adapted
to these measurement conditions, all the most when several
surfaces have to be compared. A dynamometric device mounted
to the horse is a preferable alternative. Several models of
dynamometric horseshoe (DHS) have been described in the
literature most of them using uniaxial force sensors (Frederick and
Henderson 1970; Barrey 1990; Ratzlaff et al. 1990; Roepstorff and
Drevemo 1993; Kaï et al. 2000). To the authors’ knowledge, to date
only two 3-dimensional (3D) DHS models have been developed
and applied in equine biomechanical studies: based on strain gauge
transducers (Roland et al. 2005) and piezoelectric sensors (Chateau
et al. 2009). After proper validation, both have been used to
compare the effects of track surfaces on the 3D GRF, either in
Thoroughbred racehorses (Setterbo et al. 2009) or in French
trotters (Robin et al. 2009) under outside training conditions. One
of the main advantages of the piezoelectric technology based DHS
is its weight (490 vs. 860 g for the strain gauges device).
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*Corresponding author email: [email protected].
[Paper received for publication 19.01.10; Accepted 26.06.10]
© 2010 EVJ Ltd
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In man, it is well known that walking or running on sand
requires a greater effort than on firm ground. Zamparo et al.
(1992) suggested that the increase in energy cost when running on
soft sand (compared with a firm terrain) was mainly attributable to
a reduced capacity of the runner to store and recover elastic
energy. Lejeune et al. (1998) demonstrated that the increase in
energy cost during walking and running on sand was primarily
due to an increase in the mechanical work (force(displacement)
done on the sand, especially during the propulsion phase and to a
decrease in the efficiency of positive work done by the muscles
and tendons. Pinnington et al. (2005) demonstrated that running
on sand resulted in a greater stance to stride duration, a shorter
stride length and a greater stride frequency compared with the
firm surface values.
Given this scientific background, the objective of the present
study was to compare, through GRF analysis and forelimb
kinematics, the loading of the forelimb on 2 tracks of beach sand
with different water content in harness trotters, under training
conditions. It was hypothesised that GRF would decrease as the
compliance of the surface increases and that deep sand would
require a larger propulsion effort compared to a firmer surface.
Materials and methods
Sand tracks
Two tracks of sand 100 m long were delimited on the Varaville
beach (Normandy, France), using for each 2 parallel and tightened
cables (2.9 m apart), equipped in their middle part with pairs of
markers placed every meter. A Firm Wet Sand (FWS) track was
defined as parallel and as close as possible to the sea; a Deep Wet
Sand (DWS) track was located parallel to and at a distance of about
20 m from the FWS. At the end of the experiment, 3 samples of
sand were taken (to a depth of 15 cm) at the entrance, in the middle
and at the exit of each of the 2 tracks and hermetically stored. In the
laboratory, the initial wet weight of each sample was measured
(Talent TE210, Sartorius1) before oven-drying it for 48 h at
105°C; then, the corresponding dry weight was measured. Both
values were then used in the following equation:
wet _ weight − dry _ weight . The water contents
water _ content =
wet _ weight
of the 3 samples were averaged.
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Horses
Two females and 2 geldings French trotters (mean ! s.d. body
weight: 550 ! 22 kg; age 10 ! 7 years) were used. All horses were
clinically sound, with no subjectively observed gait abnormalities.
Experimental set-up
After trimming of both front hooves by an experienced farrier, the
right front hoof of each horse was equipped with an instrumented
shoe composed of 4 triaxial piezoelectric force sensors (Model
260A11, PCB2) sandwiched between 2 aluminium plates (Chateau
et al. 2009). The assembly between the instrumented shoe and hoof
was achieved with a third thin (4 mm) aluminium shoe classically
nailed to the hoof wall. This support shoe and the instrumented
system were fixed together by means of 3 bolts. Total weight of the
device with sensors was 490 g and total height 22 mm. A
noninstrumented horseshoe with equal height and weight was fixed
to the left front hoof. The transducers were laid out along the
horseshoe profile, symmetrically oriented relatively to the sagittal
plane of the hoof, 2 towards the toe and the other 2 towards the
heels. The origin of the coordinate system was at the centre of
gravity of the 4 transducers in the sagittal plane; the associated
reference frame was defined as follows: positive in the palmarodorsal direction, positive y in the medio-lateral direction towards
the outside of the hoof and positive z was perpendicular to the shoe
plane, directed downwards. The GRF was calculated as the sum of
forces applied on each sensor. In this study we considered only the
x and z components of the GRF, designated Fx and Fz, respectively,
parallel and perpendicular to the solar surface of the hoof in the
sagittal plane (Fig 1a).
