title: Grip work estimation during sustained maximal contraction: validity and relationship with dependency and inflammation in elderly persons.
abstract: OBJECTIVE
  To validate muscle endurance estimation and to examine relationships with dependency and inflammation in elderly persons.
  
  
  METHODS
  Cross sectional validation and explorative study.
  
  
  METHODS
  Hospitalized geriatric patients and community-dwelling controls.
  
  
  METHODS
  91 elderly patients (aged 83±5 years), 100 elderly controls (aged 74±5 years) and 100 young controls (aged 23±3 years).
  
  
  METHODS
  Grip strength (GS) was recorded continuously during sustained maximal contraction until exhaustion. Fatigue resistance (FR) was expressed as the time during which GS drops to 50% of its maximum. Grip work (GW) was estimated as GW=GS*0.75*FR, and compared to the measured GW. In the elderly participants, relationships (controlling for age and physical activity) of GS, FR, GW and GW corrected for body weight (GW/BW) with dependency (Katz-scale) and inflammation (circulating IL-6 and TNF-alpha) were analyzed.
  
  
  RESULTS
  Excellent correlation between estimated and measured GW was found (r=0.98, p<0.001). The method error coefficient of variance was 10% for all participants; 7% for all elderly and 8% for young controls. Better GS, FR, GW and GW/BW was significantly related with less dependency (all p<0.05 or p<0.01, except for FR in the male) and with lower circulating IL-6 (all p<0.05 or p<0.01, except for GS in both genders). Higher IL-6 was significantly related to worse dependency (p<0.01). No significant relationships with TNF-alpha were found.
  
  
  CONCLUSIONS
  GW estimation is a valid parameter reflecting muscle endurance in elderly persons presenting diverse clinical conditions. GW is significantly related to both dependency and circulating IL-6, and is a promising outcome parameter in comprehensive geriatric assessment.
authors.affiliation: Gerontology and Frailty in Ageing Research Department, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium. ivan.bautmans@vub.ac.be
authors.forename: I
authors.initials: I
authors.lastname: Bautmans
authors.forename: O
authors.initials: O
authors.lastname: Onyema
authors.forename: K
authors.initials: K
authors.lastname: Van Puyvelde
authors.forename: S
authors.initials: S
authors.lastname: Pleck
authors.forename: T
authors.initials: T
authors.lastname: Mets
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D016207:Cytokines / Q000097:blood; D005260:Female; D015577:Geriatric Assessment; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000150:complications*; D018836:Inflammation Mediators / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue; D018908:Muscle Weakness / Q000209:etiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology; D015203:Reproducibility of Results; D012737:Sex Factors; D014409:Tumor Necrosis Factor-alpha / Q000097:blood; D055815:Young Adult
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha