EPHE 201
Qualitative Biomechanics Analysis of
Hurdling
Tierney Heinrich
Simone Beattie
Josh Clouthier
Doug Oxland
Table of Contents
Section
Page
Introduction
3
Qualitative Anatomical Analysis
5
Phases of Hurdling
7
Free Body Diagrams
9
Description of Expert Performance
10
Deterministic Model
13
Mechanical Explanation
14
Observation
29
Evaluation/Diagnosis
33
Correcting Errors/Implementation
37
Conclusion
38
References
41
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Introduction
Qualitative biomechanical analysis is the process of observing, comparing and
critiquing movement within a particular skill that can be used to determine the optimal
way of performing a skill. The goal is then to transfer those techniques to teaching novice
performers as they learn and develop the skill movements and to also provide efficient
instruction in order to reach that goal.
The skill we have chosen to analyze is hurdling. The objective of this skill is
to jump over the hurdle in as an efficient manner as possible. In this analysis, the context
is a single hurdle set up on a rubber track straightaway.
The purpose of this skill is to clear the hurdle efficiently without wasting exerted force or
energy to allow the athlete to perform optimally in the race. The skill can be broken into
four main components that directly affect the goal; take off, flight, and landing distances,
as well as the optimization of motion during the performance. Each of these components
has their own set of varying factors that affect them. Ultimately, optimizing all four of
these factors is what will lead to the most efficient performance. The main elements,
velocity, momentum, impulse, forces, and torque, all need to be examined when
determining the optimal hurdling technique.
Variation and limitations associated with this skill in context to the environment
are not high in regards to the track style but do change with the weather conditions and
audience present. Hurdling is always performed on an oval 400m track, made of rubber,
mondo (a synthetic rubber nonslip material), or dirt. The hurdles are consistent in their
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shape, but vary in height. Weather can influence the visibility and perception of the jump,
and an audience can affect the amount of attention a performer allocates to the skill and
how they perceive the importance of the goal. The biggest variation in hurdling is the
distance raced over the hurdles. The two main events involving hurdles are 100m
(women) or 110m (men) hurdles and 400m hurdles (Ward-Smith, 1997). These distances
will affect the velocity at takeoff which influences the flight distance. The number of
hurdles in a race determines the change in technique from the beginning hurdle to the
final hurdle. As the performer progresses through the course they increase their velocity
over the first few hurdles which increases their take off distance from the hurdle. The
final hurdle jumps in a race must compensate for fatigue that causes the performer to
slow down; as a result the take off distance decreases. The performance we analyzed
occurred over only one hurdle and therefore a limitation to observing hurdling in the
context of a race is that one hurdle jump does not exemplify the variation of hurdle jumps
from the beginning, middle and end of a race.
The only rule in a hurdle race is that you cannot leave your assigned lane
(International Association of Athletics Federations [IAAF], 2008). This does not greatly
affect the analysis of the optimal performance of this skill as any lateral movements that
would cause one to leave their lane would greatly compromise the efficiency of the jump
and waste significant amounts of energy.
The equipment that is used in hurdling events are the hurdles and the performer’s
choice of clothing and footwear. The hurdle heights varies for each distance; 42 inches
for men’s 110m hurdles, 36 inches for men’s 400m hurdles, 33 inches for women’s 400m
hurdles, and 30 inches for women’s 100m hurdles (IAAF, 2008). For our analysis we
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used a 33 inch hurdle due to our novice’s lack of experience with hurdle jumps. Track
spikes are usually worn by hurdlers, and were worn by both of our performers.
There is only one technique used by hurdlers to get over the hurdle, which we
explain in this analysis, and it remains relatively the same across different race lengths
and for different performers. The absolute features of this technique are what change due
to the performer’s physique and the characteristics of their race. The efficiency at which
this technique is performed also changes from performance to performance and can be
improved with training; therefore it is the focus of our analysis.
QAA
Qualitative anatomical analysis of expert performer from sagittal view
Figure number of sequence:
1. Lead up position
2. Loading position
3. Maximum joint extension
4. Moment of takeoff
5. Maximum height
6. First contact
7. Absorption
8. Extension into run
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1
2
Joint
Figure
number
of
sequence
R.Shoulder 1-2
2-3
R. Hip
R. Knee
R. Ankle
3
4
5
6
7
8
Joint
Motion
Muscle
Active
contraction muscle
group
Rapid
Extreme range
acceleration of motion
or impact
concentric
concentric
isometric
concentric
concentric
concentric
concentric
concentric
concentric
isometric
concentric
eccentric
flexors
flexors and
abductors
flexors
extensors
extensors
flexors
flexors
extensors
extensors
extensors
flexors
flexors
yes
3-4
4-5
5-6
6-7
7-8
1-2
2-3
3-4
4-5
5-6
flexion
flexion and
abduction
No motion
extension
extension
flexion
flexion
extension
extension
No motion
Flexion
extension
6-7
7-8
1-2
2-3
3-4
4-5
5-6
6-7
7-8
1-2
2-3
extension
extension
flexion
extension
No motion
flexion
Extension
No motion
extension
dorsiflexion
Plantar
eccentric
concentric
concentric
concentric
isometric
concentric
concentric
isometric
concentric
concentric
concentric
flexors
extensors
flexors
extensors
extensors
flexors
extensors
extensors
extnsors
Dorsiflexors
Plantar
yes
Yes
yes
hyperextension
hyperextension
hyperextension
yes
Impact on
the ground
yes
yes
hyperextension
yes
Yes
yes
yes
yes
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3-4
4-5
5-6
6-7
7-8
flexion
Plantar
flexion
dorsiflexion
Plantar
flexion
Plantar
flexion then
dorsiflexion
Plantar
flexion
concentric
concentric
eccentric
concentric
concentric
flexors
Plantar
flexors
dorsiflexors yes
Dorsiflexors
Plantar
Impact on
flexors to
ground
dorsi flexors
Plantar
yes
flexors
Phases of Hurdling
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Run Up:
The run up is the phase that completes the sprint and leads into the hurdle jump. This
phases is where the highest velocity can be attained in a horizontal direction.
