Hydration for Training in Extreme Heat – Staying Hydrated on Hot Summer Days & Being Aware of the Biofeedback Signs from Your Body. By Influencer Todd Parker, M.A., M.S.

June 28, 2018

Summer heat and humidity is here for most of us, and a lack of hydration – typically referred to as dehydration – can have negative impact training adaptations, race performance, but most importantly, your health.  Therefore, “water is king”, and carbohydrate and electrolyte drinks follow very close behind – especially during extreme heat performance during training/events lasting 2-3 hours or more.  Those who exercise for more than 4 hours and are typically vigilant about hydration, and at times, to the extent they may often drink more fluid than they lose in sweat.  Over time this leads to a large enough intake of water to dilute the blood sodium (See Hyponatremia Below).  Typical cycling road races can last anywhere from 3-6 hours, while Ironman, Ultra Marathon Cycling, and Ultras (Ultra-Running) Races perhaps up to 12-24 hours or more!  This leaves a large room for error if you don’t have your onset and sweat-rates “dialed-in” for every duration, intensity, climate, and course profile. Like anything, “trial and error” by testing various fluids and water intake during training is the only way to know what your body needs and responds well to.  This takes time; so the more you experiment, the better you’ll be at keeping up with water and electrolyte loss, and subsequent ramifications on your performance and health if you don’t.

Water Loss

While dehydration is the far more common concern than over-hydration, all endurance athletes can avoid either problem by knowing their sweat-rates. To learn your sweat-rate, weigh yourself naked before and after you exercise. A one-pound drop equates to losing 16 ounces of sweat, and generally translates that you should target drinking at least 8-16 ounces of fluid during similar exercise bouts.  It is rare that one can keep up with the rate of water loss, but we need to strive to find our optimal hydration intake rates.  Unfortunately, we’re all different, and therefore it’s “trial and error” through the range of experiences until you know how much and how often to drink under various conditions.  As a guide, water or other fluid intake every 10-15 minutes of 2-3 good size (3-4oz) gulps (not sips).  If sipping more frequently works better for you, then obviously stay with what works for you.  Having knowledge about your sweat-rate takes the guesswork out of drinking during long training sessions and races , and reduces the risk of health problems associated with consuming too much or too little water.  Electrolytes are ionized minerals that conduct electrical impulses and action potentials (e.g. contraction of a muscle), and are present throughout the human body.  Simply put, the balance of the electrolytes is critical for normal function of cells and organs.

Defining Common Terminology to Know & Practice – an In-depth Look.

Too Little Water = Hypernatremia, commonly referred to as Dehydration.  Hypernatremia occurs when you lose (too) much more water than you take in, resulting in your blood/fluid sodium concentration reaches higher than acceptable levels.  It implies a deficit of total body water relative to total body sodium caused by water intake being less than water lost in sweat and urination…etc.  A major symptom is thirst; other issues are primarily neuro-muscular.  This is primarily due to a transfer of water out of our brain cells – a protective measure to keep cooling the body and organs functioning.  Latter symptoms may surface such as including confusion, neuromuscular excitability (i.e. muscular twitching, cramping, locking), seizures, and ultimately coma and death.  Bottom line, the body does not have enough fluids to carry out normal functions.

Too Much Water = Hyponatremia, a response from too much water – severely lowering blood sodium levels, ultimately affecting brain function and muscular contraction.   Typically due to drinking too much water, hyponatremia is a result of the sodium in your body to become too diluted.  When this happens, your body’s water levels rise, and your cells begin to swell.  This swelling can cause many health problems, from mild to life-threatening.  Symptoms usually surface in a severity downward spiral starting with nausea and vomiting, headache, confusion, loss of energy, drowsiness, and fatigue, muscle weakness, spasms or severe cramping,  restlessness and irritability (others will notice), seizures, coma, and ultimately death.

Critical Electrolytes – which I refer to as “The Big 4”. 

