Functional capacity and body composition in top weight-lifters,swimmers, runners and skiers

Summary Groups of top weight lifters, swimmers, runners and skiers were examined as regards functional capacity (maximal oxygen consumption measured during graded work load on a horizontal tread-mill), body build and composition (densitometry). Significant differences in mean ages (highest in skiers, lowest in swimmers) and body dimensions, attributable to natural selection, were found (highest length dimensions in swimmers, lowest in weight lifters). According to the specificity of training in individual disciplines studied, runners had lowest body weight and highest lean body mass proportion, and weight-lifters (who had highest relative weight) had lowest lean body mass proportion. Highest values of ventilation, breathing frequency, maximal oxygen consumption and oxygen pulse in skiers simultaneously with lowest pulse frequency were found; the reverse applies for weight lifters. Mutual relationships between somatic and functional characteristics in individual groups were evaluated.     

Total blood volume in endurance-trained postmenopausal females: relation to exercise mode and maximal aerobic capacity.

We have recently shown that postmenopausal female distance runners demonstrate elevated levels of blood volume compared with sedentary healthy peers. We also found a strong positive relation between blood volume and maximal oxygen consumption. In young adult males, endurance exercise training increases blood volume when performed in the upright, but not in the supine body position. Based on these observations, we hypothesized that among postmenopausal females, the elevation in blood volume would be absent or attenuated in women who train in the horizontal vs. upright body position, and that the lower blood volume in the former would be associated with lower maximal aerobic capacity. Thus, we measured supine resting plasma and total blood volumes (Evans blue dye) and maximal oxygen consumption in postmenopausal women: 10 sedentary controls, 10 swimmers and 10 runners matched for age (60 +/- 2; 59 +/- 2; 58 +/- 2 years, mean +/- SE) and hormone replacement use (5 per group). The swimmers and runners were further matched for training volume (4.5 +/- 0.2 vs. 4.8 +/- 0.6 h week-1), relative performance (78 +/- 5 vs. 75 +/- 3% of age-group world record) and fat-free mass (45.5 +/- 0. 8 vs. 44.9 +/- 1.5 kg). Total blood volume and maximal oxygen consumption were highest in the runners (81.2 +/- 4; 52.4 +/- 3 mL kg-1, respectively) and progressively lower in the swimmers (68.8 +/- 3; 44.2 +/- 2) and controls (59.2 +/- 2; 37.9 +/- 2; all P < 0. 05). In the pooled population, blood volume was positively related to maximal oxygen consumption (r = 0.72, P < 0.0001). We conclude that in endurance-trained postmenopausal females matched for training volume and competitive performance: (1) blood volume is lower in those who train in the horizontal (swimmers) compared with the upright position (runners); (2) the lower blood volume is associated with a lower maximal aerobic capacity. Nevertheless, blood volume and maximal oxygen consumption are higher in postmenopausal women who train in the horizontal position than in sedentary controls.     

Bio-impedance analysis for estimation of total body potassium,total body water,and fat-free mass in white,black, and Asian adults

Bio-impedance analysis (BIA) measurements have been used to predict components of body composition. Their validation is required for populations varying in race, sex, and age. In 371 Whites, 182 Blacks and 225 Asians, single-frequency BIA at 50 kHz (RJL-100) resistance and reactance measurements were correlated with same-day measurements of total body water (TBW) by THO dilution, total body potassium (TBK) by whole body ⁴⁰K counting, and fat-free mass (FFM) by dual-photon absorptiometry. BIA correlation coefficients with TBW, TBK, FFM, and fat varied by sex and race for all measured body composition components. The highest correlation was for FFM, and the lowest was for fat mass. Prediction equations were further improved by including age, stature, and weight for each of the study cohorts. The SEE for predictions were in the ranges of 5–6, 6–8, and 7–10% of measured FFM, TBW, and TBK, respectively. BIA was effective in predicting body composition when subjects are specified by age, sex, stature, weight, and race for subjects from 18 to 94 years of age. © 1995 Wiley-Liss, Inc.     