The DHS was connected via wires, secured to the limb, to an
analogue-to-digital converter (NI-USB 62183) plugged into a
ruggedized computer (Toughbook CF-30, Panasonic4). The data
acquisition devices were placed in a box fixed on the sulky
(Fig 1b). For each trial, data acquisition was performed at
10 kHz.
The speed of the horse was measured and recorded by a third,
smaller, wheel equipped with a hub dynamo (Nabendynamo,
Schmidt5) fixed behind the sulky (Fig 1b). The speed was also
controlled in real time by the driver by means of a digital
speedometer (BC 506, Sigma6).
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GRF sand
z
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Fig 1: Experimental set-up: (a) Right forelimb equipped with the dynamometric horseshoe (with indication of its reference frame), as well as the 7 reflective
markers indicating the main limb joints (shoulder, elbow, carpus, fetlock, coffin) and the hoof. The angle considered for the fetlock joint (dorsal angle) is
indicated. (b) Equipped horse trotting on a sand beach track. Data acquisition devices are placed in a box fixed on the sulky. The third, smaller wheel behind
the sulky is equipped with a hub dynamo that allows to record the horse’s speed.
© 2010 EVJ Ltd
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–1000
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Time (% of stance duration)
Fig 2: Mean (! s.d.; n = 120 strides) of the 2 components of the ground reaction force, Fx and Fz (respectively parallel and perpendicular to the hoof solar
surface) measured during the stance phase in 4 harness trotters running at about 7 m/s on Firm Wet Sand (black) and Deep Wet Sand (grey). Time is
expressed in % of stance duration. The horses’ individual body masses are: 576 kg (No 1), 558 kg (No 2), 542 kg (No 3), 524 kg (No 4).
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During the tests the 4 horses were filmed with a high-speed
camera (600 Hz, Phantom v5.1, Vision Research7) mounted to a
vehicle following the right side of the horse at a distance of about
7 m. The resolution of the camera was 1024 (640 pixels and the
field of view was approximately 4.5 m long by 2.8 m high. The
high frequency movies were synchronised with the DHS and speed
data using the lighting of a LED (Light-Emitting Diod) placed on
the sulky right branch, the signal of which was retrieved on the
same acquisition card as the other devices. Seven reflective markers
were placed on the right forelimb, indicating the main limb joints
and the hoof (Fig 1a).
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Recording protocol
The 4 horses were led by the same experienced driver. Recordings
on each surface (tested on a straight line) were randomly repeated
3 times. The speed that was aimed at was 25 km/h (about 7 m/s),
i.e. a speed that could be theoretically reached easily by all horses
even on the deep sand (DWS).
Data processing
Ten consecutive strides were analysed for each trial. From the
DHS recordings, the 3-dimensional GRF was calculated.
Temporal parameters of the stride were calculated using the
vertical GRF data. To delimit the stance phase, the threshold was
set to 50 N and the frames designed as first contact and toe off,
were, respectively, the frames just before and after this value. The
stride length was calculated as stride duration multiplied by the
horse’s speed. Custom software8 was used to calculate peak
forces, impulses (integral of force over time), stride frequency and
temporal parameters of each force peak (beside the early impact
peaks, there were 1 peak per stance in Fz: Fz max and 2 in Fx: Fx
max and Fx min; see Fig 2). The overall loading rate was
calculated for Fz max and Fx max by dividing peak force (in
Newton) by peak force time (in seconds). DHS and speed data
were calculated by averaging 120 strides on each surface (10
strides per trial, 3 trials per horse).
In addition, for 3 horses and for at least two trials for each
surface, the fetlock dorsal angle was calculated from the 2D
coordinates of the markers placed on the carpus, fetlock and hoof.
