Optimal Spine and Back Health with PUSH as Rx Fitness & Athletic Training pushes the barriers of average gyms. We believe in committing to change your lifestyle. Blending Crossfit and Personal Training, we can tailor-make workouts that are very specific and individualized to everyone, no matter what shape they’re in.
PUSH as Rx also offers strength and conditioning programs, which improve the athletic ability of kids and teams of any sport at any age. PUSH Kids program uses a combination of skill practice, workouts, and games to build strength and condition children. Our classes include gymnastics, weight lifting, bodyweight movements, running, jump rope, and more.
We are here to support your physical transformation and are happy to steer you in the right direction. We offer nutritional coaching to help our members learn how to fuel their bodies properly. Count on us to design a program to keep you on track and to motivate you every step of the way.
Stay Hydrated: Summer fun means outside activities in the warm sun, from strenuous pursuits like biking, hiking, and volleyball-playing, to more leisurely enjoyments like sunbathing on a float. No matter how you plan to enjoy the steamy summer months, maintaining hydration should be right up there with sunscreen on your list of important hot weather priorities.
Dehydration is a condition that ranges from mild to serious, and can happen quicker than you think. Right Diagnosis defines dehydration as “an abnormal condition in which the body’s cells are deprived of an adequate amount of water.” One of the main situations factoring into a person becoming dehydrated is heat.
Think you drink enough water and don’t need to worry about dehydration? Consider these points:
The ability to recognize thirst diminishes in individuals in their late 30’s or older.
A person’s body is made up of roughly 70% water.
When you lose 2% of the body’s water content, you are considered dehydrated.
Dehydration symptoms range from unpleasant confusion, muscle weakness, and fatigue to extremely dangerous ones like seizures, kidney failure, and death. The good news is that if you stay hydrated in the first place is relatively easy if you take a few precautions up front.
#1: Drink Plenty Of Water
Make it a habit of carrying water with you during the summer months, and sipping on it throughout the day, especially if you are planning on outside activities. Invest in a couple of BPA-free water bottles for yourself and your family to tote with them on their summer adventures.
Not a big fan of plain water? Try adding lemon, cucumber, and mint sprigs to liven it up! Mix up in a big pitcher the night before so the flavor has time to penetrate. Another option is flavor packets, which are individual packets of flavors like green tea, watermelon, and peach.
#2: Eat The Right Foods
Liquids aren’t the only way your body gets water. Avoid dehydration by eating foods with a high water content.
Choices like celery, watermelon, cucumbers, carrots, and citrus fruits all offer exceptional hydrating ability. Pack these as snacks for the pool or beach, or to enjoy before and after an outdoor workout.
#3: Steer Clear Of Certain Drinks
As yummy and refreshing as an icy beer or frosty margarita tastes, alcohol can contribute to dehydration. If you decide to indulge, limit yourself to one or two, and drink a large glass of water along with your beverage to counteract the alcohol’s effects.
#4: Avoid Overexertion
Exercise is a wonderfully healthy pursuit; however, keep an eye on the temperature. If it is going to be exceptionally hot and humid, choose to exercise either early in the morning, or after sunset, when temperatures are lower and the sun isn’t beaming.
#5: Wear Proper Attire
Dress in light, airy clothing in fabrics that breathe. Protect your head with a cap or hat that shades your face. Avoid black clothing, which tends to absorb the sun and make you hotter.
#6: Stay Hydrated & Be Prepared
Extreme heat makes everyday issues like a flat tire or dead battery life-threatening. Visit a mechanic to confirm your vehicle is in good shape to lessen the chances of getting stranded. Carry extra water or sports drinks in your vehicle, and keep your cell phone charged. If your car breaks down, either stay in your car to wait for help, or stand in the grass instead of on the sizzling pavement.
When you stay hydrated is essential for good health all the time, and during the summer in particular. Implement these easy tips into your daily routine so you and your family maintain hydration and enjoy hot weather outdoor fun.
Chiropractic Treatment For Concussions
This article is copyrighted by Blogging Chiros LLC for its Doctor of Chiropractic members and may not be copied or duplicated in any manner including printed or electronic media, regardless of whether for a fee or gratis without the prior written permission of Blogging Chiros, LLC.
School is out, and the cool, fresh water of the local swimming pool awaits beckoning. Long, sunny days, the smell of sunscreen, and the laughter of the playing children will fill the next few months.
However, there are elements of this delightful picture that can end up causing harm to children and adults alike. It’s important to take a few key precautions when enjoying a day at the pool this summer. Doing so will minimize the risk of the summer laughter turning to tears.
Here are six bright ways for adults and children to stay safe at the pool this summer.
Pool Safety Tips:
#1: Enroll In Swimming Lessons
Playing in the water is a fun, refreshing activity, but can turn dangerous quickly. According to the Red Cross, the single biggest precaution to take to ensure summer safety is to make sure your children are able to swim. Book age appropriate swimming lessons for your children as young as possible.
#2: Avoid Spills With Water Shoes Or Rough Bottom Sandals
Nothing brings a playful pool day to a screeching halt like a slip and fall on the side of the pool. This goes for you, too, Mom and Dad!
Bare feet offer no traction on wet and slick concrete, and falling can cause serious accidents that require stitches, casts, and, well, chiropractic visits! Make it a rule to wear water shoes or sandals around the pool at all times.
#3: Take Measures To Fight Off Swimmer’s Ear
Swimmer’s ear is a common condition that is brought on by water remaining in the ear canal, allowing germs to grow. Yuk!
The CDC reports that this condition results in an astonishing 2.4 million doctor visits every year. Guard against this by teaching your children to tilt each side of their heads toward the ground to drain their ears, and to dry their ears thoroughly with a towel every time they get out of the pool.
If you or one of your little swimmers experience ear pain after a pool day, take them to the doctor as soon as possible to begin treatment.
#4: Beware Of Little Critters
Hot days and bare skin are too much temptation for bees, mosquitoes, and ticks. Bites from these creatures range from itchy to extremely serious. Ward them off with bug spray, or sunscreen with insect repellent.
Ticks in particular are dangerous. If you or your child gets bitten by a tick, remove it promptly and clean the area thoroughly.
#5: Be Cautious Of Overdoing It
A day at the pool can be a blast for the young ones, but wagging the cooler and lawn chairs back and forth to the pool can exhaust an adult, causing injury. Remember to lift heavy items with your legs, and don’t overload yourself. An extra trip to the car is worth it to avoid a neck or back strain.
#6: Prepare For Disaster
Okay, that is a little melodramatic, but it pays to be prepared in the event of an emergency. Pack a small kit with alcohol, tweezers, bug bite cream, and bandages. Keep the kit in your car or pool bag. Better safe than sorry.
Pool days are a big part of the hot summer months, and are usually lazy and enjoyable. Keep them that way by taking these six tips to heart and talking to your children about the pool rules. With a little preparation up front, the chance of fun-dampening or dangerous instances happening to your family will be greatly minimized.
Prevention, Recognition & Management of Youth Sports Injuries
This article is copyrighted by Blogging Chiros LLC for its Doctor of Chiropractic members and may not be copied or duplicated in any manner including printed or electronic media, regardless of whether for a fee or gratis without the prior written permission of Blogging Chiros, LLC.
It’s a warm sunny day with a bit of a breeze, you are on the back nine about to sink a putt. When you swing, your back seizes up with severe pain. The beautiful day of golf turns into painfully riding in the golf cart back to the clubhouse, and you limping painfully to your car.
If you have ever strained your back during a golf game, you are not alone. It’s estimated of the 30 million golfers in the United States, 80% have experienced some sort of back pain. As fun as it is, swinging at golf balls puts an individual’s body in an awkward position, opening up the opportunity for injury.
While some golfers suffer through the pain by popping over-the-counter medications, others back away from playing as often, or stop altogether. There’s another way to combat back injuries caused by golfing, without meds. It’s not a magic wand, it’s chiropractic care!
Golfers are increasingly finding chiropractic care to be a valuable tool to help them deal with back injuries. Here are FORE! ways chiropractors can help injured golfers get off the couch and back on the green.
Golfers: Consistent Adjustments Can Avoid Injuries In The First Place.
Golfing, or any activity, is more enjoyable and causes less chance of injury if an individual’s body is in top condition and operating normally. Periodic spinal adjustments keep the body functioning at maximum capacity, and reduce the chances of being injured. If the neck and back are aligned correctly, awkward positioning such as a golf swing will have a less negative impact.
Chiropractic Treatment Can Reduce A Golfer’s Pain.
Back injuries can be extremely painful, and many turn to pain medications to gain relief and comfort. By treating the origin of the pain instead of just the symptoms, a chiropractor helps their patients manage the pain through manipulations, instead of drugs. Over the course of a few treatments, pain is often drastically diminished and much more manageable.
A Golf Injury Can Heal Quicker With Chiropractic Care.