Total blood volume in endurance-trained postmenopausal females: relation to exercise mode and maximal aerobic capacity

We have recently shown that postmenopausal female distance runners demonstrate elevated levels of blood volume compared with sedentary healthy peers. We also found a strong positive relation between blood volume and maximal oxygen consumption. In young adult males, endurance exercise training increases blood volume when performed in the upright, but not in the supine body position. Based on these observations, we hypothesized that among postmenopausal females, the elevation in blood volume would be absent or attenuated in women who train in the horizontal vs. upright body position, and that the lower blood volume in the former would be associated with lower maximal aerobic capacity. Thus, we measured supine resting plasma and total blood volumes (Evans blue dye) and maximal oxygen consumption in postmenopausal women: 10 sedentary controls, 10 swimmers and 10 runners matched for age (60 ± 2; 59 ± 2; 58 ± 2 years, mean ± SE) and hormone replacement use (5 per group). The swimmers and runners were further matched for training volume (4.5 ± 0.2 vs. 4.8 ± 0.6 h week^–1), relative performance (78 ± 5 vs. 75 ± 3% of age-group world record) and fat-free mass (45.5 ± 0.8 vs. 44.9 ± 1.5 kg). Total blood volume and maximal oxygen consumption were highest in the runners (81.2 ± 4; 52.4 ± 3 mL kg^–1, respectively) and progressively lower in the swimmers (68.8 ± 3; 44.2 ± 2) and controls (59.2 ± 2; 37.9 ± 2; all P < 0.05). In the pooled population, blood volume was positively related to maximal oxygen consumption (r= 0.72, P < 0.0001). We conclude that in endurance-trained postmenopausal females matched for training volume and competitive performance: (1) blood volume is lower in those who train in the horizontal (swimmers) compared with the upright position (runners); (2) the lower blood volume is associated with a lower maximal aerobic capacity. Nevertheless, blood volume and maximal oxygen consumption are higher in postmenopausal women who train in the horizontal position than in sedentary controls.     

Validation of body composition estimates in male and female distance runners using estimates from a four-component model

This study used estimates of body composition from a four-component model (%Fat_d,w,m) to determine whether the assumed density (D_ffm) and the composition of the fat-free mass (FFM), and estimates of body composition from methods based on two- and three-component models are valid in distance runners. Measures of body density (D_b) by underwater weighing, total body water by deuterium dilution, and bone mineral by dual-energy X-ray absorptiometry (DXA) were obtained in 10 female and 12 male runners and an equal number of controls matched for age, height, weight, gender, and ethnicity. D_ffm of the runners did not differ from 1.1 g·cm⁻³ or from the controls even though the composition of the FFM differed from that assumed. Therefore, percentage of body fat (%Fat) from densitometry did not differ from %Fat_d,w,m in the runners, although individual variation was substantial (−5.3 to 3.0% body mass, SD_diff = 2.1% body mass). Three-component model estimates of %Fat from D_b and body water agreed quite closely with %Fat_d,w,m (x ≤ 1.6% body mass, SD_diff = 0.5% body mass), whereas those from D_b and body mineral (x _diff = 1.6–2.9% body mass, SD_diff = 2.3% body mass) and from DXA (x _diff = 2.2–4.0% body mass, SD_diff = 2.1% body mass) were less accurate and underestimated %Fat_d,w,m. We conclude that D_ffm does not differ from 1.1 g·cm⁻³ and that densitometry is a valid method to estimate group mean body composition, but that measurement of D_b and total body water are necessary for accurate individual estimates of body composition in male and female distance runners. Am. J. Hum. Biol. 12:301–314, 2000. © 2000 Wiley-Liss, Inc.     

