The Tour De France is a unique crucible. Weeks long, extreme temperature variations, exhaustive exercise day after day, and otherworldly nutritional demands; Is there a better place to learn and maximize performance for the athlete? One of the areas of deep interest over the last several years is the relationship of hydration, thermoregulation, and performance.
By Matt McNamara
Last week I went to a presentation by Dr. Stacy Sims, a post doctoral research fellow, and exercise physiologist at Stanford University. Dr. Sims was part of an exciting project with Dr. Allen Lim, chief physiologist for Garmin-Slipstream. Their goal was to help the team optimally prepare for the Tour De France, and to create effective thermoregulation and hydration fueling strategies for the race.
They project focused on a few critical components, namely a pre-race preparation/acclimation phase, the daily nutrition and recovery of the athletes, and the pre, during, and post event hydration needs. Through the course of the presentation Dr Sims touched on some rather interesting approaches and outcomes.
Hydration and Thermoregulation
First some background on water, hydration and thermoregulation. The human body is 55-65% water. Water is an essential aid in biochemical and metabolic reactions, it cools the body, and helps maintain the acid base balance.
Hydration is the equilibration of total body water (TBW) carried in the intracellular (66% of TBW) and extracellular (33% of TBW) spaces. Dehydration, medically speaking, is when the body contains insufficient water volume to maintain normal body function.
One of the foundational responsibilities of water is thermoregulation. Thermoregulation is “the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different.” For you and I, that means maintaining homeostasis between 37 – 40C (92-100F). Thermoregulation is vital to the maintenance of exercise intensity. Find yourself much on either side of that range and you are in for some trouble.
The Problem(s)
Dehydration, and its role in thermoregulation and performance is broad and complex.
It has been shown that a state of dehydration of as little as one percent (1%) leads to decreased aerobic endurance. At three percent (3%) there is a decrease in muscular endurance, while at four percent (4%) there is decreased muscle strength, fine motor skill, and heat cramps. In addition the maintenance of blood volume is essential for maintaining stroke volume and plasma volume.
Different athletes have different sweat rates, but most will sweat at between 1.5 – 3.0 Liters per hour. That means a 150 pound cyclist can reach 3% dehydration in as little as 45 – 60 minutes with no fluid intake (1 Liter = 1 Kilogram = 2.2 pounds). Unfortunately, gastric emptying is typically in the range of 0.8 – 1.3 Liters per hour, so you are on the defensive immediately. The more so if you start your race or training session hypohydrated (0.5-1% dehydrated) as most of us do by some estimates. You simply can’t drink enough fluid to offset the loss from sweating.
All of this sweating leads to thirst. There are two kinds of thirst. Hypovolemic thirst is the result of sweating, respiration, and/or bleeding. It is a decrease in the extracellular fluid and blood volume. Osmotic thirst is the result of a decrease in the intracellular fluid (e.g. too many solutes). Both depletions must be addressed prior to the onset of thirst.
While there are many products on the market that purport to help with your hydration and electrolyte balance, the truth is that most of them also contain a significant carbohydrate (CHO) load in order to also be seen as a viable fuel source (yet not quite enough to actually be a viable fuel source) and to be palatable. There are a couple of downsides to this. First, the CHO actually serves to increase core temperature (gotta process that food!), secondly it impedes gastric emptying. Often these sports-drinks contain too little sodium to effectively replace sweat salt losses as well. Sodium loss through sweating ranges between 0.8 – 4.0g/hr
The Solution
Dr Sims came up with a comprehensive set of solutions to the problems presented above. First, the team undertook a preparation/acclimation phase that included 30 minute bouts in the Sauna at 100 degrees immediately after their regular training rides. This was to both increase tolerance of warm temperatures and to systematically dehydrate the athletes to create a natural increase in Red Blood Cell (RBC) volume; a natural ergogenic aid.
The next step was to create a specific “Pre Event” drink in order to attenuate dehydration and to provide an ergogenic buffering effect. This pre-event drink was used primarily in the time trials and contained sodium bicarbonate and sodium citrate mix in a proprietary ratio (sorry, can’t give away ALL the secrets!), and a 1.5% sucrose concentration. The team used approximately 100 Liters of this mixture during the race.
The goal of the ‘During” drink was to attenuate dehydration. Carbohydrate was generally supplied via food stuffs. The “During” drink was a proprietary ratio of sucrose:glucose, with sodium citrate, magnesium, b-vitamins, and potassium. It contained no Sodium Choloride (NaCL), instead they used Sodium Citrate due to its decreased gastrointestinal stress and higher water retention rate, and inherent buffering effect. The team used approximately 10,000 Liters during the race
The “Post” drink was intended to stop the stress response, rehydrate, promote muscle repair and glycogen regeneration. It contained, among the list, a 1.5% solution of maltodextrim, potassium, amino acids, antioxidants, calcium, magnesium, and vitamins. They mixed over 8,000 Liters during the race.
