Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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.