Ageing, exercise and food restriction: effects on body composition

This study was undertaken to reevaluate the effect of ageing on body composition and to compare the effects of exercise and food restriction on body fat content in rats. Body fat content increased progressively between ages 12 and 28 months in sedentary freely eating male Long-Evans rats. A program of 3 h of swimming/day caused body weight to plateau at a level approximately 20% below that of the freely eating sedentary rats, primarily due to a more than 100 g lower body fat content in the swimmers. Lean body mass and protein content decreased progressively with ageing; in the sedentary animals, this decrease was significant by 18 months. The swimming protected against the decline in lean body mass and protein content up to age 18 months, but did not prevent a large decrease in lean body mass between ages 18 and 24 months. Food restriction that kept the sedentary rats at the same weight as the swimmers had its major effect on body fat content, which was approximately 40% lower than in the sedentary freely eating rats at all ages. The differences in body composition between the swimmers and food restricted sedentary animals were relatively small and consisted primarily of a lower body fat content in the swimmers. In conclusion, our results show that lean body mass declines with ageing in rats and that this loss of lean tissue is counterbalanced by an increase in fat. Exercise is highly effective in minimizing the increase in body fat, and may delay the decline in lean body mass, with ageing.     

Bone cross-sectional geometry in male runners,gymnasts, swimmers and non-athletic controls: a hip-structural analysis study

Loading of the skeleton is important for the development of a functionally and mechanically appropriate bone structure, and can be achieved through impact exercise. Proximal femur cross-sectional geometry was assessed in the male athletes (n = 55) representing gymnastics, endurance running and swimming, and non-athletic controls (n = 22). Dual energy X-ray absorptiometry (iDXA, GE Healthcare, UK) measurements of the total body (for body composition) and the left proximal femur were obtained. Advanced hip structural analysis (AHA) was utilised to determine the areal bone mineral density (aBMD), hip axis length (HAL), cross-sectional area (CSA), cross-sectional moment of inertia (CSMI) and the femoral strength index (FSI). Gymnasts and runners had greater age, height and weight adjusted aBMD than in swimmers and controls (p < 0.05). Gymnasts and runners had greater resistance to axial loads (CSA) and the runners had increased resistance against bending forces (CSMI) compared to swimmers and controls (p < 0.01). Controls had a lower FSI compared to gymnasts and runners (1.4 vs. 1.8 and 2.1, respectively, p < 0.005). Lean mass correlated with aBMD, CSA and FSI (r = 0.365–0.457, p < 0.01), particularly in controls (r = 0.657–0.759, p < 0.005). Skeletal loading through the gymnastics and running appears to confer a superior bone geometrical advantage in the young adult men. The importance of lean body mass appears to be of particular significance for non-athletes. Further characterisation of the bone structural advantages associated with different sports would be of value to inform the strategies directed at maximising bone strength and thus, preventing fracture.     

Sex hormone profiles of premenarcheal athletes

Summary Female gymnasts have a delayed onset and probably retarded progression of puberty. The aim of this study was to test the hypothesis that the delay in onset of puberty in gymnasts as compared to girl swimmers is modulated by a lower estrone level due to a smaller amount of body fat. The sex-hormone and gonadotropin levels of 46 gymnasts and 37 girl swimmers of the same biological maturation (breast development: M=1 or M=2) were studied. In each subject the following hormones were measured in plasma: estrone, 17--estradiol, DHEAS, testosterone, androstenedione, LH, and FSH. In prepubertal children (M=1) the levels of estrone, testosterone, and androstenedione were lower in the gymnastic group as compared to the swimming group. In the early pubertal (M=2) gymnastic and swimming groups these hormone levels were no longer different. The other hormone levels were not significantly different in either the prepubertal groups or the early pubertal ones. Within the total prepubertal group there is a clear relationship between the estrone levels and the levels of testosterone and androstenedione, but not between estrone and 17--estradiol, nor between the calculated fat mass and any of the hormone levels. It appears that the androstenedione and testosterone levels are responsible for the difference in estrone level, rather than the amount of body fat.     

