Learn Triathlon from the best (DVDs)
Good podcast interview with Dave Scott and Jason Ash
Submitted by admin on Fri, 09/25/2009 - 14:40 This is a good audio interview of Dave Scott and Jason Ash. Enjoy. One interesting note is that Dave Scott advocates working injury prevention into your program.
Rules of Training
Submitted by admin on Tue, 09/22/2009 - 16:30 For many, this is the season they rest or maybe you're thinking about racing next year. If you're coming off a long rest or starting here are the "Cardinal Rule of Training" excerpt from Joe Friel. Although this excerpt is about cycling, the principles apply to fitness in general. This excerpt from Cycling Past 50 is reprinted with permission by Human Kinetics.
"Since 1971, I’ve trained and coached athletes in a variety of sports with abilities ranging from beginner to professional. Some became national- and world-class competitors; others achieved less impressive, but no less important, personal goals. All improved their physical abilities in some way.
The first question to ask at the start of a week is, "How often should I ride?" Training to race, for example, in the United States Cycling Federation’s national age-group championship, requires a different response to this question than if the goal is general health and fitness. The higher the goal for ultimate performance, the more often you need to ride.
Potential is an elusive concept: an ability that is possible but not yet realized. None of us ever knows how close we are to our potential. We do know, however, that getting there demands many sacrifices, one of which involves being on a bike several times a week instead of sitting in front of a TV nibbling on potato chips. When it comes to frequency, there are suggested minimums and maximums, depending on goals. If your reasons for riding are strictly health and basic fitness, the minimum number of rides each week is three. This assumes you ride only and don’t cross train. Because training in other aerobic sports has a cardiovascular benefit, you could get away with riding less frequently and still improve the most basic elements of health and fitness.
Other than achieving high levels of fitness, another frequency issue is how to get in shape the fastest. When first starting to train on a bike, five or six rides each week will cause the most rapid change in fitness. Scientific research shows an increase in aerobic capacity, one measure of fitness, of about 43 percent for novices training this frequently. Three to four rides each week bring a 20- to 25-percent improvement.
If you already have a high aerobic capacity from many weeks of consistent training, all you need to maintain it is four rides a week. High-performance racers, however, usually ride five to seven times a week.
Intensity
Regardless of training frequency and time, the single most critical training variable is how hard and fast you ride. There are several ways of measuring intensity. The one you’re most likely to have available is heart rate. The greatest changes in aerobic capacity come from training at high heart rates, in excess of 90 percent of maximum. Although the highly motivated athlete often seeks such benefits, frequent training over 90 percent of maximum heart rate obviously violates the Cardinal Rule of moderation and will eventually lead to inconsistency and loss of fitness.
The key to cycling intensity is knowing when to ride at higher heart rates and when to slow down. So, 90 percent plus is the high side, but what about the low end? Riding less than 50 percent of maximum heart rate has little or no impact on aerobic fitness. Such low-effort riding is of little physiological value except, perhaps, for recovery.
Getting intensity right is the trickiest aspect of training. Later, this chapter will teach you how to use a heart rate monitor, and chapters 5 and 6 will pull all pieces of the training puzzle together with suggested routines based on riding goals.
Time
The duration of your rides is the second most effective variable in improving fitness. In fact, there’s good reason to believe that longer, slower workouts are equivalent to shorter, faster training sessions in improving aerobic capacity. Because lower intensity workouts are easier on the body, most athletes and coaches recommend building a base of endurance with long, steady rides before starting to do high-intensity workouts, such as intervals, later in the training year.
The length of your rides depends on what you’re used to. In your first five years of cycling, you should be able to increase riding mileage or time by about 10 percent over the previous year’s volume. However, if you’ve ridden for several years, there’s a limit to how many miles you need to improve. Through experience, you may have already discovered that limit - due primarily to an inability to recover and go again."
"Since 1971, I’ve trained and coached athletes in a variety of sports with abilities ranging from beginner to professional. Some became national- and world-class competitors; others achieved less impressive, but no less important, personal goals. All improved their physical abilities in some way.
I don’t know who learned more - me or
them. My lessons came from observing how small changes in training
brought big results. Some riders obviously had a lot of potential when
they came to me. They were highly motivated and did challenging
workouts, but for some reason they weren’t getting all they could from
training. At first this was perplexing. How could athletes with such
great potential achieve so little? After years of reviewing hundreds of
training logs, I began to see patterns and understand why a person with
latent ability was not coming close to attaining it. He or she was
breaking one of what I call the Cardinal Rules of Training.
No
matter what you want from riding, there are three rules you must obey.
Breaking any of these means, at best, limited improvement, and, at
worst, overtraining and loss of fitness. The Cardinal Rules of Training
are as follows:
- Rule 1. Ride consistently.
- Rule 2. Ride moderately.
- Rule 3. Rest frequently.
These may seem overly simple. Sometimes, however, the most
important things in life are the simplest. Such is the case with
training.
Rule 1 is based on the premise that nothing does
more to limit or reduce fitness than missed rides. The human body
thrives on regular patterns of living. When cycling routinely and
uniformly progressing for weeks, months, and years, fitness steadily
improves. Interruptions from injury, burnout, illness, and overtraining
cause setbacks. Each setback means a substantial loss of cycling
fitness and time reestablishing a level previously attained.
Inconsistent riding is like pushing a boulder up a hill only to see it
roll back down before reaching the top - frustrating.
Riders
who violate the first rule of training are usually frustrated. The
solution to their problem is simple: Train consistently. "Okay," they
say, "but how do I do that?" Good question, and that leads to the other
Cardinal Rules. The second Rule, ride moderately, is the first step in
becoming more consistent. This one usually scares highly motivated,
hard-charging cyclists. They can see themselves noodling around the
block in slow motion and not even working up a sweat. However, that’s
not what moderate means.
Moderate riding is that level of
training to which your body is already adapted, plus about 10 percent.
For example, if the longest recent ride is 40 miles, then a reasonable
increase is to 45 miles next week. That’s moderate. A 60-mile ride
would not be moderate and could lead to something bad, such as an
injury or overtraining that forces several days off the bike and a
lapse in consistency. Another moderate change is steadily progressing
from riding flat terrain to rolling hills, to riding longer hills, to
riding steep and long hills. Going from riding on the flats to steep,
long hills is not moderate.
Consistent riding also requires
frequent resting. That means planning rest at the right times, such as
after challenging rides or hard weeks. Chapter 7 discusses this
misunderstood concept in greater detail. Rest taken in adequate doses
and at appropriate times produces consistent training and increased
fitness.
Even though the Cardinal Rules of Training are basic,
if you follow them, fitness will improve regardless of what else you do
on the bike. They are deceptively simple to read about; incorporating
them into training is a different matter. At first, it may be difficult
to ride moderately and rest frequently. Keep working at it. Old habits
are hard to break. When you initially train this way, it’s better to
err on the side of being conservative with moderation and rest if
you’re a rider who has frequent breakdowns and missed workouts. With
experience you’ll become better at determining what is right for you.
Although what we have discussed so far came strictly from experience,
the following basic components of training come mostly from science.
F.I.T. for Riding
Even though moderation is necessary, it’s obvious that a portion of
your riding must be somewhat stressful to cause a positive change in
fitness. Moderate stress comes from carefully manipulating three
workout variables:
- Frequency - how often to ride
- Intensity - how hard to ride
- Time - how long to ride
The first question to ask at the start of a week is, "How often should I ride?" Training to race, for example, in the United States Cycling Federation’s national age-group championship, requires a different response to this question than if the goal is general health and fitness. The higher the goal for ultimate performance, the more often you need to ride.
Potential is an elusive concept: an ability that is possible but not yet realized. None of us ever knows how close we are to our potential. We do know, however, that getting there demands many sacrifices, one of which involves being on a bike several times a week instead of sitting in front of a TV nibbling on potato chips. When it comes to frequency, there are suggested minimums and maximums, depending on goals. If your reasons for riding are strictly health and basic fitness, the minimum number of rides each week is three. This assumes you ride only and don’t cross train. Because training in other aerobic sports has a cardiovascular benefit, you could get away with riding less frequently and still improve the most basic elements of health and fitness.
Other than achieving high levels of fitness, another frequency issue is how to get in shape the fastest. When first starting to train on a bike, five or six rides each week will cause the most rapid change in fitness. Scientific research shows an increase in aerobic capacity, one measure of fitness, of about 43 percent for novices training this frequently. Three to four rides each week bring a 20- to 25-percent improvement.
If you already have a high aerobic capacity from many weeks of consistent training, all you need to maintain it is four rides a week. High-performance racers, however, usually ride five to seven times a week.
Intensity
Regardless of training frequency and time, the single most critical training variable is how hard and fast you ride. There are several ways of measuring intensity. The one you’re most likely to have available is heart rate. The greatest changes in aerobic capacity come from training at high heart rates, in excess of 90 percent of maximum. Although the highly motivated athlete often seeks such benefits, frequent training over 90 percent of maximum heart rate obviously violates the Cardinal Rule of moderation and will eventually lead to inconsistency and loss of fitness.
The key to cycling intensity is knowing when to ride at higher heart rates and when to slow down. So, 90 percent plus is the high side, but what about the low end? Riding less than 50 percent of maximum heart rate has little or no impact on aerobic fitness. Such low-effort riding is of little physiological value except, perhaps, for recovery.
Getting intensity right is the trickiest aspect of training. Later, this chapter will teach you how to use a heart rate monitor, and chapters 5 and 6 will pull all pieces of the training puzzle together with suggested routines based on riding goals.
Time
The duration of your rides is the second most effective variable in improving fitness. In fact, there’s good reason to believe that longer, slower workouts are equivalent to shorter, faster training sessions in improving aerobic capacity. Because lower intensity workouts are easier on the body, most athletes and coaches recommend building a base of endurance with long, steady rides before starting to do high-intensity workouts, such as intervals, later in the training year.
The length of your rides depends on what you’re used to. In your first five years of cycling, you should be able to increase riding mileage or time by about 10 percent over the previous year’s volume. However, if you’ve ridden for several years, there’s a limit to how many miles you need to improve. Through experience, you may have already discovered that limit - due primarily to an inability to recover and go again."
Connection between diet and muscle cramping
Submitted by admin on Thu, 09/17/2009 - 01:00 Base training starts soon if it hasn't already which brings on longer bouts of exercise. The longer you go, you more you need to know how your body's chemical reactions are happening. This excerpt from Vegetarian Sports Nutrition is reprinted with permission by Human Kinetics.
"If you look at the information presented in most exercise physiology and sports nutrition books, you will notice an obvious omission of discussions of muscle cramps. This is probably because little is known about muscle cramps. Nonetheless, I am a true believer that imbalances of fluid or the mineral electrolytes—sodium, potassium, calcium, and magnesium—in the diet should be ruled out as contributors to all nocturnal and exercise-associated cramps.
Fluid Imbalances and Dehydration
Whether fluid imbalances and mild dehydration can trigger muscle cramping is open to debate. Although we know that muscle cramps can and do occur with severe dehydration and heat injury, there is no conclusive evidence that consuming adequate fluid with or without electrolytes will prevent typical nocturnal or exercise-associated cramping. In fact, studies have found that runners, cyclists, and triathletes who develop cramps during an endurance event are no more likely to be dehydrated or to have lost greater amounts of bodily water than are those who do not develop cramps during the same race. In my practice, however, I have noted anecdotally that maintaining a proper fluid balance indeed helps many endurance and team athletes avoid cramps, particularly those that occur after exercise or when sleeping at night. In one case, I worked with a male tennis player from Switzerland who had a history of severe cramping and fatigue after practice that was relieved by a regular and diligent fluid-consumption schedule. In her book, well-known sport nutritionist Nancy Clark tells an amusing story about a runner who eliminated his painful muscle cramps by following the simple postexercise advice to first drink water for fluid replacement and then have a beer for social fun.
Sodium
Sodium is one of the main positively charged mineral ions or electrolytes in body fluid. The body needs it to help maintain normal body-fluid balance and blood pressure, and in conjunction with several other electrolytes, it is critical for nerve impulse generation and muscle contraction. Sodium is distributed widely in nature but is found in rather small amounts in most unprocessed foods. In most developed countries, however, a significant amount of sodium is added from the salt shaker (1 teaspoon [6 g] contains 2,325 milligrams of sodium) or by food manufacturers in processing (as listed on the food label). Because sodium intake can vary, the typical Western diet contains 10 to 12 grams of salt (3.9 to 4.7 g of sodium) per day.
Because sodium plays an important role in regulating blood pressure and fluid and electrolyte balance, the body has an effective mechanism to help regulate the levels of sodium in the blood on a variety of sodium intakes. If the sodium concentration in the blood starts to drop, a series of complex events leads to the secretion of a hormone called aldosterone, which signals the kidneys to retain sodium. If sodium levels are too high, aldosterone secretion is inhibited, which allows the kidneys to eliminate some sodium through urination. Another hormone, called antidiuretic hormone (ADH), also helps maintain normal sodium levels in body fluids by signaling the kidney to retain water and sodium. Typically, levels of both aldosterone and ADH increase during exercise, which helps conserve the body’s water and sodium stores.