© 2010 EVJ Ltd
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GRF sand
TABLE 1: Least squares (LS) mean and standard error (s.e.) of stride parameters, ground reaction force and kinematic variables (adjusted for speed)
for 4 horses (3 for the kinematic variables) trotting on 2 beach sand tracks with different water content: Firm Wet Sand (FWS) and Deep Wet Sand
(DWS). Statistical comparison between tracks is based on LS means; the observed means (and standard deviations, s.d.) are only mentioned here for
a descriptive purpose
Stride parameters
(n = 120)
Ground Reaction Force
(n = 120)
Fz
Fx
Kinematics
(n = 70)
FWS
DWS
Water content (%)
19.0 (0.8)
13.5 (3.7)
Speed (m.s-1)
7.21 (0.53)
6.65 (0.72)
Variables
LS mean
s.e.
Stance duration (ms)
Stance to stride duration (%)
Stride length (m)
Stride frequency (Hz)
Fz max (N)
Fz max time (% sta.d.)
Fz max loading rate (kN.s-1)
Fz impulse (N.s)
Fx 0 time (% sta.d.)
Fx max (N)
Fx max time (% sta.d.)
Fx max loading rate (kN.s-1)
Fx min (N)
Fx min time (% sta.d.)
Total Fx impulse (abs) (N.s)
Positive Fx impulse (N.s)
Negative Fx impulse (N.s)
Net Fx impulse (N.s)
Fetlock min. angle (°)
Fetlock min. angle time (% sta.d.)
Limb axis-track angle at landing (°)
163.6
27.9
4.06
1.71
7037
52.4
85.1
748.0
62.9
1707
15.6
71.3
-822*
85.8
119.2
91.9
-27.3
64.5
91.5
55.9
64.9
0.6
0.11
0.01
0.005
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1.0
6.2
1.2
30
0.9
1.7
22
0.2
2.7
2.7
1.9
3.8
0.3
0.5
0.5
The orientation of the elbow-fetlock axis to the track
was also determined at landing, using the markers placed
every meter along the 2 tightened cables delimiting each
track. To eliminate parallax errors, this angle was calculated
using the 2D DLT (Direct Linear Transformation) technique
(Abdel-Aziz and Karara 1971). Kinematic data were calculated
by averaging 70 strides on each surface (10 strides per trial, 2–3
trials per horse).
(11.8)
(2.2)
(0.28)
(0.06)
(779)
(2.6)
(16.7)
(63.5)
(8.7)
(318)
(5.6)
(23.9)
(241)
(3.2)
(27.4)
(34.9)
(11.0)
(44.0)
(7.9)
(4.5)
(2.4)
s.e.
169.6
29.6
3.98
1.75
6136
60.1
62.9
656.0
52.9
938
21.7
33.6
-869*
86.9
88.1
44.6
-43.5
1.1
95.1
60.8
60.3
0.6
0.11
0.01
0.005
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0.3
1.0
6.2
1.1
30
0.9
1.7
20
0.2
2.5
2.5
1.8
3.5
0.3
0.4
0.4
Observed mean (s.d.)
174.8
30.4
3.84
1.74
5914
61.1
57.5
649.6
51.1
818
21.0
28.1
-834
87.0
83.6
39.2
-44.4
-5.2
95.5
61.0
60.7
(18.0)
(3.6)
(0.44)
(0.08)
(776)
(4.7)
(15.4)
(57.6)
(22.6)
(434)
(12.3)
(17.0)
(326)
(4.6)
(27.1)
(33.5)
(30.4)
(58.0)
(10.0)
(4.5)
(4.8)
Speed
In spite of the driver’s attempt to reach exactly the same speed on
the 2 surfaces, the 4 horses were in average slightly slower on DWS
(mean ! s.d.: 6.65 ! 0.72 m/s) compared to FWS (7.21 ! 0.53 m/
s). However, the statistical comparison between tracks (Table 1 and
description below) is based on the least squares means that take in
account these speed variations.
Stride parameters
Statistical analysis
Data were analysed by the General Linear Model procedure in
SAS (SAS v.9.29). The models included horse as a repeated
effect and speed as a covariate. Least square means differences
were used for pair wise comparisons between track surfaces.