Hierarchical differences in body composition of professional Sumo wrestlers

The body composition of 36 professional Sumo wrestlers and 39 collegiate male students were assessed densitometrically. The means of body weight, BMI and %fat for Sumo wrestlers were 117.1 kg, 36.5 and 26.2%, extraordinarily large compared with untrained men (p < 0.001). Results of the analysis of variance of divisions of Sumo wrestlers revealed significant differences in body weight, fat-free mass, fat mass, BMI, fat-free mass index (FFM/height2) and fat mass index (FM/height2). For the visual expression of the hierarchical differences of body composition, fat mass index and fat-free mass index of the wrestlers in various leagues were plotted on a body composition chart. Wrestlers in the Sekitori division had significantly larger fat-free mass index scores in comparison with wrestlers from the lower divisions who share a common area of the chart. The cut-off point of fat-free mass index which divided Sekitori wrestlers from other wrestlers is approximately 30 and this value may be one of the anthropometrical indications of whether or not a Sumo wrestler is destined to be successful.     

Assessment of the composition of major body regions by dual-energy X-ray absorptiometry (DEXA), with special reference to limb muscle mass.

Dual-energy X-ray absorptiometry (DEXA) has been used to assess and compare the composition of whole body and major body regions in 12 female (weight, 56.9 +/- 6.2 kg; BMI, 17-25 kg m-2) and 16 male (weight, 73.1 +/- 9.6 kg; BMI, 20-28 kg m-2) healthy subjects. Standard deviations (and % coefficients of variation) of the differences between repeated measurements of fat ranged from 0.11 kg (9.0%) for arms to 0.42 kg (3.0%) for whole body; for arm bone mineral, 0.01 kg (2.0%), and for fat-free soft tissue of the whole body, 0.42 kg (0.8%). Limb muscle mass was estimated using a new theoretical model of body composition, and the corresponding precision ranged from 0.15 kg (3.8%) to 0.27 kg (1.5%) for arms and total limb muscle mass, respectively. Proportions of each region consisting of fat were greater in females than in males (range, 20-31% vs. 16-18%), respectively, but the ratio of trunk to leg fat was lower (34:49% vs. 46:38%, respectively). Regional proportions of bone were similar between the sexes (all in the range 2.9-5.6%, for both females and males). Mean total limb muscle masses were 14.2 kg (arms, 2.8 kg; legs, 11.4 kg) for females and 22.2 kg (arms, 4.8 kg; legs, 17.4 kg) for males, which were 33.6% and 36.0% of fat-free mass, respectively. The correlation coefficients between limb muscle (DEXA) and other indices of muscle mass were: for DEXA vs. total body potassium, 0.90 (SEE 1.1 kg muscle mass) to 0.94 (1.6 kg); and for DEXA vs. anthropometry, 0.43 (1.2 kg) to 0.85 (1.3 kg). Those for limb volume (DEXA) vs. anthropometric volume, 0.91 (0.78 1) to 0.94 (1.91 1). It is concluded that DEXA enables the valid and reproducible estimation of fat, fat-free soft tissue, bone, and limb muscle mass.     

Body water compartments with human aging using fat-free mass as the reference standard.

Forty-five healthy men and women aged 16-39 and 59-89 yr were studied for total body water (TBW) and extracellular water (ECW); intracellular water (ICW) was calculated as the difference (ICW = TBW - ECW). An independent measurement of total body fat by inert gas uptake provided a value (+/- 2%) for fat-free mass (FFB is wt minus body fat). Results agreed with observations by others that TBW and ICW are lower in the aged and lower in women, whether expressed as absolute volumes or per unit of weight, surface area, or height. However, with FFB as the reference standard very different aging trends appeared. TBW/FFB remained constant to our oldest measured subjects (704 +/- 7 ml/kg). ICW/FFB was slightly lower at advanced age, but the 4-5% decrease for each sex was within statistical variability. With age ECW increased slightly and its proportion within the fat-free body (ECW/FFB) was significantly higher. Based upon FFB, the distribution, proportions, and aging trends of body water compartments were similar for men, women, and male rats. Although its potential limitations must be appreciated, the FFB appears widely useful as a reference standard. The stability of ICW volume and of fat-free mass in aging man does not support the hypothesis that cellular mass is lost by healthy mammals with age.     

