Posts

Athletes And Fuel – Feeling Fuelish?

runnerWhen it comes to fueling an athlete, there had been as many approaches as there are sports to play. Several respected bodies have merged philosophies to incorporate and publicize nutritional recommendations that can be adapted to most athletic pursuits. There is much about diet that is common sense, but the habits cultivated from family traditions just might fly in the face of that. Ethnic or regional cuisines may feature foods that upset the balance of both macro- and micro-nutrient intake. There is no doubt that the physiological needs of serious athletes have to be the first consideration in finding and combining the right fuels.

Optimal nutrition is mandatory if an athlete wants to realize his full potential during an event. Not only performance, but also recovery, is enhanced by food intake. A position paper issued jointly by the American Dietetic Association, the Dietitians of Canada, and the American College of Sports Medicine, states, “Energy and macronutrient needs, especially carbohydrate and protein, must be met during times of high physical activity to maintain body weight, replenish glycogen stores, and provide adequate protein to build and repair tissue,” continuing that, “Adequate food and fluid should be consumed before, during, and after exercise to help maintain blood glucose concentration during exercise, maximize exercise performance, and improve recovery time. Athletes should be well hydrated before exercise and drink enough fluid during and after exercise to balance fluid losses.”  (Rodriguez. 2009)

Your performance will be affected by genetics (over which you have zero control), training (over which you have total control), and diet (ditto). If you fail to consume enough energy, the body will use both fat and lean tissue as fuel. Strength and endurance will then suffer, and the immune system and endocrine glands will pay a stiff price. If you’re trying to lose weight, you still have to pay attention to energy intake. It takes calories to burn calories. This is especially true for women, who may experience amenorrhea and osteoporosis if they aren’t careful.

You can store about 400 to 600 grams of carbohydrates, or 1600 to 2400 calories’ worth. These glycogen stores can be burned in 1 ½ to 2 hours, after which fat is mobilized and you “hit the wall.”  You don’t want to get more than about 60 grams of carbohydrates (CHO) an hour while in a marathon, for example, or you might cramp, but your daily intake could be 5-7 grams per kilogram a day (about 3 grams per pound) for moderate exercise that lasts less than 1 ½ hours. For more intense exercise, like that marathon or a cycling event, that lasts more than a couple hours, you’ll need 8-12 grams of CHO a day per kilogram of body weight. Do this prior to, not during, an event. (Burke. 2011)  You might as well convert your body weight to kilograms now. Divide pounds by 2.2 and you’ll have it.

Eating before an event will enhance performance compared to fasting. Common sense says to eat lesser amounts an hour before an event than you would eat four hours ahead of a strenuous workout. Traditional wisdom says that consuming up to 1 gram of CHO per kg is fine one hour before the start; Consuming 4.5 gm/kg is O.K. four hours before. Take it easy on the fiber and fat, though, or you might experience GI distress. During practice sessions is the time to experiment with different foods to come up with effective refueling strategies that fit you.

Protein intake depends on the type and duration of exercise. 0.8 gm/kg/day is fine for the general public, but you’ll probably need more. An endurance athlete will need 1.2-1.4 gm/kg/day, while a weight lifter needs up to 1.7 gm/kg/day. More than 2.0 mg/kg can tax the kidneys and won’t make much physiological difference. It’s important to get protein right after exercise. There’s a 15 minute to 2-hour window during which muscle balance can be increased and muscle tissue can be repaired. Protein supplements are nothing more than a convenience. Besides, such supplements can become delivery systems for things you neither want nor need, like steroids and other illicit substances.

At the end of your performance you need to refill your buckets. That’s called recovery. Adding protein to your carbohydrate intake at a ratio of 3:1 or 4:1, CHO:Pro, can enhance recovery. (Ivy. 2001)  We know of a few marathoners who eat tuna sandwiches with chocolate milk. You might opt for a bowl of Cheerios and a banana, or a yogurt-fruit smoothie and pretzels. Listen to your body. You might end with steak and potatoes. Lemon meringue pie, and carrot cake, and oatmeal cookies, and…  Dream on….PSST, you can do without the sugar.

*These statements have not been evaluated by the FDA.
These products are not intended to treat, diagnose, cure, or prevent any disease.

