title: Maximal force and tremor changes across the menstrual cycle.
abstract: OBJECTIVE
  Sex hormones have profound effects on the nervous system in vitro and in vivo. The present study examines the effect of the menstrual cycle on maximal isometric force (MVC) and tremor during an endurance task.
  
  
  METHODS
  Nine eumenorrheic females participated in five study visits across their menstrual cycle. In each menstrual phase, an MVC and an endurance task to failure were performed. Tremor across the endurance task was quantified as the coefficient of variation in force and was assessed in absolute time and relative percent time to task failure.
  
  
  RESULTS
  MVC decreases 23% from ovulation to the mid luteal phase of the menstrual cycle. In absolute time, the mid luteal phase has the highest initial tremor, though the early follicular phase has substantially higher tremor than other phases after 150 s of task performance. In relative time, the mid luteal phase has the highest level of tremor throughout the endurance task.
  
  
  CONCLUSIONS
  Both MVC and tremor during an endurance task are modified by the menstrual cycle. Performance of tasks and sports which require high force and steadiness to exhaustion may be decreased in the mid luteal phase compared to other menstrual phases.
authors.affiliation: Human Research and Engineering Directorate, RDRL-HRS-B, US Army Research Laboratory, Aberdeen Proving Ground, MD, USA. matthew.s.tenan.civ@mail.mil.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Tenan
authors.affiliation: Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.|Department of Nutrition, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Hackney
authors.affiliation: Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Griffin
mesh_terms: D000293:Adolescent; D000328:Adult; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D006801:Humans; D008597:Menstrual Cycle / Q000502:physiology*; D008598:Menstruation / Q000502:physiology*; D013647:Task Performance and Analysis; D014202:Tremor / Q000378:metabolism* / Q000503:physiopathology*; D055815:Young Adult
chemical_list: D004967:Estrogens
keywords: Estrogen; Fatigue; Maximal force; Menstrual cycle; Progesterone; Tremor