title: Effect of sex hormones on neuromuscular control patterns during landing.
abstract: The purpose of the study was to investigate the effects of sex hormones across menstrual cycle phases on lower extremity neuromuscular control patterns during the landing phase of a drop jump. A repeated-measures design was utilized to examine sex hormone effects in 26 recreationally active eumenorrheic women. Varus/valgus knee angle and EMG activity from six lower extremity muscles were recorded during three drop jumps from a 50 cm platform in each phase of the menstrual cycle. Blood assays verified sex hormone levels and cycle phase. The semitendinosus muscle exhibited onset delays (p0.006) relative to ground contact during the luteal phase, and demonstrated a significant (p0.05) difference between early and late follicular phases. Muscle timing differences between the gluteus maximus and semitendinosus were decreased (p0.05) in the luteal compared to early follicular phases. These results suggest a different co-contractive behavior between the gluteus maximus and semitendinosus, signifying a shift in neuromuscular control patterns. It appears that female recreational athletes utilize a different neuromuscular control pattern for performing a drop jump sequence when estrogen levels are high (luteal phase) compared to when they are low (early follicular phase).
authors.affiliation: Department of Rehabilitation Sciences, Texas Tech University Health Sciences Center, Doctor of Science in Physical Therapy Program, Center for Clinical Rehabilitation Research, Lubbock, TX 79430-6226, USA. gregory.dedrick@ttuhsc.edu
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Dedrick
authors.forename: Phillip S
authors.initials: PS
authors.lastname: Sizer
authors.forename: Jennifer N
authors.initials: JN
authors.lastname: Merkle
authors.forename: Troy R
authors.initials: TR
authors.lastname: Hounshell
authors.forename: Jacalyn J
authors.initials: JJ
authors.lastname: Robert-McComb
authors.forename: Steven F
authors.initials: SF
authors.lastname: Sawyer
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Brismée
authors.forename: C
authors.initials: C
authors.lastname: Roger James
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D035002:Lower Extremity / Q000502:physiology*; D008597:Menstrual Cycle / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D013997:Time Factors; D016474:Weight-Bearing
chemical_list: D012739:Gonadal Steroid Hormones