Deadlift uses similar musculature as the Squat
in varying degrees (also see Squat
Analysis), in addition to muscles of the shoulder girdle
and forearms to support the load.
The Hips are extended by the Gluteus
Maximus and Adductor
Magnus. In the lower half the lift, the Hamstrings
act as a Dynamic Stabilizers
moving through the hips and knee with little change in length.
The Hamstrings act more as a Synergist
through the upper half of the movement. See Involvement
of Hamstring below.
The knee is extended by the Quadriceps.
The Soleus Planter Flexes
the ankle allowing the shin to become upright from the forward
angled position at the bottom of the deadlift. The Gastrocnemius
acts as a Dynamic Stabilizer, traveling through the ankle and
knee with little change in length.
The Spine is held ridged by the Erector
Spinae acting as a Stabilizer
with the Rectus Abdominis
and Obliques acting as
countering the pull of the Erector Spinae. Under very heavy loads,
the spine may tend to flex forward under the weight of a load.
The flexion of the spine temporarily decreases the moment arm
consisting of the hip and the barbell increasing leverage at
this more challenging portion of the lift. If the spine buckles
under the weight of the barbell it typically occurs in the thoracic
spine. It does not represent a loss of position if this braced
flexed position is held until the hips extend near the top of
the motion. At this point, the flexed spinal position creates
a secondary moment from the shoulders to the hips. This final
moment arm gap is resolved by straightening the spine in an upright
posture which is facilitated by pulling back the shoulders. This
final extension of the flexed spine position requires the Erector Spinae to act
as synergists near the top of the motion.
Although many may have issue with such extraneous movement
(see Controversial Exercises),
the spine structures and the accommodating musculature can adapt
to these forces with adequate training. To condition the spine
in these positions both Dave Tate, world famous champion powerlifter,
and Louie Simmons
of Westside Barbell recommends both arched back and rounded-back
in addition to Reverse
Hyper-extensions. Also see Adaptation
With the torso angled forward in the lower portion of the
lift, the shoulder girdle is primarily stabilized by the Middle Trapezius and
the Rhomboids, to some
degree. When the torso is more upright the shoulder girdle is
stabilized by the Middle and Trapezius,
Upper as well as the Levator
The Latissmus Dorsi
is the primary muscle that pulls the bar closer to the body in
effort to decrease the moment arm consisting largely of distance
between the barbell and hip.
Involvement of Hamstrings
At first glance of the Deadlift, the Hamstrings
appear to work as a Dynamic
Stabilizers essentially like they do in the Squat (see Torque Forces During Squat).
The beginning and ending positions of the hip and knee are somewhat
similar to the squat although the angle of the knee is less in
the lower position of the deadlift. However there are subtle
differences between the squat and conventional-style Deadlift
which make the hamstrings acts as both a synergist and a dynamic
The Hamstrings appear to contract through the hip in the Deadlift,
but obviously not to the same extent as they would if the knees
where kept totally straight through out the movement (ie: Straight-leg
deadlift) since the quadriceps are obviously extending the knee
during the deadlift.
The hips begin in a nearly full flexion where as the knees
may start in a 75% flexed position (90 degree flexion / 120 degree
full-range). Observing beginning and ending joint positions only,
that hamstrings appear to act as both a synergist (25%) and a
dynamic stabilizer 75% since the net contraction is 100% hip
extension (hamstring shortens) minus 75% knee extension (hamstrings
lengthens). With this information, it could be argued that the
hamstrings could be classified more as a Dynamic Stabilizer than
a Synergist since the actual contractions through the hamstrings
is relatively small.
*Romanian Deadlift 35-70 degree knee bend (30-60% ROM) , 115-130
degree hip bend (100% ROM)
However, when observing the actual movement of the deadlift
(between beginning and ending positions), the majority of knee
extension actually occurs early in the lift (allowing the bar
to clear the knees), leaving a significant portion of the remaining
hip extension to occur nearer the end of the lift with less concomitant
knee extension. When the bar clears the knees, the knees and
hip flexion are approximately 30-40 degrees (25-33% flexed) and
70 degrees (60%) respectively. These means at this position (bar
just above knees), the knees travel from 75% to about 30% flexion
(40% full ROM). In this same position, the hips travel from near
100% flexion to 70% flexion (<30% Full ROM). As the lift continues,
the knees become nearly straight (increasing hamstring efficiency
in effort to partially resolving a active
insufficiency of the Hamstrings while the hips continue to
However since the Hamstrings have entered partial active insufficiency
as the hips approach full extension with knees bent, the glutes
are still the primary hip extensor although they too are contracting
beyond their optimal tension potential.
