Last week we ended our discussion looking at how poor posturing loads various portions of the body. We will continue to see how this posturing impacts thoracic spine on down to the foot.
Thoracic scoliosis
·
Causative factors – because baseball and especially pitching is an
asymmetrical sport, pitchers tend to over develop on one side and under develop
on the other side as noted earlier. In
the thoracic spine, this results in increased muscle tension on one side of the
spine and decreased muscle tension on the contralateral side. Since the spine is a mobile structure, this can
result in the bending toward the stronger side or the side with increased
tension. This will present as
scoliosis. It should also be mentioned
that baseball, especially professional baseball, tends to attract demographics
and recruit internationally from regions which tend to have higher incidences
of scoliosis. So, although scoliosis in
the example may be associated with the factors mentioned above, this can also
be associated with genetic factors as well.
·
Potential injuries – with thoracic scoliosis, because of the abnormal
position of the spine there is also abnormal loading of the spine. The human spine is meant to be loaded in an 80/20
relationship where 80% of the weight is absorbed through the bone disc bone
interface and 20% of the weight is absorbed through the facet joints. Abnormal spine positioning of the spine alters
this loading relationship. This can add
to accelerated breakdown of tissues and pain in the joints, ligaments or
muscles of the thoracic spine. Curvature
in the frontal
plane also adds to distraction of the costalvetebral joints on the concave side
and compression on the convex side. This
can add to costalvetebral pain as well as increase the potential for
costalvetebral subluxations.
·
Performance issues – with a change in position of the spine, there is also a
significant change in the length tension relationships of the musculature that
attaches at various portions of the spine.
With curvature in the frontal plane, muscles are lengthened and
shortened on the convex and concave side.
These altered length tension relationships add to imbalances in strength
along the spine and the lower extremities.
This not only impacts transfer of kinetic energy but also then power
output. In instances where there is
pain, this results in even further weakness of the spinal extensors, which if
not addressed can lead to loss of up to 25% of the cross sectional area of the
muscle (Hides et al, Spine, 1996).[i] In the
pitcher example, this can cause increased fatigue in the thoracic spine earlier
in the game which puts increased demands on the shoulder and scapula
stabilizers. If they are also weakened,
this accentuates the impact on overall performance, pitching velocity and
pitching tolerance or endurance.
Pelvic asymmetry
·
Causative factors – in a closed kinetic chain situation, positioning of one
end of the chain impacts positioning on the other end. In the spine and pelvis, this is especially
true since the two are connected via the sacroiliac joint (SI). Therefore, one cause of pelvic asymmetry can
be scoliosis. However, if there is a
pelvic asymmetry, this will also cause curvature of the lumbar and thoracic
spine in the frontal plane. So, does
pelvic asymmetry cause curvature of the spine in the frontal plane or does curvature
in the frontal plane cause the pelvic asymmetry? This is an important question to answer during
a differential diagnosis. Another factor
that can lead to a pelvic asymmetry is a leg length discrepancy. Although a “true” leg length discrepancy is rare
and usually the result of genetic factors (hemihypertrophy), tumors (hemangioma
- blood vessel tumor or Wilm’s tumor – tumor of kidney causing hypertrophy of
the limb) or epiphyseal issues (injuries or infections in the growth plate),
these are typically not diagnosed during a visual examination alone and require
further testing to uncover. An “apparent”
leg length discrepancy, though, can be assessed during visual and
musculoskeletal evaluation. There can be
a plethora of causative factors, including lumbar spine and core weakness or tightness,
pelvic weakness or excessive flexibility (common in women who carry a child on a
single hip predominantly) or excessive foot pronation.
·
Potential injuries – with pelvic asymmetry, many tissues and structures are
abnormally loaded. In reviewing just the
most proximal and distal structures, one could expect to see abnormal loading
of the lumbar spine, the sacroiliac (SI) joint, the hip joint, trochanteric
bursa and the iliotibial band. The
lumbar spine is placed in a more side bending position with pelvic asymmetry,
and therefore there is increased potential for low back pain. There is increased shear stress in the SI
joint which can contribute to pain. At
the hip, there is increased compression of the femoral head in the acetabulum
which may contribute to hip labral tears, wearing of articular cartilage and
pain. On the side of the hip, where the
ilium appears to be elevated, there is increased tension on the iliotibial
band. This can add to increased
incidence of trochanteric bursitis and IT band friction syndrome.
·
Performance issues – besides the indirect impact the asymmetry would have on
performance as a result of potential pain issues, pelvic asymmetry also can
have a more direct impact on performance as well. As a result of the frontal plane motion that
occurs during gait and sport related activities, when there is pelvic asymmetry
there can be marked decrease in endurance of the hip, core and lower
extremity. Endurance and overall power
output are also affected because of the change in the length tension
relationships of the musculature of the lower extremity, hip and core. In the example of the pitcher, pelvic
asymmetry can result in increased fatigue in the lumbar spine, hips and lower
extremity which places increased demands on the upper body to maintain velocity
or power output. The impact on overall
performance, pitching velocity and pitching tolerance or endurance is compounded
if there are weaknesses and poor postural alignments higher up the kinetic
chain.
