Evidence-Based Hydration and Supplementation Strategies for the Miami Marathon
Marathons are tough. But the Miami Marathon is a different kind of challenge — especially when heat and humidity push your body harder than usual. If you want to perform your best, a solid strategy for hydration and supplementation is not optional — it’s necessary.
In this guide, we break down the research-backed recommendations for fluid intake, electrolyte balance, and fueling that will help you stay safer and faster on race day. Everything here is based on peer-reviewed science and real exercise physiology.
Why Hydration & Supplementation Matter — Especially in Miami
Running 26.2 miles is already taxing on your body. When you add high heat and humidity, several things happen:
1. Your sweat rate increases
As your core temperature rises, your body sweats more to cool down. In warm environments, research shows that athletes easily lose large amounts of fluid through sweat — and drinking “whenever you’re thirsty” often does not keep up with sweat loss.
2. Sweat contains important electrolytes
Sweat is not just water — it contains sodium, chloride, and potassium. These electrolytes help your muscles fire and your nerves communicate. Losing too much sodium can impair performance, and not all runners lose it at the same rate.
3. Fluid alone isn’t enough
Drinking plain water replaces fluids but doesn’t replace electrolytes. In the heat, this can lead to low blood sodium — a dangerous condition called exercise-associated hyponatremia (EAH).
Understanding Sweat Rates: The First Step in Creating Your Plan
Every runner is unique. Your sweat rate depends on:
Your fitness level
Temperature and humidity
Running pace
Body size
Heat acclimation
According to a review of athlete sweat data, sweat rates and composition can vary widely between athletes. This means one runner might lose a little sodium, while another loses a lot.
How to measure your sweat rate
Weigh yourself before a run (nude if possible).
Run at your planned race pace for 60 minutes in conditions similar to Miami.
Drink a known amount of fluid.
Weigh yourself after the run.
Use this formula:
Sweat rate = (weight before – weight after + fluid consumed) ÷ running time
This gives you a personal sweat number to work with.
Science-Backed Hydration Targets
There’s no one perfect number for everyone, but evidence suggests:
Replace ~60–80% of your sweat loss during the marathon
Trying to replace 100% of your sweat loss during the race can cause stomach discomfort and slow you down.
Example:
If you sweat 1.5 liters per hour, aim to drink 900 – 1,200 mL per hour through a mix of sports drink and water.
That amount supports performance without causing racing GI issues.
Sodium: The Electrolyte You Can’t Ignore
One of the most important electrolytes for endurance athletes is sodium. When you sweat in hot weather, you lose sodium rapidly. Too little sodium can contribute to:
Poor muscle function
Cramping
Low blood sodium (EAH)
Higher perceived effort
According to research, science supports the idea that:
In long races like marathons, consuming >450 mg of sodium per hour helps maintain sodium levels and performance.
In hot conditions, slightly higher sodium intakes (e.g., 300–600 mg per hour or more) may benefit many runners.
But sodium needs differ from runner to runner — some need much more than others.
The Role of Carbohydrates and Fuel During The Race
Hydration is linked to fuel in long races. Carbohydrates serve two main purposes:
They provide energy for muscles.
They enhance fluid absorption when consumed with sodium.
For most marathoners:
45–60 grams of carbohydrates per hour is a good target.
Some elite runners tolerate up to 90 grams per hour with multiple types of carbs. (This is well above basic recommendations but supported in some endurance studies.)
Combining sodium with carbohydrates helps your body absorb fluids more efficiently and delays fatigue.
Does Sodium Supplementation Prevent Low Blood Sodium (EAH)?
Research on sodium supplementation’s role in preventing EAH is mixed:
Some studies show sodium intake helps maintain body weight and blood sodium better than water alone.
Other research suggests supplemental sodium doesn’t prevent hyponatremia by itself — overhydration is often the real cause.
Key takeaway: Sodium helps maintain balance if you are sweating a lot, but it’s not a cure-all for low sodium — drinking behavior matters too.
Hydration Strategy Recommendations for the Miami Marathon
Here’s a clear, research-based plan for race day:
Day Before the Race
Stay well hydrated with fluids throughout the day
Include sodium-rich foods (e.g., salty snacks, broth, sports drink)
Avoid excessive water loading — it doesn’t improve performance and may lower sodium
Race Morning
Drink 8–16 oz (~240–480 mL) of fluid 2 hours before start
Include sodium with your pre-race drink
During the Race
Aim for:
Fluids: ~900–1,200 mL/hour
Sodium: 300–700+ mg/hour
Carbohydrates: 45–90 g/hour
(use sports drinks, electrolyte capsules, gels, etc.)
Spread intake evenly through the race.
Hydration Mistakes to Avoid
❌ Drinking only water
This can dilute sodium and increase hyponatremia risk.
❌ Chugging too much fluid at once
Your stomach can only handle a certain volume at a time.
❌ Trying new products on race day
Practice every part of your hydration plan in training first.
How Heat Acclimation Improves Hydration Tolerance
Training in hot weather changes your physiology so that:
You sweat earlier
Your sweat becomes more dilute (less sodium lost per liter)
Your body cools more efficiently
This improves performance in races like Miami where heat is a major factor.
Post-Race Recovery Essentials
After you finish the Miami Marathon:
✔ Rehydrate slowly over several hours
✔ Include sodium and carbohydrates
✔ Food + fluids are better than fluids alone
This helps your body restore balance and reduces soreness.
Common Questions From Runners
Do I have to take sodium tabs?
Not always — but in heat, most runners benefit from including electrolytes regularly.
Can I just drink at the aid stations?
Yes — but plan your intake and know what’s offered so you hit your targets.
Will too much sodium hurt me?
Excess sodium is rarely a problem in marathon conditions — but balance with fluids and carbohydrates matters.
Scholarly References
Sawka MN, Cheuvront SN, Kenefick RW. Hydration and Aerobic Performance: Impact of Environment. Gatorade Sports Science Institute. https://www.gssiweb.org/en/Article/sse-152-hydration-and-aerobic-performance-impact-of-environment
Baker LB et al. Interindividual variability in sweat electrolyte concentration in marathoners. PubMed. https://pubmed.ncbi.nlm.nih.gov/27478425/
Smith E et al. Sweating Rate and Sweat Sodium Concentration in Athletes. Sports Med. https://link.springer.com/article/10.1007/s40279-017-0691-5
Costa RJ et al. Water and sodium intake habits in hot racing conditions. Nutrition J. https://doi.org/10.1186/1475-2891-12-13
International Society of Sports Nutrition. Nutrition for endurance events. https://link.springer.com/article/10.1186/s12970-019-0312-9
Del Coso J et al. Exercise-Associated Hyponatremia in Marathon Runners. MDPI. https://www.mdpi.com/2077-0383/11/22/6775