Take Off:
The take off is the phase where the performer exerts force onto the ground in order to
project them on a parabolic path over the hurdle. The take off is the last moment that the
performer can exert force to produce momentum in both vertical and horizontal
directions.
Midflight:
The midflight is the phase in which the performer is no longer in contact with the ground
and only non-contact forces, such as gravity and air resistance, have an effect on their
momentum.
Landing:
The landing is the phase where the performer makes contact with the ground and absorbs
the forces of impact before they can transition to the recovery phase.
Recovery:
The recovery is the phase where the performer exerts forces to accelerate back up to a
high velocity and continue running in a forward direction.
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Free Body Diagrams:
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Description of Expert Performance
Characteristics of the most effective technique:
The ideal hurdle technique has 5 main elements: velocity, momentum, impulse,
forces, and torque which are discussed in relation to our key phases. These elements link
together in a way that allows the performer to clear the hurdle efficiently without
breaking his stride and continue running after the hurdle.
Run up:
The run up includes the frames prior to and including the lead-up frame (1) and
the loading frame (2). During the run up the expert is accelerating to a high velocity in his
running stride. A high velocity in the run up is important to generating a maximal
horizontal force that allows the hurdler to take off at a greater distance prior to the hurdle
and at a smaller angle of take off. The performer has a slight forward lean in order to
move his center of gravity to the front of his base of support, which maximizes his
mobility in the direction he is traveling. In the final run up step before take-off, the
hurdler plants his loading (trail) foot on the ground and flexes the hip, knee, and ankle
joints of that leg in order to prepare for extension at take off. The arm on the loading
(trail) side moves from extension into slight flexion synchronized with the lead leg in
order to maintain balance as well as minimize angular momentum (Winckler, 2003).
Takeoff:
The take off includes the maximum joint-extension frame (3) and the moment-oftake off frame (4). During the take-off, the expert performer goes into rapid full
extension at the hip and knee of the trail leg, as well as full plantar flexion at the ankle
(Winckler, 2003). The hurdler drives the knee of his lead leg up as he begins to extend
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the trail lower leg (Winckler, 2003). The arm on opposite side to the lead leg is flexed, in
preparation for the rapid arm extension which will balance out the large angular
momentum generated by the trail leg during mid-flight (Winckler, 2003).
Mid-flight:
The mid-flight phase occurs from the point of take off to the point of landing and
is represented by the maximum height frame (5). During mid-flight the expert performer
brings the trail leg forward in flexion and medially rotated at the hip as well as slightly
abducted (Winckler, 2003). The lower trail leg is pulled up close to the body and parallel
to the hurdle in order to increase efficiency in bring it over the hurdle. As the trail leg is
brought up close the torso, decrease the distance from the center of gravity, the torso is
flexed at the hip over top of the lead leg as much as possible in order to keep the center of
gravity low, close to the hurdle, and forward in the direction of motion (Hebberd, 2011).
Landing
The landing includes the first contact frame (6) and absorption frame (7).
The hurdler makes first contact with the ground using his lead leg, and then absorbs
the landing with his trail leg. At this phase the torso is perpendicular to the direction
of motion and hips and shoulders are in line (Hebberd, 2011). The arms are
positioned opposite to each other and parallel with the body. The center of gravity is
positioned over the base of support (Coh, ND).
Recovery
The recovery is when the performer accelerates back up to high velocity and
continues into a run. It is represented by the extension into run frame (8). The hurdler
extends their hip, knee and ankle of the trail leg after absorption and he continues
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into his normal running stride, slightly accelerating in order to regain momentum
lost from the flight and landing. The performer keeps their torso in line with their
trail leg and ensures that their force production is through the center of gravity
(Mcdonald, 2002). This optimizes the horizontal momentum and accelerates them
towards the next anticipated hurdle.
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Mechanical Explanation
Body Position at Take Off
Explanation of deterministic model: Takeoff distance (relative to the hurdle), horizontal
and vertical displacement and height of take off
Body position at take off affects the take off distance, relative to the hurdle,
because how close the performer launches into their take off over the hurdle will be
subjective to how much momentum the performer generates before and at take off. This
momentum is based on the velocity in the run up (Hebberd, 2011). The amount of force
the performer applies on the ground at takeoff and how rapidly they flex their lead leg is
the body positioning that affects the horizontal and vertical displacement (Hebberd,
2011). The body position at take off also affects the height at which the parabolic path
begins. As soon as the trail leg leaves the ground the center of gravity is set on its path.
