Download tsa acl prevention 2 - Tucson Soccer Academy

CAUSES & PREVENTION OF ACL INJURIES
Adapted for TSA by Ron Fox MS. CSCS. ADPE (Carnegie)
GENDER-RELATED DIFFERENCES
Knee VALGUS motion in high school players may help determine why females
display a higher incidence of non-contact ACL injuries compared with males.
Female athletes displayed greater MAXIMUM VALGUS ANGLES during the
stance phase of their dominant side compared to the male athletes. This
represents a key neuromuscular gender difference in the performance of a
sport specific movement. The observed increase in motion at the knee
(valgus knee motion & angle) suggests altered muscular control. LIMB
DOMINANCE may potentially place both limbs at an increased risk of ACL
injury. The weaker limb may be compromised in its ability to manage even
average forces & torques, whereas the stronger limb may experience
exceptionally high forces & torques due to increased dependence &
increased loading on that side in high-force situations. Studies have
demonstrated that females had significant side-to-side differences in
HAMSTRINGS PEAK TORQUE & HAMSTRINGS to QUADRICEPS PEAK
TOQUE RATIOS before participating in a neuromuscular training program.
Upon completion of the training program, these side-to-side imbalances were
diminished. Recent data support that dynamic neuromuscular training
should be utilized in female athletes to decrease the incidence of ACL
injuries. Studies have demonstrated significant decreases in landing forces
& valgus & varus torques at the knee, significant increases in hamstrings
power & correction of hamstrings strength imbalances in a similar group of
female high school athletes after neuromuscular training. High landing
forces & resultant knee torques have been reported to be related to knee
injury. Gender differences in neuromuscular recruitment characteristics of
the muscles that stabilize the knee are often implicated as a factor in this
discrepancy.
STUDIES
There is considerable research in the area of gender differences in regards
to neuromuscular characteristics of the lower extremity in response to
perturbation. One study compared muscular preactivation of vastus medialis,
rectus femoris & medial/lateral hamstrings, in adolescent female basketball
athletes, male basketball athletes & female non-athletes in response to a
drop landing. The Female non-athlete group = recruited rectus femoris
significantly slower than both the female athlete & male athlete groups.
Female non-athlete group = significantly slower vastus medialis compared to
the female athlete group, but not significantly slower than the male group.
No differences between female athletes & male athletes for time to initial
contraction of any muscle groups. No differences were found among the
groups for medial or lateral hamstring activation.
This study demonstrates that physical conditioning due to basketball
participation appears to affect neuromuscular recruitment in adolescents &
reveals a necessity to find alternate methods of training the hamstrings for
improved neuromuscular capabilities to prevent injury.
NEUROMUSCULAR RECRUITMENT
At the knee, neuromuscular recruitment patterns & recruitment velocity of
the thigh muscles play a role in providing stiffness & dynamic stability at the
knee. There is a preparatory & a reflexive cocontraction of the quadriceps &
hamstrings to stiffen the area around the joint to prevent injury. The
preparatory action is the neuromuscular activity before foot contact, while
reflexive action is the activity. There has been a considerable push to
understand the factors that may predispose females to non-contact ACL
injuries. Several intrinsic & extrinsic factors have been examined in order to
explain this discrepancy. No specific difference between genders has been
identified to explain all contribution to the greater incidence of lower
extremity injuries in females, however, the neuromuscular function of the
muscles that control the hip and knee during functional tasks is a particular
extrinsic factor that has gained attention. Previous studies have examined
after foot contact. There is a need for efficient neuromuscular control of the
thigh muscles to create this dynamic joint stiffness and protective stability.
There are numerous studies evaluating the neuromuscular differences
between males & females. In these studies, females demonstrated muscular
recruitment characteristics that may be predispositions to ACL injury,
including preferential recruitment of the quadriceps over the hamstrings
shorter latency periods of the quadriceps less muscular stiffness of the
thigh muscles & unbalanced quadriceps-to- hamstrings strength ratios. A
study to investigate males & females differences in their control strategies
of Quadriceps & Hamstrings, found significant variances in knee control
strategies.
Female Predisposition to ACL injuries appears to be a multifactorial
combination of Anatomic  Physiological Hormonal factors
Most ACL injuries occur by noncontact mechanisms, often during landing
from a jump or making a lateral pivot while running. Biomechanical +
Neuromuscular + Physiologic + Hormonal + Anatomic mechanisms may underlie
these differences in the incidence of ACL injuries in men & women. However,
it is believed that women use different neuromuscular control mechanisms
than men & this is the primary reason for the increased incidence of knee
injury in female athletes. Women have measurable neuromuscular imbalances
that cause them to control their knees like ball-and-socket joints attached
to loose springs, while mens’ knees behave more like hinge joints attached to
stiff springs.The equalization of sports programs has been the direct cause
of the large infusion of girls & women into high-risk sports. Female athletes
who participate in jumping & pivoting sports are 4 to 8 times more likely to
sustain an ACL injury than male athletes. Since the enactment of Federal
Title IX in 1972, male sports participation at the high school level has
increased only 2.7% (3.7-3.8 million), while female participation has
increased 10 times, roughly doubling every 10 years (0.3-3.2 million). This
geometric growth in participation, combined with the 4 to 6 times higher
injury rate, has led to a widening gender gap in the number of ACL injuries.
JUMP LANDING CHARACTERISTICS OF FEMALES
ACL injuries often occur during landing from a jump, decelerating, or
pivoting on one foot while running. When women land, decelerate & pivot,
increased knee instability, due to four neuromuscular imbalances commonly
observed in female athletes—contribute to the ACL INJURY MECHANISM.
Female athlete performs a dynamic landing exercise.
These neuromuscular imbalances include:
1. Ligament Dominance - decreased dynamic neuromuscular control of the
joint, related to the knee abduction component of the injury mechanism.
2. Quadriceps Dominance - increased quadriceps recruitment & decreased
hamstring strength & recruitment, which is related to the extended knee
position component of the injury mechanism.
3. Leg Dominance - Side-to-side differences in strength, flexibility, &
coordination, which is related to the asymmetrical foot weighting component
of the injury mechanism.
4. Core Instability - Increased trunk motion, which is related to the foot
displaced away from the body center of mass component of the injury
mechanism.