Actual sodium-deficient states caused by inadequate dietary sodium are not common because the body’s regulatory mechanisms are typically very effective. Humans even have a natural appetite for salt, which helps assure that they take in enough sodium to maintain sodium balance. Indeed, I have great memories of eating salty tortilla chips wet with a little water—so more salt would stick—after long cycling races in Arizona. Thankfully, these sodium-conserving mechanisms are activated in athletes who lose excessive sodium and other electrolytes during prolonged sweating.
Although muscle cramps are reported to occur during the sodium-deficient state, some researchers believe that alterations in sodium balance are not involved in exercise-associated cramps. This is despite the fact that significantly lower postexercise serum sodium concentrations have been found in endurance athletes who experienced cramps during a race compared to those who did not develop cramps. One of the reasons this is downplayed may be because serum sodium concentrations remain within the normal range, despite being significantly lower in the athletes with muscle cramps.
Nevertheless, it is important for athletes to consume enough sodium to replace what is lost through sweat. Despite the regulatory mechanisms discussed earlier, it is possible for vegetarian athletes to be at risk for muscle cramps and other problems because of low sodium intake. The reason is most likely because they ignore their salt craving cues—eating mostly unprocessed and unsalted foods—while continuing to lose considerable salt through sweating. The recommendation set by the USDA’s Dietary Guidelines for Americans to keep sodium intake to 2.3 grams or less per day is not appropriate for most athletes because of their higher sodium losses. Thus, while it is not likely that low sodium intake is the cause of cramps in most athletes, it is certainly possible that a vegetarian athlete prudently following a low-sodium diet for health reasons might experience muscle cramps that would be relieved with more liberal use of the salt shaker.
Potassium
Potassium is the major electrolyte found inside all body cells, including muscle and nerve cells. It works in close association with sodium and chloride in the generation of electrical impulses in the nerves and the muscles, including the heart muscle. Potassium is found in most foods, but is especially abundant in fresh vegetables, potatoes, certain fruits (melon, bananas, berries, citrus fruit), milk, meat, and fish.
Potassium balance, like sodium balance, is regulated by the hormone aldosterone. A high serum potassium level stimulates the release of the hormone aldosterone, which leads to increased potassium excretion by the kidneys into the urine. A decrease in serum potassium concentration elicits a drop in aldosterone secretion and hence less potassium loss in the urine. As with sodium and calcium, potassium is typically precisely regulated, and deficiencies or excessive accumulation are rare. Potassium deficiencies, however, can occur with conditions such as fasting, diarrhea, and regular diuretic use. In such cases, low blood–potassium concentrations, called hypokalemia, can lead to muscle cramps and weakness, and even cardiac arrest caused by impairment in the generation of nerve impulses. Similarly, high blood–potassium concentrations, or hyperkalemia, are also not common but can occur in people who take potassium supplements far exceeding the recommended daily allowance. High blood–potassium concentrations can also disturb electrical impulses and induce cardiac arrhythmia.
Even though little evidence is available to support a link between potassium intake and muscle cramps, it is quite interesting that most athletes—and non-athletes alike—think that the banana is the first line of defense in preventing muscle cramps. If only it were that simple. Furthermore, athletes following vegetarian diets are not likely to experience muscle cramping as a result of low potassium intake because the vegetarian diet provides an abundance of potassium. An athlete who is recovering from an intestinal illness, restricting calories, or taking diuretics or laxatives should, nevertheless, make an effort to consume potassium-rich foods, particularly if he or she is experiencing muscle cramping. Because of the dangers of hyperkalemia, potassium supplements are not recommended unless closely monitored by a physician. The recommended daily intake for potassium is 4,700 milligrams per day for adults.
Calcium
As discussed in chapter 6, the vast majority of calcium found in the body is found in the skeleton where it lends strength to bone. Calcium, however, is involved in muscle contractions, including that of the heart, skeletal muscles, and smooth muscle found in blood vessels and intestines, as well as the generation of nerve impulses. Blood calcium is tightly controlled and regulated by several hormones, including parathyroid hormone and vitamin D.
