The purpose of the present study was to describe the extent of the variation in some of the common characteristics of human skeletal muscle. A total of 418 biopsies was obtained from the vastus lateralis muscle of 270 healthy sedentary and 148 physically active individuals of both sexes. The lowest and highest proportion of type I muscle fiber observed were 15 and 85%, respectively. Coefficients of variation (CV) reached approximately 30% for the proportion of types I and IIA fibers and were two times higher for the proportion of type IIB fiber. The smallest and largest mean muscle fiber cross-sectional areas (CSA) were approximately 1,100 microns 2 and 9,500 microns 2, respectively. Mean CSA of the various fiber types exhibited CV of approximately 23%. CV reached 30% for the activity of creatine kinase, ranged between 28 and 41% for the glycolytic enzyme markers, and between 34 and 44% for the aerobic-oxidative enzyme markers. The mean proportion of type I fiber was lower in male than in female muscles, whereas the mean CSA of all fiber types was smaller in female than in male muscles. Levels of glycolytic enzyme markers were higher in male than in female skeletal muscles. However, activities of aerobic-oxidative enzyme markers were similar in males and females. These results reveal the existence of large interindividual variability and gender differences in the most common characteristics of the human skeletal muscle.
This paper reviews succinctly the evidence for a role of regular exercise in the prevention and the treatment of obesity and of its metabolic complications. Seventeen propositions relevant to an understanding of the topic are considered. The evidence suggests that regular exercise can be an important factor in the development of sustained negative energy balance conditions provided the volume of activity is high. This implies a program of low to moderate intensity exercise performed on an almost daily basis for at least one hour per session. To induce significant weight and fat losses and to treat overweight and obese patients, compliance to the program for several years becomes a necessity. Exercise increases lipid substrate oxidation and may favor carbohydrate intake for the same amount of energy intake. The acute effects of exercise on resting metabolic rate are well documented, but the long-term influences of exercise training seem to be small and are rapidly suppressed with the cessation of training. The obese benefits also from a regular exercise regimen in terms of improved insulin sensitivity, lipid and lipoprotein profile, and blood pressure, as well as reduced risk of death. Regular exercise, such as walking, is a healthy course of action for the overweight or the obese patients.
. Rosmond R, Bouchard C, Björntorp P (Sahlgrenska University Hospital, Göteborg, Sweden; Pennington Biomedical Research Center, LA, USA). A C‐1291G polymorphism in the α 2A ‐adrenergic receptor gene ( ADRA2A ) promoter is associated with cortisol escape from dexamethasone and elevated glucose levels. J Intern Med 2002; 251 : 252–257. Objectives. The objective of the current study was to examine the potential impact of a C → G substitution at position −1291 of the α 2A ‐adrenergic receptor gene ( ADRA2A ) promoter on obesity and estimates of insulin, glucose, and lipid metabolism as well as circulating hormones, including salivary cortisol in 284 unrelated Swedish men born in 1944. Main outcome measures. The subjects were genotyped by using PCR amplification of the promoter region of the ADRA2A gene followed by digestion with the restriction enzyme Msp I. Results. The frequencies were 0.23 for allele C and 0.77 for allele G. The observed genotype frequencies were 45.8 and 54.2% for C/G and G/G, respectively. Heterozygotes ( n =121) had significantly ( P =0.009) higher salivary cortisol levels after 0.5 mg dexamethasone compared with G/G homozygotes ( n =143). Fasting glucose was found to be significantly ( P =0.017) higher in heterozygotes than in G/G homozygotes. The latter group had also a borderline significantly ( P =0.080) higher mean diastolic blood pressure. These results were all adjusted for the potential confounding effect of body mass index (BMI) and waist‐to‐hip ratio (WHR). Other measurements such as BMI, WHR, abdominal sagittal diameter, total testosterone, insulin‐like growth factor I, serum leptin, fasting insulin and serum lipids were not different across the ADRA2A genotype groups. Conclusions. In conclusion, we have shown that an C → G polymorphism at position −1291 of the ADRA2A gene is associated with a subnormal cortisol response to dexamethasone, elevated glucose levels and perhaps increased diastolic blood pressure. The pathophysiology could involve an altered density of the α 2A ‐AR that destabilizes the sympathetic–hypothalamic–pituitary–adrenal systems in those with genetic vulnerability in the α 2A ‐adrenergic receptor gene promoter.
