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Akef Khowailed I1
1University of Saint Augustine, Physical Therapy, San Marcos, United States
Background: A female athlete's increased risk for non-contact anterior cruciate ligament (ACL) injury has been well documented. The discrepancy in ACL injury risk between sexes has been attributed to multiple factors including differences in anatomical, hormonal, biomechanical, and neuromuscular characteristics. Several studies have demonstrated a relationship between peaks in estrogen serum concentration and increased laxity in the ACL. This associated change in tissue tolerance may predispose the ACL to failure at lower tensile loads and/or alter the protective muscle reflex actions associated with ACL tissue receptor stimulation. Imbalanced or ineffectively timed neuromuscular firing may lead to limb positioning during athletic maneuvers that puts the female ACL under increased strain and risk of injury.
Purpose: To investigate the effects of 17β-Estradiol across phases of menstrual cycle on lower extremity neuromuscular control patterns and ACL laxity during running.
Methods: Twelve healthy female runners mean (±SD) age was 25.6 (±3.7) years, who reported normal menstrual cycles were tested twice across one complete menstrual cycle for serum levels of 17β Estradiol (E = pg/mL), knee joint laxity (KLax = mm displacement at 130N), measured with a standard knee arthrometer. Maximum voluntary contraction normalized electromyographic (EMG) activity of the quadriceps and hamstrings muscles was recorded during running on a treadmill.
Results: Normality was confirmed for the data using Kolmogorov-Smirnov test. Independent T tests were conducted to compare the changes in mean E, KJL and EMG activity at different phases of menstrual cycle. 17β estradiol serum concentration was significantly higher in the ovulatory (P 0.001) associated with increased ATT. The quadriceps muscle exhibited increased activity during the early follicular phase in the precontact and weight acceptance phase (p= 0.019, 0.043 respectively). The average peak hamstring activity during the precontact and weight acceptance phase was significantly increased during ovulation compared with the early follicular phase.
Conclusion(s): A change in KJL during the menstrual cycle in response to 17β-Estradiol fluctuations changes the neuromuscular control around the knee. High level of plasma concentration of estrogen was associated with a marked increase in joint laxity behavior following peak ovulatory levels. The increased knee joint laxity showed increased levels of muscle preactivity in the hamstring muscles before impact as well as during weight acceptance phase. Increased coactivation of the hamstring muscles plays an important role in providing a compensatory strategy to reduce anterior tibial translation in functional conditions that include knee extension.
During follicular phase, female runners place greater reliance on their quadriceps to modulate the torsional joint stiffness about the knee joint during running. Low ratio of medial to lateral quadriceps recruitment combined with increased lateral hamstring firing may compress the lateral joint, open the medial joint which directly loads ACL. The disproportional recruitment of the vastus musculature increases anterior shear force at the low knee flexion angles which may increase the potential for valgus lower extremity position and possibly increased risk of ACL injury.
Implications: Understanding the underlying neuromuscular mechanism female utilize during different phases of menstrual cycles would be beneficial for clinicians in the development of more effective ACL injury prevention programs.
Keywords: Anterior Curciate Ligament, EMG, Neuromuscular
Funding acknowledgements: None
Purpose: To investigate the effects of 17β-Estradiol across phases of menstrual cycle on lower extremity neuromuscular control patterns and ACL laxity during running.
Methods: Twelve healthy female runners mean (±SD) age was 25.6 (±3.7) years, who reported normal menstrual cycles were tested twice across one complete menstrual cycle for serum levels of 17β Estradiol (E = pg/mL), knee joint laxity (KLax = mm displacement at 130N), measured with a standard knee arthrometer. Maximum voluntary contraction normalized electromyographic (EMG) activity of the quadriceps and hamstrings muscles was recorded during running on a treadmill.
Results: Normality was confirmed for the data using Kolmogorov-Smirnov test. Independent T tests were conducted to compare the changes in mean E, KJL and EMG activity at different phases of menstrual cycle. 17β estradiol serum concentration was significantly higher in the ovulatory (P 0.001) associated with increased ATT. The quadriceps muscle exhibited increased activity during the early follicular phase in the precontact and weight acceptance phase (p= 0.019, 0.043 respectively). The average peak hamstring activity during the precontact and weight acceptance phase was significantly increased during ovulation compared with the early follicular phase.
Conclusion(s): A change in KJL during the menstrual cycle in response to 17β-Estradiol fluctuations changes the neuromuscular control around the knee. High level of plasma concentration of estrogen was associated with a marked increase in joint laxity behavior following peak ovulatory levels. The increased knee joint laxity showed increased levels of muscle preactivity in the hamstring muscles before impact as well as during weight acceptance phase. Increased coactivation of the hamstring muscles plays an important role in providing a compensatory strategy to reduce anterior tibial translation in functional conditions that include knee extension.
During follicular phase, female runners place greater reliance on their quadriceps to modulate the torsional joint stiffness about the knee joint during running. Low ratio of medial to lateral quadriceps recruitment combined with increased lateral hamstring firing may compress the lateral joint, open the medial joint which directly loads ACL. The disproportional recruitment of the vastus musculature increases anterior shear force at the low knee flexion angles which may increase the potential for valgus lower extremity position and possibly increased risk of ACL injury.
Implications: Understanding the underlying neuromuscular mechanism female utilize during different phases of menstrual cycles would be beneficial for clinicians in the development of more effective ACL injury prevention programs.
Keywords: Anterior Curciate Ligament, EMG, Neuromuscular
Funding acknowledgements: None
Topic: Women's & men's pelvic health; Human movement analysis; Sport & sports injuries
Ethics approval required: Yes
Institution: Loma Linda University
Ethics committee: Institutional Review Board of Loma Linda University
Ethics number: 5130372
All authors, affiliations and abstracts have been published as submitted.
