Exercise performance as a function of semi-solid and liquid carbohydrate feedings during prolonged exercise.

Aim of this study was to examine the effects of a semi-solid and a liquid carbohydrate feeding on exercise performance. Thirty-two male triathletes performed three exercise trials (3 hours maximal at 75% VO2max) with either a semi-solid feeding (S), an iso-caloric liquid feeding (F) or a liquid placebo (P). Exercise consisted of cycling (bout 1 and 3) and running (bout 2 and 4). Survival analysis revealed that the median maximum test time (MTT) with F, S and P was 180, 126 and 120 min, respectively. Median MTT was longer with F than with S (sign-test; p < 0.05) or P (p < 0.001), with no difference between S and P. Mean power output during supra-maximal tests after bout 2 (W1) and at the end of exercise (Wend) were 371, 365, 362 and 334, 332, 321 W with F, S and P, respectively. Differences between F and P were significant (p < 0.01). Regression analysis identified five variables that were associated with 93% of the variance in MTT. The variance in W1 was explained for 83% by three variables. Wend was explained (90%) by three variables. A significant dietary contribution to MTT and Wend was found, but not to W1. This suggests that the influence of the feedings on performance is different among performance tests.

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.

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.

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.

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.

Body fat distribution in pubertal girls quantified by magnetic resonance imaging.

We examined body fat distribution in relation to anthropometrically derived variables in 24 girls in early and late stages of puberty. The amounts of subcutaneous and intra-abdominal body fat were derived from transverse slices at the levels of the waist, hip and trochanter using magnetic resonance imaging (MRI), and were compared to the related circumferences, the circumference ratios and the trunk-to-extremity skinfold ratios. Waist, hip and trochanter circumferences were highly correlated to the respective related MRI total fat surface area both in early and late pubertal girls (r = 0.79-0.97), while waist circumference, and waist-hip, waist-thigh or skinfold ratios were not significantly correlated to intra-abdominal fat areas. Late pubertal girls (n = 11) were significantly taller, heavier and fatter compared to early pubertal girls (n = 13), yet their anthropometric waist-to-hip or waist-to-trochanter circumference ratios were significantly lower. The intra-abdominal fat area measured in a transverse MRI section at the level of the waist was 24.1 +/- 4.1 cm2 in early pubertal girls and 25.7 +/- 4.1 cm2 in late pubertal girls (mean +/- s.e.m.). As compared to early pubertal girls, the MRI derived amount of subcutaneous fat in late pubertal girls was significantly higher at the trochanter level (142.1 +/- 12.7 vs. 201.3 +/- 26.3 cm2; P less than 0.05). We conclude that circumferences at the trunk are good measures for the related amounts of fat in pubertal girls. In contrast conventional anthropometric measurements, such as trunk-to-extremity skinfold ratio or waist-to-hip circumference ratio, cannot be used to predict the amount of intra-abdominal fat in pubertal girls.(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal changes in performance and free testosterone: cortisol ratio of elite female rowers.

The aim of this study was to investigate the seasonal behaviour of the plasma free testosterone: cortisol ratio (FTCR) and to relate hormonal changes to daily training volume and performance parameters on a rowing ergometer in elite female rowers. During 9 months of training preceding the 1988 Olympic Games the resting values of the FTCR in six elite female rowers were regularly (ten times) studied. Daily training volume was analysed in terms of rowed distance (lrowed) and time (t). In addition, two performance parameters, the power at 4.0 mmol.l-1 lactate concentration in the blood and the maximal power, were determined by a test on a rowing ergometer. The results indicated that the mean FTCR test value did not differ significantly from the level of the initial test or from the mean value of the directly preceding test. A significant negative correlation (r = -0.98, P less than 0.01) between FTCR and lrowed was found in a period i.e. at a training camp, when there was a sudden increase in training volume. When FTCR was related to t a significant positive correlation (r = 0.88, P less than 0.05) was found only for the period at the training camp. Our data further suggested that the FTCR alone was not an adequate indicator for the anabolic/catabolic balance in elite female rowers. This finding was contrary to previous findings in elite male rowers. However, in training practice the FTCR seems useful as an indicator of the hormonal training status of elite female rowers when complemented with data about total and free testosterone, performance parameters and knowledge concerning cyclic variations of the FTCR.