Explanation of body position
The body position at take off requires producing the correct force vectors
(impulse) onto the ground and using the angles at the joints to set the body on an optimal
path that will clear the hurdle. The curvilinear path that the performer travels on is
created by gravity, the changing velocity vectors and momentum that act on the body
during flight. At the point that the trail leg leaves the ground, the performer has their lead
leg flexed in order to raise their center of gravity and therefore increase the height of their
parabolic path.
The takeoff of the performer, relative to the hurdle, occurs at a distance that will
result in the performer reaching their peak height when they over top of the hurdle. If the
performer is too far or too close to the hurdle when they take off they will likely collide
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with the hurdle because they will either be on their way up to their peak or coming down
from it when they reach the hurdle.
When running up to the hurdle the take off exhibits the lead leg in flexion and the trail leg
fully extended (Hebberd ,2011). Fast acceleration of the lead leg into flexion adds to the
body’s momentum upwards and full flexion at the hip raises the center of gravity so that
it will exceed the hurdle’s height at the peak.
Optimize
The goal of hurdling is to clear the hurdle quickly and efficiently. The greater the
acceleration of the lead leg into flexion, the more momentum the performer will have to
overcome the hurdle’s height and the more force that can be applied in the horizontal
direction at takeoff. This results in a faster jump and a greater parabolic path distance.
To prepare the body for clearing the hurdle, at take off, one could focus on aiming the
knee in the direction of the path that it will take over the hurdle. This is because it mirrors
the path that the body’s center of gravity (located outside the body; between the torso and
the leading leg) takes, only lower (Hebberd, 2011).
Errors
If the performer produces too much vertical force at take off, it can result in an
inefficient jump where the vertical displacement over exceeds the hurdle height and
compromises the horizontal velocity. If there is too little vertical force at take off, the
performer may collide with the hurdle as they are not exceeding the hurdles height to get
over it. Correction: Apply force on the ground at the optimal angle (through the body’s
center of gravity) in order to create the optimal parabolic path (Winckler, 2003).
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If the performer is too far or too close to the hurdle at take off this may result in a
collision with the hurdle as the performer will still be on their way up or on their way
down in their parabolic path. Correction: Determine the optimal parabolic path for
distance and height and plan to coordinate legs so the lead leg lifts of at the take off
distance for the optimal path (Winckler, 2003).
Forces at the Shoulders
Explanation of deterministic model: flight distance and optimizing motion
The forces that occur at the shoulders have an effect on both the flight distance as
well as optimizing the motion of efficiently clearing the hurdle. These forces in regard to
flight distance aid in increasing the horizontal displacement as they affect the impulse;
this in turn affects the momentum and the velocity of the hurdler in the run up before
takeoff. The forces at the shoulders also play a role in the optimization of the motion by
affecting both the angular momentum and the center of gravity of the hurdler.
Explanation of forces at the shoulder:
While the forces at the shoulder do not come in contact with any surface to create
an action force, they do create a muscular force that helps many aspects of the skill.
During many phases of the skill, the internal forces help in optimizing the forces created
on the ground, the conservation of the angular momentum, and the manipulation of the
center of gravity.
Optimization
During the run up, the internal shoulder forces counterbalance the rotational
movement of the hips and optimize the forces that are created on the ground from the
legs. In the take off phase, the shoulder forces help to raise the center of gravity as well as
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propel the hurdler vertically. In midflight these forces once again allow for the
conservation of the angular momentum and offsetting of the rotational movement of the
legs, as well as the manipulation of the center of gravity to a forward position. These
forces also have an effect on the conservation of angular momentum during both the
landing and the recovery phases.
Errors
An error in the novice performance would be in the lack of movement presented
at the shoulders during the midflight phase. The forces of the shoulder play an especially
important role during this phase as stated above, and errors, which occur during this
phase, are magnified during the landing and recovery phase. Our novice does not move
his shoulders in a manner that allows for the forward manipulation of his center of
gravity, as well as the counteraction of his angular momentum. Correction: instruct the
performer to move their arms in an opposite movement of their legs, and especially
emphasize the importance of the shoulder and arm motions during the midflight position.
Forces at the Hip
Explanation of deterministic model: flight distance
The forces at the hip are related the total forces exerted, which have an effect on
the impulse and change in momentum. This affects the velocity at take off and therefore
the horizontal displacement of the leap.
Explanation of forces at the hip
When forces at the hip increase, impulse will become larger to create an increase
in the momentum and velocity of the hurdler at take off. It is important for the velocity of
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the hurdler at take off to be high so that the maximum horizontal distance can be attained.
Optimize
In order to maximize the force at the hip, the performer needs to rapidly go from
flexion to extension of the leg at the hip. The magnitude of the force will increase with an
increased range of motion. The direction of the force must be downward and backward,
in order to set up the knee and ankle joints for an optimum foot placement and direction
of force. The direction of the force must allow the performer to clear the hurdle with most
of his momentum in a forward direction, in order to be able to conserve momentum when
continuing into a running stride at the landing.
Errors
Errors seen in the novice in the force generation of the hip are both not enough
magnitude of force, or force generation in a direction that is not optimal for clearing the
hurdle. Corrections: The novice should begin his take off phase further from the hurdle so
that maximum force generation is achieved, and should aim for a more horizontal leaping
motion over the hurdle to confirm that his angle of force is in a downward and backward
direction (Winckler, 2003).
