Category — Nutrition
With summer just around the corner, I thought I would run an excellent guest blog article on the topic of dehydration and athletic performance by my good friend, Yan Levitsky.
Yan is incredibly knowledgeable in both training and manual therapy. Aside from being a registered nurse, Yan is currently studying and researching biochemistry and hopes to attend medical school in the future.
Note: The first portion of this article is a lot of technical/nerd talk, which I enjoy, and which is important to understanding dehydration and the human body. However, if you wish to skip that portion and get right down to practical application and recommendations, then scroll down to the section titled – Implications for the Athlete.
Hope you enjoy the article and get some good info out of it.
Dehydration and Athletic Performance
By: Yan Levitsky, RN, CPT
Proper fluid balance is a requirement for not only athletic performance, but proper functioning of the human body. Dehydration is a condition that can and does affect a great many people and may cause many undesirable effects. One study found that about 15,000 episodes of dehydration and/or heat illness occurred during a two year research period in high school athletes, which led the athlete missing from 1 day to 1 week of practice or competition (Hoffman, et al). This article will attempt to talk about some issues related to dehydration and provide some strategies to avoid and correct dehydration before, during and after athletic competition.
A prerequisite for optimal functioning of the human organism is a state of homeostasis. In other words, your body not only prefers, but requires all of its components to fall within a certain range in order for it to function properly. Some components have a narrow range, while others have a relatively broad range. For instance, a slight change in the pH of your body can lead to some pretty nasty effects while your blood pressure can vary a great amount without killing you (immediately that is). When your body senses a component go out of range, the Central Nervous System sends signals to certain organs which then respond with some sort of chemical synthesis which results in an action to pull that component back into its optimal range, this is known as a feedback loop. A very simplified example is when blood pressure drops, pressure sensing receptors in the blood vessels tell your brain of the change, the brain activates the sympathetic nervous system, causes your blood vessels to constrict and voila, your blood pressure is back within a normal range.
The human body loses fluid through several mechanisms. Urine and fecal loss account for about 1700mL/day, respiratory losses account for another 300mL, 100mL is lost via sweat (this is at rest with an ambient temperature of 68 degrees F, when active or in a hot and humid environment this mechanism can go up to 5L/day), and about 400mL/day is lost via insensible water loss (Saladin pg 916-917). Insensible water loss is water that diffuses through the skin and evaporates into the air. This is not a glandular secretion of the body, in other words sweat, in response to a stimulus rather, it is just movement of water out of the body via the skin. Some of the mechanisms are variable, like urine and fecal losses which can be down regulated to conserve fluid however, there is a certain amount of water loss, named obligatory water loss, that will happen no matter how dehydrated a person gets. Obligatory water loss is something the body cannot down regulate, it must happen, and explains why the body cannot just keep cycling the water it has to prevent further dehydration.
The body regulates intake of water through the thirst reflex. Blood osmolarity (we will discuss this term in a moment) is the primary driver of this reflex through a series of signals between receptors, the brain, the salivary glands, the small intestine etc. There are feedback loops which both make us thirsty in response to a decreased fluid content in the blood and inhibit the thirst reflex to avoid over hydration. These mechanisms work constantly to maintain fluid and electrolyte balance in the body.
The next issue we should get a handle on before going any further is osmosis and osmolarity. Osmosis is the tendency of fluid to move across a semi-permeable membrane towards higher solute concentrations, for the purposes of this article, and the main drivers of fluid balance in the body, the solutes are electrolytes. Osmolarity is simply a measure of solute concentration within a solution. In other words, the more ‘stuff’ in the fluid the higher the osmolarity and the greater the tendency to draw in water will be. Membranes separate the extra cellular fluid (ECF), which contains the interstitial and vascular compartments, from the intracellular fluid (ICF), which consists of the cells of the body. Normally, in homeostasis, the osmolarity of these two compartments is balanced and fluid doesn’t shift. If for any reason electrolytes are lost from either compartment, the osmolarity of the other compartment is relatively higher (hypertonic or hyperosmolar) and the fluid will shift until a balance in osmolarity is once again reached, while the opposite occurs if fluid is lost from a compartment. This is a passive mechanism and is governed by the laws of Physics. Once one compartment is hyperosmolar, within seconds, the fluid will start to shift and a balance of osmolarity is once again reached. It should be noted here that when we speak of water moving, we are truly referring to the net movement of water across a membrane. Living systems are highly dynamic and there is always movement of solutes and water back and forth, but when the two systems are in equilibrium the rate of movement into the cell is equal to the rate of movement out of the cell.
The human body is truly a wondrous machine but it’s not perfect and can’t always fix everything on its own. Sometimes these mechanisms land us in trouble, as we will see.
Types of Dehydration
There are three types of dehydration that can occur and they are named for the relative amount of electrolyte loss in relation to water loss. The first, and most common, is isotonic dehydration. Isotonic dehydration means simply that fluid and electrolyte losses are equal (the prefix -Iso- in Greek, means equal). The danger with this type of dehydration is that the ECF becomes depleted of fluid. This depletion then leads to a reduction of blood volume and a drop in blood pressure. The decrease in blood volume leads to poor perfusion of organs, for our purposes the organ system of importance is the musculature. With poor perfusion of the working muscles, metabolic wastes accumulate and oxygen is not being delivered efficiently which may lead to a decreased performance. Aside from the poor perfusion of the musculature, we run into problems because appropriate blood pressure is necessary in the skin to maintain adequate thermoregulation. When there is not enough blood to achieve both goals (muscle and skin perfusion), and we are in the midst of strenuous physical activity, scientific literature seems to show that the body chooses the musculature to supply with blood leading to a breakdown of thermoregulatory mechanisms (González-Alonso et al).
The body has many back up mechanisms to fix this problem, the blood vessels constrict to normalize blood pressure, the kidneys begin to reabsorb water and sodium back into the blood stream, the heart starts to beat harder and faster to get that blood moving better. All of this works well to delay problems however, we only have so much water and without proper intake these defense mechanisms will eventually fail and we will not only have poor athletic performance but illness may ensue. This type of dehydration is typically caused by bleeding (well hemorrhaging, and if you are doing that on the field you shouldn’t be worried about athletic performance), vomiting, diarrhea, profuse sweating, and inadequate intake of fluids/electrolytes (Ignatavicius et al, p. 212-222).
The second type of dehydration is hypertonic dehydration. This type is characterized by a greater loss of fluid than electrolytes. Here is where osmosis comes into play. The ECF loses water but at a greater rate than it losses electrolytes. The osmolarity of the ECF relative to the ICF increases and the osmotic pressure (just a fancy name for the pull of water into the blood vessel) causes fluid to shift from the ICF to the ECF. This shift of fluids normalizes blood volume but, unfortunately, now the cells are dehydrated. A dehydrated cell is not an optimally functioning cell and our body then uses a slew of hormones to get things going and to normalize. The kidneys now reabsorb water back into the blood stream and your body makes you thirsty to get those fluids replaced. This is one reason why it is said that waiting until you are thirsty means you are already dehydrated. Your blood pressure and organ perfusion will be adequate and there is no real threat to life, however your cells have given up precious fluids in order to accomplish this task and are now working sub-optimally. And just as before, electrolytes don’t just appear from thin air and if they are not replaced the cycle will keep going until serious problems arise. This type of dehydration is typically caused by prolonged sweating, hyperventilation, fevers and watery diarrhea (IBID).
The third and least common type is hypotonic dehydration. Obviously this is where electrolyte loss is greater than fluid loss. This type of dehydration is the rarest; it does not apply to athletes, and is typically seen in chronic illnesses. A few words should be said about it anyway to reinforce some of the principles we have already discussed. The problems that we run into with this type of dehydration are from fluid shifts. Losing electrolytes from the ECF will increase the osmolarity of the ICF and the fluid will tend to shift into the cells. The problems are 3 fold. First and foremost our cells need a certain range of fluid to work optimally (remember that homeostasis thing we were talking about?). A swollen cell is not a happy cell and a swollen brain cell is particularly cranky. Brain tissue is very sensitive to swelling and neurological symptoms are very common, and are typically first complaints, like dizziness, headache, confusion etc. The second problem is the loss of fluid from the vasculature causing your blood plasma to be depleted thus making your blood more viscous and decreasing blood volume/pressure. This can affect organ perfusion as thick blood doesn’t flow so well and doesn’t deliver oxygen and nutrients so well, either. The third is a dilution of normal electrolyte levels leading to a whole host of other issues. Each electrolyte has its own problems that it can cause when out of whack and a discussion about each of them is well out of the scope of this article, however we will touch upon sodium balance as this has some implications for athletes.
Implications for the Athlete
“So what does all this mumbo jumbo mean to me?”
Well now that we have a somewhat decent understanding of the causes, mechanisms and complications of dehydration we can talk about what it means to the athlete.
Dehydration, hot, humid environments (>95 degrees F, >80% humidity) and strenuous exercise (and by extension profuse sweating) can lead to some pretty serious problems, the least of which is decreased athletic performance. But wait, this article should be about dehydration? What’s this heat exhaustion crap? These two topics pretty much go hand in hand as dehydration will potentiate heat stress and hot and humid environments will potentiate dehydration. They are undeniably linked.
Heat exhaustion is a product of dehydration coupled with hot/humid environments. Dehydration is not a pre-requisite for this condition however dehydration will severely decrease one’s ability to dissipate heat properly and in the real world heat stress is typically accompanied by dehydration. In this state the athlete may feel very ill, and may complain of flu like symptoms, which include headache, weakness, fatigue, nausea and vomiting. Although not a true medical emergency, this condition may lead to heat stroke if not adequately addressed (oral rehydration preferably with fluids containing electrolytes, cool environment, and loosening of constrictive clothing).
Heat stroke is a medical emergency and can have a pretty high mortality rate, approaching 80%, if not treated promptly. This is what happens when our defense mechanisms fail and our body can no longer maintain a safe core body temperature. There are two types of heat stroke, exertional and classic. The former is typical of athletes who are exercising or competing in hot and humid environments. The onset is very rapid. Classic heat stroke tends to occur in the elderly with long exposures to hot and humid environments and has a more insidious, or slower, onset. The athlete’s body temperature may be very high and sweating will stop (a defense mechanism to save essential fluid), as well there will be changes in mental status such as anxiety, confusion etc. Hospitalization is a necessary step at this point to reduce further, possibly permanent, organ damage (Ignatavicius et al, p. 212-222).
Environmental factors have a very big impact on athletic performance. Heat stress combined with dehydration will significantly decrease total time to exertion during aerobic work as well as negatively affecting peak power output (Maxwell et al, Goulet et al). Most of the research in this area has been done on aerobic activity with some anaerobic work built in (think long distance cycling with intermittent sprinting) however, very little research has been done on purely high intensity activities, for example weightlifting or short distance running. These types of activities are thought to not be affected as much by dehydration and heat stress as the activities do not last long enough for the cardiovascular system to be strained and the deleterious affects to be noted (Rothenberg et al). It should be noted, as well, that cold environments attenuate the effects of heat stress, meaning that in colder climates these types of performance declines are not as significant. This last bit does not mean that dehydration is not an issue in a cold environment as cold air is drier and absorbs more water from your breath. There is also the issue that exerting yourself and increasing sweat losses, while wearing lots of gear can potentiate this effect. A study done by Palmer and Spriet looked at sweat losses from hockey players during 1 hour of practice. They found that even in a cool environment (57 degrees F and 67% humidity) the players lost between 1-2L of fluid during the hour-long practice (ranging from less than 1L while many lost more than 2L). This shows that sweat losses can be significant even in colder climates and once the athlete begins to approach a 2% loss of bodyweight, the detriments in performance are noted.
Now that we have established the problems that can arise, let’s tackle the issue of adequate hydration. The unfortunate part of this, most exciting, article is that proper hydration is something that varies from person to person (what doesn’t, right?). Nevertheless we can scan through some literature and perhaps work up certain strategies to avoid dehydration.
In one study, the authors used 2 groups of athletes to compare hydration strategies. The hyperhydration group was given 26mL fluid/kg body mass coupled with 1.2g glycerol/kg body mass over an 80 minute period prior to the test while the control, or euhydrated, group was not given any fluids. Glycerol was chosen because it has been shown to aid the body in retaining water, and thus hydration, without other ergogenic properties (Goulet et al, Wingo et al, Robergs et al). Both groups were given Gatorade to drink during the exercise. Both groups cycled for 2 hours and then were given a test to measure how long they could cycle until exhaustion. The hyperhydration group had a higher peak power output, and was able to cycle for a longer period of time until exhausted. The hyperhydrated group also showed lower rectal temperatures (although the authors were not able to show this as statistically significant, a look at the data shows about a 1 degree difference between the groups at the 120min mark) and lower heart rates during the 2 hours of cycling (Goulet et al). What can we glean from this? Over hydration allows the body to cope with exercise and heat more optimally under conditions where maintaining hydration during exercise is difficult. The peak power output and time to exhaustion differences is self explanatory while the lower rectal temperatures and heart rates in the hyperhydration group show that the body was able to dissipate heat better and the cardiovascular system did not have to work as hard to keep up with the oxygen demand of the musculature. This was probably due to the maintenance of adequate blood volume and other factors having to do with the Central Nervous System (Alonzo et al). The authors concluded that beginning an exercise session hyperhydrated alleviated some of the detriments to performance seen as athletes become dehydrated during competition. For a 170 lb person the above numbers equal about 2 liters of fluid with 100g glycerol over 2 hours before exercise or competition. This method would over hydrate an individual and help to attenuate the performance detriments associated with dehydration during activity. This over hydration method should be the upper limit of fluid intake unless sufficient electrolytes accompany the water if the glycerol is not used, the reason will be discussed shortly
Another group of researchers suggest that to be appropriately hydrated before competition athletes should consume at least 6-8mL/kg of body mass of fluid containing sodium or with food about 2 hours before exercise. For a 170lb man this translates to about 450-620mL of fluid. The authors don’t deny that water needs are individual and differences and experiences are to be kept in mind when planning a hydration protocol (Shirreffs et al). The National Athletic Trainers Association recommends 500-600mL of fluid or sports drink 2-3 hours before exercise with another 200-300mL consumed 20-30 minutes before exercise/competition as a minimum for athletes across the board with individual differences to be accounted for (Casa et al, NATA Position Statement).
What can we take from all this?
