Rad ne sadrži naslov na drugom jeziku.

Abstract

Natjecatelji u olimpijskim, ali i srodnim borilačkim sportovima nastoje naglim i nekontroliranim smanjenjem tjelesne mase doseći nižu težinsku kategoriju i ostvariti natjecateljsku prednost. Najčešće, smanjenje ukupne tjelesne mase ostvaruje se na račun dinamičnoga smanjenja volumena izvanstanične tekućine. Takva praksa dovodi organizam u stanje akutne dehidracije koja pritom može izazvati brojne zdravstvene komplikacije, uključujući i smrt mladih sportaša. Stoga se važnost problematike mjerenja stupnja hidriranosti organizma ne ogleda isključivo sa stajališta potencijalno umanjenih funkcionalno-fizioloških kapaciteta sportaša, nego preventivnoga djelovanja zbog ugroženosti zdravstvenoga statusa. Trenutačno, u znanstvenoj literaturi postoji velika rasprava o metrijskim karakteristikama neinvazivnih pokazatelja (biomarkera) korištenih pri mjerenju i interpretaciji stupnja hidriranosti organizma sportaša. Stoga, temeljni je cilj ovoga istraživanja ispitati metrijske karakteristike višekratnih neinvazivnih pokazatelja stupnja hidriranosti organizma kod vrhunskih boksača juniorskoga uzrasta u stvarnim uvjetima pripremnoga kampa. U ovoj studiji prikupljeno je šezdeset devet uzoraka urina i analizirano putem terenskih i laboratorijskih metoda paralelno s procjenom ukupnoga udjela vode u tijelu i tjelesne mase, dan-za-dan pristupom tijekom tri uzastopna dana. Cjelokupan je unos markonutrijenata i vode dokumentiran tijekom istraživanja. Uzorak ispitanika sačinjen je od vrhunskih boksača juniorskoga uzrasta (n=23, dob 17.3±1.9 godina, tjelesne visine 1 .75±0.08 m, tjelesne mase 66.8±11 .8 kg, 8.3±2.3 % udjela masti u tijelu, 7.1±0.9 iskustva u boksu), isključivo nacionalnih prvaka Rusije, Srbije i Bosne i Hercegovine. Temeljem različitosti u antropometrijskim karakteristikama ispitanici su podijeljeni u dvije homogene skupine (laki/teški). Temeljna se spoznaja ove studije ogleda u opaženoj velikoj varijabilnosti i nedosljednosti urinarnih pokazatelja stupnja hidriranosti organizma (laboratorijskih i terenskih, u rasponu: ICC=0.38 - 0.58) unatoč stabilnoj tjelesnoj masi (ICC=0.99, CV<1 %) i primjerenom unosu markonutrijenata i vode. Post hoc analize utvrdile su uniforman porast u vrijednostima osmolaliteta urina (UOSM) kod obje skupine ispitanika, između prvoga i trećeg mjerenja za 11.2±12.8 % (p<0.001, η2=0.4) kod lakih boksača, i 19.9±22.7 % (p<0.001, η2=0.5) kod teških boksača, dok su vrijednosti specifične težine urina (STU) porasle za 0.5±0.4 %, (p<0.01, η2=0.4), isključivo kod teških boksača. Nalazi konkurentne valjanosti i medicinskih dijagnostičkih modela pokazuju uniformno slaganje i visoku povezanost urinarnih indikatora (r=0.87; p<0.001; III AUC=0.95, p<0.01), ali i razliku u odnosu na ukupni udio vode u tijelu (r=0.06, p=0.45, r=-0.13, p=0.53, pojedinačno). Promotrena je univerzalno visoka stopa hipohidriranosti organizma (STU=1.028±0.003 g•mL-1, UOSM=1036±158 mOsmol•kg-1), uniformno kod svih ispitanika, što dovodi u pitanje valjanost interpretacije do sada postavljenih kriterija i referentnih vrijednosti prilikom procjene deficita vode u tijelu sportaša. Ipak, usprkos porastu u vrijednostima koncetracije urina, ukupan unos markonutrijenata (35±4 kcal•kg-1) i vode (~3.0 L) bio je stabilan tokom provedbe studije. Predstavljeno istraživanje nije potvrdilo hipotezu o utjecaju povišene mišićne mase na dijagnostičku točnost STU (r=0.14, p=0.51), dok metrijske karakteristike i utjecaj ukupnih proteina u urinu iz maloga uzorka (r=0.11; p=0.59) na dijagnostičku točnost STU dan-zadan pristupom ostaju dvosmisleni. Temeljem prikazanih podataka moguće je izvesti zaključke: (i) predstavljena studija opovrgava generalno prihvaćenu teoriju, ali primjenu osmolaliteta urina kao zlatnoga standarda prilikom procjene ukupnoga deficita u tijelu, (ii) otvoreno kritizira korištenje presječnih studija čiji je cilj bio utvrđivanje metrijskih karakteristika pokazatelja stupnja hidriranosti organizma na uzorku natjecatelja iz borilačkih sportova, (iii) otvara problematiku različitosti mehanizama ostvarenja koncentriranoga urina u odnosu na dijagnostičku točnost procjene. Daljnje su studije potrebne da bi se detaljno razložili uzročni mehanizmi visoke varijabilnosti opažene u vrijednostima koncentracije urina kao posljedica odgovora bubrežnoga sustava uslijed visokointenzivnih priprema u borilačkim sportovima.Čini se kako općeprihvaćeni neinvazivni dehidracijski biomarkeri iz urina ukazuju na druga fiziološka stanja i kompenzacijske mehanizme osim isključivog deficita vode u tijelu. Neovisno o izboru tehnike mjerenja, trenutačno ne postoji u potpunosti ispravan i točan pristup problematici i interpretaciji prikupljenih podataka, što je i pokazano statističko-metodološkim pristupom ove studije.Certainly, we know that voluntary body mass loss reduction (via reduction in extracellular fluid) continues to be a habitual practice in Olympic combat sports. This practice carries an increased risk of adverse health-related effects, particularly for the adolescent combat athletes. Unfortunately, the data the acute assessment of hydration status remains equivocal. Currently, there is on-going debate within the combat sport community on how best to measure whole-body fluid changes (e.g, hypohydration) which regularly occur in these athletes. Importantly, the inconsistency of research findings on measurement resolution of urinary readings may preclude a conclusive position stand within current combat sports research. Therefore, the aim of the present study was to determine the measurement resolution of multiple non-invasive diagnostic tools in real-life settings on a day-to-day basis. Furthermore, this study also investigated the prevalence of hypohydration and the association between urinary indices of hydration status and other presumably confounding factors (e.g., urine protein content, increased muscle mass, food and fluid intake) in elite youth boxers during their weight-stable phase before competition. Sixty-nine urine samples were collected over three days from 23 elite European adolescent boxers (17.3±1.9 years of age, 1 .75 ±0.08 m in height, 66.8±11.8 kg in body mass, 8.3±2.3 % of body mass expressed as fat, 7.1±0.9 years of boxing experience) and analysed by field and laboratory measures reflecting on hydration status. Data collection took place during a mutual international training camp, prior to a major competition. Overall macronutrient and water intake were assessed using dietary records. According to their anthropometric characteristics, boxers were stratified into two groups: light-weight boxers (Lwb) and heavy-weight boxers (Hwb). The effects on all dependent variables between experimental protocols were analysed using repeated measures ANOVA to detect any systematic biases between items For post hoc analysis Bonferroni’s test was adopted for multiple comparisons of dependent variables. The results demonstrated urine specific gravity (USG) and urine osmolality (UOSM) inconsistency (ICC range=0.38–0.52) for Lwb and Hwb boxers, respectively) during their weight-stable period and regardless of the ad libitum fluid intake (~3.0 L• day-1). Post-hoc test demonstrated no differences between time trials (F=3.02; p=0.09, η2=0.23), while for Hwb there was a significant difference only between trials 1 and 3 as USG increased by 0.5±0.4 % (F=8.90, η2=0.49; β=0.94; p<0.001). The UOSM readings showed significant time effect for both groups (F=13.32; p<0.001; β=0.99; 67 η2=0.39), while there was no group (F=0.08, p=0.93) or interaction effect (F=1.19, p=0.29). In Figure 2 post-hoc test showed differences in both Lwb and Hwb boxers over the course of the study, as UOSM increased between trial 1 i 3 by 11.2±12.8 % (F=5.17; p=0.01, β=0.79, η2=0.32) and 19.9±22.7 % (F=10.2; p=0.001, β=0.98, η2=0.48, respectively). High positive correlation between urinary dehydration markers were observed (r=0.88, p<0.001); these correlations were supported by tight Bland-Altman limits of agreement (-0.92 to 0.93). The variations observed in Bland-Altman plots between both urinary indices and total body water (TBW) (i.e. the ordinate) were greater than three standard deviations. The area under curve (AUC) demonstrated similar outcomes for both urinary indices (0.93, p<0.001) with high sensitivity (93.5%) and specificity (87.5%). Sixty-five percent of adolescent boxers were severely hypohydrated in spite of being in their weight stability period. Hypohydration was universally prevalent among all athletes on both test days with USG=1.028±0.003 g•mL-1, UOSM =1036±158 mOsmol•kg-1. A trivial association between mean of both urinary values and mean water content was observed (r=0.06; p=0.45; r=- 013, p=0.53), whilst TPC was not associated with any urinary dehydration markers (USG, p=0.27; UOSM, p=0.61), indicating that the inter-assay reliability of urine sampling may remain skewed, especially for samples which have increased protein content. The present outcomes find that the most prevalent urinary dehydration markers used to classify hydration status in competition exhibit large variability, and may be influenced by external factors like intense exercise, or others, resulting in increased false-positive findings, even during the weight-stable periods of real-life competition settings. It seems that the consistency of both urinary dehydration marker readings in combat athletes depends upon research design, experimental approach (e.g., laboratory conditions vs real-life settings) in particular. In opposite to the prevailing theory, urine osmolality should not be considered a gold standard dehydration index. In conclusion, this study implies that the physiological mechanisms underlying diagnostic accuracy of the most common non-invasive hydration markers requires further investigation to validate the measures in elite adolescent boxers. Albeit, there are several critical physiological and medical reasons for the mandatory hydration evaluation of adolescent boxers throughout their season, including body development, endocrine responses, cardiovascular risk factors