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August 2003

Muscle mass

Prevalence of sarcopenia and predictors of skeletal muscle mass in healthy, older men and women.

BACKGROUND: Sarcopenia refers to the loss of skeletal muscle mass with age. The objective of this study was to determine the prevalence of sarcopenia in a population of older, community-dwelling research volunteers. METHODS: Appendicular skeletal muscle mass was measured by dual x-ray absorptiometry in 195 women aged 64 to 93 years and 142 men aged 64 to 92 years. We defined sarcopenia as appendicular skeletal muscle mass/height(2) (square meters) less than two standard deviations below the mean for young, healthy reference populations. We used two different reference populations and compared prevalence in our population to that reported in previous studies. Body mass index (BMI) was calculated and physical activity and performance were measured with the Physical Activity Scale for the Elderly, the Short Physical Performance Battery, and the Physical Performance Test. We measured health-related quality of life by using the SF-36 general health survey. Serum estrone, estradiol, sex hormone-binding globulin, parathyroid hormone and 25-hydroxy vitamin D were measured in all participants and bioavailable testosterone was measured only in men. Leg press strength and leg press power were determined in men. RESULTS: The prevalence of sarcopenia in our cohort was 22.6% in women and 26.8% in men. A subgroup analysis of women and men 80 years or older revealed prevalence rates of 31.0% and 52.9%, respectively. In women, skeletal muscle mass correlated significantly with BMI and levels of serum estrone, estradiol and 25-hydroxy vitamin D; in men, it correlated significantly with BMI, single leg stance time, leg press strength, leg press power, SF-36 general health score, Physical Performance Test total score, and bioavailable testosterone levels. With the use of linear regression analysis, BMI was the only predictor of appendicular skeletal muscle mass in women, accounting for 47.9% of the variance (p <.05). In men, BMI accounted for 50.1%, mean strength accounted for 10.3%, mean power accounted for 4.1%, and bioavailable testosterone accounted for 2.6% of the variance in appendicular skeletal muscle mass (p <.05). CONCLUSIONS: Sarcopenia is common in adults over the age of 65 years and increases with age. BMI is a strong predictor of skeletal muscle mass in women and men. Strength, power and bioavailable testosterone are further contributors in men. These data suggest that interventions to target nutrition, strength training and testosterone replacement therapy should be further investigated for their role in preventing muscle loss with age.

J Gerontol A Biol Sci Med Sci 2002 Dec;57(12):M772-7

Epidemiology of sarcopenia among the elderly in New Mexico.

Muscle mass decreases with age, leading to "sarcopenia," or low relative muscle mass, in elderly people. Sarcopenia is believed to be associated with metabolic, physiologic and functional impairments and disability. Methods of estimating the prevalence of sarcopenia and its associated risks in elderly populations are lacking. Data from a population-based survey of 883 elderly Hispanic and non-Hispanic white men and women living in New Mexico (the New Mexico Elder Health Survey, 1993 to 1995) were analyzed to develop a method for estimating the prevalence of sarcopenia. An anthropometric equation for predicting appendicular skeletal muscle mass was developed from a random subsample (n = 199) of participants and was extended to the total sample. Sarcopenia was defined as appendicular skeletal muscle mass (kg)/height2 (m2) being less than two standard deviations below the mean of a young reference group. Prevalences increased from 13% to 24% in persons under 70 years of age to >50% in persons over 80 years of age, and were slightly greater in Hispanics than in non-Hispanic whites. Sarcopenia was significantly associated with self-reported physical disability in both men and women, independent of ethnicity, age, morbidity, obesity, income and health behaviors. This study provides some of the first estimates of the extent of the public health problem posed by sarcopenia.

Am J Epidemiol 1998 Apr 15;147(8):755-63

Predictors of skeletal muscle mass in elderly men and women.

BACKGROUND: Elderly men and women lose muscle mass and strength with increasing age. Decreased physical activity, hormones, malnutrition and chronic disease have been identified as factors contributing to this loss. There are few data, however, for their multivariate associations with muscle mass and strength. This study analyzes these associations in a cross-sectional sample of elderly people from the New Mexico Aging Process Study. METHODS: Data collected in 1994 for 121 male and 180 female volunteers aged 65 to 97 years of age enrolled in The New Mexico Aging Process Study were analyzed. Body composition was measured using dual energy X-ray absorptiometry; dietary intake from three day food records; usual physical activity by questionnaire; health status from annual physical examinations; and serum testosterone, estrone, sex-hormone binding globulin (SHBG), and insulin-like growth factor (IGF1) from radioimmunoassays of fasting blood samples. Statistical analyses included partial correlation and stepwise multiple regression. RESULTS: The muscle mass and strength (adjusted for knee height) decreased with increasing age in both sexes. The muscle mass was significantly associated with serum free-testosterone, physical activity, cardiovascular disease and IGF1 in the men. In the women, the muscle mass was significantly associated with total fat mass and physical activity. Age was not associated significantly with muscle mass after controlling for these variables. Grip strength was associated with age independent of muscle mass in both sexes. Estrogen (endogenous and exogenous) was not associated with muscle mass or strength in women. CONCLUSIONS: Age-related loss of muscle mass and strength occurs in relatively healthy, well-nourished elderly men and women and has a multifactorial basis. Sex hormone status is an important factor in men but not in women. Physical activity is an important predictor of muscle mass in both sexes.