These differences took into account potential effects of speed
and/or horse on each dependent variable since speed and
horse variables were included in the model. Significance was set
at P<0.05.
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158.3
27.2
4.20
1.72
7259
51.4
90.5
754.4
63.0
1827
16.4
76.9
-901
85.1
122.5
93.7
-28.8
64.9
92.4
55.4
65.1
LS mean
Except *, all differences were significantly different between FWS and DWS (P<0.05). % sta.d. % of stance duration.
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Observed mean (s.d.)
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Results
Water content
Water content was 19% for the FWS vs. 13.5% for the DWS
(Table 1). For Horse No 4, DWS water content was higher than for
the other horses; therefore the water content difference between
FWS and DWS was less for this horse than for the other 3 (2% vs.
about 7%).
© 2010 EVJ Ltd
Stride frequency was increased on DWS compared to FWS (+2%,
P<0.0001), whereas stride length was reduced (-2%, P<0.0001).
Stance duration was increased on DWS (+4%, P<0.0001); the
increase was even larger when considering the relative stance
duration (+6%, P<0.0001).
Ground reaction force
The Fx and Fz vs. time (normalised to stance duration) graphs are
presented in Figure 2. They both appeared different on the 2
surfaces, as illustrated also in Figure 4 (with Horse No 2 as
an example).
After an early impact peak (the analysis of which is dealt with
in Chateau et al. 2010), the Fz (‘vertical’ force) rises progressively
to a maximum, then decreases to zero at lift-off. Figure 2 and
Table 1 show that the Fz max was lower (-13%, P<0.0001) and that
it occurred later (+15%, P<0.0001) on DWS than on FWS; as a
consequence, the Fz max loading rate was less on DWS (-26%,
P<0.0001). The Fz impulse was also lower on DWS (-12%,
P<0.0001).
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Fetlock angle (°)
Fetlock angle (°)
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Fig 3: Mean (! s.d.; n = 70 strides) of the dorsal angle of the fetlock joint measured during the stance phase in 3 harness trotters running at about 7 m/s
on Firm Wet Sand (black) and Deep Wet Sand (grey). Time is expressed in % of stance duration.
During the stance phase, Fx initially has a positive phase,
followed by a negative phase (positive/negative signs depend on
the convention chosen for the DHS reference frame); these phases
are generally designated ‘braking’ and ‘propulsive’ phases,
respectively. Figure 2 and Table 1 show that the Fx0 time,
separating the positive and negative phases, was less on DWS
(-16%, P<0.0001), indicative of a longer ‘propulsive’ phase. Fx
max was almost 2-fold lower on DWS compared to FWS (-45%,
P<0.0001) and it occurred later (+39%, P<0.0001). There was
inter-individual variability in Fx max time on DWS, but in all
horses the Fx max loading rate was drastically lower compared to
FWS (-53%, P<0.0001). Contrary to Fx max, Fx min was not
significantly different between the 2 sand tracks (P = 0.155); Fx
min time was nevertheless significantly delayed, although only
slightly, on DWS (+1%, P = 0.014).
The total Fx impulse (absolute values) was significantly lower
on DWS (-26%, P<0.0001). Besides, whereas Fx positive impulse
was much lower (-52%, P<0.0001), Fx negative impulse was
drastically higher (+59%, P<0.0001), on DWS compared to FWS.
As a consequence, the net Fx impulse was positive on the FWS,
meaning an overall net ‘braking’ effect, whereas it was about nil on
the DWS.
Observation of both Fz and Fx plots for the 4 horses (Fig 2)
reveals that at the end of the stance phase, especially at about
90% of stance duration, both GRF components were higher on
DWS (maximal Fz difference of 300–950 N depending on
the horse).
Limb kinematics
Figure 3 illustrates the angle-time graphs of the fetlock joint (dorsal
angle) for the 3 horses on which this angle could be measured. The
minimal dorsal angle was significantly higher (+4%; P<0.0001),
i.e. the joint was less extended and this minimum occurred later
(+9%, P<0.0001), on DWS compared to FWS (see also Fig 4b).
