Hormone Induced Effects on Ligament Laxity and Lower Extremity Motor Control
Condition: Hormone Influence on Ligament Laxity and Motor Control
Study type: Observational

Summary: 
      The purpose of this study is to expand on previous knowledge of the hormonal effects,
      specifically estrogen, on ligament laxity, motor control and timing of muscle activation in
      females. A significant amount of research has previously been done on the effects of estrogen
      throughout the menstrual cycle on ligament laxity with some showing a correlation of
      increased estrogen levels with increased ligament laxity. There have also been several
      studies that investigated muscle activation and ground reaction forces as related to hormone
      levels and stages of the menstrual cycle. A recent systematic review found a lack of research
      investigating muscle activation timing as related to hormonal changes despite theories
      suggesting muscle function including timing could be an explanation as to the potential
      causes for increased ACL injury correlated with the luteal phase of the menstrual cycle. The
      aim of this study is therefore to investigate whether hormonal changes throughout the
      menstrual cycle correlate with changes in ligament laxity, motor control, muscle activation
      and timing.

      This study will be a longitudinal controlled study with two groups both containing females
      ages 18-35 years of age. The subjects will be placed into either the Experimental Group (no
      birth control) or the Control Group (on birth control) depending on the status of their
      contraceptive use.
    

Detailed description: 
      The purpose of this study is to expand on previous knowledge of the hormonal effects,
      specifically estrogen, on ligament laxity, motor control and timing of muscle activation in
      females. A significant amount of research has previously been done on the effects of estrogen
      throughout the menstrual cycle on ligament laxity with some showing a correlation of
      increased estrogen levels with increased ligament laxity. There have also been several
      studies that investigated muscle activation and ground reaction forces as related to hormone
      levels and stages of the menstrual cycle. A recent systematic review found a lack of research
      investigating muscle activation timing as related to hormonal changes despite theories
      suggesting muscle function including timing could be an explanation as to the potential
      causes for increased ACL injury correlated with the luteal phase of the menstrual cycle. The
      aim of this study is therefore to investigate whether hormonal changes throughout the
      menstrual cycle correlate with changes in ligament laxity, motor control, muscle activation
      and timing.

      This study will be a longitudinal controlled study with two groups both containing females
      ages 18-35 years of age. The subjects will be placed into either the Experimental Group (no
      birth control) or the Control Group (on birth control) depending on the status of their
      contraceptive use. To ensure subject privacy, all investigators will be blinded to which
      group the subject is in during data collection except for the primary investigator who will
      do the initial meeting with the subjects to go through the informed consent, determine phase
      of menstrual cycle, and allocate the subject to a group based on their contraceptive use.
      From this point on, the subject will be identified by a subject number and all data intake
      and analysis will be done with the number identifier. Ovulation cycle will be identified by a
      self-administered ovulation kit, hormonal samples of Estrogen will be obtained by a saliva
      sample and sent to Salimetrics lab for analysis. Dependent measures will include recording
      subject single and double-leg jump off a 12- inch block and landing on a force plate to
      record muscle timing and ground reaction forces upon landing. Electromyography will be used
      to measure muscle activation timing of the quadriceps, hamstrings, gluteus maximus, gluteal
      medius, and gastrocnemius muscles. A 3-D measuring system will record trunk and hip flexion,
      femoral internal rotation angle, and knee flexion, extension and valgus angles. Finally,
      ligament laxity will be measured with a knee arthrometer (KT1000 or similar) device to record
      tibial anterior translation. Each subject will be tested, and each variable above will be
      recorded 2 separate times corresponding to 2 main phases in the menstrual cycle (Follicular
      and Ovulatory phases).
    

Intervention name(s): No interventions
Intervention type(s): Other
Intervention description(s): Observational. Data will be gathered and analyzed on ligament laxity, EMG, kinetics and kinematics during a landing and jumping activity
Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        52 healthy females (26 on birth control, 26 not on birth control), with healthy knees aged
        18-35 years old.
      
Biospecimen description: 
      saliva samples to be frozen and sent to lab for amount of estrogen analysis