Mech Ageing Dev 1999 Mar 1;107(2):123-36

Exercise training guidelines for the elderly.

The capacity of older men and women to adapt to increased levels of physical activity is preserved, even in the most elderly. Aerobic exercise results in improvements in functional capacity and reduced risk of developing Type II diabetes in the elderly. High-intensity resistance training (above 60% of the one repetition maximum) has been demonstrated to cause large increases in strength in the elderly. In addition, resistance training result in significant increases in muscle size in elderly men and women. Resistance training has also been shown to significantly increase energy requirements and insulin action of the elderly. PURPOSE: We have recently demonstrated that resistance training has a positive effect on multiple risk factors for osteoporotic fracture in previously sedentary postmenopausal women. METHODS: Because the sedentary lifestyle of a long-term care facility may exacerbate losses of muscle function, we have applied this same training program to frail, institutionalized elderly men and women. RESULTS: In a population of 100 nursing home residents, a randomly assigned high-intensity strength-training program resulted in significant gains in strength and functional status. In addition, spontaneous activity, measured by activity monitors, increased significantly in those participating in the exercise program whereas there was no change in the sedentary control group. Before the strength training intervention, the relationship of whole body potassium and leg strength was seen to be relatively weak (r2 = 0.29, P < 0.001), indicating that in the very old, muscle mass is an important but not the only determining factor of functional status. CONCLUSIONS: Thus, exercise may minimize or reverse the syndrome of physical frailty, which is so prevalent among the most elderly. Because of their low functional status and high incidence of chronic disease, there is no segment of the population that can benefit more from exercise than the elderly.

Med Sci Sports Exerc 1999 Jan;31(1):12-17

Creatine supplementation improves muscular performance in older men.

PURPOSE: Creatine supplementation has been shown to enhance muscle strength and power after only five to seven days in young adults. Creatine supplementation could therefore benefit older individuals because aging is associated with a decrease in muscle strength and explosive power. METHODS: We examined the effects of seven days of creatine supplementation in normally active older men (59 to 72 year) by using a double-blind, placebo-controlled design with repeated measures. After a three-week familiarization period to minimize learning effects, a battery of tests was completed on three occasions separated by seven days (T1, T2, and T3). After T1, subjects were matched and randomly assigned into creatine (N = 10) and placebo (N = 8) groups. After T2, subjects consumed supplements (0.3 g x kg(-1) x d(-1)) for seven days until T3. All subjects were tested for maximal dynamic strength (one-repetition maximum leg press and bench press), maximal isometric strength (knee extension/flexion), upper- and lower-body explosive power (6 x 10-s sprints on a cycle ergometer), and lower-extremity functional ability (timed sit-stand test and tandem gait test). Body composition was assessed via hydrostatic weighing, and blood samples were obtained to assess renal and hepatic responses and muscle creatine concentrations. RESULTS: No significant increases in any performance measures were observed from T1 to T2 with the exception of isometric right-knee flexion in the placebo group indicating stability in the testing protocols. Significant group-by -time interactions indicated the responses from T2 to T3 were significantly greater (P < or= 0.05) in the creatine compared with the placebo group, respectively, for body mass (1.86 and -1.01 kg), fat-free mass (2.22 and 0.00 kg), maximal dynamic strength (7 to 8 and 1% to 2%), maximal isometric strength (9 to 15 and -6% to 1%), lower-body mean power (11% and 0%) and lower-extremity functional capacity (6 to 9 and 1% to 2%). No adverse side effects were observed. CONCLUSION: These data indicate that seven days of creatine supplementation is effective at increasing several indices of muscle performance, including functional tests in older men without adverse side effects. Creatine supplementation may be a useful therapeutic strategy for older adults to attenuate loss in muscle strength and performance of functional living tasks.

Med Sci Sports Exerc 2002 Mar;34(3):537-43

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