Staying hydrated is best accomplished not only by drinking during the activity, but also by ensuring that you are appropriately hydrated before the exercise/competition. This is especially true if the conditions are hot and humid, as these conditions can greatly increase fluid loss through sweating.
During exercise and competition is where things get a bit dicey. Some sports are not exactly conducive to stopping for water breaks, like marathons. Other sports lend themselves to this but many athletes choose to forego or like to just take a sip of water and get back to working. This is all well and good and shows a good work ethic however, when sweat losses are in the liters and the athlete is replacing fluid with sips (we’re talking mL’s here), he/she is shooting themselves in the foot. A good practice to establish is to take a nice big drink of fluid when the opportunity arises and not just a sip or two, especially if the exercise will last over an hour or is taking place in a hot/humid environment. Using containers, which are measurable, is a great way to figure out how much one ingested and whether or not one should drink more or less. Drinking half of a 1L bottle means you ingested 500mL and if hydration was not maintained that amount can be bumped to getting ¾ or the whole bottle in.
There exist a few methods to establish how dehydrated an individual gets during exercise. There are Urine Specific Gravity measuring devices, urine color charts and such but the one I will discuss is very simple and is available to most people. This method is simply weighing oneself. Weigh once pre-exercise and once again post-exercise. If the change is greater than 2%, then it is a fairly safe bet that you have become dehydrated at some point during the session. So if a 170lb person (pre-exercise) weighs in at 166-167lbs after exercise, he/she should take a closer look at what and how much was consumed before the exercise and what and how much was consumed during. A 1-liter loss of fluid amounts to about 1 kilogram (2.2 pounds) loss of weight (Ignatavicius et al, p. 212-222). Conversely, the NATA recommends ingestion of 1-1.25L of fluid for every kilogram lost during exercise as a rehydration strategy (Binkley et al, NATA position statement; Exertional Illness).
Exertional Hyponatremia or Water Intoxication
Natrium is the chemical name for sodium and is the most abundant electrolyte in the ECF. It accounts for 90-95% of the ECF osmolarity (Saladin, pg 922). As we have learned in the beginning of the article the most prevalent form of dehydration tends to be isotonic dehydration, meaning the body has lost about an equal amount of water and electrolytes. If water is replaced without any replacement of electrolytes, the situation created resembles one of hypotonic dehydration. Fluid starts to shift to maintain an osmotic equilibrium and this may potentially lead to death as cells can swell and possibly even rupture. This is a pretty easily rectified situation; don’t just drink pure water if a training session is going to last over an hour, or if the temperature and humidity are high, and especially if you haven’t had any solid food or other sources of electrolytes before the training.
So this long-winded article has finally come to a close. What have we learned? Dehydration can be, at worst, a very serious health concern and, at the least, can decrease performance on the field or in the gym or wherever you may choose to exert yourself. Maintaining adequate hydration is not just a matter of taking a couple of sips of water during the training session but is really more about maintaining a consistent hydration status throughout the day. Pre workout hydration may be more important than intra-workout hydration, as certain activities do not allow for breaks. Continuing with the same theme, assessing one’s own hydration status may be as simple as monitoring the weight changes pre/post workout and qualitatively analyzing urine color. Just as important is rehydrating oneself post training, and this is where the idea of hyponatremia comes into play. I say it is always better to be safe than sorry, so a whole food meal (with water of course) or some type of electrolyte rich sports drink is the preferred method to ensure safe and effective rehydration.
Binkley, Helen M. et al. National Athletic Trainers’ Association Position Statement: Exertional Heat Illnesses. J Athl Train. 2002 Jul–Sep; 37(3): 329–343.
Casa, Douglas J et al. National Athletic Trainers’ Association Position Statement: Fluid Replacement for Athletes. J Athl Train. 2000 Apr–Jun; 35(2): 212–224.
González-Alonso, Jose et al. The cardiovascular challenge of exercising in the heat. J Physiol. 2008 January 1; 586(Pt 1): 45–53.
Goulet, Eric DB. Rousseau, Stephanie F. et al. Pre-Exercise Hyperhydration Delays Dehydration and Improves Endurance Capacity during 2 h of Cycling in a Temperate Climate. Journal of Physical Anthropology, Vol. 27 (2008) , No. 5 pp.263-271
Huffman, Elizabeth A. Yard, Ellen E. Fields, Sarah K. Collins, Christy L. Comstock, Dawn. Epidemiology of Rare Injuries and Conditions Among United States High School Athletes During the 2005–2006 and 2006–2007 School Years. J Athl Train. 2008 Nov–Dec; 43(6): 624–630.
Ignatavicius, Donna D. Workman, Linda M. Medical-Surgical Nursing 5th Edition. Elsevier Saunders, 2006.
Maxwell NS, McKenzie RW, Bishop D. Influence of hypohydration on intermittent sprint performance in the heat. Int J Sports Physiol Perform. 2009 Mar;4(1):54-67.
