Two runners training on a sunny Louisiana road for MOVE Journal's heat, hydration and fueling guide

The Heat Is Different Here: The Louisiana Athlete's Guide to Heat, Sweat, Sodium, Hydration & Fueling

Posted by MOVE Journal on

Louisiana heat does not care what the label on your shirt says. It exposes weak preparation quickly: the athlete who does not know how much fluid they lose, the heavy sweater following somebody else's sodium plan, the runner under-fueled for the work, and the “performance” garment that becomes hot, heavy and clingy once it is soaked.

The answer is not a universal electrolyte packet, a magic fabric, or a single number copied from an elite athlete. It is a process:

MEASURE WHAT MATTERS. MOVE BETTER. PERFORM BETTER.

This is the MOVE approach to performing in heat and humidity.

THE PROBLEM: HEAT CHANGES THE COST OF THE WORK

Exercise already generates heat. Hot, humid conditions make getting rid of that heat harder. Humidity limits evaporation, and evaporation is one of the body's major avenues for cooling during exercise. Heat stress and inadequate hydration can increase cardiovascular strain and reduce the ability to sustain demanding work. Heat can also increase reliance on carbohydrate, making fueling strategy part of the heat-performance problem rather than a separate topic.

That is why “drink more water” is not a performance plan. Neither is “take more salt.” The useful question is: What are you losing, what are you burning, what can your gut tolerate, and what does the environment require today?

MEASURE WHAT MATTERS

1. Start with sweat rate

A practical field estimate starts with body mass before and after a representative session, adjusted for what you drank and any urine produced.

Estimated sweat loss = pre-exercise body mass − post-exercise body mass + fluid consumed − urine produced.

Divide that loss by exercise time to estimate an hourly sweat rate. One kilogram of acute body-mass loss is approximately one liter of fluid for this field calculation.

The important part is context. A cool easy run does not tell you what you will lose during a hard August session. Repeat the measurement across relevant temperatures, humidity, intensities and sports.

2. Sweat volume and sweat sodium are different numbers

Two athletes can finish the same workout with very different sodium losses. One may sweat more fluid but at a lower sodium concentration; another may sweat less fluid but lose far more sodium per liter. Total sodium loss depends on both.

Estimated sodium loss per hour = sweat rate (L/h) × sweat sodium concentration (mg/L).

This is why an arbitrary “milligrams of sodium per hour” target can miss the athlete in either direction.

Elite case studies make the variability obvious. Precision Fuel & Hydration reports sweat sodium concentrations ranging from the hundreds of milligrams per liter into well over 1,000 mg/L among tested endurance athletes. Those examples are useful illustrations, not universal prescriptions.

3. Measure the environment and the session

Temperature matters. Humidity matters. Sun exposure, wind, clothing, equipment, duration, intensity and acclimatization matter. A football player in pads, a runner at threshold pace and a golfer walking 18 holes may all be outside in the same Louisiana afternoon and face very different demands.

HYDRATION: REPLACE LOSSES WITHOUT TURNING THE PLAN INTO A DRINKING CONTEST

The goal is not to replace every drop at any cost. The goal is to begin appropriately hydrated, understand likely losses, drink at a rate that supports performance and safety, and avoid both excessive dehydration and excessive fluid intake.

For an athlete who loses 1.2 L/h in a particular environment and has a sweat sodium concentration of 800 mg/L, estimated sweat sodium loss is about 960 mg/h. That does not automatically mean the athlete should consume exactly 1.2 L and 960 mg sodium every hour. Intake has to account for event duration, access to fluid, gut tolerance, pre-event status, food, pace, conditions and the consequences of overdrinking.

That is the difference between measuring a loss and prescribing a replacement strategy.

FUELING: HEAT DOES NOT CANCEL THE NEED FOR CARBOHYDRATE

Long or demanding exercise creates a second problem: fuel. Carbohydrate helps maintain blood glucose and carbohydrate oxidation and can delay fatigue during prolonged endurance exercise.

