Sarcopenia is defined as the loss of skeletal muscle mass and strength with aging. Loss of muscle tissue begins around age 50, but becomes more dramatic after age 60. Loss of muscle fiber number is the principal cause of sarcopenia, although fiber atrophy - particularly among type II fibers - is also involved. Denervation results in the loss of motor units and thus, muscle fibers. A decrease in the production of anabolic hormones such as testosterone, growth hormone and insulin-like growth factor-1 impairs the capacity of skeletal muscle to incorporate amino acids and synthesize proteins. An increase in the release of catabolic agents, specifically interleukin-6, amplifies the rate of muscle wasting among the elderly. Sports Med. 2004;34(12):809-24.

Smoking, low vitamin D, low testosterone all help cause sarcopenia.

Sarcopenia Linked to Low Birth Weight: Epidemiological studies have shown that men and women who grew less well in early life have lower muscle strength. In a study of 1401 elderly, grip strength was most strongly associated with birth weight in men (r = 0.19, p <.001) and women (r = 0.16, p <.001). The associations with infant growth were weakened after allowing for adult size. Does sarcopenia originate in early life? Findings from the hertfordshire cohort study. Sayer AA, Syddall HE, Gilbody HJ, Dennison EM, Cooper C. Southampton UK J Gerontol A Biol Sci Med Sci. 2004 Sep;59(9):M930-4

Resistance Training Called Most Effective for Sarcopenia: In a review of the research through May, 2004, the author concludes testosterone replacement in elderly hypogonadal men produces only modest increases in muscle mass and strength. Higher doses have not been given for fear of accelerating prostate cancer. Growth hormone replacement in elderly subjects produces a high incidence of side-effects and does not increase strength. Stimulating the growth hormone/insulin-like growth factor (IGF) pathway holds promise. Resistance training remains the most effective intervention. Adequate nutrition is sometimes a problem. Interventions for sarcopenia and muscle weakness in older people. Borst SE. Gainesville VA. Age Ageing. 2004 Sep 22

Essential Amino Acid Supplement Protects Muscles in Prolonged Bedrest: In a randomized study of 28 day bedrest inactivity, muscle biopsies and blood samples showed that the group given 16.5 g of essential amino acids and 30 g of carbohydrate three times a day preserved lean leg +0.2 kg, vs. -0.4 kg in the regular food group. Strength loss was less with the essential amino acids -8.8 kg vs. -17.8 kg. Essential amino acid and carbohydrate supplementation ameliorates muscle protein loss in humans during 28 days bedrest. Paddon-Jones D, Sheffield-Moore M, Urban RJ, Sanford AP, Aarsland A, Wolfe RR, Ferrando AA. Galveston, Texas. J Clin Endocrinol Metab. 2004 Sep;89(9):4351-8.

Smoking, Low Vitamin D and Testosterone Bad for Muscles in Middle-Age and Elderly: In a study of 845 Frenchmen ages 45-85, arm and leg muscle mass decreased with age (r = -0.29, P < 0.0001). Current smokers had less mass than never smokers (-3.2%; P < 0.003). Muscle mass increased with the intensity of physical activity at work (P < 0.001) and regular leisure exercise (P < 0.03). Men whose values for testosterone and vitamin D were low had less mass. Hormonal and lifestyle determinants of appendicular skeletal muscle mass in men: the MINOS study. Szulc P, Duboeuf F, Marchand F, Delmas PD. Lyon, France. Am J Clin Nutr. 2004 Aug;80(2):496-503

Vegetable Anti-Oxidants Preserve Muscle in Elderly: In a study of 669 non-disabled women ages 70 to 79, higher plasma concentrations of alpha-carotene, beta-carotene, beta-cryptoxanthin, and lutein/zeaxanthin were associated with reduced risk of low grip, hip, and knee strength. Higher intake was very protecting when comparing the highest vs. lowest quarter in total carotenoids for low grip strength (OR) 0.34), low hip strength (OR 0.28), and low knee strength (OR 0.45), and there was an independent association in the highest vs. lowest quartile of alpha-tocopherol (vitamin E) for low grip strength (OR 0.44) and low knee strength (OR 0.52). Carotenoid and vitamin E status are associated with indicators of sarcopenia among older women living in the community. Semba RD, Blaum C, Guralnik JM, Moncrief DT, Ricks MO, Fried LP. Johns Hopkins. Aging Clin Exp Res. 2003 Dec;15(6):482-7.

Caloric Restriction Preserves Muscles: Rats fed only 60% as much as normal rats do when allowed to eat as much as they want had less muscle fiber loss with age, and this conservation of fiber number reduced muscle mass loss. Early-onset calorie restriction conserves fiber number in aging rat skeletal muscle. McKiernan SH, Bua E, McGorray J, Aiken J. University of Wisconsin. FASEB J. 2004 Mar;18(3):580-1

38% of Elderly with Vitamin D Receptor Gene Variation Lose More Muscle Mass: The vitamin D receptor (VDR) have three difference common (FokI) polymorphisms [FF (38%), Ff (48%), and ff (14 %)] and three BsmI polymorphisms [BB (25%), Bb (38%), and bb (37%)]. In a study of older men, the BsmI polymorphism was not associated with muscle mass in any analysis; however, the FokI polymorphism was significantly associated with total muscle mass (e.g., FF = 57.6, Ff = 59.4, ff = 59.4 kg; p <.02). There was a 2.17-fold higher risk for sarcopenia (4 pounds less muscle) in FF homozygotes (p =.03) compared to men with one or more f alleles. Vitamin D receptor genotype is associated with fat-free mass and sarcopenia in elderly men. Roth SM, Zmuda JM, Cauley JA, Shea PR, Ferrell RE. University of Pittsburgh. J Gerontol A Biol Sci Med Sci. 2004 Jan;59(1):10-5