Palmer , Matthew S. and Spriet, Lawrence L. Sweat rate, salt loss, and fluid intake during an intense on-ice practice in elite Canadian male junior hockey players. Appl. Physiol. Nutr. Metab. 33: 263–271 (2008)
Patel, Akshay V. Mihalik, Jason P. et al. Neuropsychological Performance, Postural Stability, and Symptoms After Dehydration. J Athl Train. 2007 Jan–Mar; 42(1): 66–75.
Robergs RA, Griffin SE. Glycerol. Biochemistry, pharmacokinetics and clinical and practical applications. Sports Med. 1998 Sep;26(3):145-67.
Rothenberg, Joseph A. Panagos, André. Musculoskeletal performance and hydration status. Curr Rev Musculoskelet Med. 2008 June; 1(2): 131–136.
Saladin, Kenneth S. Anatomy and Physiology: The Unity of Form and Function. McGraw-Hill, 2004.
Sawka MN, Latzka WA, Matott RP, Montain SJ. Hydration effects on temperature regulation. Int J Sports Med. 1998 Jun;19 Suppl 2:S108-10.
Shirreffs, S M. Maughan, R J. Leiper, J B. Factors influencing the restoration of fluid and electrolyte balance after exercise in the heat. Br J Sports Med 1997 31: 175-182
Wendt D, van Loon LJ, Lichtenbelt WD. Thermoregulation during exercise in the heat: strategies for maintaining health and performance. Sports Med. 2007;37(8):669-82.
Wingo, Jonathan E. et al. Influence of a Pre-Exercise Glycerol Hydration Beverage on Performance and Physiologic Function During Mountain-Bike Races in the Heat. J Athl Train. 2004 Apr–Jun; 39(2): 169–175.
March 10, 2010 6 Comments
The popular debate that surfaced this past year was between the role of exercise in fat loss.
It basically started with Time Magazine running an article titled Why Exercise Wont Make You Thin.
Right when the article came out, it began an internet firestorm from health professionals blogging about how horrible Time Magazine was for publishing this article – talk about going viral!
I read the article a few days after it came out and to tell you the truth, it wasn’t that bad! In reality, all it was saying was what we basically already know, “you can’t out work a poor diet.”
I am not going to dispute that diet is an important component to losing fat. In fact, it is the most important component as far as I am concerned. We have all seen those people in the gym who kill themselves 2 hours a day/7 days a week, yet see minimal to no results because they are constantly over-eating.
While diet is important for losing fat, exercise is essential for achieving higher levels of health. Together, an appropriate calorie-restricted diet and a sound exercise program are essential not only for improving body composition, but also improving the overall function of the body’s systems.
Researchers at the Pennigton Biomedical Research Center at Louisiana State University recently evaluated the results of caloric restriction with or without exercise.
Thirty-six overweight participants (16 males/20 females) were randomly assigned to one of three groups for the 6-month study:
- A control group who ate a weight-maintenance healthy diet
- A caloric restriction group who restricted energy intake by eating at a daily caloric deficit of 25%
- A caloric restriction plus exercise group who created a daily caloric deficit of 25% by reducing energy intake by 12.5% and increasing energy expenditure by 12.5%
The researchers posed the following question:
“Does caloric restriction with or without exercise result in different improvements in cardiometabolic risk factors which could ultimately improve longevity? The purpose of this analysis was to determine whether a deficit by energy restriction or energy restriction plus aerobic exercise that produces equal change in fatness leads to greater cardiometabolic benefits when exercise is included.”
The diets used in the study where based on the America Heart Association’s Step 1 recommendations.
During the first 12 weeks of the study food was provided for all groups based on their dietary needs. In weeks 13-22 the subjects self-selected their own diet based on their individual caloric target, and in weeks 22-24 (the final two weeks of the study) the subjects returned to the in-feeding protocol, which they used in the fist 12 weeks.
Both the control group and the caloric restriction only group where not allowed to alter their current level of physical activity for the 6-month study.
The caloric restriction plus exercise group was required to increase their energy expenditure by 12.5% above their baseline requirements. They did so by partaking in a structured aerobic exercise program (IE, walking, running or stationary cycling) for 5 days a week.
Adherence is a common problem in studies like this, and subjects are notorious for under-reporting their caloric intake and over-reporting their caloric-expenditure.
The subjects in this study attended weekly group meetings and were contacted once per week via telephone to ensure there were no adherence problems to the program.
The subjects were tested for changes in fat mass, visceral fat, Vo2 peak (using a graded treadmill test), muscular strength (isokinetic knee extension/flexion), blood lipids, blood pressure, and insulin sensitivity/secretion.
Aerobic Fitness and Muscle Strength Results
The exercise group was the only group that saw improvements in Vo2 peak, which is to be expected since they were the only group stressing their aerobic fitness.
There were no changes in muscle strength between the groups. This would be expected considering this study did not have a resistance training component to it.