Let’s discuss “The Big 4” that were covered in Part I of this article series, those being Sodium, Potassium, Magnesium, and Calcium.  [If you’d like to read Part I of the series, see contact information below.]  Chloride is often referred as the 5th electrolyte that affects performance; however, at a much less significant level, and is also highly dependent upon the intake amounts of sodium and potassium.  As important as maintaining adequate hydration, the sometimes arduous task of figuring out how to maintain adequate balance of these minerals (known as electrolytes) which facilitate electrical nerve impulses to aid in long-term muscular contraction (i.e. multi-hour endurance training and racing).  As imbalances “initially surface”, muscles often begin to spasm and twitch, and as the imbalance(s) progress, muscles start to cramp, followed by a muscular “contractile locking” – ultimately inhibiting the affected muscle(s) from further contraction.  When this stage is reached, the muscle seizes up and further performance is often not possible until homeostasis (a normal functioning balance) is reestablished.


Sodium is primary electrolyte lost in sweat. Functions include maintaining fluid balance, maintaining cognitive function, nerve impulse transmission, absorption of nutrients in the gut, and muscle contraction.  In case you didn’t know, It is estimated that the average American consumes somewhere between 8 and 12 g of table salt per day. (Table salt—sodium chloride—is 40% sodium, so there are 3.2-4.8 g sodium in 8-12 g of salt).  This amount of sodium intake is about 20 to 30 times the amount of sodium needed to replace obligatory losses from urine (~ 25 mg/day), skin (~100 mg /day), and feces (~25 mg /day).  Athletes need more sodium because they lose more sodium in sweat, and sweat much more than their sedentary counterparts.  The range of sodium lost in the sweat of athletes is wide because some athletes are salty sweaters and others are not. Sweat is saltier during the early stages of training and heat acclimation more so than a highly fit athlete that’s fully acclimated to exercise in the heat.  If you haven’t already, now is the time to experiment with different products in order to find out which ones may make you nauseous, those not palatable – which means you may not consume it often enough because you dislike the taste, and which one(s) contribute to your training success and optimal event performances.  One great way to get sodium back in quickly (and a tip I follow) post-exercise is by eating some pickles or even drinking some pickle juice.  Just like anything else, you need to test it out for yourself, keeping in mind how long and intense was your session?  As for myself, in extreme heat and humidity, I can easily lose 3-4lbs of water in just an hour or two.  Yes, for some of us with a rapid onset and high sweat-rate, we can easily lose 3-4 pounds of water in 95-100+ degrees Fahrenheit – with humidity making it even hotter.  For pickle juice, just 2-3 ounces is typically enough – carrying anywhere from 200-500mg of rapidly absorbed sodium.  While a 3-5 inch pickle can contain anywhere from 500-1,200mg of sodium!  Again, you have to learn your bodily needs during 2, 3, 4, 12+ hours of training.  And as far as anything we take in during and post-exercise, the colder the better since it’ll empty out of your gut faster (See Below for intake guidelines). 


Potassium is a mineral that is important for the body to function properly. Potassium is the element 19 on the periodic table and is represented by the symbol “K.”  Almost all the potassium in the body is found inside the cells rather than outside in the body’s fluids like blood.  The kidneys are crucial to regulating the amount of potassium in the body.  Potassium is excreted by the kidneys as well as the gastrointestinal tract.

Potassium helps maintain water and pH balance. It has a role in nervous system function allowing signals to be sent from one nerve cell to the next. Potassium is also a key player in allowing muscle contractions. Potassium often works in conjunction with sodium in the cells to generate signals for body processes.


Unfortunately, magnesium is often overlooked, yet plays a critical role for extended bouts of muscular contractions and cramp prevention – just as much as the other three.  Most people do not realize that magnesium plays an important role in calcium and oxygen transport throughout the cells of the human body.  In fact, more than 300 nerve impulses and enzymatic reactions require magnesium as a co-factor.  Besides calcium and oxygen transport, magnesium can directly affect sodium and potassium inter-cellular transport throughout cells as well.  Longer and more intense exercise can deplete magnesium levels.  Magnesium is excreted primarily through sweat and urine, therefore, cold fluids containing magnesium (and the other three) are the preferred choice for replenishment during exercise.  Regardless of the type of sport or exercise, muscular contractions could not consistently occur without magnesium’s presence. 


