Body fat mass, body fat distribution, and plasma hormones in early puberty in females.

We examined whether there is a relationship between body fat mass or body fat distribution and hormonal profiles in the plasma of early pubertal girls. Thirty-five apparently healthy caucasian schoolgirls were selected for Tanner's breast development stage M2; they had all been classified as being stage M1 6 months earlier. Body fat mass had no relationship with the total plasma sex steroid concentration or gonadotropins. However, body fat mass was correlated with the fraction of testosterone that was not bound to sex hormone-binding globulin and considered the fraction available for biological activity. Body fat distribution, rather than body fat mass, was different in relation to the total concentrations of estrone, estradiol (E2), and testosterone as well as the percentage of available E2 or testosterone. Girls with fat localized predominantly on the hips had the highest levels of sex steroids and gonadotropins. It seems likely that this type of fat distribution is a result of ovarian activity. Girls with predominantly abdominal fat were also more obese and showed increased plasma levels of total E2 and a lower androgen/estrogen ratio in plasma, possibly due to increased aromatization, especially in abdominal adipose tissue. The findings suggest a reciprocal relationship among body fat distribution, plasma sex hormone levels, and availability of sex steroids in early female puberty.

Body fat mass, body fat distribution, and pubertal development: a longitudinal study of physical and hormonal sexual maturation of girls.

The rate at which girls progress through the stages of puberty in relation to body fat mass and body fat distribution and its relation to their hormonal profiles was studied. Sixty-eight schoolgirls participated in a longitudinal study during 3 yr. The girls were divided into subgroups with increasing skinfold thicknesses and waist-hip ratio. They were also grouped depending on Tanner's breast development classification (M2 and M3). The age at M2 was only marginally correlated with the menarcheal age, but the age at M2 and the time interval from that age to menarche was negatively correlated. Age at the onset of puberty was not related to body fat mass or distribution. The rate of pubertal development after pubertal stage M3 was negatively related to the body fat mass. Age at M2 was only correlated with estrone (E1), while the rate of pubertal development was associated with higher FSH, E1, estradiol (E2), the fraction of E2 that was not bound to sex-hormone-binding globulin (non-sex-hormone-binding globulin bound E2) and androstenedione plasma levels at the onset of puberty. Body fat distribution, rather than body fat mass was related to the total and the non-sex-hormone-binding globulin bound plasma levels of E2 and testosterone at the onset of puberty. Changes in body fat distribution in early female puberty were chiefly related to the waist circumferences. We found no evidence that body fat mass or body fat distribution triggers the onset of puberty. Body fat distribution was related to early pubertal endocrine activity. Body fat mass was negatively related to the rate of pubertal development toward menarche, but no clear indications for an endocrine-related process is found. We conclude that onset of puberty and menarche are not parallel pubertal events, and that early pubertal plasma E1, E2 and androstenedione levels are predictors for the rate of pubertal development toward menarche. We propose that the control of the onset of puberty and maturation of the hypothalamic-pituitary gonadal axis, with regard to negative feedback control, are at least partially independent. This induces on the average a "catch up" pubertal maturation in girls with a late onset of puberty.

Dietary habits, sexual maturation, and plasma hormones in pubertal girls: a longitudinal study.

The relationships between dietary components and physical or hormonal sexual maturation in 63 pubertal girls were examined. The effects of vegetable protein and dietary fiber on breast development (B = -2.0, P less than 0.05; B = -2.6, P less than 0.05, respectively) became more pronounced in a multivariate analysis, after elimination of the linear effects of body height and energy intake. From the multivariate analysis with combinations of vegetable protein, polysaccharides, and fiber in the equation, fiber appeared to be the most important factor. The gonadotropin and estradiol plasma concentrations were higher in girls who consumed less grain fiber. We conclude that a diet rich in vegetable products, especially fiber, may affect the rate of physical and hormonal sexual maturation, possibly mediated by the hypothalamus-pituitary-gonad system.

Renin-angiotensin system: oral contraception and exercise in healthy female subjects.

The effect of oral contraception and of exercise on the renin-angiotensin system was studied in 20 highly trained athletes, of whom 10 were ingesting oral contraceptives (users) and 10 were not (nonusers), and in 24 sedentary age-matched healthy female subjects, of whom 13 were users and 11 were nonusers. No training-related effects were observed with the exception of renin substrate, which was significantly higher in the athletes. The plasma concentrations of active renin and of trypsin-activatable prorenin were significantly lower in the subjects taking oral contraceptives. Renin substrate, however, was significantly higher in the oral contraceptives group. No difference in plasma renin activity (PRA) was observed between users and nonusers. The results demonstrate the well-known estrogen-induced stimulation of renin substrate synthesis by the liver and suggest a decreased secretion of renin by the kidney. Exhaustive exercise of short duration, performed by the trained athletes only, stimulated the renin-angiotensin system. An increase in PRA and in active renin concentration was observed. The prorenin concentration did not change significantly. The magnitude of the exercise-induced changes was considerably influenced by oral contraceptive medication. Nonusers showed a significantly greater increase in PRA and active renin and total renin concentration than users. Renin substrate decreased significantly during exercise in the nonusers only. These results demonstrate that oral contraceptives have a suppressive effect on renin secretion at rest, an effect that becomes more prominent during exercise, i.e., physiological stimulation.

Gastrointestinal problems as a function of carbohydrate supplements and mode of exercise.

The aim of the study was to examine prevalence and duration/seriousness of gastrointestinal (GI) problems as a function of carbohydrate-rich (CHO) supplements and mode of exercise. The relationship between GI problems and a variety of physiological and personal factors (age, exercise experience) was also examined. Thirty-two male tri-athletes performed three experimental trials at 1-wk intervals, each trial on a different supplement: a conventional, semisolid supplement (S; 1.2 g CHO, 0.1 g protein, and 0.02 g fat.kg BW-1 x h-1); an almost isocaloric fluid supplement (F; 1.3 g CHO.kg BW-1 x h-1, no fat, no protein); and a fluid placebo (P). The 3 h of exercise started at 75% VO2max and consisted of alternately cycling (bouts 1 and 3) and running (bouts 2 and 4). GI symptoms were monitored by a questionnaire. Analysis of variance revealed that nausea lasted longer with P as compared with S (P < 0.05). Bloating lasted longer during bout 3 with P as compared with F and S (P < 0.05). Accounting for confounding factors, most GI symptoms occurred more frequently and lasted longer during running than during cycling. Multiple regression analysis revealed significant relationships between nausea and urge to defecate, between an urge to defecate, GI cramps and flatulence, and between belching and side ache. From all other factors energy depletion, CHO malabsorption, exercise intensity, exercise experience, and age were significantly related to GI symptoms during the exercise.

Lipids and apoproteins in relation to participation in organized sport activities and pubertal development in boys.

This study considers changes in the plasma lipid and apoprotein profiles of boys in relation to participation in organized sport activities and to testosterone (T) levels. Fifty boys, aged 9.9 ± 0.6 years (mean ± S.D.), participated in the study. During a 3 year follow-up, the following measurements were taken twice a year: stature, weight, and skinfolds. Blood samples for lipids and apoproteins and sex hormone levels, and information on participation in sport activities were also obtained. No relationship was found between participation in organized sport activities and high density lipoprotein cholesterol (HDL-C) or apoprotein A-I (apo A-I). The changes of the profile over time in more active boys (participation rate > 3 hr/wk) were similar to those of less active boys (participation rate < 1 hr/wk) (MANOVA, repeated measures, not significant.) Consistent relationships between sex hormones and lipids and apoproteins were restricted to T with total cholesterol (TC), HDL-C, and apo A-I, respectively. The common variance ranged from 5.8% (rT,TC ) to 18.5% (rT,HDL-C ) (P ⩽ 0.05.) When the boys who reached advanced puberty during the follow-up period (n = 21) were studied apart from those who did not (n =29), differences were found in TC, apo A-I, and HDL-C, TC decreased from 4.6 ± 0.65 to 4.3 ± 0.58 mmol/l in the more advanced pubertal boys, and increased from 4.6 ± 0.90 to 4.8 ± 0.79 mmol/l in the others; apo A-I decreased from 185 ± to 28.3 to 156 ± 20.4 mg/dl and from 179 ± 20.6 to 176 ± 27.7 mg/dl, respectively (MANOVA, repeated measures, P ⩽ 0.05) HDL-C was lower in advanced pubertal boys at the end of follow-up (1.4 ± 0.33 and 1.7 ± 0.38 mmol/l, respectivel; P ⩽ 0.05). The lack of a relationship with regular physical activity may be due to the high levels of HDL-C and apo A-I at the begining of the study. On the other hand, the effect of the increasing T levels on HDL-C and apo A-I may have overwhelmed the presumed effect of regular physical activitiy. © 1995 Wiley-Liss, Inc.

The onset of puberty and the availability of sex steroids in female gymnasts.

Plasma levels of gonadotropins, (sex) steroids, SHBG bound fractions of 17ß-estradiol (E2) and testosterone (T), and sex-hormone-binding globulin (SHBG) were compared at the onset of puberty in female gymnasts (n = 7) and two groups of schoolgirls with similar anthropometric characteristics. Ten schoolgirls were matched to the gymnasts on the basis of a sum of skinfolds and the waist/hip ratio, while 12 other girls were selected on the basis of the stature and bicristal breadth of the female gymnasts. All girls were in the second stage of breast development (M2) and were classified as being in the first stage (M1) 6 months earlier. When female gymnasts were compared to nonathletic schoolgirls with similar physical characteristics at the same stage of early puberty, the former had significantly lower levels of plasma luteinizing hormone (LH), total and available E2, and T. In conclusion, female gymnasts have significantly lower LH, E2, and T plasma levels than nonathletic schoolgirls in early puberty. The E2 and T plasma levels in early female gymnasts are not related to the individual physical characteristics, i.e., fat mass, short stature, or small bicristal breadth. © 1993 Wiley-Liss, Inc.

Injuries in high-risk persons and high-risk sports. A longitudinal study of 1818 school children.

In this Dutch population-based study we attempted to determine the incidence and severity of sports injuries occurring during different kind of sports in a longitudinal way. The study included 1818 school children aged 8 to 17 years. Over a period of 7 months, 399 sports injuries were reported in 324 youngsters. The most common types of injuries were contusions (43%) and sprains (21%). Medical attention was needed in 25% of all cases. Young basketball, handball and korfball players had a nearly 100% chance of suffering one sports injury per year. Volleyball especially had a high incidence rate in practice (6.7 in 1000 hours). Although physical education classes had a low incidence rate, there were significantly more fractures on the upper limb. Etiologically, sports-related factors were much more important than personal-bound factors. The injured youths spent more time in practice than the noninjured ones, both in organized and nonorganized sports (P less than 0.001). High-risk sports were characterized by contact, a high jump rate, and indoor activities. These three factors explained 78% of the total variance. The contact versus noncontact factor accounted for 48% of the medically treated injuries. An additional goal of this study was to explore the seasonal influence as an extrinsic environmental factor. We found that the duration of injury was increased in the spring (P less than 0.05). Specific preventive measures were formulated in order to reduce the number of new and recurring injuries and a proposal was made to implement injury prevention in school curriculums.

Sports injuries in school-aged children. An epidemiologic study.

In November 1982, epidemiologic data were collected in a unique, large scale, population-based survey on sports injuries in school-aged children living in Holland. A total of 7,468 pupils, aged 8 to 17, completed questionnaires covering a retrospective period of 6 weeks. Seven hundred ninety-one sports injuries were registered, amounting to an incidence of 10.6 sports injuries per 100 participants. In 31% of the cases, medical consultation was needed. Injuries incurred during the study period caused 36% of the children to miss one or more physical education classes and caused 6% to miss school for at least 1 day. Contusions and sprains were the most common lesions (77%). Three of four injuries involved the lower extremity, in particular the ankle. Sixty-two percent of all the injuries occurred in organized sports, 21% in physical education classes, and 17% in unsupervised sports activities. The highest injury rates were found in basketball and field hockey. In this study population, 15 and 16-year-old boys who had a high sports activity index and played team sports, particularly contact team sports, formed a high risk group.

[Healthy children and sports]. / Gezonde kinderen en sport.

Sport can be considered as an excellent alternative for unhealthy consumption habits and can compensate far the outcome of a sedentary lifestyle. The youngster can improve technique, coordination and flexibility in an easy way by training programs. Specific weight training programs are not recommended for those under the age of fifteen years. Regular exercise programs at young ages have positive effects on the general education, and during life habitual exercise training reduce the severity of cardiovascular and other diseases. It promotes the fitness of the body and the mind. Sport, a lifetime, must be part of a healthy lifestyle and must be encouraged younger ages. Health effects in a long term depend on exercise programs lasting years.

[Athletic injuries in children]. / Sportblessures bij kinderen.

Sports participation can have both beneficial and negative effects. Specific effects are injuries. The change of incidence is dependent on a number of personal and environmental factors. Epidemiological research in the Netherlands in school aged children has shown that sports injuries occur primarily in club sport, even more during competition. The injuries are localised in the lower limbs: especially the knee and the ankle. The injuries are distortions and contusions and fewer fractures and muscle tears. The number of overuse injuries seems to be rising because children are doing increasingly more intensive sport at younger ages. A preventive sports medical examination has been discussed as well as the preventive effect of warming-up and cooling down, stretching exercises, rehabilitation, taping, rules of play and sports facilities. Finally, attention has been given to the general care of sports injuries in the way of active and functional guidance in the healing process.

Selection of talented female gymnasts, aged 8 to 11, on the basis of motor abilities with special reference to balance: a retrospective study.

Our aim is to propose a selection procedure on the basis of motor abilities. Within this scope, we have particularly studied balance as one of the selection criteria for young female gymnasts. We have used the combination of two standardized tests: the beam-walking test and the stork-standing test. Four groups of young females (aged 8 to 11 years) were tested. The results indicate that the talented group (n = 23, those participating in national training) has better balance in comparison to the control group (n = 37), gymnasts only participating at club level) and the average group (n = 32, girls not taking part in gymnastics). The results are independent of age, height, and weight, which justify the conclusion that balance is stabilized before the age of 8 years. The fourth group (n = 192) are girls who took part in the selection procedure in 1979 and 1980. We divided this group in 1981 into a non-selected group (n = 121), a discharged, selected young talented group (n = 42), a selected young talented group (n = 16), and an older talented group (n = 13). We discuss the results of these groups at the time of the selection procedure. The two talented groups show better results on the balance tests than the discharged, selected group and the non-selected group. There is no relationship to the results of the total selection test. The results indicate that these tests can be used as one of the selection criteria within the selection procedure for young female gymnasts.

Socio-economic factors in relation to lipid profiles in young girl athletes.

The influence of socio-economic factors on blood lipid values was studied in 4 groups of young female athletes. Based on type of sport (gymnastics and swimming) and of training intensity, the participants were subdivided into 25 talented, high achievement gymnasts (age 12.3 +/- 1.6 (SD) year), 42 non-talented, low achievement gymnasts (age 12.0 +/- 1.2 (SD) year), 12 high achievement swimmers (age 10.3 +/- 1.6 (SD) year), and 24 low achievement swimmers (age 10.8 +/- 1.6 (SD) year). With respect to socio-economic factors, no significant differences were observed between the two gymnastic groups nor between the two swimming groups. The blood lipid values revealed a significantly higher low density lipoprotein-cholesterol level and significantly lower high density lipoprotein-cholesterol/total cholesterol and high density lipoprotein-cholesterol/low density lipoprotein cholesterol ratios in the talented gymnasts as compared to the non-talented gymnasts. In the high achievement swimmers, low density lipoprotein-cholesterol and triglyceride levels were significantly lower and high density lipoprotein-cholesterol/total cholesterol was significantly higher as compared to the other swimmers. The Spearman rank order correlation coefficients for the relationships between socio-economic factors and blood lipid values were mostly weak or inconsistent. Therefore, no major influence of socio-economic factors on blood lipid values could be demonstrated in the groups investigated.

Plasma lipoprotein profile in relation to sex hormones in premenarcheal athletes.

Physical activity of an endurance nature is supposed to affect the lipoprotein profile in adults as well as in children. When examining this profile in premenarcheal athletes, regard has to be paid to an interfering effect of the rising sex hormone levels due to puberty. Therefore, the purpose of this study was to investigate the plasma lipoprotein levels of premenarcheal athletes in relation to their sex hormone profile. Thirty-six elite gymnasts, 21 recreational gymnasts, 27 girl swimmers, and 25 very little active control girls participated. Their age was about 12 years. The sex hormone profiles of all groups were similar. The swimmers had the lowest level of TC, LDL-C, and TG (P less than or equal to 0.05), and apo A-I was elevated in this group as compared with the others (P less than or equal to 0.05). HDL-C was highest in the recreational gymnasts (P less than or equal to 0.05). The elite group and the control group had similar lipoprotein profiles. After adjustment for T and E-2, no change in variance of the lipoproteins was found. A low correlation existed between apo A-I, E-2, and T (P less than or equal to 0.05). Thus, in this pediatric population, the sex hormones did not play a significant role relative to the levels of plasma lipids or apo A-I. As the body composition correlated very weakly with TG, it is tentative to conclude that the variance found in the lipoprotein profile might be due to differences in physical activity. Moreover, genetic factors may have contributed to the variance.

Sex-linked variation in creatine kinase release, and its dependence on oestradiol, can be demonstrated in an in-vitro rat skeletal muscle preparation.

Creatine kinase (CK) release from male and female rat soleus muscles was studied for 4.5 h in vitro, under basal conditions and after electrical stimulation. Basal CK release was greater from male than from female muscles, and CK release from male muscles increased significantly when the muscle tension in the in-vitro set-up was increased. CK release after electrical stimulation was also more marked in male soleus muscles. Pretreatment of male rats and ovariectomized female rats with oestradiol for 3 weeks attenuated the enzyme efflux, but ovariectomy 24 h before in females, or oestradiol administration 24 h before in males, did not affect the release of CK in vitro. The data show that sex-linked differences in CK efflux are still present, under both basal and stimulated conditions, when muscles are isolated from the intact animal, and that hormone treatment of the intact animal affects these properties in the isolated muscle in vitro.

The behaviour of the plasma free testosterone/cortisol ratio during a season of elite rowing training.

During nine months of training preceding the 1988 Olympic Games, six elite male rowers were regularly subjected to an investigation to changes in the rest values of the free testosterone/cortisol ratio (FTCR). In addition, the rowers were subjected to an exercise test on rowing ergometer. When comparing the FTCR levels through the season with the initial level, the results show that during periods of heavy training (training camp) the rest levels of the FTCR decrease (range 5-50%) in most of the rowers. During periods of less intensive training, the opposite is the case for the behaviour of the FTCR. The FTCR value never dropped below 0.35*10(-3), a value which is considered to be the threshold of overstrain. Moreover, decreases in the FTCR of more than 30% relative to preceding values were often found. These decreases are not indicative for overstrain but should be related to temporary incomplete recovery from intensive training. However, it remains to be demonstrated that periods of prolonged decreases (several months) in the level of the FTCR may finally lead to a situation of overstrain or overtraining in an athlete. Power at 4.0 mmol lactate (P4.0) and maximal power (PM) did not show a relation with the hormonal parameters.

Apolipoprotein and lipid profiles in young female athletes.

The apolipoprotein and lipid profiles were investigated in 22 female gymnasts, 20 girl swimmers, and 12 controls. The average age of all groups was about 12 years, and the girls were matched for sexual development, i.e., breast development stage m = 1 or m = 2. The gymnasts appeared to have the highest level of HDL cholesterol and the highest HDL cholesterol / total cholesterol, HDL cholesterol / LDL cholesterol and HDL cholesterol/apo A-I ratios in comparison to both the swimmers and the control group. The swimmers had the highest level of apo A-I, but a lipid profile similar to that of the controls. It is concluded that in children, as in adults, regular physical activity affects the lipid and apolipoprotein profiles. In addition, it appears that the apolipoproteins discriminate between trained and nontrained subjects as well as (apo B) or better (apo A-I) than the lipid components of the corresponding lipoproteins (LDL cholesterol or HDL cholesterol).

Oral contraceptives and fibrinolysis among female cyclists before and after exercise.

The effect of oral contraceptives on a number of plasma fibrinolytic variables and antithrombin III was studied in 20 highly trained women before and immediately after exhaustive exercise on a bicycle ergometer. Two groups were studied, 11 women using an oral contraceptive agent (OCA group) and 9 women not using an oral contraceptive (control group). Factor XII, prekallikrein, plasminogen, alpha 2-antiplasmin, and antithrombin III activities were determined in plasma as well as a number of cardiovascular, respiratory, and metabolic components. Resting values showed a significantly higher level of prekallikrein and plasminogen in the OCA group compared with the control group. Exercise plasma values of components of the fibrinolytic system were significantly higher than resting values in both groups. However, when corrected for plasma volume changes, the exercise levels of prekallikrein and antithrombin III were significantly decreased in the OCA group only, whereas alpha 2-antiplasmin exercise level was significantly lower in both groups. Our results indicate that use of OCA even with an estrogen dosage as low as 30 micrograms has an effect on resting and exercise fibrinolytic variables; an effect, however, which does not seem to interfere with maximal performance in trained women.