Body Composition Results
Body fat was significantly reduced in both the caloric restriction and caloric restriction plus exercise groups, as were total body fat mass and visceral abdominal fat.
People may look at those results and think that those results aren’t very promising for the exercise group; however, I look at those results and see what I would expect to see given that both groups had created an equal caloric deficit (25%).
Cardiometabolic Risk Factors
This is where, in my opinion, things get important.
HDL (the “good” cholesterol) was significantly increased in all treatment groups, including the control group. This is possibly because their diet was set up for them based on the American Heart Association guidelines. And even though they were not eating in a caloric deficit – rather eating at a weight-maintenance level – the diet was probably healthier than the normal junk they would eat on a daily basis.
Fasting serum triglyceride concentration increased significantly in the control group, but decreased significantly in both the caloric restriction and the caloric restriction plus exercise groups.
While systolic blood pressure was not changed in any of the groups, diastolic blood pressure, total cholesterol, LDL (the “bad” cholesterol), and insulin sensitivity were significantly improved ONLY in the caloric restriction plus exercise group!
- Adding exercise to your calorie-restricted fat-loss diet has greater improvements on cardiometabolic health, which are greater than caloric restriction alone.
- The addition of aerobic exercise to a calorie-restricted diet enhances overall aerobic fitness which is helpful for improving health and wellness.
- Calorie restriction is essential for fat loss and body composition changes; however, when combined with exercise, the amount of caloric restriction needed to illicit the same results in body composition is decreased (12.5% caloric restriction with exercise intervention vs. 25% caloric restriction with no exercise).
- Aerobic exercise has been shown to improve insulin sensitivity, which is important in the health of overweight/obese individuals who may be at greater risk for diabetes and/or other metabolic disorders.
Calorie restriction is king when it comes to fat loss. A proper diet will help you achieve this goal, but exercise can be effective in not only helping you reach this goal (without having to rely as heavily on reducing calories, which typically leads to a miserable experience and lack of adherence) but also, in helping improve your overall cardiovascular and metabolic health.
Larson-Meyer DE, Redman L, Heilbronn LK, Martin CK, Ravussin E. Caloric restriction with or without exercise: The fitness versus fatness debate. Med Sci Sports Exerc 2010;42(1):152-159.
January 4, 2010 3 Comments
Excellent information on race day nutrition by San Antonio Based strength and conditioning coach Steven Bubel. These are great recommendations for athletes in any sport so CHECK IT OUT.
Stay tuned – tomorrow I’ll be talking about training for golf. As things are cooling off out here in Phoenix, the golf courses will start filling up!
August 12, 2009 No Comments
I get a variety of nutrition questions each week from concerned parents asking questions like:
- What should my son/daughter eat through the day?
- What supplements should my child take to “get an edge”?
- Other kids on the team are taking certain “supplements” and are they safe?
- Should my son/daughter drink Gatorade during practice?
- What should my son/daughter eat before and after training?
Every parent wants the best for the child and nutrition can be an extremely confusing topic, especially when dealing with high school athletes as they are growing and maturing and there are many different things taking place in their bodies. Below are a few basic principles to ensure that your youth athlete gets quality nutrition and grows to be as healthy as possible.
What should my child eat?
Most parents ask me this hoping for some magical diet or some specific menu plan. In reality, most kids (from what I have seen) have a pretty poor diet to begin with. Trying to change everything overnight is going to be a total disaster and will most likely be met with a good bit of resistance from the child.
The first goal is to evaluate what they are eating currently. Since the parent is most likely doing the grocery shopping and cooking, they should have a good idea of what is going into their child’s body – however, don’t overlook what they may be potentially purchasing/consuming in the school lunch room!
I like to tell people that they need to get back to the basics. The three basic rules to follow are:
1) Three square balanced meals a day (Breakfast, lunch and dinner).
This may change if you add something like a pre/post-training meal and some kids will probably end up eating 4-5 meals a day as they usually have a snack or two somewhere in there. That is okay! But, if you are not following this basic principle already – IE, not making time for breakfast, skipping lunch of just eating junk food, and then not having a healthy meal for dinner or skipping it to eat a bowl of ice cream – then you are surely missing the boat. So, start with 3-square meals a day and try and make those meals balanced.
2) Balanced meals are the key!
Try and shoot for each meal to have each of the three macronutrients – protein, carbohydrate, and fats. Meals should not be overly top heavy in one macronutrient (IE, having a large bowl of pasta and nothing else). In addition to balancing the meals out, I tell the young athletes (and the old) to try and eat some sort of vegetable and/or fruit at each meal. Here is an example of 3-balanced meals:
3 egg whites (protein)
1 whole egg (protein/fat)
1-slice of whole grain bread with 1tbsp of all natural peanut butter (carbohydrate/fat)
Medium sized banana (carbohydrate/fruit)
4-5oz turkey breast (protein)
2-slices of whole grain bread (carbohydrates)
Lettuce, tomato, onions (carbohydrate/vegetable)
Medium Sized apple (carbohydrate/fruit)
1oz almonds (fat)
4-5oz lean beef (protein)
Garden salad (carbohydrate/vegetable)
Oil & Vinegar Dressing (fat)
5oz of red potatoes (carbohydrate)
3) Don’t drink your calories!