However, as for the GRF components, between about 80 and 95%
of the stance phase, the order reverses and the fetlock dorsal angle
is smaller, i.e. the joint is more extended, on DWS than on FWS
(Fig 3).
At landing, the horse’s forelimb was significantly more oblique
to the ground (less vertical) on DWS than on FWS (forelimb
axis-track angle: -7%, P<0.0001), as shown in Figure 4a.
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Discussion
On beaches, horses are generally trained at the water edge. For
practical and technical reasons, our FWS condition had to be
© 2010 EVJ Ltd
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GRF sand
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Fig 4: Synchronised recordings of a harness trotter (horse No 2) running at about 7 m/s on a Firm Wet Sand (FWS, on the left) and a Deep Wet Sand (DWS,
on the right). On the top of each left and right sets: image from a high-speed film (600 Hz) with a zoom on the forelimb; on the bottom left: Fx (blue) and
Fz (red) components of the ground reaction force (in N), respectively, parallel and perpendicular to the hoof solar surface; on the bottom right (cyan):
dorsal angle of the fetlock joint (in °). Time is expressed in seconds. The vertical dotted lines on both plots of each set indicate the exact instant considered
(corresponding with the image above both plots). (a) Time of Fx max: the increased forward inclination of the forelimb (from proximal to distal) relative
to the track is clearly visible on DWS (on the right). Besides a difference in the position of the hoof, with heels lower and an increased penetration in the
sand can be seen on DWS. (b) Time of Fz max: an increased backward inclination of the forelimb (from proximal to distal) relative to the track can be
observed on DWS (on the right). The fetlock dorsal angle has approximately reached its minimum at the time of Fz max on DWS, whereas it has not yet
exactly reached its minimum on FWS. The extensive sinking into the surface of the hoof in the DWS is obvious.
slightly further from the sea (10–20 m in average) and therefore
possibly had slightly lower water content than the surfaces used
under real training conditions.
The dynamometric horseshoe affects the dynamics of the horse
because its mass and thickness are greater than a regular training
shoe. However, since the same device was used to test both sand
tracks, it should not affect surface comparison.
© 2010 EVJ Ltd
Since the experimental horses were harness trotters, the sulky
interacted with the ground surface, as discussed below. The
differences observed here between both surfaces may therefore be
more evident compared to what would have been observed in
ridden horses.
Significant differences between the 2 beach sand surfaces
tested here in 4 harness trotters were found for stride parameters,
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GRF and kinematic variables reflecting the forelimb loading during
the stance phase. An average 30% decrease (13.5 vs. 19%) of the
sand water content induced a slight increase in stride frequency and
a decrease in stride length, indicative of some discomfort of the
horses, combined with a poorer performance on DWS (Chateau
et al. 2010). The higher duration of stance observed on the deep
sand in the present study is in accordance with previous
observations, both in man and the horse (Burn and Usmar 2005;
Pinnington et al. 2005); it is explained by the yielding nature of the
surface, offering poor support and reaction. The higher stance to
stride duration is correlated with a relatively shorter swing phase
on DWS, which can be attributed to a less effective propulsion
(Lejeune et al. 1998). The shorter swing phase on the deep surface
is likely responsible, at least partly, for the increased obliquity of
the forelimb at impact on this surface (the horse has less time to
retract its forelimb before landing). In turn, the increased obliquity
of the limb, associated with an increased penetration of the hoof in
DWS (Fig 4a), induce a more gradual rise of the GRF and a more
progressive decrease in the fetlock dorsal angle, than on FWS
(Figs 2, 3).
Generally speaking, a lower water content induces a significant
decrease of the force peaks Fz max and Fx max, and of the
corresponding loading rates applied to the forelimb. Although
stance duration was greater, Fz and positive and total Fx impulses
were lower on deep sand. These results demonstrate the damping
effect, in all directions, of DWS compared with FWS. Fetlock
maximal extension was also significantly decreased on DWS.
Interestingly, in Horse No. 4 for which the difference in water
content between the 2 tracks was the least, the differences in the
GRF (both Fz and Fx) and fetlock angle plots on DWS vs. FWS
were also the least.
