Pulling movement in weightlifting exercises from a biomechanical standpoint

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Journal of Australian Strength and Conditioning
September 2009 – Volume 17 – Issue 3 Page 18
Pulling Movement In Weightlifting Exercises From A Biomechanical Standpoint. J. Aust. Strength Cond. 17(3)18 - 24. 2009 © ASCA.
PEER REVIEW
PULLING MOVEMENT IN WEIGHTLIFTING EXERCISES FROM A
BIOMECHANICAL STANDPOINT.
Naruhiro Hori ¹, Loren Z. F. Chiu ², and Naoki Kawamori ³
1) Athlete and Coach Services, Western Australian Institute of Sport, Claremont, Western Australia
2) Neuromusculoskeletal Mechanics Research Program, University of Alberta, Edmonton, Alberta, Canada
3) Team “Nippon” Multi Support Project, Japan Institute of Sports Sciences, Tokyo, Japan
INTRODUCTION
Weightlifting exercises that involve a pulling movement,
such as snatch, clean, power snatch, and power clean, are
widely utilized by many athletes as a part of their strength
and conditioning programs in order to develop explosive
strength and muscular power [3, 13, 16]. Although these
exercises are performed as a single continuous movement,
they can be divided into three phases for analytical and
coaching purposes: (a) pulling phase; (b) receiving phase;
and (c) recovery phase. The pulling phase starts when the
barbell leaves the floor and ends when the barbell reaches
its maximum vertical velocity. The neuromuscular
demands of the pulling phase make weightlifting exercises
valuable and useful as a tool to develop explosive strength
and muscular power. The powerful and explosive
extension of the hip and knee, and plantar flexion of the
ankle requires a high rate of force development (RFD)
resulting in high mechanical power output [3, 7, 8, 13]. In
order to maximize the training benefits of performing these
exercises while minimizing associated injury risks, it is
critical that athletes execute the pulling movement properly
to achieve high levels of RFD and mechanical power
output. Moreover, proper execution of the pulling phase is
important for successfully performing the subsequent
receiving and recovery phases. This will enable an athlete
to lift heavier weight in a given exercise, providing a
greater training stimulus.
There are several opportunities for practitioners to learn
how to instruct such movements. For example, text books
are commercially available [1], videos of elite weightlifters
in training and competition are available for purchase and
on the internet, and national weightlifting organizations
(e.g. Australian Weightlifting Federation, USA Weightlifting)
have excellent coaching course programs [14, 22, 23].
However, these resources primarily focus on to how to
instruct the exercises and go into less detail about the
biomechanics of weightlifting exercises. For effective
coaching, it is essential that practitioners have a good
understanding of the biomechanical principles of
weightlifting exercises. Therefore, the purpose of this
article is to explain how to correctly perform the pulling
movement in weightlifting exercises from a biomechanical
stand point. In this article, we will first describe what the
pulling movement is, and then identify key factors to
successfully and efficiently perform the pulling movement.
Later, we will provide a step-by-step description of how to
correctly perform the pulling movement.
GENERAL DESCRIPTION OF PULLING MOVEMENT
The most common technique for performing the pulling
movement is the double knee bend style [4, 7]. The
literature generally divides the double knee bend pulling
movement into three phases based on the kinematics of
movement [6, 9-12, 21]. These phases are the first pull,
second knee bend, and second pull [4, 7]. Some sources
refer to the “double knee bend” as opposed to the “second
knee bend”, however, it should be noted that the double
knee bend is the technical style and the second knee bend
is the transition between first and second pulls (the first
knee bending occurs when the athlete squats down to
grasp the bar). Importantly, although the second knee
bend and second pull are distinct kinematically, they are
intricately linked by muscle action, thus many experienced
weightlifting coaches consider the second knee bend as a
part of the second pull. The first pull starts in a semi-squat
position and the barbell on the floor (Figure 1) and finishes
when the barbell passes the knees and the knees reach
their first maximum extension (Figure 2). After the first
pull, the knees re-bend (i.e. second knee bend), preparing
the athlete for the explosive second pull (Figure 3). The
second pull is the phase from the end of second knee bend
to the time when maximum vertical velocity of the barbell is
achieved. It should be noted that the barbell reaches its
KEY WORDS - Power, Clean, Snatch & Pull

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September 2009 – Volume 17 – Issue 3 Page 19
maximum vertical velocity before the knees fully extend.
While the exercise in Figure 1 starts from the floor, the
pulling movement can be started from any bar position
(e.g. above knee, at knee, or below knee height) from the
hang (Figure 2) or off blocks (Figure 4). If the exercise is
started from above the knee (i.e. either hang or off blocks),
the lift does not have a first pull.
Figure 1 - The Beginning Of The First Pull
Figure 2 - The End Of The First Pull (i.e. The Beginning
Of Second Knee Bend)
Figure 3 - Second Knee Bend

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September 2009 – Volume 17 – Issue 3 Page 20
Figure 4 - Pulling Movement Can Be Started Off Block.
KEYS TO SUCCESSFUL PULLING MOVEMENT:
BIOMECHANICAL PERSPECTIVE
Maximize vertical barbell velocity at the completion of
the pulling phase
In the clean, snatch, and their variations, an athlete has to
quickly receive the barbell on the shoulders or overhead
after the pulling movement is completed. If an athlete has
more time to do this task, the subsequent receiving phase
becomes easier. In other words, a lift may fail if an athlete
does not have enough time to execute proper receiving.
Once the pulling movement is completed, the vertical force
an athlete can apply to the barbell is decreased, and the
barbell’s upward displacement is eventually stopped by the
influence of gravity. Therefore, an athlete needs to
generate a high vertical barbell velocity at the end of the
pull.
According to the impulse-momentum relationship, the final
momentum (mass × velocity) of an object is equal to its
initial momentum plus net impulse imparted to the object
over a given time interval. Therefore, if force is applied to
an object over time, impulse (i.e. area under force-time
curve) causes a change in momentum of the objects. If
mass of the object stays constant and impulse increases,
then the change in velocity will be greater. Alternately, a
greater impulse will allow an object of higher mass to be
lifted at the same velocity. When applied to the pulling
movement, this principle means that the barbell velocity in
a vertical direction at the completion of the pulling phase is
determined by the initial velocity of the barbell (which is
zero at the beginning of the pulling phase) and the net
impulse imparted to the barbell in a vertical direction during
the pulling phase. To receive the barbell after the pulling
phase, the barbell needs to be displaced to certain height
which is determined by the velocity at the end of pulling
phase. In the full snatch and clean, the optimal height for
elevating the barbell is 60% and 50% of the lifter’s height,
respectively [2, 17]. If an athlete displaced the barbell with
a given mass to higher than the optimal height, she/he
could displace the heavier barbell to the optimal height
instead. That is why athletes can typically lift heavier
barbell in snatch and clean (i.e. receiving the barbell at full
squat position) compare to that in power snatch and power
clean.(i.e. receiving the barbell at higher than full squat
position). Also, it is important to consider the initial starting
height of the barbell in strength and conditioning. Snatch
and clean are often performed from the hang position
(Figure 2) or starting off blocks (Figure 4). These
variations can be useful to meet specificity of certain sport
tasks in terms of range of motion and/or types of muscle
action. However, this will reduce the time available to
generate force, resulting in less impulse. Therefore, in
order to lift the heaviest loads, the snatch and clean should
be performed from the floor.
In addition to pulling from the floor, there are two ways to
increase the impulse applied. The first is to generate
higher maximum muscular force (i.e. peak force). The
second is to apply peak force for a longer duration. This
necessitates a steeper initial rise in force (i.e. greater
RFD), which appears to be characteristic of elite lifters
attempting heavy weights in the snatch and clean [8]. For
instance, Figure 5 is a force-time curve corresponding with
the lifter’s body position during the clean pull movement
(reprinted from Reference 5). If higher force is applied
toward the barbell and the duration from beginning to the
end of pulling movement stays the same, it increases
impulse applied toward the barbell, and thus barbell
velocity. Typically, shape of the force-time curve during
the second pull is quite different between novice and
experienced athletes [8]. Figure 6 shows force-time curves

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September 2009 – Volume 17 – Issue 3 Page 21
during the second pull of two lifts for the same lifter. The
lift with less impulse (dotted line) also had a lower barbell
velocity than the lift with more impulse (solid line). Also
note that the rise in force for the faster lift (points A to B) is
steeper than the slower lift (points A to C). However,
coaches should be cautioned that increasing impulse does
not mean that the barbell should be rushed off the floor.
When the barbell is pulled too rapidly from the floor, the
total time of the lift is decreased, therefore less impulse is
generated. An excessively fast first pull results in a large
decrease in velocity during the second knee bend, as
compared to a controlled first pull and transition into the
second pull. To execute the first pull properly, the
muscular tension should be generated rapidly, but only to
the level sufficient to separate the barbell from the floor.
The most important time to maximize impulse (i.e. an
explosive action) is during the second pull, as this phase
directly impacts the maximum vertical barbell velocity
achieved.
Figure 5 - Force-Time Curve During Clean Pull Movement (Reprinted From Reference [5]). Rz Is Ground Reaction
Force Obtained From A Force Platform And Bz Is Force Applied To The Barbell Calculated From The
Cinematographic Data.

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September 2009 – Volume 17 – Issue 3 Page 22
Figure 6 - Ground Reaction Forces (Left Foot) Of Two Lifts For A National Caliber Weightlifter. Only The Second
Pull Is Shown And Data Is Normalized To 101 Data Points. Bar Velocity For The Curve Depicted By The Solid
Line Was Faster Than The Curve Depicted By The Dotted Line. A – Start Of Second Pull; B – Peak Force Solid
Line; C – Peak Force Dotted Line.
Minimize horizontal movement of barbell and lifter
To successfully receive the barbell in the snatch or clean,
minimizing horizontal displacement of the barbell and the
athlete is also very important. If the barbell is thrown
forward/backward, and/or the athlete jumps
forward/backward excessively, it makes receiving the
barbell difficult. Although some horizontal displacement of
the barbell is essential during performance of the pull,
proper execution of these movements should result in a
characteristic barbell trajectory. Analysis of elite
weightlifters demonstrates consistently that the bar should
move backward (toward the athlete) during the first pull,
forward (away from the athlete) during the second knee
bend, and then backward again during the second pull [2,
24]. For instance, Stone et al. [20] reported approximately
0.05 m of backward displacement and 0.08 m of forward
displacement during successful snatch lifts at an
international competition. Winchester et al. [25] reported
that force and power output during power clean was
improved as the horizontal displacement of the bar
decreased over four weeks of training intervention of lifting
technique. In the authors’ experiences, the most common
deviations from this trajectory are forward movement of the
barbell during the first pull or a forward arc of the barbell
during the second pull. The former is due to pulling the
barbell around the knees as opposed to pushing the knees
backwards during the first pull. The latter problem occurs
when the hips or thighs thrust into the barbell at the end of
the second knee bend or start of the second pull.
Barbell height at the completion of second pull
Reiser [18] stated location of the centre of gravity (COG) at
the moment of take-off is one of the determining factors of
vertical jump height. In the pulling movement, however, it
is questionable if the position of the COG of the barbell
and/or the athlete’s body at the end of pulling phase has
that much influence on success of the lifts. When the
barbell vertical velocity reaches its peak at the end of the
second pull, the hips and knees are almost fully extended,
ankles are almost fully plantar flexed, and the height of the
barbell is close to the height required to receive it in a full
squat. Thus, rather than the height of the barbell, athletes
should focus on maximizing the barbell’s vertical velocity,
minimizing the barbell and body’s horizontal velocity, and
executing proper receiving. In fact, the authors have found
that most athletes can pull the bar high enough when they
miss the lifts, but the lift is missed due to improper
trajectory or improper receiving (e.g. not pulling
themselves under the barbell properly; detail in receiving is
discussed later.).
SUCCESSFUL PULLING MOVEMENT: STEP-BY-STEP
DESCRIPTION
In the previous section, we discussed several key
biomechanical characteristics to performing a successful
pulling movement. In this section, we provide readers a
step-by-step description of the pulling movement.
Lift-Off Position
At the beginning of the first pull (Figure 1), the athlete’s
spine and pelvis should be in a neutral curvature with the
feet flat on the floor. Ideally, the heels of the feet are
placed about hip width apart, so that the force generated
from hip and knee extension as well as ankle planter
flexion is directed vertically. If the feet are apart too wide,
more force is directed laterally, thus the vertical component
of ground reaction force (GRF) is decreased. However,
the actual foot width should be accommodated to the
athlete based on their individual anthropometrics. The

