Biomedical subjects

Cynthia Bartok

Publications and source records attributed to Cynthia Bartok.

9 recordsLinked to original sources

PubMed2005

Is leg-to-leg BIA valid for predicting minimum weight in wrestlers?

BACKGROUND: The National Collegiate Athletic Association (NCAA) and several state associations require prediction of minimum weight (MW) for collegiate and high school wrestlers. The rule requires assessment of body composition before the competitive season to minimize unhealthy weight-loss practices. Leg-to-leg bioelectrical impedance analysis (BIA) has been suggested for use with wrestlers. PURPOSE: To evaluate leg-to-leg BIA against a four-component (4C) criterion to determine whether leg-to-leg BIA predicted MW within acceptable limits for the sport of wrestling. METHODS: Criterion MW was calculated by the 4C equation of Lohman (19) using independent measurement of body density (BD) by hydrostatic weighing, bone mineral content (BMC) by dual x-ray absorptiometry (DXA), and total body water (TBW) by deuterium dilution. Subjects were 57 wrestlers (mean +/- SD; age = 19.7 +/- 1.3 yr, height = 176.6 +/- 7.3 cm, weight = 77.7 +/- 12.4 kg). Hydration was confirmed by the NCAA guidelines. Accuracy, precision, and systematic bias were examined. RESULTS: Comparable mean values (72.2 +/- 9.7 vs 72.2 +/- 10.3 kg), a high correlation (r = 0.94), and a regression line similar to the line of identity were found between BIA and 4C. However, large individual differences and systematic bias were seen across the range of MW. BIA predicted MW within 3.5 kg 68% of the time and within 7.0 kg 95% of the time. MW residuals ranged from -10.4 kg to +6.9 kg. When using 2.0 kg as an acceptable cutoff for error, only 40% of the BIA values were within 2.0 kg of the criterion. CONCLUSION: Large individual variation was seen, and, by definition, the precision was poor when estimating MW for individuals. In practical terms, the prediction error may span multiple weight classes, thus making leg-to-leg BIA unacceptable for prediction of MW in this sample under the conditions of the study.

Absorptiometry, Photon↗

PubMed2004

The validity of bioelectrical impedance models in clinical populations.

Bioelectrical impedance analysis (BIA) is the most commonly used body composition technique in published studies. Herein we review the theory and assumptions underlying the various BIA and bioelectrical impedance spectroscopy (BIS) models, because these assumptions may be invalidated in clinical populations. Single-frequency serial BIA and discrete multifrequency BIA may be of limited validity in populations other than healthy, young, euvolemic adults. Both models inaccurately predict total body water (TBW) and extracellular water (ECW) in populations with changes in trunk geometry or fluid compartmentalization, especially at the level of the individual. Single-frequency parallel BIA may predict body composition with greater accuracy than the serial model. Hand-to-hand and leg-to-leg BIA models do not accurately predict percent fat mass. BIS may predict ECW, but not TBW, more accurately than single-frequency BIA. Segmental BIS appears to be sensitive to fluid accumulation in the trunk. In general, bioelectrical impedance technology may be acceptable for determining body composition of groups and for monitoring changes in body composition within individuals over time. Use of the technology to make single measurements in individual patients, however, is not recommended. This has implications in clinical settings, in which measurement of individual patients is important.

Journal Article↗

PubMed2004

The effect of dehydration on wrestling minimum weight assessment.

UNLABELLED: Given that some wrestlers arrive for minimum weight (MW) testing in a dehydrated condition, it is important to understand the effects of dehydration on MW assessment methods. PURPOSE: To determine the effect of dehydration on the assessment of MW by three-site skinfolds with the Lohman formula (SF), leg-to-leg bioelectrical impedance analysis (BIA), and multifrequency bioelectrical impedance spectroscopy (BIS) compared with a four-component (4C) criterion. METHODS: Twenty-two male collegiate wrestlers (mean +/- SD, age: 19.9 +/- 1.4 yr, height: 174.0 +/- 6.8 cm, body mass: 77.4 +/- 9.1 kg) had their body composition assessed by the 4C criterion, hydrostatic weighing (HW), SF, BIA, and BIS in euhydration (EUH) and dehydration (DEH). Subjects dehydrated 2-5% of body weight through fluid restriction and exercise in a hot environment. RESULTS: In EUH, the total error (TE) for HW (1.75 kg) and SF (2.15 kg) were not significantly different, but the TE for HW and SF methods were significantly lower than the TE for both BIS (3.68 kg) and BIA (3.77 kg). In DEH, SF, BIA, and BIS methods had a TE approaching or exceeding 4 kg (8.8 lb). Dehydration increased the TE for SF and BIA through an artificial lowering of body weight and for BIS by an increased error in intracellular water prediction. CONCLUSION: Acute thermal dehydration violates assumptions necessary for the accurate and precise prediction of MW by SF, leg-to-leg BIA, and multifrequency BIS.