Forces at the knee
Explanation of deterministic model: flight distance
The internal forces at the knee are also important at for achieving the goal of
efficiently clearing the hurdle. The explanation of how these forces are connected to the
deterministic model as a whole is the same as those discussed for the forces at the hip.
Explanation of forces at the knee
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The tension created in the muscles of the knee is linked to how the forces at the
ankle will function. These forces create an optimal range of motion of the lower leg so
that the overall forces of the leg are directed down and backward.
Optimize
In order to optimize forces at the knee, the magnitude and the direction need to be
proportional to the angle of take off in order to clear the hurdle. The direction of the
forces at the knee needs to be the same as the direction of the forces at the ankles. This
synergy between the knee and ankle is what can cause maximum force exertion on the
ground at take off.
Errors
Errors are related to the magnitude of the internal forces in the muscles
(quadriceps, hamstrings, etc.) affecting the knee. The muscles that affect the knee must
generate the right amount of force. Novices tend to create forces at the knee that cause an
improper line of action resulting wasted energy in the vertical direction. This extends the
time spent in flight which ultimately slows the overall performance.
Forces at the ankle
Explanation of deterministic model: flight distance
The internal forces at the ankle are also important at for achieving the goal of
efficiently clearing the hurdle. The explanation of how these forces are connected to the
deterministic model as a whole is the same as those discussed for the forces at the hip.
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Explanation of forces at the ankle:
The internal forces on the ankle are very important for hurdling. The tension
created in the muscles of the ankle will be essential for clearing the hurdle in an efficient
manner.
Optimize
In order to optimize the forces at the ankle, the magnitude needs to be large and
the direction needs to forward and slightly upwards; not upwards enough to slow the
forward movement, but low enough to maintain forward momentum, at the point of take
off.
Errors
The most common error is in regard to direction of the force from the ankle, often
novice performers aim too far upwards, which interrupts forward movement, and thus
causes a loss of momentum during the landing phase, when absorbing the landing and
continuing into a running stride. This error commonly occurs in between the loading
phase and the full extension phase.
Time Forces Start and End
Explanation of deterministic model: flight distance
The time forces start and end affect the impulse, or the change in momentum. The
impulse is defined by the amount of force applied, multiplied by the time that the forces
act.
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Explanation of time forces start and end:
When going over a hurdle, we define the time that the forces start as the time that
the foot of trail leg comes in contact with the ground (as the lead leg is approaching the
hurdle), and we define the time that the forces end as the time that the foot of the trail leg
leaves the ground.
Optimize
From the time that the forces start to the time that the forces end, the foot moves
from dorsiflexion at the ankle to plantar flexion at the ankle. This joint action allows the
foot to keep in contact with the ground for a longer amount of time, increasing the
impulse, and therefore the momentum when going over a hurdle. The action of the foot
and ankle also allow for a greater force generation.
Errors
Increasing the magnitude of dorsiflexion and plantar flexion of the ankle can
maximize the amount of time that the force is applied. If the performer does not have full
dorsiflexion of the foot at the ankle during the time the forces start, or does not have full
extension of the foot at the ankle during the time the forces end, he will not maximize his
time in contact with the ground. If this is not maximized, the impulse will be decreased
and the performer may not have enough momentum to clear the hurdle and continue into
a running stride.
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Velocity in the final step
Explanation of deterministic model: Velocity at take off, horizontal and vertical
displacement, flight distance and angle of release (takeoff/ landing distance)
The velocity of the run up to a hurdle ultimately affects the velocity at takeoff
(momentum) and transfers to the magnitude of force produced to project the body
forward. The velocity in the final step dictates the horizontal and vertical displacement as
well as the flight distance due to its effect on the body’s inertia (Coh, ND). Velocity
affects the angle of release by increasing the distance of the parabolic path. The takeoff
distance can farther from the hurdle if the velocity before takeoff is increased, because
the peak will be still be high enough to clear the hurdle due to a longer travel time
upwards in the parabolic path (Ward-Smith, 1997).
Explanation of velocity in the final step
Velocity (V) in the run up to a hurdle jump affects the performer’s momentum (P)
and inertia (M). Momentum (P=MV) is directly affected by the velocity (V) that the
performer is moving at prior to the hurdle (McGinnis, 2005). The velocity vector
transfers to the performer’s body displacement in flight, in the vertical and horizontal
direction, when forces are applied on the ground at takeoff. The velocity from the run up
keeps the body moving through the air during midflight until gravity pulls the body back
towards the earth; an example of Newton’s first law of inertia: Objects in uniform motion
tend to stay in motion unless acted on by net external forces (gravity and air resistance in
this case) (McGinnis, 2005).
The summation of all vectors, including the performer’s force vectors and external forces,
results in the parabolic pathway that the center of gravity travels when in flight. A greater
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velocity in the final step before takeoff decreases the relative effect of gravity and air
resistance that occurs over time in flight.
Optimize
To optimize the velocity in the final step, the performer should be constantly
accelerating in their run up until takeoff. By creating rapid flexion of the hips and knees
at takeoff, momentum is increased as the body moves forward towards the hurdle
(Hebberd, 2003).
Errors
The performer may be too slow or too fast when approaching the hurdle. If they
are too slow, they will require a greater force vertically downwards to reach the peak in a
shorter distance and will lose momentum in the horizontal direction, ultimately stalling
the performer in the landing phase when the vertical force is absorbed. If the performer is
too fast, they may not have the time to properly coordinate their limbs and maintain
balanced over their base of support as they jump over the hurdle. Correction: Determine
an optimal velocity that balances between an efficient leap distance and optimal
coordination of the body (Winckler, 2003).
Body position at mid flight
Explanation of the deterministic model: horizontal displacement
The body position at midflight is a part of the vertical displacement which is
ultimately connected to the flight distance and the total distance of the hurdler. Even
though the only forces acting on the body in this phase are the no-contact forces of
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gravity and air resistance, this position is still an essential factor for the hurdler in
allowing them to complete the goal of efficiently clearing the hurdle.
Explanation of body position at midflight
It is important for the hurdler to manipulate their body position midflight in order
to optimize his parabolic flight path. Midflight body position determines where the
hurdler’s center of gravity will be located and ultimately how efficiently they will clear
the hurdle.
Optimize
The optimal midflight body position is flexion of the hurdlers torso toward the
leading leg, which is in full extension, so that the torso creates an acute angle with the
lead leg. Also the trail leg should be fully flexed at the knee and abducted at the hip so
that it is nearly parallel to the hurdle (Ward-Smith, 1997). This position changes the
athlete’s center of gravity to a lower position as he or she crosses over the hurdle, thus the
athlete stays closer to the hurdle, wastes less energy in a vertical motion, and overall
optimizes the movement (Ward- Smith, 1997).
Errors
Some source of error could include a lack of flexion at the spine resulting in a
perpendicular angle between the torso and the lead leg. Another source of error could be
an angled trail leg, resulting in the athlete bumping or completely knocking over the
hurdle, and ultimately slowing their performance. Corrections: The novice should
contract their core muscles and back flexor muscles to draw their upper body closer to
their lead leg. Additionally, the novice should be instructed to abduct their leg at the hip
to create a parallel position of their trail leg with the top of the hurdle (Winckler, 2003).
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Body position at landing
Explanation of deterministic model: flight distance and landing distance
The body position at landing directly relates to the flight distance and the landing
distance when it comes to efficiently clearing the hurdle. Because the height at take off
and the height at landing are equal, the relative height is zero. Therefore, the vertical
displacement is not affected by the body position at landing, but the horizontal
displacement is.
Explanation of body position at landing
The landing body position is essential for continued forward momentum after the
hurdle is cleared. This body position must absorb the shock from the jump and ensure
loss of momentum and velocity from take-off is minimal. This can be explained through
impulse, and how momentum is influenced by force and time. In order to keep the
athlete’s momentum from take off to landing as consistent as possible, we must decrease
the landing impulse on the ground.
Optimize
To do this, an optimal way of landing is to have the lead leg foot strike the ground
in a plantarflexed position so that the toe hits the ground first and then roll back to the
ball of the foot. The knee of the lead leg should also be in a slightly flexed position.
These two elements help to decrease the athlete’s force into the ground, while increasing
the time the force is exerted on the ground, thus maintaining momentum. The trail leg at
landing should be slightly flexed at the knee and plantar flexed at the ankle to prepare for
contact with the ground (Hebberd, 2011).
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Errors
One error would be landing flat-footed when contacting the ground. This would
increase the force into the ground over a short period of time, and slow momentum. This
can be corrected with verbal instruction by telling athlete to plantarflex lead foot before
landing.
Body Position in Angular Momentum
Explanation of Deterministic model: Moment of Inertia, Angular acceleration, Angular
Momentum
Angular momentum (L =Iω) is affected by the moment of inertia (I) and the
angular velocity (ω) (McGinnis, 2005). Angular momentum is the object or body’s
resistance to change in motion. By the law of conservation of momentum, if no net
external torque is applied to the body then the angular momentum about an axis will sum
to zero (McGinnis, 2005). The performer can increase and decrease their moment of
inertia about their z axis by extending and flexing their limbs farther away (increase) or
closer (decrease) to the axis (McGinnis, 2005). The angular velocity too can be changed
by how fast a limb is rotated or moved in a circular path, such as the trail leg as it brought
over the hurdle.
Explanation of Body Position in Angular Momentum
Angular momentum can be generated and transferred about the body’s joints and
axes. It is important that the performer compensates for any rotation in the flight in order
to be facing forward with their shoulders, torso and hips perpendicular to their direction
of travel when they land(McDonald, 2002). The critical section of the jump where
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angular momentum is pertinent is midflight, just as the performer brings their trail leg
over the hurdle to when they make contact with the ground at landing.
The trail leg is brought over the hurdle fast like a whip, in order to clear the hurdle
in the moment that the performer is at their highest point over the hurdle and before they
begin to descend. This movement creates angular momentum of the trail leg which
transfers to the hips and causes rotation about the z axis and rotates the performer’s torso
to their left (McDonald, 2002). To correct the rotation in the hips, the right arm is
extended back at the shoulder as the trail lower leg is extended at the knee over the hurdle
and the left arm flexes forward. The arm movements collectively create angular
momentum about the shoulders that rotates the torso back to the right (McDonald, 2002).