Although impaired muscle contraction and muscle cramps are commonly listed as symptoms of calcium deficiency, many exercise scientists feel that low calcium intake is not likely to play a role in most muscle cramps. This is because if dietary calcium intake were low, calcium would be released from the bones to maintain blood concentrations and theoretically provide what would be needed for muscle contraction. This thinking, however, does not completely rule out the possibility that muscle cramping could be caused by a temporary imbalance of calcium in the muscle during exercise. Certainly, we know that people with inborn errors in calcium metabolism in skeletal muscle (which will be discussed later) are prone to muscle cramping.
Despite so little being known about low calcium intake and muscle cramps, calcium is one of the nutritional factors people most associate with relieving cramps, second only to the potassium-rich banana. Although to my knowledge studies have not assessed whether dietary or supplemental calcium affects exercise cramps in athletes, a recent report found that calcium supplementation was not effective in treating leg cramps associated with pregnancy. On the other hand, anecdotal reports from athletes are common. Nancy Clark tells of a hiker who resolved muscle cramps by taking calcium-rich Tums and of a ballet dancer whose cramping disappeared after adding milk and yogurt to her diet. Because calcium intake can be low in the diet of some vegans and vegetarians, inadequate calcium should also be ruled out in vegetarians experiencing muscle cramps.
Magnesium
In addition to its role in bone health, magnesium plays an important role in stabilizing adenosine triphosphate (ATP), the energy source for muscle contraction, and also serves as an electrolyte in body fluids. Muscle weakness, muscle twitching, and muscle cramps are common symptoms of magnesium deficiency.
Limited data have suggested that magnesium status is indirectly related to the incidence of muscle cramps. In these studies of endurance athletes, the athletes who developed muscle cramps were found to have serum magnesium concentrations that were different from their competitors who did not cramp. The research, however, presents a confusing story because serum magnesium was significantly lower in cyclists who cramped during a 100-mile (160 km) bike ride and significantly higher in runners who cramped during an ultradistance race. In both studies, serum magnesium remained within the normal range but was low-normal in the cyclists who cramped and high-normal in the runners. Interestingly, studies in pregnant women have found that supplementation with magnesium (taken as magnesium lactate or magnesium citrate in doses of 5 millimoles in the morning and 10 millimoles in the evening ) show promise for treating pregnancy-associated leg cramps. Research, however, has not addressed whether dietary or supplemental magnesium can prevent or reduce muscle cramps in athletes.
Vegetarian athletes are not likely to experience muscle cramping as a result of low magnesium intake because the typical vegetarian diet is abundant in magnesium. Low magnesium intake, however, is possible for people restricting calories or eating a diet high in processed foods. Low magnesium intake should be ruled out in cramp-prone athletes.
Carbohydrate
Inadequate carbohydrate stores have also been implicated as a potential cause of muscle cramps. Theoretically, it makes sense that hard-working muscles might experience cramping in association with the depletion of its power source—carbohydrate. While all athletes should consider the recommendations presented earlier to optimize performance, athletes with a history of cramping during prolonged exercise should ensure that they consume adequate carbohydrate during exercise and in the days before and days following an endurance event."
"If you look at the information presented in most exercise physiology and sports nutrition books, you will notice an obvious omission of discussions of muscle cramps. This is probably because little is known about muscle cramps. Nonetheless, I am a true believer that imbalances of fluid or the mineral electrolytes—sodium, potassium, calcium, and magnesium—in the diet should be ruled out as contributors to all nocturnal and exercise-associated cramps.
Fluid Imbalances and Dehydration
Whether fluid imbalances and mild dehydration can trigger muscle cramping is open to debate. Although we know that muscle cramps can and do occur with severe dehydration and heat injury, there is no conclusive evidence that consuming adequate fluid with or without electrolytes will prevent typical nocturnal or exercise-associated cramping. In fact, studies have found that runners, cyclists, and triathletes who develop cramps during an endurance event are no more likely to be dehydrated or to have lost greater amounts of bodily water than are those who do not develop cramps during the same race. In my practice, however, I have noted anecdotally that maintaining a proper fluid balance indeed helps many endurance and team athletes avoid cramps, particularly those that occur after exercise or when sleeping at night. In one case, I worked with a male tennis player from Switzerland who had a history of severe cramping and fatigue after practice that was relieved by a regular and diligent fluid-consumption schedule. In her book, well-known sport nutritionist Nancy Clark tells an amusing story about a runner who eliminated his painful muscle cramps by following the simple postexercise advice to first drink water for fluid replacement and then have a beer for social fun.
