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Hydration, Fluid Homeostasis and Their Impact on Athletic Performance

A special issue of Nutrients (ISSN 2072-6643). This special issue belongs to the section "Sports Nutrition".

Deadline for manuscript submissions: 20 June 2026 | Viewed by 494

Special Issue Editors


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Guest Editor
Department of Physiology and Biochemistry, Faculty of Physical Education and Sport, University of Physical Education, Kraków, Poland
Interests: sports physiology; human physiology; sports biochemistry; exercise testing; exercise; hormonal profiles
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
Faculty of Physical Education and Sport, Institute of Sports Sciences, University of Physical Culture, 31-571 Kraków, Poland
Interests: sports science; exercise performance; exercise science; athletic performance; strength & conditioning; sports injuries; exercise physiology; sport physiology; physical fitness; muscle physiology
Special Issues, Collections and Topics in MDPI journals

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Guest Editor Assistant
Faculty of Physical Education and Sport, Institute of Sports Sciences, University of Physical Culture, 31-571 Kraków, Poland
Interests: physical education; sports science; physical fitness; sport; energy expenditure; physical activity assessment; physical activity; diet; health science; nutrition; health

Special Issue Information

Dear Colleagues

Adequate water intake and optimal fluid balance are fundamental determinants of health and physical performance, yet the complexity of hydration in athletic contexts remains an active and evolving research field. Physical exercise induces significant changes in thermoregulation, cardiovascular function, metabolic activity and hormonal responses, making athletes particularly vulnerable to dehydration, overhydration and electrolyte imbalance. Recent studies highlight that even mild dehydration may impair cognitive function, technical skill execution and endurance capacity, while excessive fluid consumption without appropriate electrolyte replacement can increase the risk of hyponatremia. Despite growing scientific interest, important gaps remain regarding individual hydration needs, sex-specific responses, sport-dependent strategies and the role of nutrition in supporting fluid homeostasis. This Special Issue, entitled “Hydration, Fluid Homeostasis and Their Impact on Athletic Performance” will bring together cutting-edge research exploring hydration assessment techniques, environmental influences, evidence-based fluid-replacement protocols and innovative nutritional approaches that optimize performance and recovery. Manuscripts addressing experimental, clinical, mechanistic or applied perspectives are welcome, with our goal being advancing practical recommendations for athletes, coaches and practitioners.

Prof. Dr. Tomasz A. Pałka
Dr. Łukasz Rydzik
Guest Editors

Dr. Monika Bigosińska
Guest Editor Assistant

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • hydration
  • water intake
  • fluid balance
  • dehydration
  • hyponatremia
  • electrolyte homeostasis
  • thermoregulation
  • sweat rate
  • endurance performance
  • exercise physiology
  • rehydration strategies
  • sport nutrition
  • environmental stress
  • heat adaptation
  • athletic performance

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Published Papers (1 paper)

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Research

10 pages, 981 KB  
Article
Agreement and Reliability Between Urine Reagent Strips and Refractometry for Field Assessment of Hydration in Ultra-Trail Runners
by Daniel Rojas-Valverde, Volker Scheer, Marcelo Tuesta and Carlos D. Gómez-Carmona
Nutrients 2026, 18(3), 466; https://doi.org/10.3390/nu18030466 - 31 Jan 2026
Viewed by 326
Abstract
Background/Objectives: Accurate hydration assessment is critical for optimizing performance and preventing heat-related complications in ultra-endurance athletes. This study evaluated the agreement and reliability between urine reagent strips and refractometry for field-based hydration assessment via urine-specific gravity (USG) in ultra-trail runners. Methods: [...] Read more.
Background/Objectives: Accurate hydration assessment is critical for optimizing performance and preventing heat-related complications in ultra-endurance athletes. This study evaluated the agreement and reliability between urine reagent strips and refractometry for field-based hydration assessment via urine-specific gravity (USG) in ultra-trail runners. Methods: Thirty-four ultra-trail runners (22 males, 12 females; mean age 43.71 ± 11.50 years) participated during The Coastal Challenge, a 241-km multi-stage ultra-trail competition. Urine samples were collected before and after the first two stages (Stage 1: 41 km, 1071 m elevation; Stage 2: 40 km, 1828 m elevation). USG was measured using semi-quantitative urine reagent strips (Combur10Test M) and a handheld digital refractometer (Palm Abbe™). Agreement was assessed via paired t-tests, Pearson and Spearman correlations, intraclass correlation coefficients, and Bland-Altman plots across four measurement time points. Results: Strong agreement existed between methods with correlation coefficients of 0.92–0.99 (p < 0.01) within the hydration range typical of well-prepared ultra-endurance athletes (USG 1.010–1.020). No significant differences were found between devices at any time point (all p > 0.05). Bland-Altman analyses revealed minimal mean bias (range: −0.002 to +0.001 g/mL) and narrow limits of agreement, with fewer than 5% of values falling outside limits. Both methods detected significant increases in USG from pre- to post-stage (p < 0.01), indicating exercise-induced hypohydration. Conclusions: Semi-quantitative urine reagent strips and handheld refractometers demonstrate strong agreement for hydration assessment in ultra-trail runners under field conditions when not severely hypohydrated, supporting their interchangeable use for practical monitoring. Full article
(This article belongs to the Special Issue Hydration, Fluid Homeostasis and Their Impact on Athletic Performance)
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