Optimize
The optimal position to decreasing and compensating for angular momentum
during midflight is to have the trail lower leg in full flexion and medial rotation before it
is brought over the hurdle in order to shorten the moment of inertia from the z axis of
rotation. This decreases the angular momentum that is generated about the hips and the
rotation to the left. The arm on the trail side should be in full flexion and the arm on the
lead side should be in full extension before the trail leg goes over the hurdle. When the
trail leg is extended angularly over the hurdle, the arms drive in opposite directions in the
sagittal plane to optimally counteract the rotation at the hips while maintaining control
(Herbberd, 2011).
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Errors
The performer may not efficiently counteract the angular momentum generated by
the trail leg and can result in the body being twisted away from the direction that it is
travelling when they land. The forces at landing are then used to create a torque that
corrects the direction, but this ultimately affects the horizontal velocity that the performer
can generate, slowing them down (McDonald, 2002). Correction: Flex the trail leg up
close to the body before they bring it over the hurdle and coordinate the arms to move at
the same time as the trail leg ensuring that it generates an equal angular momentum in the
opposite direction (Winckler, 2003).
Body Position for Center of Gravity Manipulation
Explanation of Deterministic model: Center of Gravity and Body Position
The center of gravity is important for the optimization of the motion to efficiently
clear the hurdle.
Explanation of Center of Gravity for Mid-Flight Body Position
The expert is manipulating his center of gravity by changing his body position
midflight. This is important because by manipulating his center of gravity he can be more
efficient in clearing the hurdle, which is his ultimate goal. The hurdler needs to lower his
center of gravity so that he spends less time in the air, and thus conserves more velocity
and momentum when landing (Ward-Smith, 1997).
Optimize
To bring his center of gravity closer to the hurdle he must manipulate his body in
two major ways. First, the expert lowers his trunk toward his lead leg, consequently
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lowering his center of gravity closer to the hurdle. Additionally, the expert launches his
right arm forward which results in his center of gravity to also move forward. Overall
from these two movements, the expert’s center of gravity moves down and forward in
relation to his body position (Ward-Smith, 1997).
Errors
An error could be that the performer fails to move their trunk toward their lead leg
and does not drive their right arm forward. Correction: contraction of the core and back
flexors muscles to pull their trunk closer to their lead leg. Additionally, they should focus
on driving their arm forward during the beginning of the flight.
Observation
Who to observe:
The performer that we are observing is a novice at hurdling, but an expert at track
running. The performer is regularly coached for track and field; therefore, they are likely
familiar with critiquing their body position to optimize their movement. For evaluation,
we will aim to keep terminology and descriptions related to running as this is easier to
grasp for our novice. The jump itself is novel; therefore it would optimal to focus on
major flaws as opposed to detail when first introducing the skill. Some key flaws for
correction are the torso flexion at take off and midflight, the arm movements in
coordination with the legs (angular momentum), balance (direction of forces at takeoff
and landing), and takeoff angle with respect to the hurdle.
Observation conditions:
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Given that hurdling in practice and in a race both occurs on a track, this is our
location for observation. For our initial observation we would want optimal conditions
such as a dry track, moderate temperatures and few observers. This would allow the
hurdler to completely focus on their performance and show their best effort. For
continued practice and observation, the ideal conditions would be those similar to a
competition, such that the weather is not always perfect and that there is some pressure
from an observing audience.
Where to observe:
Optimally we would view our performer from the sagittal and frontal planes
which is plausible in a practice setting, although frontal plane viewing during a race
would be difficult. From the sagittal plane we can see the angles of the legs, arms and
torso movements and from the frontal plane we can see the distinct movements of each
arm anteriorly and posteriorly relative to one another and laterally and medially to body.
In coordination with the legs, the angular momentum effects are prominent in the
frontal plane view and we can clearly see the trail leg movement as it moves in the
transverse plane over the hurdle. For viewing a novice performer, we would view far
enough back that the entire jump is in focus and the take-off and landing positions are
seen from an almost perpendicular angle. In this way, the general gross movements could
be evaluated easily and the feedback would result in a greater improvement in the basics
of the movement.
As the performer becomes more experienced, the details will become more
important to continuing the performer’s improvement. Zooming in to particular areas of
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the jump will reveal imperfections, such as the degree of flexion in the limbs and the
head and ankle movements, which could not be seen from farther back.
Expert Diagram
Observational strategies:
To optimally view the hurdler, it is important to view the movement from the
height of the hips as this is where majority of the movement is centralized and where the
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height of the center of gravity is located. To analyze the jump from a height equal to the
hips, the angles about the hips, knees and arms are clear and relatively undistorted by the
viewing plane. It is also important to focus on the body itself (neck and down) and not the
head (in the novice phase particularly) as the head tends to follow a linear path, where as
the rest of the body manipulates the center of gravity and reflects the parabolic path that it
travels.
What to look for:
Biomechanics of a Hurdle Jump Observation Checklist
Athlete Name:
Level of Expertise:
Observer Name:
Date:
Phase
Position of body or body
segments
Duration or range
of motion
Run Up
Force
producing
phase
Take off
Force
producing
phase
Sequential and deliberate
leg drives
Moderate range of
motion at the key
joints
Lead leg flexion
Mid flight
Landing
Velocity
and/or
acceleration
Constant
acceleration
Timing or body motions
Full
Moderate-High
Knee aimed at direction of
travel
Trail leg extension
and force exertion at correct
angle on ground
Hyperextension
Force exerted from
the heel to the toe
Fully extended through force
production
Torso straight, angled
towards the direction of
motion and flexed at the hip
Trail leg parallel with hurdle
Full
Low
Acceleration
up and over the
hurdle
Moderate-High
Body aiming forward
Entire flight
Trail arm counteract trail leg
angular momentum
Full
Center of gravity low and
forward over the hurdle
Low center of gravity at
touchdown
Full extension of the lead
leg at contact
Full
Fast
acceleration in
time with the
trail leg
No
None
No
Arms parallel with body and
flexed at elbow
Moderate
No
Full
Fast
acceleration
over the hurdle
No
Balanced and coordinated
running gait
Torso close to trail leg
(flexion).