Sodium
Sodium is one of the main positively charged mineral ions or electrolytes in body fluid. The body needs it to help maintain normal body-fluid balance and blood pressure, and in conjunction with several other electrolytes, it is critical for nerve impulse generation and muscle contraction. Sodium is distributed widely in nature but is found in rather small amounts in most unprocessed foods. In most developed countries, however, a significant amount of sodium is added from the salt shaker (1 teaspoon [6 g] contains 2,325 milligrams of sodium) or by food manufacturers in processing (as listed on the food label). Because sodium intake can vary, the typical Western diet contains 10 to 12 grams of salt (3.9 to 4.7 g of sodium) per day.
Because sodium plays an important role in regulating blood pressure and fluid and electrolyte balance, the body has an effective mechanism to help regulate the levels of sodium in the blood on a variety of sodium intakes. If the sodium concentration in the blood starts to drop, a series of complex events leads to the secretion of a hormone called aldosterone, which signals the kidneys to retain sodium. If sodium levels are too high, aldosterone secretion is inhibited, which allows the kidneys to eliminate some sodium through urination. Another hormone, called antidiuretic hormone (ADH), also helps maintain normal sodium levels in body fluids by signaling the kidney to retain water and sodium. Typically, levels of both aldosterone and ADH increase during exercise, which helps conserve the body’s water and sodium stores.
Actual sodium-deficient states caused by inadequate dietary sodium are not common because the body’s regulatory mechanisms are typically very effective. Humans even have a natural appetite for salt, which helps assure that they take in enough sodium to maintain sodium balance. Indeed, I have great memories of eating salty tortilla chips wet with a little water—so more salt would stick—after long cycling races in Arizona. Thankfully, these sodium-conserving mechanisms are activated in athletes who lose excessive sodium and other electrolytes during prolonged sweating.
Although muscle cramps are reported to occur during the sodium-deficient state, some researchers believe that alterations in sodium balance are not involved in exercise-associated cramps. This is despite the fact that significantly lower postexercise serum sodium concentrations have been found in endurance athletes who experienced cramps during a race compared to those who did not develop cramps. One of the reasons this is downplayed may be because serum sodium concentrations remain within the normal range, despite being significantly lower in the athletes with muscle cramps.
Nevertheless, it is important for athletes to consume enough sodium to replace what is lost through sweat. Despite the regulatory mechanisms discussed earlier, it is possible for vegetarian athletes to be at risk for muscle cramps and other problems because of low sodium intake. The reason is most likely because they ignore their salt craving cues—eating mostly unprocessed and unsalted foods—while continuing to lose considerable salt through sweating. The recommendation set by the USDA’s Dietary Guidelines for Americans to keep sodium intake to 2.3 grams or less per day is not appropriate for most athletes because of their higher sodium losses. Thus, while it is not likely that low sodium intake is the cause of cramps in most athletes, it is certainly possible that a vegetarian athlete prudently following a low-sodium diet for health reasons might experience muscle cramps that would be relieved with more liberal use of the salt shaker.
Potassium
Potassium is the major electrolyte found inside all body cells, including muscle and nerve cells. It works in close association with sodium and chloride in the generation of electrical impulses in the nerves and the muscles, including the heart muscle. Potassium is found in most foods, but is especially abundant in fresh vegetables, potatoes, certain fruits (melon, bananas, berries, citrus fruit), milk, meat, and fish.
Potassium balance, like sodium balance, is regulated by the hormone aldosterone. A high serum potassium level stimulates the release of the hormone aldosterone, which leads to increased potassium excretion by the kidneys into the urine. A decrease in serum potassium concentration elicits a drop in aldosterone secretion and hence less potassium loss in the urine. As with sodium and calcium, potassium is typically precisely regulated, and deficiencies or excessive accumulation are rare. Potassium deficiencies, however, can occur with conditions such as fasting, diarrhea, and regular diuretic use. In such cases, low blood–potassium concentrations, called hypokalemia, can lead to muscle cramps and weakness, and even cardiac arrest caused by impairment in the generation of nerve impulses. Similarly, high blood–potassium concentrations, or hyperkalemia, are also not common but can occur in people who take potassium supplements far exceeding the recommended daily allowance. High blood–potassium concentrations can also disturb electrical impulses and induce cardiac arrhythmia.