Keeping Your Electrolytes in Balance

Gym girlWithout electrolytes, physiological stability—called homeostasis—goes haywire and nerve and muscle function are disturbed, body fluid balance is upset, and other critical body workings are interrupted. These tiny particles of metals carry electrical charges and are present in all body fluids, including urine, blood and plasma. Without the proper timing and intensity of electrical impulses, nerve, heart and muscle function suffer, and might even stop in severe instances. If electrolytes are lost, as would happen in extreme exercise or sickness, replenishment is necessary, but in appropriate amounts. Imbalances can have terrible effects, and they can be caused by a deficiency or an excess. In the chemistry jargon, the prefix hypo- means “too little,” and the prefix hyper- means “too much.”

There is a laundry list of conditions that can lead to electrolyte imbalances, including dehydration and over-hydration, diabetic ketoacidosis, cancer, and head injuries like concussions. Kidney disease, though, is at the top of the list because the kidney’s job is to control fluid, electrolyte, and acid-base balance (Claure, 2012). The surest way to deal with electrolytes is through diet or supplementation, using an electrolyte replacement if necessary, as you might when exercising in the hot weather or when participating in endurance events.

We’ll start with sodium, since it’s the most abundant cation (positive ion) in the extracellular fluid (outside the cell). We need sodium to maintain normal blood pressure in addition to sending electrical messages to initiate a muscle contraction. Water will follow salt into the body. Too much salt will increase blood osmolality, meaning, in a way, that blood has more stuff floating in it because there is too little liquid. If that happens you get thirsty, and anti-diuretic hormone tells the kidneys not to let go of water. Opposite that, low osmolality means that the blood is more watery. If too much water is lost from sweat, respiration, urination, or the weather, or if too much salt is taken in, you have hypernatremia and may suffer symptoms such as disorientation, nausea without vomiting, rapid heartbeat, sunken eyes, or trembling. Your cells are drying out and the kidneys are conserving water, so you don’t urinate.

Losing sodium—hyponatremia—can happen when you drink volumes of plain water during a bout of intense exercise, especially in hot weather. Add lethargy and confusion to the hypernatremia symptoms. If sodium falls too low, permanent neurological damage can occur.  People who have been forced to drink water to take a work-related urine drug test have fainted from hyponatremia, and have experienced hypertension and difficulty breathing.

Potassium is the primary cation inside the cell, where its major physiological role is the regulation of muscle and nerve excitability as the director of relaxation immediately following a muscular contraction initiated by sodium. Potassium imbalance is particularly monitored because of its relationship to coronary health and the heart’s ability to change electrical potential. Imbalance may cause arrhythmia. Excess (hyperkalemia) will cause cardiac arrest; deficit (hypokalemia) will irritate cardiac muscle and increase the chance of premature atrial or ventricular contractions, possibly leading to death. Potassium balance leaves little room for error (van der Meer, 1986) (Lindinger, 1995).

Magnesium, like potassium, is also found inside the cell, where it affects muscle function, energy production and carbohydrate and protein metabolism. Kidney disease is a major cause of hypermagnesemia, although taking too many magnesium-bearing antacids can contribute. Too much magnesium will cause lethargy, which is understandable because magnesium is a relaxant (Gold, 1990) (Spivey, 1990). Too little magnesium is common in the critically ill (Dacey, 2001), among whom mortality is high. Similar to hypokalemia, hypomagnesemia may induce cardiac arrhythmia, although milder signs occur before that happens. Muscle weakness, tremors, anorexia and dizziness are the more common. Can’t sleep?  Got leg cramps?  Magnesium may help (Young, 2002, 2009) (Geurrera, 2009) (Allen, 2012).

Although calcium is electrolytic, it seldom appears in electrolyte replacement drinks because most Americans, especially women, supplement at the behest of their doctors. Calcium works with phosphorus in an inverse relationship. When the value of one is high, the other is generally low. Calcium is involved in contraction of cardiac and smooth muscle, but also enhances the clotting mechanism, maintains cell membrane permeability and helps to transmit nerve impulses. You already know about the bones and teeth. Phosphorus also plays a role in bone formation, but is also needed for energy production and for macronutrient metabolism. By buffering hydrogen ions, it helps to maintain acid-base balance, as well. Like calcium, phosphorus needs are easily met without an electrolyte beverage. Deficiency is rare and occurs secondary to other conditions rather than as a result of low dietary intake. High doses of antacids may deplete phosphorus.

