Skeletal muscle fatigue, strength, and quality in the elderly: the Health ABC Study

1 Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh, Pittsburgh; 2 Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh; 3 Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh; 4 Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania; 5 Section on Geriatrics, Wake Forest University School of Medicine, Winston-Salem, North Carolina; 6 Department of Preventive Medicine, Health Science Center, University of Tennessee, Memphis, Tennessee; 7 Laboratory of Epidemiology, Biometry, and Demography, National Institute on Aging, National Institutes of Health, Bethesda, Maryland; and 8 Department of Epidemiology and Biostatistics, University of California, San Francisco, California Submitted 11 November 2004 ; accepted in final form 15 February 2005 We examined the muscle fatigue characteristics in older men and women and determined whether these were related to the size, strength, or quality of muscle. A total of 1,512 men and women aged 70–79 yr from the Health, Aging, and Body Composition Study participated in this study. Muscle cross-sectional area and attenuation were determined with computed tomography. Skeletal muscle fatigue and strength (peak torque) of the knee extensors and flexors were measured using isokinetic dynamometry. Men were more fatigue resistant than women for both knee extension (fatigue index: 70.4 ± 15.3 vs. 66.9 ± 14.3%; P < 0.05) and knee flexion (67.9 ± 16.4 vs. 64.9 ± 17.6%; P < 0.05). Peak torque and muscle quality (specific torque) were higher in men than women for knee extension (99.6 ± 28.2 vs. 63.0 ± 16.8 N·m and 1.62 ± 0.43 vs. 1.51 ± 0.39 N·m/cm 2 ; both P < 0.05) and for knee flexion (74.0 ± 26.4 vs. 49.6 ± 15.9 N·m and 2.47 ± 1.29 vs. 2.22 ± 0.78 N·m/cm 2 ; both P < 0.05). Total work and power output was greater in men compared with women for both the quadriceps (1,353 ± 451 vs. 832 ± 264 J and 87.7 ± 33.5 vs. 53.3 ± 19.2 W; both P < 0.05) and the hamstrings (741 ± 244 vs. 510 ± 141 J and 35.4 ± 16.0 vs. 23.7 ± 10.2 W; both P < 0.05). In both genders, the quadriceps was able to perform more work with greater power compared with the hamstrings. Those who were stronger actually had greater fatigue after adjusting for age, race, physical activity, and total body fat. In conclusion, older men were more fatigue resistant than wome