This means in the early phase of the Deadlift (bar below knees),
the Hamstrings act as a Dynamic Stabilizer. However,
as the movement progresses (bar above knees), the Hamstrings
act increasing like a Synergist (greater net contraction) although
a small countering movement through the knees still occurs.
In the lowering phase, the hip and knee movements become more
distinct, with significantly less knee bend, particularly until
the bar was lowered below the knees. With less knee bend in the
initial portion of the in the lowering phase, the hamstrings
act more like a synergist during the eccentric phase of the movement.
In the case a competitive powerlifter, the knees never regain
their original bend during the actual descent, only bending a
maximum of 35 degrees during the lowering phase, as opposed to
a 90 degree bend in the initiation of the lift. Since powerlifters
dont need to train the lowering phase of the deadlift they
commonly either drop the weight part way down or rapidly lower
the weight in what could be described as a controlled drop. The
90 degree initial knee bend is only reset after the weight is
at rest on the floor. Without the hip and knee bending simultaneously,
the hamstrings can act as a synergist in the eccentric phase,
however the eccentric portion of a competitive powerlifters
deadlift can be nearly non-existent due to their style of unloading.
The distinction between Dynamic Stabilizer and Synergist is not
cut and dry (as with many other classification systems). Other
muscles besides the Hamstrings exhibit qualities of both a synergist
and dynamic stabilizer. See analysis
of the biceps involvement during different variations of
the pull-up and chin-up.
Sumo Deadlift vs Conventional Deadlift
The Sumo Deadlift offers various mechanical trade-offs as
compared to the conventional deadlift. The wide stance of the
Sumo Deadlifts allows the bar to positioned closer to the hips.
The sumo position, along with the lower positioning of the hips,
allows the torso to begin in a slightly more upright posture.
Although this allows for a shorter moment arm between the hips
and barbell, the lower position of the hips creates longer moment
arms between the knees and hip.
The wide stances of the Sumo Deadlift also positions the body
slightly lower to the ground thereby reducing the need to bend
over as far. It could be said that the sumo stance decreases
the distance the bar needs to be lifted but in effect it actually
decreases the moment arm distances on the sagittal plane (<
spine angle) while positioning moment arms more in the coronal
plane (hip adduction). The legs push both outward and downward
into the floor at lateral angles creating a converging reactive
force driving the hips upward.
The Sumo Deadlift uses similar muscles
as the Conventional Deadlift with a few notable variations. The
Sumo Deadlift has a greater reliance on the powerful hip musculature
with relatively less emphasis on the spinal musculature.
The wider stance and deeper initial squatting
position relies heavily on the Gluteus
Maximus and particularly the Adductor
Magnus. Like the Squat, the hamstrings act as Dynamic
Stabilizers moving through the hips and knee with little
change in length. The hamstring may act as a Synergist
nearer the top of the lift if the knees extend significantly
sooner than the hips, which may be caused by a narrower sumo
stance or long femura, possibly requiring the knees to be extended
early in the upper mid position thereby permitting the bar to
clear the knees.
Although the knees do not extend as far
beyond the ankle with the wide stance with knees pointing outward,
significant knee torque is still generated by the bilateral forces
angled slightly outward and downward, eliciting quadriceps evolvement.
Spinae and their antagonist stabilizers, Rectus
Abdominis and Obliques,
while still heavily involved in stabilizing the spine are proportionally
less evolved in the Sumo Deadlift due to the more upright posture
of the torso as compared to the more bent over positioning of
the Conventional Deadlift. This more upright posture also decreases
the tendency for the spine to flex forward under the weight of
The Sumo Deadlift is typically relatively
easier nearer the top of the motion as compared to the Conventional
Deadlift. However placing the arms narrower than shoulder width
creates unneeded torque near the top of the motion potentially
interfering with a full upright lockout since the bar cannot
held as close to the center of gravity at the top of the lift
with the arms positioned anteriorly on the body.