Blood, Sweat, and Tears: Implications for Hydration Testing in Combat Sports-Investigating Body Mass Loss and Biomarker Changes.

Combat sports athletes often undergo rapid body mass loss (BML), which presents health risks. Hydration testing has been proposed as a possible solution to reduce or eliminate rapid BML. However, combat sports athletes may exhibit distinct physiological characteristics due to repeated exposure to BML. Thus, traditional and emerging hydration biomarkers should be investigated to determine their potential suitability for field use in this cohort. This study examined whether BML can explain changes in serum and urine osmolality (SosmΔ, UosmΔ), tear osmolarity (TosmΔ), hematocrit (HctΔ), and urine-specific gravity (USGΔ) after mild-moderate passive dehydration. Biomarker reliability was also assessed across two trials. Fifteen male and female combat sports athletes (age: 26.3 ± 5.3 years, body mass: 67.7 ± 9.9 kg) underwent a sauna protocol twice (5-28 days apart) aiming for 4% BML. The average BML in Trials 1 and 2 was 3.0 ± 0.7%. Regression analysis revealed that BML explained HctΔ (R2 = 0.22, p = 0.009) but not SosmΔ (R2 = 0.11, p = 0.079) or other biomarkers. Intraclass correlation coefficients (ICCs) were significant for all biomarkers except TosmΔ (ICC = 0.06, p = 0.37) and post-Tosm (ICC = 0.04, p = 0.42); post-Hct performed best (ICC = 0.82, p < 0.001). Contingency tables with post-Sosm (295 mOsm/kg) and post-USG (1.020) cutoffs revealed an 80% true negative rate (TNR) and a 62% true positive rate (TPR). Increasing the Sosm cutoff to 301 mOsm/kg decreased the TNR to 52% but increased the TPR to 83%. Although blood parameters were most sensitive to BML, they could only explain 11%-22% of biomarker variation. The typical USG cutoff misclassified 42% of athletes postdehydration, and reliability was generally poor-moderate. Alternative strategies should be pursued to manage rapid BML in combat sports.

Prevalence of disordered eating and its relationship with rapid weight loss amongst male and female combat sport competitors: A prospective study.

OBJECTIVES: To compare prevalence and change scores of disordered eating (DE) in combat sport athletes by sex and explore the potential relationship between rapid weight loss (RWL) and DE scores. DESIGN: Prospective study based on 24 events (September 2022-2023). METHODS: A body mass (BM) questionnaire was completed at ~1 day post-competition providing pre-competition BM data for -7 days, -24 h, and weigh-in. The Athletic Disordered Eating (ADE) online questionnaire was completed at ~7 and ~28 days post-competition, providing overall DE and four subscale scores (food and energy control, bingeing, body control, and body discontent). RESULTS: There were 122, 132, and 89 respondents for the BM (77 % male), and ADE questionnaires at 7 (79 % male), and 28 days (74 % male). A large proportion of males' (83 %) and females' (89 %) DE scores were moderate to very high; minimal (17 % vs. 11 %), moderate (36 % vs. 32 %), high (37 % vs. 36 %), and very high (11 % vs. 21 %). Comparing DE change scores in males and females indicated deterioration (5 % vs. 0 %), improvement (3 % vs. 25 %, p = 0.013), and no difference (92 % vs. 75 %). Body discontent change score showed a significant sex difference (p = 0.014), with females improving (42 % vs. 17 %, p = 0.035) and males deteriorating (35 % vs. 4 %, p = 0.008). Correlation analyses were significant for RWL -7 days and males' food control score (R = 0.22, p = 0.031). CONCLUSIONS: Moderate to very high DE indications were identified in 4 of every 5 combat sport competitors. A sex-specific change in body discontent is evident, and most competitors struggle with their food-body relationship post-competition, irrespective of RWL magnitude.

Sex Differences in Hydration Biomarkers and Test-Retest Reliability Following Passive Dehydration.

This study investigated (a) differences between males and females for changes in serum, tear, and urine osmolality, hematocrit, and urine specific gravity following acute passive dehydration and (b) assessed the reliability of these biomarkers separately for each sex. Fifteen males (age: 26.3 ± 3.5 years, body mass: 76 ± 7 kg) and 15 females (age: 28.8 ± 6.4 years, body mass: 63 ± 7 kg) completed a sauna protocol twice (5-28 days apart), aiming for 4% body mass loss (BML). Urine, blood, and tear markers were collected pre- and postdehydration, and change scores were calculated. Male BML was significantly greater than that of females in Trial 1 (3.53% ± 0.55% vs. 2.53% ± 0.43%, p < .001) and Trial 2 (3.36% ± 0.66% vs. 2.53% ± 0.44%, p = .01). Despite significant differences in BML, change in hematocrit was the only change marker that displayed a significant difference in Trial 1 (males: 3% ± 1%, females: 2% ± 1%, p = .004) and Trial 2 (males: 3% ± 1%, females: 1% ± 1%, p = .008). Regression analysis showed a significant effect for sex (male) predicting change in hematocrit (ß = 0.8, p = .032) and change in serum osmolality (ß = -3.3, p = .005) when controlling for BML but not for urinary or tear measures. The intraclass correlation coefficients for females (ICC 2, 1) were highest for change in urine specific gravity (ICC = .62, p = .006) and lowest for change in tear osmolarity (ICC = -.14, p = .689), whereas for males, it was posthematocrit (ICC = .65, p = .003) and post tear osmolarity (ICC = .18, p = .256). Generally, biomarkers showed lower test-retest reliability in males compared with females but, overall, were classified as poor-moderate in both sexes. These findings suggest that the response and reliability of hydration biomarkers are sex specific and highlight the importance of accounting for BML differences.