GRIP WORK ESTIMATION DURING SUSTAINED MAXIMAL CONTRACTION: VALIDITY AND RELATIONSHIP WITH DEPENDENCY AND INFLAMMATION IN ELDERLY PERSONS

Objectives: To validate muscle endurance estimation and to examine relationships with dependency and inflammation in elderly persons. Design: Cross sectional validation and explorative study. Setting: Hospitalized geriatric patients and community-dwelling controls. Participants: 91 elderly patients (aged 83+/-5 years), 100 elderly controls (aged 74+/-5 years) and 100 young controls (aged 23+/-3 years). Measurements: 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. Conclusion: 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.