Fz max peak was significantly delayed on DWS, which can be
attributed to at least 2 factors. As discussed above, a kinematic
delay exists from the beginning of the stance on DWS since the
initial position of the forelimb at landing is more oblique to the
track (by almost 5°); this delay persists throughout the stance.
Besides, energy is lost as the distal limbs penetrate the deep sand,
especially the hindlimbs as they start to support the body.
Therefore, it takes more time and effort to get the centre of mass of
the horse in the same position relative to the forelimb hoof at Fz
max time, which is also correlated with the more backward
orientation of the forelimb, on DWS compared with FWS (Fig 4b).
This is likely aggravated by the presence of the sulky (and driver)
that also interacts with the ground.
At the beginning of the stance phase, since more load is
applied on the caudal part of the hoof, the heels tend to penetrate
in the ground, all the most when the surface is more compliant
(Fig 4a); heel penetration is therefore increased on DWS. As a
consequence, since the reference frame of the dynamometric
horseshoe is related to the hoof, Fx is slightly less (and Fz slightly
greater) thus becoming negative earlier than if - for the same GRF
- the hoof solar surface had been more horizontal. This is more
notable the more the position of the hoof at landing is heel first, as
illustrated by the differences between Horses Nos 1 and 2, the
hoof surface of Horse No 1 becoming horizontal earlier during the
stance phase. These observations stress the advantage of using a
dynamometric horseshoe (vs. a force platform) for comparison of
ground surface effects: it better represents the forces effectively
applied on the hoof and information relative to the hoof
orientation can be deduced from Fx and Fz plots. However, highspeed films and kinematic data, as included in the present
7
protocol, are required for confirmation and thorough analysis. On
the basis of previous works (Denoix 1994; Crevier-Denoix et al.
2001), the lower heel position of the hoof can contribute to
explain the larger fetlock dorsal angle on DWS compared with
FWS in the first part of stance.
As the resistance the DWS offers is low, the horse receives less
propulsion from the same amount of force generation than on FWS
(Clayton 2004). Therefore, if the force generation had been the
same, the absolute value of Fx (including Fx min) and Fz, would
have been lower on DWS. It is not the case since Fx min values are
not significantly different, and at about 90% of the stance, Fz, and
Fx (in absolute values), are even larger on DWS compared with
FWS. Furthermore, because of hoof rotation towards the toe during
propulsion, likely larger on the more compliant DWS, the absolute
value of Fx in the reference frame of the hoof is less compared to
what would have been observed for the same GRF with a more
horizontal position of the hoof and a fortiori in the reference frame
of the track. This confirms that the propulsion force developed by
the horse’s forelimb is increased on DWS compared with FWS.
This result is also correlated with the strong increase in the Fx
negative impulse on DWS. As a consequence, whereas the net Fx
impulse is positive on FWS (‘braking impulse’), as it is
traditionally observed on the forelimbs (Clayton 2004), this
impulse is close to 0 (even slightly negative according to the
observed means, Table 1) on DWS. This clearly demonstrates the
increased contribution of the forelimbs to propulsion on deep sand.
The efficiency of the propulsive effort is nevertheless obviously
lower on DWS compared to FWS, as indicated by the dorsal fetlock
angle that is less on DWS at 90% of the stance phase (Fig 3). This
may be explained, at least partly, by the difference in fetlock
maximal extension on the 2 surfaces. Indeed during the support
phase, the equine palmar tendons, especially the superficial digital
flexor tendon (SDFT) and suspensory ligament (SL), are highly
strained, and more when the fetlock is more extended. These
tendons thus store elastic energy that is passively released during
propulsion. On DWS, maximal fetlock extension is reduced
compared with FWS; therefore the SDFT and SL are less strained
and their passive contribution to propulsion is less. Consequently,
active contribution of the digital flexor muscles to propulsion is
more required on DWS. Incidentally, an increased muscular
contraction from the flexor tendons could also contribute to explain
the lesser fetlock maximal extension observed on DWS (at about
60% of the stance). However, measurement of tendon force is
required to confirm, or not, this hypothesis.
It is well known that hard surfaces are a predisposing factor for
SDFT and SL injuries, especially at high speeds (Williams et al.
2001). However it is also admitted that deep surfaces can induce
tendon lesions as well. It appears from this study that when a horse
runs on a deep surface, propulsion is a critical phase (especially at
about 80% of stance): limb loading forces are still high (since Fz
max is delayed compared to a firmer surface), the fetlock joint is
still submaximally extended (and more extended than on a firmer
surface at the same speed), and digital flexor muscles have to
develop more force to push the limb off. In this situation, tendons,
especially the SDFT, are very likely more stressed and therefore
more prone to injury than on a firmer surface. Furthermore,
because the forward rotation of the hoof during propulsion, likely
increased on deep sand, induces a correlative decrease of the distal
interphalangeal palmar angle (Chateau et al. 2006), the deep digital
flexor tendon is relatively released, which puts even more stress on
the SDFT to support the fetlock joint.
© 2010 EVJ Ltd
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Through this study, clear kinetic and kinematic differences have
been established in horses trotting on deep vs. firm sand beach at a
moderate training speed: the loading of the limb is overall reduced
and more progressive; however the propulsive muscular effort is
increased, which may be accompanied by an increased tension on
the SDFT at the end of stance. These data should contribute to
improve safety and efficiency of equine training on beaches.
Cheney, J.-A., Shen, C.K. and Wheat, J.-D. (1973) Relationship of racetrack
surface to lameness in the thoroughbred racehorse. Am. J. vet. Res. 34,
1285-1289.
Acknowledgements
Crevier-Denoix, N., Roosen, C., Dardillat, C., Pourcelot, P., Jerbi, H., Sanaa, M. and
Denoix, J.-M. (2001) Effects of heel and toe elevation upon the digital joints
angles in the standing horse. Equine vet. J., Suppl. 33, 74-78.
The authors thank the Conseil Régional de Basse-Normandie, the
Fonds unique interministériel, The French Ministry of Agriculture,
the Haras Nationaux and the FEDER for their financial support to
this project, and the Pôle de compétitivité Filière Equine for their
technical assistance.
The authors also thank the farriers of the Haras du Pin and the
Garde Républicaine, and J. Jecker, for their contribution, and the
City Hall of Varaville.
Manufacturers’ addresses
1
Sartorius, Goettingen, Germany.
PCB Piezotronics Inc., New York, USA.
National Instruments Corp., Austin, USA.
4
Panasonic, Osaka, Japan.
5
Schmidt, Tübingen, Germany.
6
SIGMA Elektro GmbH, Neustadt, Germany.
7
Vision Research Inc, Wayne, USA.
8
Matlab, The MathWorks, Natick, USA.
9
SAS Institute Inc., Cary, USA.
2
3
References
Abdel-Aziz, Y.I. and Karara, H.M. (1971) Direct linear transformation from
comparator coordinates into object-space coordinates in close-range
photogrammetry. Proceedings of the ASP/UI Symposium on Close-Range
Photogrammetry. American Society of Photogrammetry, Falls Church, VA. pp
1-18.
Barrey, E. (1990) Investigation of the vertical hoof force distribution in the equine
forelimb with an instrumented horseboot. Equine vet. J., Suppl. 9, 35-38.
Burn, J.F. and Usmar, S.J. (2005) Hoof landing velocity is related to track surface
properties in trotting horses. Equine Comp. Exerc. Physiol. 2, 37-41.
Chateau, H., Degueurce, C. and Denoix, J.-M. (2006) Three-dimensional kinematics
of the distal forelimb in horses trotting on a treadmill and effects of elevation of
heel and toe. Equine vet. J. 38, 164-169.
5
GRF sand
Chateau, H., Holden, L., Robin, D., Falala, S., Pourcelot, P., Estoup, P., Denoix, J.-M.
and Crevier-Denoix, N. (2010) accepted for publication) Biomechanical analysis
of foot landing and stride parameters in harness trotter horses running on different
tracks of a sand beach (from wet to dry) and on an asphalt road. Equine vet. J.,
Suppl. ••, ••-••.
Chateau, H., Robin, D., Simonelli, T., Pacquet, L., Luinge, H., Pourcelot, P., Renard,
L., Denoix, J.-M. and Crevier-Denoix, N. (2009) Design and validation of a
dynamometric horseshoe for the measurement of 3D ground reaction force on a
moving horse. J. Biomech. 42, 336-340.
