Jennifer M. Hootman, Shannon FitzGerald, Carol A. Macera and Steven N. Blair
The purpose of this study was to investigate the gender-specific longitudinal association between quadriceps strength and self-reported, physician-diagnosed hip or knee osteoarthritis (OA).
Subjects were 3081 community-dwelling adults who were free of OA, joint symptoms and injuries, completed a maximum treadmill exercise test, had isokinetic knee extension and flexion and isotonic leg press strength measurements taken at baseline and returned at least one written follow-up survey. Multivariate logistic regression was used to estimate odds ratios and 95% confidence intervals.
Women with moderate or high isokinetic quadriceps strength had a significantly reduced risk (55% to 64%) of hip or knee OA. A similar, nonsignificant trend was noted among men. Moderate isotonic leg press strength was protective for hip or knee osteoarthritis among men only.
These results suggest that quadriceps weakness is an independent and modifiable risk factor for lower extremity OA, particularly among women.
Shannon J. FitzGerald, Carolyn E. Barlow, James B. Kampert, James R. Morrow Jr., Allen W. Jackson and Steven N. Blair
The beneficial effects of cardiorespiratory fitness on mortality are well known; however, the relation of muscular fitness, specifically muscular strength and endurance, to mortality risk has not been thoroughly examined. The purpose of the current study is to determine if a dose-response relation exists between muscular fitness and mortality after controlling for factors such as age and cardiorespiratory fitness.
The study included 9105 men and women, 20–82 years of age, in the Aerobics Center Longitudinal Study who have completed at least one medical examination at the Cooper Clinic in Dallas, TX between 1981 and 1989. The exam included a muscular fitness assessment, based on 1-min sit-up and 1-repetition maximal leg and bench press scores, and a maximal treadmill test. We conducted mortality follow-up through 1996 primarily using the National Death Index, with a total follow-up of 106,046 person-years. All-cause mortality rates were examined across low, moderate, and high muscular fitness strata.
Mortality was confirmed in 194 of 9105 participants (2.1%). The age- and sex-adjusted mortality rate of those in the lowest muscular fitness category was higher than that of those in the moderate fitness category (26.8 vs. 15.3 per 10,000 person-years, respectively). Those in the high fitness category had a mortality rate of 20.6 per 10,000 person-years. The moderate and high muscular fitness groups had relative risks of 0.64 (95%CI = 0.44–0.93) and 0.80 (95%CI = 0.49–1.31), adjusting for age, health status, body mass index, cigarette smoking, and cardio-respiratory fitness when compared with the low muscular fitness group.
Mortality rates were lower for individuals with moderate/high muscular fitness compared to individuals with low muscular fitness. These findings warrant further research to confirm the apparent threshold effect between low and moderate/high muscular fitness and all-cause mortality.