For longer endurance work, established sports-nutrition guidance has commonly extended carbohydrate intake toward about 90 g/h using multiple transportable carbohydrates. Newer work and high-level field practice are pushing the conversation toward roughly 120 g/h in trained athletes who have developed the tolerance for it. The important distinction is that 120 g/h is not simply “better” for everybody, and reports of athletes consuming 120–200 g/h should not be mistaken for proof that those intakes are optimal for the general athlete.

Gut training is training. High carbohydrate intake should be practiced progressively during training, with the same products, concentrations and approximate race conditions whenever possible.

WHAT HIGH PERFORMERS ACTUALLY DO

High-performance programs increasingly measure rather than guess. LSU Performance Nutrition publicly describes using sweat analysis, body-weight changes and urine specific gravity to assess hydration, alongside body-composition testing and individualized nutrition planning. NCAA Sport Science Institute resources likewise emphasize hydration before, during and after activity and recognize that intense exercise, hot/humid weather and dehydration can compromise performance and increase exertional heat-illness risk.

Endurance sport shows the same principle at the individual level. At the 2024 Western States 100, Precision Fuel & Hydration's case study of Caleb Olson reported approximately 104 g carbohydrate/h and 886 mL fluid/h. His measured sweat sodium concentration was 655 mg/L, while the sodium concentration of what he consumed averaged about 750 mg/L. Another athlete can have a completely different sweat profile and require a different strategy. The useful lesson is not to copy Caleb's bottles. It is to copy the process of knowing the variables.

MOVE BETTER: WHAT YOU WEAR IS PART OF THE SYSTEM

Apparel cannot override physiology. It can either help the environment impose less unnecessary burden—or make the experience worse.

That distinction matters because the research on sports clothing in the heat is not as simple as “synthetic beats natural.” A 2022 Sports Medicine - Open review found that few wearer studies showed meaningful differences in thermoregulation, perception or performance between natural and synthetic fabrics, while also warning that much of the literature failed to reproduce the heat, humidity, duration and intensity experienced by trained athletes. The authors specifically called for testing in hot, humid conditions (at least 30°C and 70% relative humidity) and for exercise lasting more than 45 minutes. Read the review on PubMed.

The studies behind and after that review sharpen the point. A 2001 trial found no thermoregulatory advantage for an evaporative polyester fabric over cotton during exercise in moderate heat. A 2017 trial likewise found no overall difference in core or skin temperature, heart rate, perceived exertion or comfort among cotton, cotton/soy and polyester garments, although the synthetic construction lowered chest microclimate temperature and some post-session perceptions. A separate moisture-wicking study at 33°C and 60% relative humidity found lower rectal temperature late in exercise and less retained sweat with the synthetic shirt. More recently, a 2023 randomized crossover study of trained and national-level runners at 35°C found no significant difference in running speed, physiological heat strain or overall perceptual responses among cotton, sweat-wicking, compression and aluminum-dot shirts. In other words: fabric labels alone do not tell the whole story. Construction, fit, ventilation, saturation, airflow, exposure and the actual task matter. The 2013 Sports Medicine review reached a similar conclusion.

Comfort deserves its own measurement. Research on clothing comfort during exercise found that fabric saturation and the resulting stickiness can become more important to discomfort than the absolute amount of sweat held in a garment. That supports evaluating a shirt after it is wet: retained mass, saturation, cling, skin contact, airflow and movement should be part of the test—not just fiber composition or a “moisture-wicking” label. See the clothing-comfort study.

The MOVE standard: do not claim a garment is better because of the fabric name. Test the finished garment under the environment and movement it is supposed to handle. Louisiana gives us a demanding place to do exactly that.