Each of these drinks was formulated to be slightly hypotonic to increase absorption rates since water goes into the higher solute compartment in simple osmosis. The drinks were <270mmol/L solution compared to the blood plasma which is ~285-290 mmol/L. The ideal composition included roughly 100 mmol/L of Sodium, 6 mmol/L of Potassium, and 1.5 – 2% CHO solution (most sports beverage drinks are in the 6-8% CHO range).
Carbohydrate was also optimized. A sucrose/glucose solution was used during the races as it provided the best balance between increased water and sodium absorption and the highest possible CHO load without negatively affecting the osmolality (an indicator of fluid balance and ease of transport across cell membranes). The recovery drink used a 1.5% solution of maltodextrins, which are absorbed almost as rapidly as glucose with less gastric distress and impact on osmolality.
The Results
The validity of the project can be seen in a number of ways.
The preparation and acclimation component, especially the dehydration protocol, saw the athletes’ red blood cell concentration rise by up to 4%, and total plasma volume to increase by ~7%. This is a natural ergogenic aid akin to erythropoietin supplementation. There was also a decrease in exercising heart rate, an increase in work capacity and less total sweat loss during the race.
The “Pre” event drink was shown, anecdotally (n = 1), to increase power by ~7-8% on a 40Km time trial from 365W to 385-390W (time equivalent of 57 seconds!).
During the race the athletes routinely ingested two times the normal volume of liquid, yet suffered no GI distress. For the balance of the Tour the team used NO IV Drips! That is virtually unheard of in grand tours. At several points the athletes’ urine was ruled ‘too dilute to test’ a testament to the effectiveness of the hydration strategy.
On the results sheet the team placed two riders in the top 10, finished second overall in the team competition and team time trial. During the Stage 18 individual time trial the team had three riders in the top 10, all within a minute of the stage winner.
Summary
Each year a variety of new technologies and methodologies are rolled out in the search for speed and consistency. Technicians buzz around checking details, tightening torque wrenches and generally pondering the speed to be gained. Similarly, the athletes and soigneurs engage in their own daily performance dance. Legs are embrocated, stretched and massaged. Food is constantly ingested and chased by fluids, prodigious amounts of fluids. All in the quest to take the athlete right to the edge of performance
One of the most demanding elements of the race is the quest to maintain hydration, electrolyte balance, and thermoregulation. This year Garmin-Slipstream brought in a leading researcher to help create the perfect plan for the team. By combining a rigorous pre event acclimation camp with the creation of some truly high tech mixtures for each phase of the race the team was able to succeed in the battle for results and the battle for the long term health of their riders. With notable increases in work capacity, fluid retention, and red blood cell volume; and with notable decreases in gastrointestinal distress, exercise heart rate and overall heat stress it can be argued that this type of cutting edge research and implementation was a key element in the team’s success. You can expect this project to make it into your list of hydration and fluid options within the next 12 months or so
References
Maughan, R. J., and T. D. Noakes; Fluid replacement and exercise stress: a brief review of studies on fluid replacement and some guidelines for the athlete. Sports Med. 12:16-31, 1991.
Takamara, A., Y. Tetsuya, N. Nishida, and T. Morimoto; Relationship of osmotic inhibition in thermoregulatory responses and sweat sodium concentration in humans. Am J Physiol Regulatory Integrative Comp Physiol 280: R623–R629, 2001.
Gillen, C. M., T. Nishiyasu, G. Langhans, C. Weseman, G. W. Mack, and E. R. Nadel; Cardiovascular and renal function during exercise-induced blood volume expansion in men. J Appl Physiol, 76: 2602 – 2610, 1994.
Hargreaves, M., and M. Febbraio; Limits to exercise performance in the heat. J Sports Med., 19: S115-S116, 1998.
Montain S. J., and E. F. Coyle; Influence of graded dehydration on hyperthermia and cardiovascular drift during exercise. J Appl Physiol, 73(4):1340-1350, 1992.
Sanders, B., T. D. Noakes, and S. C. Dennis; Sodium replacement and fluid shifts during prolonged exercise in humans. Eur. J. Appl. Physiol., 84:419-425, 2001.
Sims ST, Rehrer NJ, Bell ML, Cotter JD. Preexercise sodium loading aids fluid balance and endurance for women exercising in the heat. J Appl Physiol 103: 534–541, 2007.
Sims, ST, L vanVliet, JD Cotter, and NJ Rehrer. “Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat.” Medicine and Sciences in Sports and Exercise, 39 (1), 123-130, 2007
About Matt McNamara: Matt is a USA Cycling Level 1 coach with over 20 years of racing, coaching and team management experience. He is the founder and president of Sterling Sports Group, a performance coaching company focused on creating a seamless interface between athlete and coach, technology and personal attention. Learn more by visiting his website at www.sterlingwins.com.
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