In exercising and physically active individuals, muscle strength or muscle mass is directly correlated with the mass of bone associated with the specific muscle or group of muscles. Increases in bone mass also accrue in parallel with incremental gains in muscle mass.  This is why weight-bearing activities such as walking, running, strength training, gardening…etc. are crucial to healthy bone mineral density.  Calcium supplementation can correct a negative calcium balance – a result of too low calcium dietary intake, as well as additional losses from exercise or activity sweat.  Decreased blood-calcium levels can be normalized by daily supplementation before exercise.  Much research has identified that calcium taken in conjunction with Vitamin D, has a better absorption rate, as well as aid in terms of how much bone density one may have or not.

Below are the general amounts of these electrolytes are normally within the body, estimated loss rates, and intake guidelines during multi-hour endurance training and racing.

Normal Daily Dietary Intake (to include the Upper Intake Level (UIL)) Guide for the Big 4:

  • Sodium: variable; average 5.6–7.2 g
  • Potassium: 1,950 – 3,900mg
  • Chloride: Varies with potassium and sodium intake – ~2.5-3.6g/day (or 2,500-3,600mg/day)
  • Magnesium: 300–400 mg
  • Calcium: ~1,000-1,200 mg

Many endurance athletes will require much more than the tolerable UIL for sodium (2.3 g/day) and chloride (3.6g/day).

 In order to ensure that one is getting enough calcium, magnesium, and potassium, it is best to eat a variety of different foods, particularly fruits and vegetables which are low calorie sources of these electrolytes. 

Onset:  how long until your body begins to sweat, to start cooling down skin temperature at first.

Sweat-Rate: the amount of sweat (fluid and electrolytes) you lose per given training session.

Sweat Sodium Concentration: the amount of sodium (mg) you lose per liter of sweat. This level is largely genetically determined.

Fluid intake and sodium replacement go hand in hand. Much of the body is comprised of water, most of this being inside the cells (intracellular). Sodium is located outside of the cells (extracellular). When you lose extracellular fluids (sweat, urination, etc.), you lose sodium with it. Again, when losses are large and sodium isn’t replaced, but high volumes of water are, then hyponatremia can rear its ugly head. Low sodium levels are characterized by increased strain on the cardiovascular system, decreased ability to cool the body, muscle cramps and fatigue.  Another sign of the body attempting to retain water is that our feet will swell in our cycling and running shoes.  This is a safety measure that our brain will signal to the body as fluid loss (especially in extreme heat) becomes a significant factor to long-term sessions.  [Besides knowing my onset and sweat-rates well.]  One tip that I use, with the harder solid sole and leather of my cycling shoes is that I stuff large “tea towels” into my shoes once I’m finished.  This isn’t necessarily to sop up the sweat, although that’s a great reason, but more importantly, to keep the toe-box stretched out a bit to accommodate the swelling of my feet during long extreme heat rides.

Consuming sodium-containing sports drinks helps, but does not protect against hyponatremia because a sports drink offers far more water than sodium.  The typical sports drink may have only 1/5th the concentration of normal blood serum, and typically even less for the other critical electrolytes.  For very long events in extreme heat, this amount is far from sufficient for many.  Train as you race, compete, or when active!

Endnote.  In recent months there have been several articles that counter what I’m stating as the primary cause for cramping…etc.; however, in my decades of racing and coaching experience in endurance sports, as well as my credentials, I will continue to write about my experiences and findings over the years – all stated above.  For those who disagree, I guess we’ll just have to agree to disagree.

Best of Luck, Train Safe, and Train Smart!

Coach Parker

Todd Parker is a World-Renowned Cycling, Running, & Triathlon Coach, Influencer within the Sports & Fitness Industries, and Corporate Wellness Consultant – consulted by Coaches, Athletes, Corporations, Governing Bodies, and Sports Supplement, Gear, and Apparel Companies Worldwide.  Todd’s a former Professional Triathlete, Elite Cyclist, Personal Trainer, Strength Coach, Public Speaker, Guest Lecturer, and Professor. Todd is also an experienced exercise physiologist, professional bike fitter, certified cycling coach, and strength and conditioning coach.  You can reach Todd at: TP2Coaching@gmail.com , by appointment only, or at his secure site https://toddparkertrainingprograms.com/ 


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