Even though little evidence is available to support a link between potassium intake and muscle cramps, it is quite interesting that most athletes—and non-athletes alike—think that the banana is the first line of defense in preventing muscle cramps. If only it were that simple. Furthermore, athletes following vegetarian diets are not likely to experience muscle cramping as a result of low potassium intake because the vegetarian diet provides an abundance of potassium. An athlete who is recovering from an intestinal illness, restricting calories, or taking diuretics or laxatives should, nevertheless, make an effort to consume potassium-rich foods, particularly if he or she is experiencing muscle cramping. Because of the dangers of hyperkalemia, potassium supplements are not recommended unless closely monitored by a physician. The recommended daily intake for potassium is 4,700 milligrams per day for adults.
Calcium
As discussed in chapter 6, the vast majority of calcium found in the body is found in the skeleton where it lends strength to bone. Calcium, however, is involved in muscle contractions, including that of the heart, skeletal muscles, and smooth muscle found in blood vessels and intestines, as well as the generation of nerve impulses. Blood calcium is tightly controlled and regulated by several hormones, including parathyroid hormone and vitamin D.
Although impaired muscle contraction and muscle cramps are commonly listed as symptoms of calcium deficiency, many exercise scientists feel that low calcium intake is not likely to play a role in most muscle cramps. This is because if dietary calcium intake were low, calcium would be released from the bones to maintain blood concentrations and theoretically provide what would be needed for muscle contraction. This thinking, however, does not completely rule out the possibility that muscle cramping could be caused by a temporary imbalance of calcium in the muscle during exercise. Certainly, we know that people with inborn errors in calcium metabolism in skeletal muscle (which will be discussed later) are prone to muscle cramping.
Despite so little being known about low calcium intake and muscle cramps, calcium is one of the nutritional factors people most associate with relieving cramps, second only to the potassium-rich banana. Although to my knowledge studies have not assessed whether dietary or supplemental calcium affects exercise cramps in athletes, a recent report found that calcium supplementation was not effective in treating leg cramps associated with pregnancy. On the other hand, anecdotal reports from athletes are common. Nancy Clark tells of a hiker who resolved muscle cramps by taking calcium-rich Tums and of a ballet dancer whose cramping disappeared after adding milk and yogurt to her diet. Because calcium intake can be low in the diet of some vegans and vegetarians, inadequate calcium should also be ruled out in vegetarians experiencing muscle cramps.
Magnesium
In addition to its role in bone health, magnesium plays an important role in stabilizing adenosine triphosphate (ATP), the energy source for muscle contraction, and also serves as an electrolyte in body fluids. Muscle weakness, muscle twitching, and muscle cramps are common symptoms of magnesium deficiency.
Limited data have suggested that magnesium status is indirectly related to the incidence of muscle cramps. In these studies of endurance athletes, the athletes who developed muscle cramps were found to have serum magnesium concentrations that were different from their competitors who did not cramp. The research, however, presents a confusing story because serum magnesium was significantly lower in cyclists who cramped during a 100-mile (160 km) bike ride and significantly higher in runners who cramped during an ultradistance race. In both studies, serum magnesium remained within the normal range but was low-normal in the cyclists who cramped and high-normal in the runners. Interestingly, studies in pregnant women have found that supplementation with magnesium (taken as magnesium lactate or magnesium citrate in doses of 5 millimoles in the morning and 10 millimoles in the evening ) show promise for treating pregnancy-associated leg cramps. Research, however, has not addressed whether dietary or supplemental magnesium can prevent or reduce muscle cramps in athletes.
Vegetarian athletes are not likely to experience muscle cramping as a result of low magnesium intake because the typical vegetarian diet is abundant in magnesium. Low magnesium intake, however, is possible for people restricting calories or eating a diet high in processed foods. Low magnesium intake should be ruled out in cramp-prone athletes.
Carbohydrate
Inadequate carbohydrate stores have also been implicated as a potential cause of muscle cramps. Theoretically, it makes sense that hard-working muscles might experience cramping in association with the depletion of its power source—carbohydrate. While all athletes should consider the recommendations presented earlier to optimize performance, athletes with a history of cramping during prolonged exercise should ensure that they consume adequate carbohydrate during exercise and in the days before and days following an endurance event."
Celebrity triatletes
Submitted by admin on Mon, 09/14/2009 - 19:02 Just saw this and thought it was might have an audience here. It's the celebrity results sheet from the 2008 Nautica Malibu Triathlon.