Analysis of seasonal training volume and working capacity in elite female rowers.

Preceding the 1988 Olympic Games 6 elite female rowers were regularly subjected to an exercise test on a rowing ergometer (REM-test) with a time interval of about 5 weeks. Daily training volume was analysed in terms of rowed kilometres (RKM) and training time (TOTMIN, rowing and land training). The purpose of this study was to investigate the training volume during a season and to study possible changes in the working capacity of elite female rowers. The REM-test consisted of 3 consecutive blocks: 3 min warming up, 5 min standard load at anaerobic threshold and 2 min "all-out". Blood lactic acid concentration (LA) was determined for the construction of a LA-power curve. The power at 4.0 mmol/l (P4) was estimated as a measure of the aerobic capacity. The "all-out" score was used for calculating the maximal power (PM). Results show that both RKM and TOTMIN increase (range resp. 40-400% and 20-25%) when compared with the initial value. P4 also increases, in parallel with changes in both RKM and TOTMIN, with 8-10% of the initial value. PM increases continuously during the season up to 10% of its initial value. However, based on maximal heart rate and lactate values, it is concluded that PM was maximal in only 15% of the tests. Our data suggests that evaluation of training volume in elite female rowers is better done with P4 than with PM. The behaviour of P4 shows a parallel with the seasonal changes in the training load.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

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.

Plasma lipids and apoproteins, body fat distribution and body fatness in early pubertal children.

Besides body fatness, the body fat distribution is associated with coronary risk in adults, but little has been reported on this aspect in children. This study describes body fatness, body fat distribution (waist-to-hip ratio, WHR) and the plasma lipid and apoprotein profile (TC, HDL-C, LDL-C, TG, apo A-I and apo B) in 60 boys (age 10.8 +/- 0.1 year; mean +/- s.e.m.) and 64 girls (age 10.2 +/- 0.1 year), all caucasian. To avoid interference by the large changes in plasma sex hormone levels during puberty, only pre- and early pubertal children (Tanner stages of genital c.q. breast development 1 or 2) participated. Physical and sports activity was scored in hours per week using a questionnaire. The boys were taller than the girls (146.2 +/- 0.7 vs 143.2 +/- 0.9 cm; ANOVA, P less than or equal to 0.05) and their WHR was larger (0.88 +/- 0.01 vs 0.83 +/- 0.01; ANOVA, P less than or equal to 0.05). The boys spent 8.0 +/- 0.4 hours weekly on physical and sports activities, the girls 5.5 +/- 0.3 (ANOVA, P less than or equal to 0.05). The plasma lipid and apoprotein profiles were similar in both groups. Body fatness was significantly associated with the lipid and apoprotein profile, although in different ways in boys and girls. In boys there was a relationship with TG (r = 0.49), with apo B (r = 0.33) and with the apo A-I to apo B ratio (r = -0.24); in girls with TG (r = 0.25), HDL-C (r = -0.39), apo A-I (r = -0.28) and with the HDL-C to TC ratio (r = -0.31); P less than 0.05 for all correlations. A regional component of the subcutaneous fatmass, assessed by the partial correlations of the individual skinfold thicknesses with the plasma lipid and apoprotein profile after controlling for body fatness, was lacking in these early and prepubertal children. The WHR was associated with TC (r = 0.35), LDL-C (r = 0.32), apo B (r = 0.36) and with apo A-I/apo B (r = -0.34) in the girls after controlling for body fatness. Although closer investigation into the validity of the WHR as a measure of fat distribution in children is needed, the tentative conclusion is that in pre- and early pubertal girls the WHR has an impact on the plasma lipid and apoprotein profile similar to that seen in adults. It is suggested that in boys these relationships develop later in puberty.

[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.

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.

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.

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.

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.