If your exercise regimen lasts more than an hour, especially in warm weather, you’re a candidate for electrolyte replacement. Hard games like tennis, cycling and marathon running, and assiduous resistance training call for such a beverage. During these times, you might need to drink a cup of electrolyte replacement every fifteen or twenty minutes to keep a steady pace and to avoid cramps. Thirst is not always the best barometer for gauging electrolyte needs. A beverage with sugar will compromise the bioavailability of minerals. Since sodium is the first electrolyte lost to heavy sweating, it’s a major consideration in repletion, so don’t be alarmed if you see high levels of sodium in your drink. If you’re interested in balancing electrolytes for yourself and the family, which is especially important when the kids get sick, take a look here:
http://crampnomore.com/sportshealth/electrolytes-101.html. There’s an informative bulletin explaining the how and why of electrolytes, the balance of which is no laughing matter.

References

Allen RE, Kirby KA.
Nocturnal leg cramps.
Am Fam Physician. 2012 Aug 15;86(4):350-5.

Chiasson JL, Aris-Jilwan N, Bélanger R, Bertrand S, Beauregard H, Ekoé JM, Fournier H, Havrankova J.
Diagnosis and treatment of diabetic ketoacidosis and the hyperglycemic hyperosmolar state.
CMAJ. 2003 Apr 1;168(7):859-66.

Claure R, Bouchard J.
Acid-base and electrolyte abnormalities during renal support for acute kidney injury: recognition and management.
Blood Purif. 2012;34(2):186-9

Dacey MJ.
Hypomagnesemic disorders.
Crit Care Clin. 2001 Jan;17(1):155-73, viii.

Gold ME, Buga GM, Wood KS, Byrns RE, Chaudhuri G, Ignarro LJ.
Antagonistic modulatory roles of magnesium and calcium on release of endothelium-derived relaxing factor and smooth muscle tone.
Circ Res. 1990 Feb;66(2):355-66.

Guerrera MP, Volpe SL, Mao JJ.
Therapeutic uses of magnesium.
Am Fam Physician. 2009 Jul 15;80(2):157-62.

Heinrich S, Wagner A, Gross P.
Hyponatremia.
Med Klin Intensivmed Notfmed. 2012 Sep 6.

Lindinger MI.
Potassium regulation during exercise and recovery in humans: implications for skeletal and cardiac muscle.
J Mol Cell Cardiol. 1995 Apr;27(4):1011-22.

Nakao I, Ito T, Kasai N.
Electrolyte metabolism and emergency.
Gan To Kagaku Ryoho. 1983 Feb;10(2 Pt):198-203.

Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS.
American College of Sports Medicine position stand. Exercise and fluid replacement.
Med Sci Sports Exerc. 2007 Feb;39(2):377-90.

Shibata H.
Cancer and electrolytes imbalance.
Gan To Kagaku Ryoho. 2010 Jun;37(6):1006-10.

Spivey WH, Skobeloff EM, Levin RM.
Effect of magnesium chloride on rabbit bronchial smooth muscle.
Ann Emerg Med. 1990 Oct;19(10):1107-12.

van der Meer C, Valkenburg PW, Snijders PM.
Studies on hyperkalemia as a cause of death in intestinal ischemia shock in rats.
Circ Shock. 1986;19(3):329-45.

Young GL, Jewell D.
Interventions for leg cramps in pregnancy.
Cochrane Database Syst Rev. 2002;(1):CD000121.

Young G.
Leg cramps.
Clin Evid (Online). 2009 Mar 26;2009. pii: 1113.

Zümrütdal A.
Basic principles in liquid electrolyte treatment
Anadolu Kardiyol Derg. 2012 Dec 17. doi: 10.5152/akd.2013.043.

*These statements have not been evaluated by the FDA.
These products are not intended to treat, diagnose, cure, or prevent any disease.