title: Blunting of adaptive responses to resistance exercise training in women over 75y.
abstract: BACKGROUND
  It is unclear how aging affects adaptive responses to resistance exercise training (RET), especially in women. We hypothesized that (i) increases in muscle mass and function after RET would be blunted in older women, and (ii) reduced 'pro-anabolic' changes in gene expression after a single bout of RE may underlie the blunting.
  
  
  METHODS
  Muscle biopsies were obtained from 9 older (76-82y) and 16 younger (19-30y) women at rest and 2.5h after RE (6×20 quadriceps maximal voluntary contractions (MVCs)) for measurement of select anabolic (e.g. IGFs, MyoD) and catabolic (e.g. MAFBx, MuRF-1) transcripts by RT-PCR. Thereafter participants undertook a supervised program of RET (4×15 MVCs 3× wk/12wk). We measured knee extensor muscle volume, fatty infiltration, and mechanical muscle quality before and after RET.
  
  
  RESULTS
  Before RET, older women were ~30% weaker (MVC 208 vs. 297N) and had ~40% less quadriceps muscle (0.97 vs. 1.54L) with greater fatty infiltration (14% vs. 10%). The most notable difference in mRNA expression after RE was for regulated in development and DNA damage response 1 (REDD1) (an endogenous suppressor of mammalian target of rapamycin (mTOR) signaling), which was depressed (-80%), but only in young women. Moreover, adaptive responses to RET were blunted in older women with respect to increases in muscle volume (+2.5% (old) vs. +6.2% (young)) and strength (+16% (old) vs. +27% (young)).
  
  
  CONCLUSIONS
  Adaptations to RET are markedly blunted in older women, perhaps in-part due to the inability to downregulate REDD1 and thus upregulate mTOR signaling after RE.
authors.affiliation: University of Edinburgh School of Clinical Sciences and Community Health, Royal Infirmary Edinburgh, 51 Little France Crescent, Edinburgh, UK. Cal.Greig@ed.ac.uk
authors.forename: C A
authors.initials: CA
authors.lastname: Greig
authors.forename: C
authors.initials: C
authors.lastname: Gray
authors.forename: D
authors.initials: D
authors.lastname: Rankin
authors.forename: A
authors.initials: A
authors.lastname: Young
authors.forename: V
authors.initials: V
authors.lastname: Mann
authors.forename: B
authors.initials: B
authors.lastname: Noble
authors.forename: P J
authors.initials: PJ
authors.lastname: Atherton
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism* / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D046188:Protein Modification, Translational; D052097:Quadriceps Muscle / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D055070:Resistance Training; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C469991:DDIT4 protein, human; D009124:Muscle Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases