A woman runs a marathon in $90^{\circ} \mathrm{F}$ weather and replaces all volume lost in sweat by drinking distilled water. After the marathon, she will have

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[ $\mathrm{C} 2 \mathrm{f}$; Table 5.2]. By sweating and then replacing all volume by drinking $\mathrm{H}_{2} \mathrm{O}$, the woman has a net loss of $\mathrm{NaCl}$ without a net loss of $\mathrm{H}_{2} \mathrm{O}$. Therefore, her extracellular and plasma osmolarity will be decreased, and as a result, water will flow from extracellular fluid (ECF) to intracellular fluid (ICF). The intracellular osmolarity will also be decreased after the shift of water. Total body water (TBW) will be unchanged because the woman replaced all volume lost in sweat by drinking water. Hematocrit will be increased because of the shift of water from ECF to ICF and the shift of water into the red blood cells (RBCs), which causes their volume to increase.

A Woman Runs a Marathon In 90∘F90^{\circ} \mathrm{F}90∘F Weather and Replaces All Volume Lost in Sweat by Drinking

A Woman Runs a Marathon In $90^{\circ} \mathrm{F}$ Weather and Replaces All Volume Lost in Sweat by Drinking