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September 2009 – Volume 17 – Issue 3 Page 23
shanks should be inclined forward, with the kneecaps
slightly forward of the toes. The barbell should be located
close to the shanks, over the balls of the feet. The hips
should be kept higher than the knees, and the shoulders
higher than the hips. The shoulders are directly over or in
front of the barbell. If the shoulders are behind the barbell,
it typically means the trunk is too upright and the centre of
pressure (COP) is shifted towards the heel, whereas it
should be located in the fore- or mid-foot. If this is the
case, an athlete needs to swing the bar away from the
body during the first pull, in order to avoid the bar from
hitting the shanks or knees.
First pull
From the lift-off position, the barbell moves upward and
towards the lifter, and the lifter’s knees should move
backwards until the bar passes the knees [5, 14, 20], with
the shoulders remaining over or in front of the barbell [15].
The COP of the system (the barbell and lifter) shifts
backward toward the heels [5]. During the first pull,
angular displacements occur at the hip, knee and ankle
joints. However, it is important to note that the angle
between the back and floor remains relatively constant [4].
At the end of the first pull, the bar is about 0.1 – 0.2m
above the knee (Figure 2). At that time, the knees
approach full extension, however, remain slightly bent.
Second Knee Bend
As the knees approach full extension at the end of the first
pull, the body is in a mechanically disadvantageous
position, particularly for the torso. As a natural response,
the body prevents falling forward by shifting the knees
under the bar while the hips continue to extend. While the
gluteus maximus is the most important muscle during the
first pull, the hamstrings assist in hip extension at the end
of the first pull while initiating knee flexion during the
second knee bend. This motion results in a forward shift
in the COP. At the start of the second knee bend, the
barbell has reached its most posterior trajectory. Thus it is
important to consider that the knees and thighs are shifted
forward as the barbell continues to travel upwards. Due to
the orientation of the thigh segment, the barbell will lightly
brush against the upper thigh or pelvis. A common error is
to pull the barbell into the thighs, or to thrust the thighs and
pelvis into the barbell, however, these will throw the barbell
forward and prevent the second pull from being performed
properly. The second knee bend is an advantageous
phenomenon for the following reasons; 1) because of knee
flexion and hip extension, the distance between the hip
joints and the COG of segments above the hip joints
(head, arm, trunk, and barbell) decreases, so that it
reduces the torque at the hip joint [4]; 2) the length of the
knee extensor muscles are at a more optimal length [4,
15], and 3) the rapid lengthening of the quadriceps
generates a stretch-shortening cycle for the subsequent
second pull [4, 15, 21].
Second Pull
Once the second knee bend is finished, then knee and hip
extension, and ankle plantar flexion occur in a sequenced
manner. The appropriate onset of each movement and
relative contribution of each movement to the creation of
upward momentum of the barbell varies between individual
lifters. COP continues to shift forward during the second
pull. At the end of the second pull, the athlete has
explosively extended the hips and knees, and planter
flexed the ankles, pushing the ground away. The
combined angular motions at each of these joints results in
a coordinated effort that elevates the barbell in the vertical
direction. Although some weightlifting coaches encourage
their athletes to shrug their shoulders explosively at the
end of second pull, the contribution of scapular elevation to
increasing the barbell’s height or vertical velocity appears
to be small. In the authors’ experience, scapular elevation
occurs after the barbell reaches its maximum vertical
velocity. Thus, scapular elevation is important for receiving
the bar (i.e. pulling the athlete under the barbell) rather
than to elevate the bar higher. From this point,
practitioners may consider scapula elevation as a part of
the receiving rather than the second pull.
Receiving the Barbell
After the explosive second pull, the athlete continues to
pull on the barbell, while simultaneously “tearing their feet”
from the platform. Once the feet lose contact with the
floor, the athlete can no longer apply force to the combined
lifter-barbell system. However, the athlete can alter the
relative position between her/his COG and the COG of the
barbell by pulling her/himself toward the barbell during the
upward barbell movement. As a result of this action-
reaction, the athlete starts the receiving phase immediately
after the barbell reaches its maximum vertical velocity (i.e.
the end of the second pull). The position of the feet in the
receiving position should be similar to the feet position the
individual would squat with. Ideally, the feet should be the
same width or slightly wider than utilized during the pulling
movement. An excessively wide stance (i.e. greater than
shoulder/hip width) may prevent the athlete from proper
squatting to a maximum depth. It is generally advised that
the feet not move fore or aft, however, some authors
believe slight backward movement (e.g. about 0.05 m) is
permissible [19].
SUMMARY
The pulling movement consists three phases: the first pull,
second knee bend, and second pull. It is essential that
each phase is executed appropriately in sequence to allow
successive phases to be performed properly. Although
each phase is kinematically distinct, they are sequenced
together by complex muscle actions, requiring each phase
to be executed properly for successful lifting. The first pull
elevates the barbell from the floor, and the second knee

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September 2009 – Volume 17 – Issue 3 Page 24
bend places the lifter in a mechanically advantageous
position for the second pull. In the second pull, the rapid
coordinated efforts of the hip and knee extensors, and
ankle plantar flexors generates large forces in a short time,
imparting momentum to the barbell. From a biomechanical
standpoint, the successful pulling movement can be
characterized by the following three points: 1) pull the
barbell through an appropriate trajectory, minimizing
excessive horizontal movement, 2) generate large
muscular forces at appropriate times in the movement and
3) maximize vertical velocity of the barbell at the end of the
second pull.
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