The purpose of this paper is (a) to present brief historical notes on the concept of race, (b) to define race in the context of evolutionary biology, (c) to quantify the extent of human genetic variation, (d) to estimate genetic differences within and between races, and (e) to comment on the implications of these concepts for racial differences in sport performance. Research shows that genetic variation in gene products and in the non-coding sequence of DNA is quite extensive in humans. Variation is found more frequently in non-coding DNA sequences than in coding exons, and while this variation does not influence the primary structure of the proteins, it may have considerable impact on gene expression. However, much of that genetic variation is shared by all human beings, and only about 10% is specific to races or populations within races. At this time, it is not possible to conclude satisfactorily the significance of these modest racial differences in genetic variation for racial differences in performance. It may turn out that this low level of genetic heterogeneity may have considerable implication for performance.
Objective: There is considerable evidence that cortisol secretion is associated with obesity. The regulation of the 5‐hydroxytryptamine receptor 2A ( 5‐HT 2A ) gene might play an essential role because it is involved in the control of cortisol secretion. Therefore, we examined the potential impact of the 5‐HT 2A −1438G/A promoter polymorphism 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. Research Methods and Procedures: The subjects were genotyped by using polymerase chain reaction amplification of the promoter region of the gene for 5‐HT 2A followed by digestion of the reaction product with the restriction enzyme Msp I. Results: The frequencies were 0.39 for allele − 1438A and 0.61 for allele − 1438G . Homozygotes for the − 1438G allele had, in comparison with − 1438A/A subjects, higher body mass index, waist‐to‐hip ratio, and abdominal sagittal diameter. Moreover, cortisol escape from 0.25‐mg dexamethasone suppression was found in subjects with the − 1438A/G genotype. Serum leptin, fasting insulin, and glucose, as well as serum lipids, were not different across the − 1438G/A genotype groups. Discussion: From these results, we suggest the possibility that an abnormal production rate of the 5‐HT 2A gene product might lead to the development of abdominal obesity. The pathophysiology could involve stress factors that destabilize the serotonin‐hypothalamic‐pituitary‐adrenal system in those with genetic vulnerability in the serotonin receptor gene.
THE ROLE of inherited and nongenetic factors in individual differences observed in the level of sc fat on the trunk and abdominal areas and in the abdominal visceral deposit is reviewed. First, the metabolic and clinical implications of variation in body fat topography are summarized. Second, the results of genetic epidemiology studies on the heritability and other evidence for a role of the genotype in the amount of truncal-abdominal sc fat and abdominal visceral fat are reviewed. Third, the impact of total body fat, age, and gender on regional fat distribution is highlighted. Fourth, adipose tissue lipoprotein lipase activity is considered as a determinant of fat topography, with a discussion of site and gender differences, the effects of steroid hormones, and evidence from genetic epidemiology. Fifth, the contribution of adipose tissue lipolysis is reviewed with an emphasis on the various regulatory factors of the lipolytic pathways including catecholamines, insulin, adenosine, steroids, and other modulators. The role of lipolytic characteristics on fat topography is further assessed by considering changes with age, differences between men and women, effects of excess body fat, and data from heritability studies. Although the study of regional variation of in vitro adipose tissue metabolism has provided valuable information, a better understanding of variation in fat topography and of the role played by adipose tissue in the regulation of whole body carbohydrate and lipid metabolism will likely require extensive in situ and in vivo investigations. Sixth, as enlargement of a specific fat deposit is associated with increases in fat cell size and number, these topics are considered with an emphasis on the role of adipose cell differentiation. Seventh, the importance of blood levels of sex steroids and glucocorticoids for regional fat distribution is discussed. Then, a unifying hypothesis, defined as the hypothalamic arousal and neuroendocrine dysregulation model, is briefly described. Finally, the issue of whether body fat distribution can be altered by caloric restriction or regular exercise is addressed.
The purpose of the present study was to test the hypothesis that gender differences are present in the extent and time course of exercise training-induced changes in maximal 10- and 90-s performance test. Thirty-six sedentary subjects (19 women and 17 men) were submitted to 15 weeks of training involving both continuous and interval ergocycle exercise sessions, while 13 other subjects (5 women and 8 men) served as a control group. Maximal power output after 10 s (P10) and 90s (P90) of cycling exercise was measured before and at each 5-week interval of the 15-week training period in both groups. Significant (p < 0.01) training-induced increases in performance were noted after 5 weeks, 10 weeks and 15 weeks of training for P10, and after 5 and 10 weeks for P90 in both genders. P10 and P90 were significantly increased in both genders (about 25% in men and 35% in women) following the 15-week training program and overall absolute increases were not statistically different between men and women. Slight increases (about 5%) in performance tests were observed in control subjects, but only during the first 5-week interval. P10 and P90 of women expressed as a percentage of that of men remained the same throughout the 15-week program. No significant relationship between pre-training values of P10 and their responses to training was found in men and women. In conclusion, results of the present study indicate that women have the same capacity to increase maximal short-term performance in response to training in comparison to men.