© 2010 EVJ Ltd
Clayton, H.M. (2004) Ground reaction forces. In: The Dynamic Horse, Eds: •• •• and
•• ••, Sport Horse Publications, ••, ••, MI. pp 195-216.
Crevier-Denoix, N., Pourcelot, P., Ravary, B., Robin, D., Falala, S., Uzel, S., Grison,
A.-C., Valette, J.-P., Denoix, J.-M. and Chateau, H. (2009) Influence of track
surface on the equine superficial digital flexor tendon loading in two horses at high
speed trot. Equine vet. J. 41, 257-261.
Denoix, J.-M. (1994) Functional anatomy of tendons and ligaments in the distal limbs
(manus and pes). Vet. Clin. N. Am.: Equine Pract. 10, 273-322.
Frederick, F.H. and Henderson, J.M. (1970) Impact force measurement using
preloaded transducers. Am. J. vet. Res. 31, 2279-2283.
Kaï, M., Aoki, O., Hiraga, A., Oki, H. and Tokuriki, M. (2000) Use of an instrument
sandwiched between the hoof and shoe to measure vertical ground reaction forces
and three-dimensional acceleration at the walk, trot and canter in horses. Am. J.
vet. Res. 61, 979-985.
Lejeune, T.M., Willems, P.A. and Heglund, N.C. (1998) Mechanics and energetics of
human locomotion on sand. J. Exp. Biol. 201, 2071-2080.
McMahon, T.A. and Greene, P.R. (1979) The influence of track compliance on
running. J. Biomech. 12, 893-904.
Pinnington, H.C., Lloyd, D.G., Besier, T.F. and Dawson, B. (2005) Kinematic and
electromyography analysis of submaximal differences running on a firm surface
compared with soft, dry sand. Eur. J.Appl. Physiol. 94, 242-253.
Ratzlaff, M.H., Hyde, M.L., Grant, B.D., Balch, O. and Wilson, P.D. (1990)
Measurement of vertical forces and temporal components of the strides of horses
using instrumented shoes. J. equine vet. Sci. 10, 23-35.
Richie, D.H., DeVries, H.A. and Endo, C.K. (1993) Shin muscle activity and
sports surfaces. An electromyographic study. J. Am. Podiatr. Med. Ass. 83, 181190.
Robin, D., Chateau, H., Pacquet, L., Falala, S., Valette, J.P., Pourcelot, P., Ravary, B.,
Denoix, J.M. and Crevier-Denoix, N. (2009) Use of a 3D dynamometric horseshoe
to assess the effects of an all-weather waxed track and a crushed sand track at high
speed trot: preliminary study. Equine vet. J. 41, 253-256.
Roepstorff, L. and Drevemo, S. (1993) Concept of a force-measuring horseshoe. Acta
Anat. 146, 114-119.
Roland, E.S., Hull, M.L. and Stover, S.M. (2005) Design and demonstration of a
dynamometric horseshoe for measuring ground reaction loads of horses during
racing conditions. J. Biomech. 38, 2102-2112.
Setterbo, J.J., Garcia, T.C., Campbell, I.P., Reese, J.L., Morgan, J.M., Kim, S.Y.,
Hubbard, M. and Stover, S.M. (2009) Hoof accelerations and ground reaction
forces of Thoroughbred racehorses measured on dirt, synthetic, and turf track
surfaces. Am. J. vet. Res. 70, 1220-1229.
Thomason, J.J. and Peterson, M.L. (2008) Biomechanical and mechanical
investigations of the hoof-track interface in racing horses. Vet. Clin. N. Am.:
Equine Pract. 24, 53-77.
Williams, R.B., Harkins, L.S., Hamond, C.J. and Wood, J.L.N. (2001) Racehorse
injuries, clinical problems and fatalities recorded on British racecourses from flat
racing and National Hunt racing during 1996, 1997 and 1998. Equine vet. J. 33,
478-486.
Zamparo, P., Perini, R., Orizio, C., Sacher, M. and Ferretti, G. (1992) The energy cost
of walking or running on sand. Eur. J. appl. Physiol. 65, 183-187.
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Journal Code: EVJ
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