Force produced through c of g.
Medial rotation and slight
abduction of the hip. Whip
action.
Angular momentum
conservation
Extension at the shoulder
Legs in flexion at the hip, arms
close to the body and low
Arms down and upper body
angled forward
Extension at the knee, slight
flexion at the hip and plantar
flexion at the ankle.
Extension to flexion at the hip
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Recovery
Force
producing
phase
Balance in regaining
running pattern
For the entire
contact time of
each leg
No
Hamstrings extend to exert a
force down and back; in line
with the center of gravity
Arm coordination to
allocate direction and
compensate for forces
absorbed in landing
Acceleration
Moderate and
consistent duration
Low-moderate
Flexion and extension of arms
opposite to leg movements.
Long enough to
regain momentum
lost during flight
Moderate
Extension and Flexion of legs
and arms alternately; fast
running pace
Evaluation and Diagnosis
Novice Diagram
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Identifying Errors:
When observing our novice performer, several errors were noticed that affected
his overall performance when it came to efficiently clearing the hurdle. As stated above,
our novice performer is an expert track runner; therefore his run up phase has little errors
when it comes to producing the proper amount of force needed to clear the hurdle. The
take off phase is where the majority of his errors begin. In this phase, his torso is too
perpendicular to his direction of take off, resulting in a decrease of velocity due to air
resistance on the body. Additionally, the novice’s direction of force from his trail leg into
the ground is at a perpendicular angle, where as the expert exerts his force at an acute
angle. This will cause the novice to project himself in a vertical direction slowing his
overall performance by wasting energy vertically, and decreasing his velocity and
momentum at landing.
In the midflight phase, the novice demonstrates more errors which will hinder his
performance. His trail leg is not parallel with the hurdle making it difficult for him to
rotate his body and correct the force of the torque rotating him to the left. In conserving
his angular momentum, the novice’s goal should be to remain in a forward facing
position throughout the entire flight phase, of which his does not. He slightly over rotates
his trunk to the right because of the arm movements made in an attempt to counteract the
rotation at the legs. This requires more effort to correct the direction at landing;
consequently his forward momentum and velocity are decreased. His trail arm lags
behind which results in the rotation of his body to right and angular momentum and
torque not being properly conserved at landing for the intention of this skill. To help
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remedy this angled body position and lagging trail arm, the novice should counteract the
forward motion of the trail leg by driving the trial arm backward. Finally, the novice
demonstrates errors by not moving his center of gravity low towards the hurdle and
forward in the midflight phase. His trunk is perpendicular to his lead leg and his trail arm
is behind and above him. This results in a higher center of gravity that is slightly behind
the hurdle. This will result in a longer flight time which decreases the velocity at landing,
as well as an improper landing position which decreases mobility as he transitions into
the recovery phase.
In the landing phase he makes a few more errors which are consequential of the
errors made during the take off and mid-flight phases. At landing his center of gravity is
still too high and his arms are not parallel and flexed at the elbow. These two errors are
due to a center of gravity that is high and to the back and improper conservation of
angular momentum during midflight. This results in the novice to be off balance at
landing and have to overcorrect for his errors during midflight.
In the recovery phase, the novice has no errors as he had regained his balance and
is ready to continue on with the sprint.
Evaluating the Errors
The possible improvements that the novice should make in order to effectively
complete his goal of efficiently clearing the hurdle are as follows:
Phase
Errors
Improvements
Take off
Force exertion not at correct angle on ground
Create force at more oblique angle by pushing off
ground in more horizontal direction rather than
vertical.
Torso perpendicular to the direction of motion
Flex back as take off is about to occur in order to
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lower torso to a more horizontal position
Mid flight
Trail leg not parallel with hurdle
Abduct at hip so that lower leg is more parallel to
the hurdle
Body slightly rotating at end of phase
Drive trail arm back to counteract the forward
motion of the trail leg
Trail arm does not counteract trail leg
Concentrate on driving arm backward after initial
forward motion to counteract the forward motion
of the trail leg
Center of gravity high and rearward over the hurdle
Continue to flex back in order to keep center of
gravity low over hurdle, and concentrate on initial
drive forward of arm to bring center of gravity
forward.
Landing
high center of gravity at touchdown
Continue to flex back slightly so that upper body is
in a forward position
Arms not parallel with body and flexed at elbow
Correction of arm rotation during midflight phase
will correct this error, as the novice’s arms are
high because of lack of balance at landing.