A relationship between bioelectrical impedance and total body water in young adults

Total body water was measured using the stable isotope H2(18)O in 14 young adults. Body resistance was assessed using a tetrapolar technique using a Holtain body-composition analyzer. Total body water was highly correlated (r = 0.96; p less than 0.001) with height2/resistance. The inclusion of body weight in the prediction equation reduced the standard error of estimate from 1.9 to 1.51. Bioelectrical resistance can be used to assess other body-composition parameters such as fat-free mass and fat mass, but this use involves a number of assumptions which may confound the relationship. We suggest that the measurement of bioelectrical impedance may, however, have a role in the estimation of total body water.     

Comparison of nutritional parameters among adult and elderly hemodialysis patients

Aim: The aim of this study was to compare the nutritional biochemical parameters, prealbumin levels, and bioimpedance analysis parameters of adult and elderly hemodialysis (HD) patients.Methods: This prospective cross-sectional study included 50 adult HD patients (42.0 % female). Nutritional status was assessed by post-dialysis multifrequency bioimpedance analysis (BIA), serum prealbumin and other nutritional biochemical parameters.Results: Mean age of patients was 57.4±15.1 years (range: 30-83 years) and mean dialysis duration was 68.3 ± 54.5 months (range: 3-240 months). When the patients were divided into two groups according to age of patients (<65 and ≥65), prealbumin (p=0.003), blood urea nitrogen (BUN) (p=0.000), serum creatinine (p=0.013), albumin (p=0.016), protein catabolic rate per normalized body weight (nPCR) (p=0.001), intracellular water (ICW)/total body weight (0.003) , body fat mass (p00.000), lean body mass (p=0.031), lean dry mass (p=0.001), illness marker (p=0.005), basal metabolism (p=0.007), body mass index (BMI) (p=0.028), body fat mass index (BFMI) (p=0.000), fat free mass index (FFMI) (p=0.040) values were significantly different between the groups. In the elderly patients (age ≥65), body fat mass, illness marker, BMI, BFMI were higher compared to adult patients (age <65). Additionally, in the elderly patients, prealbumin, BUN, creatinine, albumin, nPCR, ICW/ total body weight, lean body weight, lean dry weight, basal metabolism and FFMI were lower than adult patients.Conclusions: Our results indicate that BFMI were higher, albumin, prealbumin, nPCR and lean body mass and FFMI were lower in elderly patients compared to adults. These results imply that elderly HD patients may be prone sarcopenic obesity and may require special nutritional support.     

The Effects of Low-Dose Creatine Supplementation Versus Creatine Loading in Collegiate Football Players

OBJECTIVE: To compare the effects of low doses of creatine and creatine loading on strength, urinary creatinine concentration, and percentage of body fat. DESIGN AND SETTING: Division IA collegiate football players took creatine monohydrate for 10 weeks during a sport-specific, periodized, off-season strength and conditioning program. One-repetition maximum (1-RM) squat, urinary creatinine concentrations, and percentage of body fat were analyzed. SUBJECTS: Twenty-five highly trained, Division IA collegiate football players with at least 1 year of college playing experience. MEASUREMENTS: We tested strength with a 1-RM squat exercise before, during, and after creatine supplementation. Percentage of body fat was measured by hydrostatic weighing before and after supplementation. Urinary creatinine concentration was measured via light spectrophotometer at 0, 1, 3, 7, 14, 21, 28, 35, 42, 48, 56, and 63 days. An analysis of variance with repeated measures was computed to compare means for all variables. RESULTS: Creatine supplementation had no significant group, time, or interaction effects on strength, urinary creatinine concentration, or percentage of body fat. However, significant time effects were found for 1-RM squat and fat-free mass in all groups. CONCLUSIONS: Our data suggest that creatine monohydrate in any amount does not have any beneficial ergogenic effects in highly trained collegiate football players. However, a proper resistance training stimulus for 10 weeks can increase strength and fat-free mass in highly trained athletes.     

Testosterone, aging, and body composition in men from Harare, Zimbabwe.

