W. W. Campbell

Sarcopenia and Age-Related Changes in Body Composition and Functional Capacity

Advancing adult age is associated with profound changes in body composition. One of the most prominent of these changes is sarcopenia, defined as the age-related loss in skeletal muscle mass, which results in decreased strength and aerobic capacity and thus functional capacity. Sarcopenia is also closely linked to age-related losses in bone mineral, basal metabolic rate and increased body fat content. Through physical exercise and training, especially resistance training, it may be possible to prevent sarcopenia and the remarkable array of associated abnormalities, such as type II diabetes, coronary artery disease, hypertension, osteoporosis and obesity. Using an exercise program of sufficient frequency, intensity and duration, it is quite possible to increase muscle strength and endurance at any age. There is no pharmacological intervention that holds a greater promise of improving health and promoting independence in the elderly than does exercise.

Aged human muscle demonstrates an altered gene expression profile consistent with an impaired response to exercise

The gene expression profile of skeletal muscle from healthy older (62-75 years old) compared with younger (20-34 years old) men demonstrated elevated expression of genes typical of a stress or damage response, and decreased expression of a gene encoding a DNA repair/cell cycle checkpoint protein. Although the expression of these genes was relatively unaffected by a single bout of resistance exercise in older men, acute exercise altered gene expression in younger men such that post-exercise gene expression in younger men was similar to baseline gene expression in older men. The lack of response of muscle from older subjects to resistance exercise was also apparent in the expression of the inflammatory response gene IL-1beta, which did not differ between the age groups at baseline, but increased within 24 h of the exercise bout only in younger subjects. Other genes with potentially important roles in the adaptation of muscle to exercise, specifically in the processes of angiogenesis and cell proliferation, showed a similar response to exercise in older compared with younger subjects. Only one gene encoding the multifunctional, early growth response transcription factor EGR-1, showed an opposite pattern of expression in response to exercise, acutely decreasing in younger and increasing in older subjects. These results may provide a molecular basis for the inherent variability in the response of muscle from older as compared with younger individuals to resistance training.

Effects of a moderate glycemic meal on exercise duration and substrate utilization

PURPOSEnTo determine whether eating a breakfast cereal with a moderate glycemic index could alter substrate utilization and improve exercise duration.nnnMETHODSnSix active women (age, 24 +/- 2 yr; weight, 62.2 +/- 2.6 kg; VO(2peak), 46.6 +/- 3.8 mL x kg(-1) x min(-1)) ate 75 g of available carbohydrate in the form of regular whole grain rolled oats (RO) mixed with 300 mL of water or water alone (CON). The trials were performed in random order and the meal or water was ingested 45 min before performing cycling exercise to exhaustion (60% of VO(2peak)). Blood samples were drawn for glucose, glucose kinetics, free fatty acids (FFA), glycerol, insulin, epinephrine (EPI), and norepinephrine (NE) determination. A muscle biopsy was obtained from the vastus lateralis muscle before the trial and immediately after exercise for glycogen determination. Glucose kinetics (Ra) were determined using a [6,6-(2)H] glucose tracer.nnnRESULTSnCompared with CON, plasma FFA and glycerol levels were suppressed (P < 0.05) during the first 120 min of exercise for the RO trial. Respiratory exchange ratios (RER) were also higher (P < 0.05) for the first 120 min of exercise for the RO trial. At exhaustion, glucose, insulin, FFA, glycerol, EPI, NE, RER, and muscle glycogen were not different between trials. Glucose Ra was greater (P < 0.05) during the RO trial compared with CON (2.36 +/- 0.22 and 1.92 +/- 0.27 mg x kg(-1) x min(-1), respectively). Exercise duration was 5% longer during RO, but the mean times were not significantly different (253.6 +/- 6 and 242.0 +/- 15 min, respectively).nnnCONCLUSIONSnIncreased hepatic glucose output before fatigue provides some evidence of glucose sparing after the breakfast cereal trial. However, exercise duration was not significantly altered, possibly because of the sustained suppression of lipid metabolism and increased carbohydrate utilization throughout much of the exercise period.