title: Time-course of muscle growth, and its relationship with muscle strength in both young and older women.
abstract: OBJECTIVE
  The time-course for changes in muscle size and strength is not well understood, particularly in women. In addition, contributions of muscle size to strength are commonly assessed utilizing a pre-post change score; however, a more appropriate within-subject correlational analysis has never been used.
  
  
  METHODS
  To determine the time-course for thigh muscle size and strength in young (aged 18-25 years) and older (aged 50-65 years) women, and determine the relationship between size and strength after 8 weeks of training carried our three times per week.
  
  
  RESULTS
  Anterior muscle thickness at the 50% site increased after 1 week of training, and exceeded the measurement error after 2 weeks (mean difference 0.23 cm, 95% CI 0.12-0.34 cm). Anterior muscle thickness at the 70% site increased and exceeded the measurement error after 2 weeks (mean difference 0.30 cm, 95% CI 0.15-0.45 cm). Posterior muscle thickness at the 50% site increased after 1 week of training, and exceeded the measurement error after 2 weeks (mean difference 0.24 cm, 95% CI 0.03-0.44 cm). Posterior muscle thickness at the 70% site increased after 1 week, and exceeded the measurement error after 3 weeks (mean difference 0.21 cm, 95% CI 0.07-0.35 cm). Muscle strength, assessed through one-repetition maximum, increased by 2 weeks in most measurements, and the within-subject variance explained by changes in muscle size ranged between 9% and 35%.
  
  
  CONCLUSIONS
  Muscle growth appeared to occur early into a training program in both young and older women. Furthermore, although a large portion remains unexplained, the variance in muscle strength explained by muscle size is greater than previous studies not utilizing within-subject correlations. Geriatr Gerontol Int 2017; 17: 2000-2007.
authors.affiliation: Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, University, Mississippi, USA.
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Loenneke
authors.affiliation: Department of Exercise Science, Lindenwood Belleville, Belleville, Illinois, USA.
authors.forename: Lindy M
authors.initials: LM
authors.lastname: Rossow
authors.affiliation: Department of Exercise Science, Lindenwood Belleville, Belleville, Illinois, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Fahs
authors.affiliation: Texas Wesleyan University, Fort Worth, Texas, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Thiebaud
authors.affiliation: Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, University, Mississippi, USA.
authors.forename: J
authors.initials: J
authors.lastname: Grant Mouser
authors.affiliation: University of Oklahoma, Norman, Oklahoma, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Bemben
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008875:Middle Aged; D024510:Muscle Development; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000254:growth & development*; D009929:Organ Size; D055070:Resistance Training; D055815:Young Adult
keywords: female; hypertrophy; muscle size; resistance exercise