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.

Relationship between muscle water and glycogen recovery after prolonged exercise in the heat in humans

“…Upon completion of the dehydrating exercise, participants toweled dry and their post-exercise nude body mass was measured again. Then, participants lay down 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 on a stretcher for an hour to ensure that body fluids were evenly redistributed among fluid compartments (Mora-Rodriguez et al 2014) and subsequently a second muscle biopsy was obtained (i.e., Post-exercise biopsy). Then participants drank either 250 g of carbohydrates in 400 mL of water (REH LOW ) or the same syrup plus as much water as needed to replace body fluids losses (REH FULL ).…”

“…During prolonged exercise in the heat, muscle water content is maintained but declines when fluid compartments equilibrate soon after exercise (Mora-Rodriguez et al 2014).…”

Hyperthermia, but not muscle water deficit, increases glycogen use during intense exercise

“…Upon completion of the dehydrating exercise, participants toweled dry and their post‐exercise nude body mass was measured again before they voided. Then, participants lay down on a stretcher for an hour to ensure equilibration between body fluids spaces (Mora‐Rodriguez et al., ). Subsequently a second muscle biopsy was obtained.…”

“…Upon arrival at the laboratory, subjects voided and their nude body weight was measured. Afterwards, a urine sample was collected and analyzed for specific gravity (Usg) to confirm euhydration (i.e., < 1.020; Sawka et al, 2007;Fernandez-Elias et al, 2014). Then, subjects lay down on a stretcher and were catheterized (20-gauge Teflon®; BD Insyte, Becton Dickinson, Madrid, Spain) in an antecubital vein.…”

The effect of different water vapor permeable jackets on moisture management, subjective perceptions and physiological parameters during submaximal exercise in a cool environment

“…To ensure consistent hydration status, participants were asked to drink 500 ml of water one hour before and to empty their bladder immediately before testing. 25 Each subject was tested with all jackets at a constant time of day (exact measurement times were arranged with each participant) to avoid potential bias resulting from the influence of the individual circadian rhythm on thermoregulation. 26 To minimize the effect of their menstrual cycle on thermoregulation, only women on oral contraception were included and tested between the 8 th and 20 th day of pill intake.…”