In hot, humid conditions, evaluate a garment after it is wet, not while it is hanging on a rack. Ask:

  • How heavy does it become when saturated?
  • Does it cling or restrict movement?
  • Does the construction allow useful airflow?
  • Does the fit create unnecessary friction or trapped heat?
  • Does it remain comfortable through repeated sweating?
  • Is the garment appropriate for the actual activity rather than merely marketed as “performance”?

A running top, training shirt and golf polo solve different problems. Performance apparel should be judged by the movement and environment it was asked to handle. Explore MOVE Sport Apparel's athletic performance collection for pieces designed around running, training and active movement.

THE SPORT CHANGES THE ANSWER

Endurance running and triathlon

Long duration makes fluid, sodium, carbohydrate and gut tolerance progressively more important. The plan should be rehearsed, not invented on race morning.

Football and intermittent field sports

The work is different: repeated high-intensity efforts, equipment, body size, limited drinking opportunities and long practices can change heat storage and fluid needs. NCAA health-and-safety guidance emphasizes intentionally and progressively increasing training during transition periods, with particular attention to the first seven days of a new conditioning cycle.

Golf and everyday outdoor movement

The intensity may be lower, but duration and exposure can be long. Comfort, sun exposure, fluid access and clothing that transitions between heat and indoor cooling become more important than chasing an elite race-fueling number.

WHERE PEOPLE GET IT WRONG

  • Copying someone else's sodium number. Their sweat is not your sweat.
  • Using thirst, urine color or body weight as if one marker tells the entire story. Context matters.
  • Assuming more carbohydrate is always better. The dose must match the work and the athlete's trained tolerance.
  • Replacing sweat loss blindly. Measuring loss informs a plan; it does not mandate one-for-one replacement every hour.
  • Believing clothing makes heat safe. Better apparel can improve comfort and function. It does not eliminate heat illness.
  • Testing nothing until race day. The best plan is the one already rehearsed under conditions that resemble the event.

PERFORM BETTER: BUILD THE PLAN, THEN MEASURE AGAIN

A useful performance plan is a loop:

  1. Measure sweat rate in relevant conditions.
  2. Measure or estimate sweat sodium when the athlete and duration justify it.
  3. Define the carbohydrate demands of the session or event.
  4. Build a fluid, sodium and fueling plan the athlete can actually tolerate.
  5. Choose clothing and equipment for the environment and activity.
  6. Practice the strategy.
  7. Record body-mass change, intake, GI comfort, perceived exertion, performance and environmental conditions.
  8. Adjust.

Measure. Move. Perform. Measure again.

THE MOVE APPLICATION

This is where the three parts of MOVE connect.

MOVE Sport Performance — Measure What Matters.
Understand the athlete: sweat, physiology, fueling, heat response and the performance limiter. Build the plan around the person instead of the average.

MOVE Sport Apparel — Move Better.
What you wear should support the movement and environment rather than add another problem. Shop MOVE athletic performance apparel built for running, training and active movement.

MOVE Sport & Spine — Perform Better.
When pain, injury or movement dysfunction becomes the limiter, restore capacity and get back to doing the work.

FROM LOUISIANA, FOR ANYWHERE THE CONDITIONS GET HARD

Natchitoches gives us a useful laboratory. Heat and humidity expose bad assumptions quickly. But the principle travels—to Houston, New Orleans, Florida, the Gulf Coast, an August football field, an IRONMAN bike course or an ultramarathon aid station.

The objective is not to chase somebody else's perfect number.

Know yours.

MEASURE WHAT MATTERS. MOVE BETTER. PERFORM BETTER.

Ready to put the movement side into practice? Explore MOVE Sport Apparel's athletic collection, built in Louisiana for running, training and everyday movement.

SOURCES & FURTHER READING

Performance and safety note: This article is educational. Individual fluid, sodium, carbohydrate and heat-management needs vary with health, medications, acclimatization, body size, environment, intensity, duration and other factors. Elite-athlete practices and case studies are examples, not prescriptions. Confusion, collapse, altered mental status or other signs of severe heat illness require immediate emergency evaluation and rapid cooling.