Exertional heat stress presents a different acute challenge to salt balance compared to at rest. Sodium (Na⁺) and chloride (Cl⁻) losses during exercise are overwhelmingly driven by eccrine sweat glands (the “leader”), with minimal urinary excretion. Total salt losses are therefore largely influenced by thermoregulatory need, although adaptations from prior heat exposure or altered dietary intake influences sweat gland ion reabsorption, and therefore sweat Na⁺ ([Na⁺]_sweat) and Cl⁻ concentrations. The hypotheses that body Na⁺ and Cl⁻ conservation, or their release from osmotically inactive stores, can occur during the timeframe of a single bout of exertional heat stress, has not been studied to date. The consequences of unreplaced Na⁺ and Cl⁻ losses during exertional heat stress appear limited primarily to their interactions with water balance. However, the water volume ingested is substantially more influential than salt intake on total body water, plasma volume, osmolality, and thermoregulation during exercise. Acute salt and water loading 1–3 h prior to exercise can induce isosmotic hyperhydration in situations where this is deemed beneficial. During exercise, only scenarios of whole body [Na⁺]_sweat > 75th centile, combined with fluid replacement >80% of losses, are likely to require significant replacement to prevent hyponatremia. Post-exercise, natriuresis resumes as the main regulator of salt losses, with the kidneys (the “follower”) working to restore salt balance incurred from any exercise-induced deficit. If such a deficit exceeds usual dietary intake, and rapid restoration of hydration status is desirable, a deliberate increase in salt intake may assist in volume restoration.

与休息时相比，劳累性热应激对盐平衡提出了不同的急性挑战。运动期间钠 (Na ⁺ ) 和氯化物 (Cl ^- ) 的损失主要由外分泌汗腺（“领导者”）驱动，尿排泄量极少。因此，总盐分损失在很大程度上受体温调节需要的影响，尽管先前热暴露或饮食摄入改变的适应会影响汗腺离子的重吸收，因此汗液 Na ⁺ ([Na ⁺ ]_汗液) 和 Cl ^-浓度。假设身体 Na ⁺和 Cl ^-在单次劳累性热应激的时间范围内，保存或从渗透性非活性储存中释放它们，迄今为止尚未进行研究。劳力性热应激期间未替换的 Na ⁺和 Cl ^-损失的后果似乎主要限于它们与水平衡的相互作用。然而，在运动期间摄入的水量比盐摄入量对全身水分、血浆量、渗透压和体温调节的影响要大得多。在认为有益的情况下，运动前 1-3 小时的急性盐和水负荷可引起等渗性过度水合。运动时，只有全身 [Na ⁺ ]_{出汗的情况} > 75th 百分位，加上补液 > 80% 的损失，可能需要大量补液以防止低钠血症。运动后，尿钠排泄恢复成为盐分流失的主要调节器，肾脏（“跟随者”）努力恢复因运动引起的任何不足引起的盐分平衡。如果这种不足超过了通常的饮食摄入量，并且需要快速恢复水合状态，则有意增加盐摄入量可能有助于恢复容量。