Fitness Training News
Saturday, March 10, 2012Dehydration...More Salt, less Salt, Drink, Drink, Drink. Ahhhhhhhhhhhh. What to eat? What to drink? When to do either or both?
You've picked out and thought about your 2012 "A" race/event. It's your most important event of the season. Will it be in Europe? Canada? South Africa? The US? Hot climate? Humid? Cold? Supported or self supported?
It's a good idea to start thinking about working on your food and fluid intake while riding or racing before you get too far into the season. Think about what foods you've already practiced taking on your training rides and shorter races/events. How can you fine tune it? How much water and electrolyte drinks do you expend or sweat out? Lots to think about and practice.
One thing that comes to mind is the question(s) about drinking while exercising... how does it affect thermoregulation?
A couple of years ago I was attending a presentation, at the Olympic Training Center, by Stacy T Sims, Phd, on Thermoregulation: Manipulation for Performance. Great presentation and an eye opener.
Dr. Sims works with individual endurance athletes to find the optimal formulae of hydration and nutrition to succeed in their sport. Currently she is a consultant for Team RadioShack and Dr. Allen Lim, individuals of TeamTibco and Webcor professional women’s cycling, Matt Dixon of PurplePatchFitness, and Craig Upton of PerformanceLabsHC. She worked with Garmin-Slipstream for the 2009 Tour de France and USACycling West Coast Development camps Exercise Physiologist and Sport Nutritionist at Stanford University) .at the Olympic Training Center.
The big take-a-way from the talk, for me, was we need to be hydrated in order to help our bodies deal with heat.
Dehydration causes: Increased strain on the heart, reduced aerobic endurance, reduced muscular endurance, reduced muscles strength, reduced fine motor sills, heat cramps, heat exhaustion, reduced mental capacity, physical exhaustion, heat stroke and coma. WOW!
A good formula to remember:
Max sweat rates can be 1.5 - 3.0 L/h but gastric emptying max rates are only 0.8 – 1.3L/h
We lose water and electrolytes through breathing, sweat, and bleeding (women). The rate of water loss is higher than the rate of solute loss. It's also good to know that on a daily basis, most of us are not hydrated enough. Only 1% or body weight loss is detrimental to exercise performance. I think I'll go get a glass of water now.
Another thing Stacy told us was that we can "train" our bodies to do better in heat. And I thought all those crazy riders training in green houses were silly. hhhmmm.
Repeated, prolonged exercising in a heated environment can cause adaptations to the heat stress placed upon the body. The thermoregulatory system can be stressed so that it adapts to the heat demand by enabling the body to eliminate excess body heat more effectively. This process is known as heat acclimatization. With this adaptation, many adjustments are made in both blood flow and sweating. The rate of sweating during activity in the heat increases with heat acclimatization, and the amount of sweat produced often increases in the most exposed areas that are most effective at dissipating body heat. We want this all to occur so that we can have a lowered skin temperature. Being hydrated helps this!
When to take on more sodium. Know your sweat rate. Get up in the morning and drink about 4 ounces of water. Wait 15 minutes and then go weigh yourself. After you do a training ride in the heat or or high volume come home and weigh yourself. If you lost weight-you lost sweat and that means you lost sodium and fluids.
When is drinking drinking too much? Hyponatremia: This is a good thing for me to know as I do not sweat very much, at all.
Hyponatremia is a condition that results in an abnormally low concentration of sodium in the blood. This can be caused by the ingestion of too little sodium or by the ingestion of so much water that the concentration of sodium is decreased. An athlete who experiences a low rate of sweating that continues to ingest large quantities of water over a several hour period of exercise is vulnerable to this injury. A very low concentration of sodium can compromise the central nervous system, thus creating a potentially life-threatening condition. Hyponatremia can be completely avoided with adequate ingestion of sodium. You have to play around with this--meaning practice. I am not a fan of the salt tablets, instead I prefer to make sure my food intake or electrolyte drinks have what I need. For this reason, I am a fan of drinking before I am thirsty (remember, many of us are already 50% dehydrated when our bodies tell us we are thirsty) about a bottle an hour on an average temperature day. More if very hot.
When it's hot it is so important that we continually replaces lost fluids by drinking enough quantities of water and take enough electrolytes to replace what we give off. (Coyle E: Fluid and carbohydrate replacement during exercise: how much and why? Sports Sci Exchange 7(50):1, 1994).
The average adult performing minimal physical activity requires a minimum of 2.5 liters of water a day. A normal sweat loss rate for a person during an hour of exercise ranges between 0.8 and 3 liters of water. (Murray R: Guidelines for fluid replacement during exercise. Australian Journal of Nutrition and Dietetics 53(4 suppl):S17, 1996).
Ok-now that we know we want to make sure we take in an electrolyte drink while exercising longer than a couple of hours. It's not just about sodium, but this is one of the more critical electrolytes. Too, there is enough research to show that when conditions are hot, we likely cannot get enough sodium in a sports drink.
Your body knows the importance of maintaining adequate water saturation levels. If you ignore the signals of being thirsty your body water will continue to decrease, resulting in dehydration.
It is important to note that we cannot always rely on our thirst response as a signal to ingest water. If you are waiting to drink (only) when you feel thirsty, you could already have lost 50% of your water lost through sweating and evaporation. By the time you feel thirsty, dehydration is already occurring on a wide-scale level; therefore, athletes must drink water before they feel thirsty. (Newburgh LH: Physiology of heat regulation. Philadelphia: Saunders, 1949.)
Not all sports drinks are the same and you will have to try different electrolyte sports drinks to see which is best for you. I prefer Clif Bar's Clif Shot Electrolyte drink. My husband needs more salt and so he'll generally use The Clif Shot drink to start and then switch over to Gatoraide 5 hours into a long ride. You have to try different drinks to make sure which one works best for you.
Have fun-tis the season to practice, practice, practice. # posted by Michelle Grainger @ 2:41 PM