Adolescent↗

PubMed2004

Hydration testing in collegiate wrestlers undergoing hypertonic dehydration.

UNLABELLED: Because dehydration (DEH) violates assumptions used in the assessment of body composition, hydration testing has become an integral part of minimal weight (MW) assessment. PURPOSE: To determine the accuracy of hydration tests for the detection and quantification of hypertonic DEH. METHODS: Twenty-five male collegiate wrestlers (mean +/- SD, age: 20.0 +/- 1.4 yr, height: 175.0 +/- 7.1 cm, body mass: 81.7 +/- 15.3 kg) had their hydration assessed under well-controlled conditions of euhydration (EUH) and DEH. The DEH phase occurred on the same day as EUH, after subjects acutely dehydrated 2-6% of body weight through fluid/food restriction and exercise in a hot environment. RESULTS: All hydration tests except plasma potassium significantly increased from EUH to DEH, and meaningful cutoff values could be established for most tests. Cutoff values for urine tests were 586 mOsm.L(-1) for osmolality and 71 mEq.L(-1) for potassium. Plasma cutoff values were 293 mOsm.L(-1) for osmolality, 140 mEq.L(-1) for sodium, 103 mEq.L(-1) for chloride, and 3.5 pg.mL(-1) for arginine vasopressin. For ratio tests, a urine:plasma osmolality of 2.06 and an extracellular:intracellular water of 0.533 measured by the bioelectrical impedance spectroscopy were cutoff values. For urine specific gravity, a cutoff value of 1.020 g.mL(-1) had a sensitivity and specificity of 96% each for the automated harmonic oscillation technique and 87% and 91% (respectively) for the dipstick technique. Protein (by dipstick) was detected in 5% of subjects in EUH, and 100% of subjects in DEH. Correlations between hydration tests and dehydration were only low to moderate. CONCLUSION: This study supports a specific gravity cutoff of 1.020 g.mL(-1) for the identification of hypertonic DEH. Future research should test the cutoff values established in this study and explore the relationship between DEH and urine protein.

Adult↗

PubMed2004

Minimum weight prediction methods cross-validated by the four-component model.

UNLABELLED: The National Collegiate Athletic Association (NCAA) requires prediction of minimum weight (MW) for collegiate wrestlers. The rule was implemented to minimize unhealthy weight loss practices and requires assessment of body composition before the competitive season. PURPOSE: This study cross-validated the body composition methods of dual energy x-ray absorptiometry (DXA), leg-to-leg bioelectrical impedance analysis (BIA), hydrostatic weighing (HW), and skinfolds (SF) for predicting MW using a four-component criterion (4C). METHODS: Criterion MW was calculated by the 4C model using independent measurement of body density (BD), bone mineral content (BMC), and total body water (TBW). Subjects were 53 Division I athletes from the University of Wisconsin (mean +/- SD; age = 19.7 +/- 1.3 yr, height = 176.2 +/- 7.4 cm, weight = 75.6 +/- 8.9 kg). Accuracy, precision, and systematic bias were examined in the predictions. RESULTS: There were no significant differences in mean MW from HW (70.5 +/- 7.3 kg, P = 0.57), SF (70.5 +/- 7.2 kg, P = 0.29) BIA (70.6 +/- 7.6 kg, P = 0.39), DXA (70.3 +/- 7.5, P = 0.97), and the 4C criterion (70.3 +/- 7.4 kg). The regression for the relationships between 4C and HW (y = 0.994 x HW + 0.077 kg), 4C and SF (y = 1.003 x SF-0.437 kg), 4C and DXA (y = 0.942 x DXA + 4.034 kg), and 4C and BIA (y = 0.896 x BIA + 6.987 kg) did not significantly deviate from the line of identity. Pure error (PE) values ranged from 1.34 kg for HW to 3.08 kg for BIA. CONCLUSION: Comparable means, high correlations, regression lines that did not significantly deviate from the line of identity, and no systematic bias were found. However, the methods differed widely in precision. The best precision, based on SEE and PE values, were seen in the HW and SF methods. In conclusion, this rigorous four-component cross-validation study supports the NCAA methods as the most accurate and precise MW prediction methods in this sample.

Absorptiometry, Photon↗

PubMed2003

Estimation of segmental muscle volume by bioelectrical impedance spectroscopy.

This study validated bioelectrical impedance spectroscopy (BIS) with Cole-Cole modeled measurements of calf and arm segmental water volume and volume changes during 72 h of simulated microgravity and caloric restriction by using magnetic resonance imaging (MRI) muscle volume as a criterion method. MRI and BIS measurements of calf and upper arm segments were made in 18 healthy men and women [age, 29 +/- 8 (SD) yr; height, 171 +/- 11 cm; mass, 71 +/- 16 kg] before and after the intervention. Muscle volume of arm and leg segments by MRI was on average 15 +/- 10 and 14 +/- 8% lower, respectively, than the estimated total water volume by BIS (P < 0.01), but their correlations were excellent (r = 0.96 and r = 0.93, respectively). MRI- vs. BIS-predicted volume changes were a decrease of 49 +/- 68 vs. 41 +/- 62 ml in the calf and a decrease of 18 +/- 23 vs. 11 +/- 24 ml in the arm, respectively (P > 0.05 for both). BIS detected the extracellular water shifts in the calf resulting from the head-down tilt treatment, but the underfeeding protocol was not of sufficient duration or intensity to produce limb intracellular water changes detectable by BIS. BIS was highly correlated with segmental muscle volume and tracked changes associated with head-down tilt. Further research, however, is needed to determine whether BIS can accurately access separate changes in intracellular and extracellular volume.

Adult↗

PubMed2003

Measurement of nutritional status in simulated microgravity by bioelectrical impedance spectroscopy.

The potential of bioelectrical impedance spectroscopy (BIS) for assessing nutritional status in spaceflight was tested in two head-down-tilt bed-rest studies. BIS-predicted extracellular water (ECW), intracellular water (ICW), and total body water (TBW) measured using knee-elbow electrode placement were compared with deuterium and bromide dilution (DIL) volumes in healthy, 19- to 45-yr-old subjects. BIS was accurate during 44 h of head-down tilt with mean differences (BIS - DIL) of 0-0.1 kg for ECW, 0.3-0.5 for ICW, and 0.4-0.6 kg for TBW (n = 28). At 44 h, BIS followed the within-individual change in body water compartments with a relative prediction error (standard error of the estimate/baseline volume) of 2.0-3.6% of water space. In the second study, BIS did not detect an acute decrease (-1.41 +/- 0.91 kg) in ICW secondary to 48 h of a protein-free, 800 kcal/day diet (n = 18). BIS's insensitivity to ICW losses may be because they were predominantly (65%) localized to the trunk and/or because there was a general failure of BIS to measure ICW independently of ECW and TBW. BIS may have potential for measuring nutritional status during spaceflight, but its limitations in precision and insensitivity to acute ICW changes warrant further validation studies.

Adult↗

PubMed2003

Multicomponent cross-validation of minimum weight predictions for college wrestlers.

UNLABELLED: In 1998, the National Collegiate Athletic Association (NCAA) adopted a rule requiring that skinfolds (SF) or hydrostatic weighing (HW) be used to estimate minimum weight (MW) in college wrestlers. PURPOSE: To cross-validate the NCAA methods for estimation of MW using a multicomponent criterion (4C). METHODS: Criterion MW was calculated from body density (BD), bone mineral content (BMC), and total body water (TBW) using the 4C equation of Lohman (1992). BMC was measured by dual energy x-ray absorptiometry (DXA), TBW by deuterium dilution, and BD by HW. Subjects were Division I athletes from the University of Wisconsin (mean +/- SD; N = 33, age = 19.5 +/- 1.3 yr, height = 177.3 +/- 7.8 cm, weight = 74.2 +/- 9.3kg). RESULTS: There was no significant difference between mean MW from HW (69.6 +/- 8.5 kg) and SF (70.1 +/- 8.3 kg) ( P = 0.113), and between mean MW from HW (69.6 +/- 8.5 kg) and 4C (69.5 +/- 8.6 kg) ( P = 0.46). A clinically small, yet significant difference was seen when comparing mean MW from SF to 4C ( P = 0.013). The regression for the relationship between 4C and HW (y = 0.994 x HW + 0.294 kg, R2 = 0.985) and 4C and SF (y = 1.019 x SF - 1.885 kg, R2 = 0.979) did not significantly deviate from the line of identity. Pure error (PE) values of 1.04 kg and 1.35 kg were found for HW and SF, respectively. The difference between the methods was plotted as a function of the 4C criterion. The regression line for HW and 4C (y = -0.009x + 0.743, r = -0.07, P = 0.69) and SF and 4C (y = -0.038x + 3.259, r = -0.27, P = 0.13) suggest that no systematic differences in the prediction were associated with the size of the criterion. CONCLUSION: These data support the NCAA methods of HW and SF to predict MW when cross-validated using a 4C criterion in this sample.

Absorptiometry, Photon↗

PubMed2002

Hydration testing of athletes.

Dehydration not only reduces athletic performance, but also places athletes at risk of health problems and even death. For athletes, monitoring hydration has significant value in maximising performance during training and competition. It also offers medical personnel the opportunity to reduce health risks in situations where athletes engage in intentional weight loss. Simple non-invasive techniques, including weight monitoring and urine tests, can provide useful information. Bioimpedance methods tend to be easy to use and fairly inexpensive, but generally lack the precision and accuracy necessary for hydration monitoring. Blood tests appear to be the most accurate monitoring method, but are impractical because of cost and invasiveness. Although future research is needed to determine which hydration tests are the most accurate, we encourage sports teams to develop and implement hydration monitoring protocols based on the currently available methods. Medical personnel can use this information to maximise their team's athletic performance and minimise heat- and dehydration-related health risks to athletes.

Body Weight↗