The final rule is a simple one. Try and stay away from high calorie beverages like soda and energy drinks. Drink water as much as you can and save the extra calories that you get from these drinks for whole food that will give you more nutrition and a bigger bang for your buck.
Make Small Changes
As I stated above, don’t try and change everything at once! If your child is used to drinking 3 cans of soda through the day and eating Twinkies for lunch, the last thing you want to do is force them into a plan like I laid out above. Start small and educate them that this is a healthier way of eating/living. In addition, this will set them up for healthy habits as they move into their adult lives. It might be something as little as trying to substitute 1-can of soda for a bottle of water each day for a week or two, and then substitute 2-cans of soda for 2-bottles of water and gradually work from there. Or, try and switch out the twinkie for an apple or piece of fruit every other day for a week or two, until you can swap it out for good.
Set small goals (IE, drop from 3-cans of soda to 2 per day), achieve those small goals and move on. Small victories strung together will lead to a championship season.
Supplements: Are they Safe? Which ones should my child take?
The first thing I will say about supplements is please master the three basic rules first to ensure that you are getting nutritious whole foods and staying hydrated by drinking an appropriate amount of water through out the day.
As far as which supplements I recommend, I think having a protein powder on hand is okay and I stand behind taking fish oil capsules or some sort of essential fatty acid supplement, as we don’t get enough of those in our normal daily diets. Obviously, consult your physician before adding these supplements into your nutritional program.
A lot of parents are concerned about protein powder as if it has some magical properties like taking steroids or that it will destroy the kidneys. The best way I can describe it is to think about protein powder as you would a piece of chicken (or any other type of protein you can think of). It is really just a convenient way to get protein when eating a whole meal is not convenient or possible (for example, immediately following a workout). It is nothing more than protein ground up into a convenient and easy to transport form.
As far as other supplements go, I know creatine is highly popular among youth athletes (especially the high school football crowd). While I think that creatine has a number of benefits, not just in the realm of performance, to my knowledge there has been no research looking at creatine and youth athletes. For this reason, it is hard for me to encourage an athlete to take this supplement, even though many athletes do and have had no ill effects. As stated above, please consult your physician prior to taking any sports supplement. I would stay clear of the testosterone boosters and/or the supplements on the market that mimic testosterone, as the last thing a youth athlete needs to do is try and mess with their own hormonal system when it is in the developmental stages. This is definitely not a safe road to travel. In addition, there are several other supplements out there that claim amazing results. A lot of this is over-hyped marketing, put together to lure people into making a purchase. Don’t be fooled! Educate yourself as much as you can on every single thing you put into your body. Don’t just read the back label or the article in the magazine and assume that this is something you need to be taking.
As always, the greatest supplement you can possibly consume is water!
Nutrition Before and After Training
Prior to training/competition, athletes should have a small snack. The length of time prior to training and the type of food that you will eat can be a very individual thing. I typically tell youth athletes to consume a small snack 90min to 2-hours prior to training. This doesn’t have to be a large 4-course meal, but just a small snack to get some energy into the body. You will have to try things out to determine what works for you, as some things may not sit well in your stomach and may make you feel a little sick during the workout.
After training would be a fine time to drink your protein shake. If you choose not to use supplemental protein or it doesn’t sit well with you (some may be lactose intolerant), then a whole meal will do just fine as well.
During the workout, if your workouts are particularly long and taxing, you may consider drinking some sort of carbohydrate/electrolyte beverage like Gatorade or Powerade. I stated above to not consume liquid calories, and these drinks are loaded with calories (all from sugar). I typically do not advocate these for the youth athletes (trying to push them to drink more water), however if you are an endurance athlete and out logging long hours of training, this may be an option for you. In addition, living here in Phoenix can make things really tough when training outside – especially right now as we are in the thick of monsoon season (lots of heat and humidity) and most high schools are now starting their football training camps. In these instances you may choose to use one of the carbohydrate/electrolyte beverages to make sure you are properly fueled. You may, however, be able to find some electrolyte beverage that are calorie free (they may be in a powdered form that you have to mix yourself) and this may be a better option for you than drinking your calories – just be sure to eat appropriately before training to ensure that you are consuming adequate energy to fuel you through practice.
The real message here is to keep things simple! Youth athletes need to learn basic healthy habits both in the weight room and at the dinner table that will help them grow into healthy adults. The more you can educate them on what they put into their bodies the more aware of their nutrition they will be, and that is something that they can carry with them throughout their entire lives.
August 4, 2009 2 Comments
Last month we were lucky enough to get Toronto based nutritionist Brad Pilon on the Reality Based Fitness Podcast. Brad talked about the concept of 24-hour intermittent fasting and how it could be used for fat loss.
While Brad favors the 24-hour fast, this may be a little harder to accept for some individuals. A new study just published in Medical Hypotheses, A “mini-fast with exercise” protocol for fat loss (July 2, 2009) looked at the results of using small 12-14 hour fasts with exercise.
The research details
Twenty-seven subjects (10-female and 17-male) participated in the study. During every 24-hour day, the subjects were instructed to have a 12-14 hour fast during which they were also asked to participate in moderate intensity exercise. Subjects were encouraged to perform exercises in which they had to support their own body weight – IE, treadmill, stair climber, elliptical, etc – and to work up to 45min. of continuous activity.
The exercise and fasting protocol could have been performed whenever was convenient for the subject:
- If they wanted to exercise in the morning, they would skip breakfast and not eat until lunch.
- If they wanted to exercise in the afternoon, they would skip lunch and not eat until dinner.
- If they wanted to exercise in the evening, they would eat a light dinner. Wait approximately 2-hours and then exercise. Following exercise, they would not eat until breakfast the next morning.
Subjects were given some food selection guidelines, which instructed them to maintain a diet low in saturated fats and high glycemic carbohydrates; however, caloric intake was not restricted.
The research findings
Following the 12-week protocol subjects had an average weight loss of 4.2kg (9.25lbs). More impressively, the subjects saw an average 7.4kg loss in fat mass (16.28lbs), corresponding to a 25% reduction in initial fat mass! In addition, there was a 25% reduction in fasting insulin (possibly showing enhanced insulin sensitivity) and an average waist circumference reduction of 7.9cm.
Interesting facts about the findings
- Subjects were not supervised during this study! That is a huge problem with most studies conducted on dietary and/or exercise interventions for weight loss, as subjects typically over-estimate caloric intake and/or under-estimate exercise activity. So, without someone standing there watching them every minute of the day, subjects basically self-sabotage themselves. Perhaps the flexibility of the guidelines in this study made it easier for subjects to adhere to.
- A questionnaire revealed that a number of subjects were only intermittently compliant with the program. This is particularly interesting given the results! If the subjects were only moderately following the program plan and they had these kind of results, imagine what would have happened if they were religious about the program. The male subject who followed the program perfectly saw a 20kg (44lb) loss of fat while the most compliant female (40-years old) lost 14.1kg (31lbs) of fat.
- Fat loss in the second half of the study was slightly greater than in the first half of the study. This is interesting to note, because typically studies on fat loss show a decrease or plateau in results after a certain period of time. This suggests that if the study had been carried out for longer than 12-weeks, we may have still seen even greater results.
- The ease of the studies protocol and the fact that subjects did not have to adhere to a specific caloric intake or worry about not eating carbohydrates, showed that subjects who are motivated can achieve significant fat-loss without having to over-complicate their diet – a problem that is common in today’s world of information overload.
- None of the subjects in the study exercised more than 1-hour per day and they all had at least two rest days each week.
- The authors note that while this study used moderate aerobic exercise for in its protocol, brief periods of intense interval training may illicit greater results with regard to fat oxidation.
- The authors concluded that this protocol might be beneficial for individuals seeking weight loss as it is easy to follow and does not require emphasis on calorie or carbohydrate counting. This is particularly important for individuals in the “real world” who lead busy lives. The authors did take a jab at a favorite American reality show without actually naming the name (BIGGEST LOSER) by stating:
“A currently popular American TV series is regaling viewers with exploits of overweight volunteers who lose massive amounts of weight by engaging in several hours of vigorous exercise daily while consuming semi starvation diets. Yet for most people such a regimen would be both impractical and unsustainable. It would actually be a lot more impressive and meaningful to watch people cutting their body fat in half while holding down a full-time job, raising a family, and enjoying their meals.”
Judging by the results the subjects in this particular study had, I think it is safe to say they were relatively over-weight/de-conditioned individuals who may (or may not) have had much exercise experience. However, this should not discourage you if you are an avid exerciser who is not satisfied with your results. If anything, the brief periods of fasting and the fact that you can handle greater intensities of training (remember what the researchers noted above) leaves the door wide open for you to still have some impressive results. Especially given the fact that you don’t have to sit there and be miserable counting carbohydrates all day and failing on the plan or falling off the wagon like so many do each year.
Just to give you an example of how I set it up, I have been doing one 24-hour fast each week and then a few short mini-fasts on other days. I don’t have the goal of weight loss or fat loss, mainly just maintenance, so I don’t do the fasting every day. I lift 3-days per week (Mon, Wed, Fri) performing total body workouts on each day. Each of my lifting days I perform intervals at the end of my resistance training. On in between days I perform moderate cardio or tempo runs and it is on these days that I place my fasting.
Give fasting a shot. Whether you perform a 24-hour fast or the short mini-fasts I think you will be delighted with your results.
July 26, 2009 15 Comments