Foot Asymmetry
·
Causative factors – because the foot is the first portion of the kinetic
chain to impact or be in
contact with the ground, misalignment of the foot will
have a dramatic impact on the alignment and loading of all of the proximal
joints, including the ankle, knee, hip and lumbar spine. Two common alignment issues that we see in a
postural assessment are supination (in relation to position of the calcaneous) resulting
in pes cavus (in relation to the position of the medial arch) of the foot and
pronation resulting in pes plantus of the foot. The position we most often observe in
athletics however is calcaneal pronation resulting in pes plantus. This may present bilaterally but in many
cases will present with an asymmetrical pattern, meaning that it will be much
more pronounced on one side versus the other or be present on one side and not
present at all on the other. In cases
that present asymmetrically, we often see much greater dysfunction during
sports performance and/or increased injury potential on the side with the most
pronounced pronation. This can result in
the athlete being plagued with injuries along the kinetic chain on the side
with the greatest magnitude of pronation.
When the calcaneous falls into excessive pronation in a closed kinetic
chain the result is genu valgum at the knee, adduction at the hip and pelvic
asymmetry. Although many believe this is
the “main cause” of pathokinematics, research has shown us that proximal
weakness in the hip and core can also result in pronation and pes plantus at
the foot and ankle. In fact, pronation
and pes plantus can be caused by a multitude of factors including weakness of
the posterior tibialis, intrinsics of the foot on the plantar aspect, hypermobility
of the plantar fascia or calcaneous, or proximal weakness in the hips and
core.
[i] Hides, Julie A. PhD; Richardson, Carolyn A.
PhD; Jull, Gwendolen A. MPhty. Multifidus Muscle Recovery Is Not Automatic
After Resolution of Acute, First-Episode Low Back Pain. Spine.
21(23):2763-2769,1996
·
Potential injuries – with calcaneal pronation, many structures are loaded in
an abnormal fashion. In reviewing
proximal and distal structures, one could expect to see abnormal loading of the
medial arch of the foot, the retrocalcaneal bursa and Achilles tendon, the anterior
tibialis, tibia (shins) and knee. With
the decreased arch, the foot becomes flat footed in full weight bearing (pes
plantus) which increases potential for pain in the arch of the foot as well as the
heel, and posterior heel. With the loss
of shock absorption with the fallen arch, this can place more work and strain
on the anterior tibialis and the shins adding to anterior shin pain. At the knee, there is a resultant genu valgum
which increases the potential for strain on the cruciate ligaments and meniscal
injuries. Along with this positioning of
the knee, there is alteration of the “normal” articulating pattern of the
patella in the femoral groove which can lead to patellar tendonitis or
patellofemoral syndrome.
·
Performance issues -- besides the indirect impact the asymmetry would have on
performance as a result of potential pain issues, pronation can also have a
more direct impact on performance as well.
As a result of the large degree of motion that occurs during gait and
sport related activities, when there is excessive calcaneal pronation there can
be a marked decrease in endurance of the foot, ankle, lower leg, knee and
hip. Endurance and overall power output
are also affected as a result of the abnormal positioning and alignment of the
joints in the closed kinetic chain. In
an example of a basket ball player, vertical height may be compromised when
attempting to achieve a jump shot. With
excessive pronation of the foot and accompanying genu valgum, the force the
athlete is able to generate through the quads and hamstrings is affected and
the transfer of that energy to the foot/ankle and ground is also
compromised. Therefore there is not only
a decrease in the force that is generated but also a decrease in the energy
transfer as it is crossing a less efficient system.
So, we can tell a lot about an
athlete’s potential for certain types of injury as well as potential
performance issues and limitations he or she might face by looking at posture
as seen in these examples. Addressing
deviations like these can reduce the potential for injury, improve efficiency
of the entire system and lead to higher athletic performance.
As basic as it sounds, to
truly change movement, we must change the way that we think. And although it is not 100% data driven, it
is 150% science driven. And that is, assess it
better. Move better, feel better,
perform better and last longer. That
simple!
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Dr. Nessler is a practicing physical therapist with over 20 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment and ACL injury prevention. He is the founder | developer of the ViPerform AMI, the ACL Play It Safe Program, Run Safe Program and author of a college textbook on this subject. Trent has performed >5000 athletic movement assessments in the US and abroad. He serves as the National Director of Sports Medicine Innovation for Select Medical, is Vice Chairman of Medical Services for USA Obstacle Racing and movement consultant for numerous colleges and professional teams. Trent is also a competitive athlete in Brazilian Jiu Jitsu.
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