Page 90 - JSOM Spring 2023

An Ongoing Series

Hydration

Tactical and Practical Strategies

Jonathan M. Scott *; J. Russell Linderman ; Patricia A. Deuster 3
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ABSTRACT
Full-spectrum Human Performance Optimization (HPO) is maintain normal body temperature. First, heart rate increases
essential for Special Operations Forces (SOF). Adequate hy- to deliver more blood to the periphery and skin to release ex-
dration is essential to all aspects of performance (physical and cess heat from the body to the environment, and sweating oc-
cognitive) and recovery. Water losses occur as a result of physi- curs. The body releases water onto the surface of the skin as
cal activity and can increase further depending on clothing and sweat, which then directs more blood towards the skin surface.
environmental conditions. Without intentional and appropri- Thus, both heat and water are lost. Although this does help
ate strategic hydration planning, Operators are at increased resolve the issue of excess heat production, it also increases
risk for degradation in performance and exertional heat ill- the likelihood of dehydration. Dehydration is defined as the
ness. The purpose of this article is to highlight current best process of going from a state of euhydration (“good” or
practices for maintaining hydration before, during, and after normal hydration) to hypohydration (insufficient amount of
activity, while considering various environmental conditions. water). If dehydration is not addressed through appropriate
Effective leadership and planning are necessary for preparing and strategic hydration/fluid replacement plans, it can lead to
Operators for successful military operations. performance (physical and cognitive) detriments, heat illness,
and even loss of life. Environmental factors, including ambient
Keywords: hydration; special operations forces; SOF; human temperature, humidity, and atmospheric pressure, can accel-
performance optimization; HPO; nutrition erate the onset and degree of dehydration. For example, fluid
losses may be greater at altitude, in the cold, and in the heat
compared to normobaric, thermoneutral conditions, even with
low levels of physical activity. 1,3,4
Introduction
Water is an essential nutrient and is critically needed for Hu- Dehydration can predispose an Operator to heat illness and
man Performance Optimization (HPO). Water helps maintain can cause significant cognitive and physical performance det-
intravascular volume, regulates body temperature, eliminates riments to an individual’s performance depending on the level
waste, and allows for muscle contraction. Without sufficient of dehydration. Mild dehydration is defined as water loss
1,5
water, blood pressure could not be maintained, and organs leading to a 1–2% loss of body weight, moderate dehydration
would not receive adequate blood, which would ultimately is a 2–5% loss of body weight, and severe dehydration is a loss
lead to organ failure and death. However, fluid needs vary of body weight greater than 5%. For reference, a 2–3% loss
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based on age, type of activity, fitness level, acclimation status, of water in a 175-pound Operator would translate into 3.5- to
clothing, and environmental conditions. Average daily fluid 5-pound loss in body weight.
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intake for Operators should be 2 to 5 quarts (qt) (64–160 fluid
onces (fl oz) but may be as high as 8 to 10-qt (256–320 fl oz) Fluid Ingestion and Timing
of water. Note, one quart is equal to 32 fl oz or approximately
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1L or 1,000mL. Fluids should be consumed before, during, and after physi-
cal training or missions, depending on the venue. Operators
should strive to be well-hydrated prior to physical exertion,
Dehydration
which can be achieved by consuming 14–22 fl oz of liquid 2–4
The human body operates best within a narrow temperature hours prior to the activity. For more personalized recom-
1,4
range. When exercising, the body produces excess heat, and mendations, fluid ingestion can also be specified according to
if that heat is not dissipated efficiently, core body tempera- body weight: approximately 2–4mL per pound of fluid is gen-
ture will rise. Likewise, when sitting in a moderately hot en- erally adequate to hydrate an Operator prior to engaging in
vironment, the body must work to rid itself of excess heat to physical activities. Further, fluids containing small amounts
1,4
*Correspondence to jonathan.scott@usuhs.edu
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1 Jonathan M. Scott, J. Russell Linderman, and Patricia A. Deuster are affiliated with the Consortium for Health and Military Performance,
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Department of Military and Emergency Medicine, F. Edward Hébert School of Medicine, Uniformed Services University, Bethesda, MD.
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