To examine age-related changes in body composition and testosterone (T) among men in an urban sub-Saharan African population, measures of body composition and salivary T were obtained from 109 males ages 20-78 in Harare, Zimbabwe. Measures included height, weight, suprailiac and triceps skinfold, and percent body fat by bioelectric impedance (BIA). Saliva samples were assayed for T using radioimmunoassay. Average BMI of the overall sample (23.16 (SD = 18.12) kg/m(2) was close to Western populations, while salivary T levels (AM = 196 +/- 96 pmol/l; pm = 172 +/- 98 pmol/l) were much lower. Both morning (beta = -0.535; P < 0.001) and afternoon salivary T declined with age (beta = -0.385; P < 0.001). Multiple regression models indicate that pm salivary T (beta = 0.24; P = 0.025), was a predictor of fat-free mass, but neither am nor pm salivary T was related to fat mass or other measures of body composition. In addition, height was significantly related to pm salivary T levels in men under the age of 60. Multivariate regression indicates that pm salivary T is a predictor of fat-free mass when controlled for height and adiposity. These findings suggest that T is related to both lean mass and overall body size among men from a non-Western nonsubsistence population. As such they are consistent with the hypothesis that bioavailable T plays a role in energetic allocation among human males.     

Vital capacity in trained and untrained healthy young adults in the Netherlands

Summary Slow inspiratory vital capacity was measured in 226 healthy young adults, aged from 17 to 35 years. The group included 119 men and 107 women, 87 trained subjects, 71 untrained subjects who intended to take part in a training program for competitive rowing, and 68 untrained subjects who never took part in any competitive sport.The vital capacity increased with height, weight, fat-free mass, height×fat-free mass, and height-independent fat-free mass, with men having significantly higher vital capacities than women of the same height or weight. In both males and females vital capacity showed the best relation with height×fat-free mass (correlation coefficients are 0.78 and 0.57 respectively). Multiple regression on vital capacity with height, weight, fat-free mass, height×fat-free mass, height-independent fat-free mass, percentage body fat, and age increased the correlation coefficient only slightly (0.80 and 0.59 respectively).The subjects had vital capacities that were much higher than those predicted for them by equations originating from the USA. There was no difference between the observed vital capacities and those predicted by equations originating from Europe. There is a difference in vital capacity between the European subjects studied and subjects of similar height studied in the USA. This implies that equations derived from subjects in the USA cannot be applied to European subjects.From our results we conclude that vital capacity is not increased by physical activity.We derived one simple equation that can be used to predict the vital capacity for both male and female, trained and untrained young adults, who have a similar genetic background to our subjects.     

Differences in physical fitness among indoor and outdoor elite male soccer players

This study compared anthropometric (body height, body mass, percent body fat, fat-free body mass) and physical fitness characteristics (vertical jump height, power-load curve of the leg, 5 and 15 m sprint running time and blood lactate concentrations ([La]_b) at submaximal running velocities) among 15 elite male indoor soccer (IS) and 25 elite male outdoor soccer (OS) players. IS players had similar values in body height, body mass, fat-free body mass and endurance running than OS players. However, the IS group showed higher (P < 0.05–0.01) values in percent body fat (28%) and sprint running time (2%) but lower values in vertical jump (15%) and half-squat power (20%) than the OS group. Significant negative correlations (P < 0.05–0.01) were observed between maximal sprint running time, power production during half-squat actions, as well as [La]_b at submaximal running velocities. Percent body fat correlated positively with maximal sprint time and [La]_b, but correlated negatively with vertical jump height. The present results show that compared to elite OS players, elite IS players present clearly lower physical fitness (lower maximal leg extension power production) characteristics associated with higher values of percent body fat. This should give IS players a disadvantage during soccer game actions.     

Effects of tibolone on body composition in postmenopausal women: a 1-year follow up study

Objective: We investigated the effects of 1-year tibolone treatment on body weight, body composition and indices of android obesity in postmenopausal women.

Methods: Forty-four postmenopausal women participated in this open-label controlled study; mean age was 51.8 ± 2.21 years and all women were menopausal for 3.8 ± 1.40 years. Twenty-two of them started taking 2.5 mg tibolone (TIB) daily for 1 year, whereas the remaining 22 served as age-matched controls. All subjects underwent a structured interview, physical examination, body composition measurements performed by dual-energy X-ray absorptiometry (DXA) — Hologic QDR 4500 A, as well as bioelectrical body impedance analysis (BI) — Tanita TBF-215, Japan.

Results: The TIB group did not significantly increase their weight (+0.4 kg), while the non-treated controls increased their mean weight by 1.4 kg (p = 0.046). In the TIB group, DXA showed a non-significant body fat decrease by a mean of 0.5 kg and a non-significant lean mass increase by 0.8 kg, while in the control group, fat mass increased by 1.7 kg (p = 0.032) and lean mass did not change. BI revealed that the TIB group had lost some fat (≈0.6 kg, n.s.) and put some free-fat mass (≈1.0 kg, p = 0.048) without changes in total body water. The control group put on some fat (≈1.1 kg, p = 0.042) and lost some body water (≈0.4 kg, n.s.).

Conclusion: Results from both methods of measuring body composition show a similar trend: a decrease in fat mass and an increase in lean mass in TIB treated subjects. From the body composition perspective, tibolone may be regarded as a preferential alternative to conventional hormonal therapy (HT) in postmenopausal women.     

Growth of the pig: patterns of changes in electrolytes, water, and protein.

In 246 pigs studied from day of birth through week 12, mean plasma concentration of Na was 144.2; K, 3.89; and Cl, 103 mEq/1. Fifty-five pigs were analyzed for total body water (TBW), Na, K, Cl, protein, and fat. TBW was 83% fat-free wet weight (FFWW) at birth and declined, but not significantly, over the 12 weeks. Water content of tissues differed from each other as well as in the rates at which their water content changed. Concentration of electrolytes Na, K, Cl (mEg/100 g FFWW) decreased significantly in whole pig, viscera, brain, and skin; while Na increased and K and Cl decreased significantly in skeletal muscle. Of the tissues, skeletal muscle contributed 32% (fat-free tissue weight as per cent of total FFWW) at birth and 44% at week 12; and viscera, 15% at birth and 21% at week 12. The contribution of skeleton decreased over the same period from 22 to 15%, skin from 14 to 6%, and brain from 2 to 0.5%. The contribution of total water by the various organs changes in the same direction as the contribution to total FFWW. Na, K, Cl, and protein as a per cent of total in skin also show the same directional change. In skeletal muscle there was a decrease in conribution to total Na and Cl, but an increase to total K and protein. In the skeleton, except for protein, there is an increase in contribution of total Na, K, and Cl. There was a correlation of 0.99 and 0.94 between the sum of total Na and K in milliequivalents and TBW in millimeters for the whole pig and skeletal muscle respectively.     

Estimation of glomerular filtration rate by MDRD equation in athletes: role of body surface area

Creatinine-based equations to estimate the glomerular filtration rate (GFR) have recently been advocated over serum creatinine values as a valuable tool to more accurately assess kidney function. The Cockcroft–Gault (CG) equation requires a body weight parameter, whereas the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) Study equations do not. In this study we evaluated the effect of the calculated body surface area (BSA) on MDRD values in professional athletes characterized from different body mass index, gender, and sport discipline. Serum creatinine concentration was measured by Jaffe reaction in 17 male rugby players and 28 male and 26 female swimmers, before the start of training and throughout the competitive season. The values of estimated GFR (eGFR) calculated for creatinine determination by means of CG and CDK-EPI with respect to MDRD formula showed a significant difference in different groups of athletes. The statistical significance was confirmed for BSA-corrected MDRD-derived eGFR values in rugby players and in male swimmers, but not in female swimmers, who showed a BSA close to the “standard” value of 1.73 m² traditionally included in MDRD equation. The CG equation can overestimate the eGFR in healthy overweight subjects such as rugby players, whereas the MDRD formula systematically underestimates it. The differences between the two equations increase as a function of BMI, appearing highest in rugby players and lowest in female swimmers. Real BSA correction of the MDRD equation could help to avoid an overestimation of renal excretory function in subjects with increased BSA.