title: Skeletal muscle water and electrolytes following prolonged dehydrating exercise.
abstract: We studied if dehydrating exercise would reduce muscle water (H2Omuscle ) and affect muscle electrolyte concentrations. Vastus lateralis muscle biopsies were collected prior, immediately after, and 1 and 4 h after prolonged dehydrating exercise (150 min at 33 ± 1 °C, 25% ± 2% humidity) on nine endurance-trained cyclists (VO2max  = 54.4 ± 1.05 mL/kg/min). Plasma volume (PV) changes and fluid shifts between compartments (Cl(-) method) were measured. Exercise dehydrated subjects 4.7% ± 0.3% of body mass by losing 2.75 ± 0.15 L of water and reducing PV 18.4% ± 1% below pre-exercise values (P < 0.05). Right after exercise H2Omuscle remained at pre-exercise values (i.e., 398 ± 6 mL/100 g dw muscle(-1)) but declined 13% ± 2% (342 ± 12 mL/100 g dw muscle(-1); P < 0.05) after 1 h of supine rest. At that time, PV recovered toward pre-exercise levels. The Cl(-) method corroborated the shift of fluid between extracellular and intracellular compartments. After 4 h of recovery, PV returned to pre-exercise values; however, H2Omuscle remained reduced at the same level. Muscle Na(+) and K(+) increased (P < 0.05) in response to the H2Omuscle reductions. Our findings suggest that active skeletal muscle does not show a net loss of H2O during prolonged dehydrating exercise. However, during the first hour of recovery H2Omuscle decreases seemly to restore PV and thus cardiovascular stability.
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla - La Mancha, Toledo, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Mora-Rodríguez
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla - La Mancha, Toledo, Spain.
authors.forename: V E
authors.initials: VE
authors.lastname: Fernández-Elías
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla - La Mancha, Toledo, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Hamouti
authors.affiliation: Exercise Physiology Laboratory at Toledo, University of Castilla - La Mancha, Toledo, Spain.
authors.forename: J F
authors.initials: JF
authors.lastname: Ortega
mesh_terms: D000293:Adolescent; D000328:Adult; D001642:Bicycling; D001834:Body Water / Q000378:metabolism*; D003681:Dehydration / Q000378:metabolism* / Q000503:physiopathology; D004573:Electrolytes / Q000378:metabolism*; D015444:Exercise; D045604:Extracellular Fluid / Q000378:metabolism*; D018495:Fluid Shifts; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D010953:Plasma Volume; D052097:Quadriceps Muscle / Q000378:metabolism*; D013542:Sweat / Q000378:metabolism; D014883:Water-Electrolyte Imbalance / Q000378:metabolism / Q000503:physiopathology; D055815:Young Adult
chemical_list: D004573:Electrolytes
keywords: Exercise; body water; extracellular fluid; intracellular fluid; plasma volume; water loss