Errors Ranked in Order of Priority:
1. Force exertion not at correct angle on ground at take off
2. Trail arm not counteracting trail leg during mid-flight
3. Center of gravity high and behind hurdle at mid-flight
4. Torso perpendicular to direction of motion at take off
5. Body slightly rotating at end of mid-flight phase
6. Trail leg not parallel with hurdle during mid-flight
7. High center of gravity at touch down
8. Arms not parallel with body and with elbow flexed at landing
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Final List of Errors to Be Corrected:
Since many of the errors ranked lower in the priority sequence above will be
eliminated with the correction of higher-ranking errors, the novice should focus on the
higher ranked errors first. An error that should be remedied immediately is the angle of
the force exerted on the ground at take off. This will help to correct the position of the
torso at take off. Secondly, correction of the trail arm to counteract the trail leg during
midflight will help to resolve the slight rotation of the body to the right at the end of the
flight phase. This adjustment will also lead to the arms being parallel to the body at
landing, as the performer will land in a balanced state. Finally, the novice should focus on
properly manipulating his center of gravity during the midflight phase. By lowering and
bringing his center of gravity forward, this too will correct his lack of balance and
instability at landing and will allow for a smoother transition into the run.
Correcting Errors and Implementation
Based on the information given in the mechanical explanation and the
deterministic model, there are several errors that need to be corrected. There are many
ways in which these errors could be fixed, but in the case of our novice performer we
would focus on augmented feedback based on the qualitative characteristics of the
performance rather than the outcome. This could be done through verbal instruction and
video analysis. The errors that were ranked highest in priority would be dealt with first
and instruction would be given to the novice on how he could fix the first main error in
his performance. Focus would remain on the first error until it was corrected, and only
then would focus move to the second major error. It is important not to overload the
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performer with too many corrections at once; this can cause confusion and efforts made
to improve performance could actually hinder it.
Conclusion
The objective of hurdling is to jump over the hurdle in the most efficient manner
possible, in order to run the fastest time possible in the race. The action of hurdling
can be broken into eight key phases; lead up position, loading position, maximum
joint extension, moment of take off, maximum height, first contact, absorption, and
extension into run. An expert performance of hurdling involves several main
elements, velocity, momentum, impulse, forces and torque, that relate to the five key
phases of the skill which are the run up, take off, midflight, landing and recovery.
These elements all combine to create efficiency in hurdling. There are four main
areas that determine one’s efficiency in hurdling; take off, flight, and landing
distances, and optimizing body motion. These components each have their own set
of determining factors, which eventually break down into eighteen final factors, all
of which have an effect on the skill whether they can be controlled or not and are
important when analyzing this skill. There are eight errors that are commonly made
by novices when hurdling. The top priority error to fix is the direction of force
exertion at take off creating an incorrect angle of takeoff. When implementing
correction it is best to help the novice with fixing each error one at a time, in order
to not overload the performer with information.
This analysis is useful for the evaluation and correction of a novice
performer. By using the goal of energy efficient hurdling, rather than gaining speed
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or height, novices will be able to focus on good form within the context of a race. The
information that was analyzed about body movements during hurdling is very
important to properly instructing novices as they likely do not have the knowledge
of how to coordinate certain body parts while hurdling, especially with the arms and
shoulders.
This qualitative biomechanical analysis of hurdling allowed us to observe the
mechanical features of how a hurdle is performed, why it is performed that way and
how errors can interfere with the achievement of the goal. This information
provides insight into how to instruct the novice hurdler to improve their
performance. However, we did experience some limitations in correcting our novice,
such as the fact that we would not be able to analyze him in a race situation from the
frontal plane and we are aware that the frontal view provides important
information about the hip and shoulder heights, the location of the limbs in relation
to the trunk and the manipulation of the trail leg as it is brought over the hurdle.
Another limitation that we found could occur is when instructing a
performer very new to hurdling and perhaps to sports in general, as opposed to our
novice, who already has experience in track racing and some hurdling. The very new
hurdler would require much more simplified instruction and errors would likely be
numerous. Modifications to the practice setting might also be necessary to properly
introducing the performer to the skill, such as jumping with a smaller hurdle or no
hurdle. Analysis and correction of their motions would change as well to allow a
greater degree of variation in their performance until they become comfortable with
the motion and specific instruction becomes effective.
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The qualitative biomechanical analysis of movement can be applied to a
variety of skills in a multitude of settings that extend beyond sports in to
rehabilitation and activities of daily living. Based on the effectiveness of our analysis
of hurdling, it is certain that the application of analysis in other situations would be
beneficial to evaluating and correcting various skills and movements.
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References
Coh, M. (ND). Colin Jackson’s hurdle clearance technique [online].
www.coachr.org/colin_jacksons_hurdle_clearance_technique.htm. Accessed
online November 16th, 2011.
Hebberd, M. (2011). The mechanics of sprinting and hurdling [online].
www.livestrong.com/article/474669-the-mechanics-of-sprinting-hurdling.
Accessed online November 15th, 2011.
McDonald, C. (2002). The angular momentum of hurdle clearance [online].
www.coachr.org/angular_momentum_of _hurdle_clearance.htm. Accessed
online November 16th, 2011.
McGinnis, P.M. (2005). Biomechanics of sport and exercise (2nd ed.). Champaign, IL:
Human Kinetics.
Ward-Smith, A.J. (1997). A mathematical analysis of the bioenergetics of hurdling.
Journal of Sports Sciences. 15: 517-526.
Winckler, G. (2003). Practical biomechanics for the 100m hurdles [online].
www.ukhurdlesclub.net/13site/coaching_aticles.asp?article_id=6. Accessed
online November 15th, 2011.
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