Studies show higher leg strength is a predictor of balance, quality of life, and lower all-cause mortality.
Association Between Muscle Mass, Leg Strength, and Fat Mass With Physical Function in Older Adults: Influence of Age and Sex
- Danielle R. Bouchard, PhD, et al
Objective: The purposes of this study were to determine the relationship between muscle mass, muscle strength, muscle quality, and fat mass with a composite measure of physical function in older adults, and to determine whether these relations differed by age and sex.
Method: Participants consisted of 1280 adults aged ≥ 55 yr from the NHANES study. Reduced rank regression was used to identify patterns of muscle mass, muscle strength, muscle quality, and fat mass related to physical function.
Results: A single relevant pattern emerged that included leg strength and fat mass as predictors of the 7 physical function variables. The leg strength loading was significantly greater than the fat mass loading in men and women aged 55-64 and ≥75, and differed between sexes.
Conclusion: Leg strength and fat mass best predict physical function in older adults and the relative importance varies according to age and sex
J Gerontol A Biol Sci Med Sci. 2006 Jan;61(1):72-7.
Strength, but not muscle mass, is associated with mortality in the health, aging and body composition study cohort.
Newman AB, et al
Although muscle strength and mass are highly correlated, the relationship between direct measures of low muscle mass (sarcopenia) and strength in association with mortality has not been examined.
Total mortality rates were examined in the Health, Aging and Body Composition (Health ABC) Study in 2292 participants (aged 70-79 years, 51.6% women, and 38.8% black). Knee extension strength was measured with isokinetic dynamometry, grip strength with isometric dynamometry. Thigh muscle area was measured by computed tomography (CT) scan, and leg and arm lean soft tissue mass were determined by dual energy x-ray absorptiometry (DXA). Both strength and muscle size were assessed as in gender-specific Cox proportional hazards models, with age, race, comorbidities, smoking status, level of physical activity, fat area by CT or fat mass by DXA, height, and markers of inflammation, including interleukin-6, C-reactive protein, and tumor necrosis factor-alpha considered as potential confounders.
There were 286 deaths over an average of 4.9 (standard deviation = 0.9) years of follow-up. Both quadriceps and grip strength were strongly related to mortality. For quadriceps strength (per standard deviation of 38 Nm), the crude hazard ratio for men was 1.51 (95% confidence interval, 1.28-1.79) and 1.65 (95% confidence interval, 1.19-2.30) for women. Muscle size, determined by either CT area or DXA regional lean mass, was not strongly related to mortality. In the models of quadriceps strength and mortality, adjustment for muscle area or regional lean mass only slightly attenuated the associations. Further adjustment for other factors also had minimal effect on the association of quadriceps strength withmortality. Associations of grip strength with mortality were similar.
Low muscle mass did not explain the strong association of strength with mortality, demonstrating that muscle strength as a marker of muscle quality is more important than quantity in estimating mortality risk. Grip strength provided risk estimates similar to those of quadricepsstrength
Gerontology. 2002 Nov-Dec;48(6):360-8.
Knee extension strength is a significant determinant of static and dynamic balance as well as quality of life in older community-dwelling women with osteoporosis.
Carter ND, Khan KM, Mallinson A, Janssen PA, Heinonen A, Petit MA, McKay HA; Fall-Free BC Research Group.
Fall-Free BC Research Group: BC Women’s Hospital and Health Centre Osteoporosis Program and Faculty of Medicine (Department. of Family Practice), University of British Columbia, Vancouver, BC, Canada.
Determinants of balance have not been well studied in women with osteoporosis yet falls are the major cause of fracture in this population.
To describe the associations among knee extension strength, medication history, medical history, physical activity and both static and dynamic balance in women diagnosed with osteoporosis.
We assessed health history, current medication and quality of life by questionnaire in 97 community-dwelling women with osteoporosis. Static balance was measured by computerized dynamic posturography (Equitest), dynamic balance by timed figure-eight run, and knee extensionstrength by dynamometry.
The 97 participants (mean (SD) age 69 (3.2) years) had a mean lumbar spine BMD of T = -3.3 (0.7) and total hip BMD of -2.9 (0.4). In stepwise linear regression, the significant determinants of static balance that explained 18% of total variance were knee extension strength (10%, p < 0.001), age (5%, p < 0.01) and tobacco use (3%, p < 0.05). The significant predictors of dynamic balance were knee extension strength (26%, p < 0.001), medications (6%, p < 0.05), age (4%, p < 0.05), height (4%, p < 0.001), as well as years of estrogen use (2%), tobacco use (2%) and weight (2%) (all p < 0.05). Knee extension strength was also associated with quality of life (r(2) = 0.12, p < 0.001). Based on these models, a 1 kg/cm ( approximately 3%) increase in mean knee extension strength was associated with 1.2, 2.4 and 3.4% greater static balance, dynamic balance and quality of life, respectively.
Knee extension strength is a significant determinant of performance on static and dynamic balance tests in 65- to 75-year-old women with osteoporosis. In this cross-sectional study, knee extension strength explained a greater proportion of the variance in balance tests than did age. Investigation into the effect of intervention to improve knee extension strength in older women with osteoporosis is warranted.
Copyright 2002 S. Karger AG, Basel
BMJ. 2008 Jul 1;337:a439. doi: 10.1136/bmj.a439.
Association between muscular strength and mortality in men: prospective cohort study.
Department of Biosciences and Nutrition at NOVUM, Unit for Preventive Nutrition, Karolinska Institutet, Huddinge, Sweden. email@example.com
To examine prospectively the association between muscular strength and mortality from all causes, cardiovascular disease, and cancer in men.
Prospective cohort study.
Aerobics centre longitudinal study.
8762 men aged 20-80.
MAIN OUTCOME MEASURES:
All cause mortality up to 31 December 2003; muscular strength, quantified by combining one repetition maximal measures for leg and bench presses and further categorised as age specific thirds of the combined strength variable; and cardiorespiratory fitness assessed by a maximal exercise test on a treadmill.
During an average follow-up of 18.9 years, 503 deaths occurred (145 cardiovascular disease, 199 cancer). Age adjusted death rates per 10,000 person years across incremental thirds of muscular strength were 38.9, 25.9, and 26.6 for all causes; 12.1, 7.6, and 6.6 for cardiovascular disease; and 6.1, 4.9, and 4.2 for cancer (all P<0.01 for linear trend). After adjusting for age, physical activity, smoking, alcohol intake, body mass index, baseline medical conditions, and family history of cardiovascular disease, hazard ratios across incremental thirds of muscular strength for all cause mortality were 1.0 (referent), 0.72 (95% confidence interval 0.58 to 0.90), and 0.77 (0.62 to 0.96); for death from cardiovascular disease were 1.0 (referent), 0.74 (0.50 to 1.10), and 0.71 (0.47 to 1.07); and for death from cancer were 1.0 (referent), 0.72 (0.51 to 1.00), and 0.68 (0.48 to 0.97). The pattern of the association between muscular strength and death from all causes and cancer persisted after further adjustment for cardiorespiratory fitness; however, the association between muscular strength and death from cardiovascular disease was attenuated after further adjustment for cardiorespiratory fitness.
Muscular strength is inversely and independently associated with death from all causes and cancer in men, even after adjusting for cardiorespiratory fitness and other potential confounders