Loss of electrolytes during exercise primarily affects fatigue because electrolytes are essential for...

• A. Skeletal muscle contractions
• B. Muscle contractions and cramps
• C. Bone density changes
• D. Respiratory rate control

Answer: (B)

Electrolytes keep the electrical charge across muscle and nerve cell membranes needed to generate nerve impulses and trigger muscle contraction. When you exercise and sweat, you lose electrolytes like sodium, potassium, and calcium. Without the right balance of these ions, nerve signals can become less effective and calcium handling in muscle cells during contraction is disrupted, so you can’t sustain strong contractions and you may experience fatigue. Cramps can also occur because muscles become hyper- or hypo-excitable when electrolyte balance is off. The option that mentions both muscle contractions and cramps best captures how electrolyte loss affects muscular function and fatigue. Bone density changes are not an immediate fatigue effect, and respiratory rate is governed mainly by CO2/pH rather than direct electrolyte loss.