Injuries to the back or neck can heal faster when chiropractors treat them than on their own. An experienced chiropractor can adjust the spine, and also work on the joints and surrounding tissue that can cause pain and hinder healing. Chiropractic evaluation considers the body as a whole. By treating the entire body, it promotes quicker healing of the injury.
Increased Mobility Can Be Gained With Chiropractic Visits.
Golfers who play often as well as those who only play a few times a year know mobility is essential to a good golf game. Stiff joints and a weak back not only mess with the golf game, but can be the very issues that end up causing an injury.
A chiropractic treatment schedule keeps the body loose and strong, and working in optimum fashion. This prevents injuries and increases the chances of playing the game of your life.
Golfers need to realize the sport can cause serious injuries just like “rougher” sports like football and rugby. It’s a good idea to stretch before playing, stay hydrated, and avoid overexertion.
If you are a golfer, chiropractic care is a valuable tool in staying healthy. Regular adjustments and manipulations keep your body on track and performing with maximum mobility at the top of your game. If you do suffer an injury, a chiropractor can help you manage your pain and decrease the time it takes to heal.
Professional Golfer Zach Johnson Trusts Chiropractic Care
Contact us today for more information on how we can help reduce the chance of injury for golfers, and promote healing.
This article is copyrighted by Blogging Chiros LLC for its Doctor of Chiropractic members and may not be copied or duplicated in any manner including printed or electronic media, regardless of whether for a fee or gratis without the prior written permission of Blogging Chiros, LLC.
Even if you have never stepped foot onto a court before, you may end up with tennis elbow. Occurring along the muscle that allows extension of the wrist, it is a painful condition that can linger for weeks or months.
Previously, tennis elbow primarily showed up in athletes. Due to the increased interest in physical fitness, tennis elbow is being found in everyday exercisers, as well as people who perform work-related repetitive motion.
Tennis elbow presents several symptoms. Pain will occur on the outside of the elbow an inch or so down from the bony part.
There may also be pain when the individual tries to extend the hand and fingers against resistance. Extreme weakness in the wrist is another symptom.
I Have Been Diagnosed With Tennis Elbow. Now What?
Tennis elbow is often difficult to diagnose, which can delay treatment. A correct diagnosis of tennis elbow is the first step towards being able to treat the condition and rehab the afflicted area. From there, a variety of treatments for tennis elbow are available.
Passive remedies like rest, ice, and arm braces are critical components to healing tennis elbow. Take measures to reduce the movements that aggravate the pain, and use ice at regular intervals to help minimize pain and inflammation.
An arm brace supports and stabilizes the area to promote healing. These remedies assist greatly in treating the condition, especially in the beginning.
Active remedies consist of stretching and strengthening exercises, and are vital aspects of improving the condition. Individuals suffering from tennis elbow should begin an exercise regimen as soon as the pain allows.
An individual dealing with tennis elbow may utilize a variety of medicinal remedies to manage pain and inflammation. Over-the-counter pain relievers and steroid injections are commonly used to treat the condition. Following doctor’s orders when taking medications is strongly recommended.
Untraditional remedies also provide vast improvements in tennis elbow, and these treatments have gained favor in the last few years due to their effectiveness. Regimens of massage therapy and acupuncture work on small areas contributing to the condition, and make significant strides in pain reduction and promote the body’s restorative healing process.
Another remedy that offers strong benefits to treating tennis elbow is chiropractic care. A chiropractor assesses the condition, then lays out a plan to promote healing.
Treatment often includes working to align the bones and treating the surrounding joints so they function at maximum capacity, and can “take up the slack” of the injured area while it heals. Chiropractic care serves the dual purpose of treating the condition directly, and healing the areas around the injury so that the body continues to strengthen and renew.
In a very small number of cases, the only remedy for tennis elbow is surgery. This is considered as the last straw, once all other forms of treatment have been exhausted.
The best way to treat tennis elbow is to avoid it in the first place. Be sure to stretch before exercising, consistently perform strengthening exercises, employ correct techniques and proper equipment during physical activity, and don’t overexert your arms (this goes for your entire body, by the way) during physical activity.
If you are diagnosed with tennis elbow, it’s essential to understand the variety of treatment options available. The best course is often a blend of more than one remedy. Chiropractic care should be part of your healing process, as it helps decrease pain, reduce healing time, and offers a non-medicinal approach to treating the body as a whole.
The Risks Of College Sports
This article is copyrighted by Blogging Chiros LLC for its Doctor of Chiropractic members and may not be copied or duplicated in any manner including printed or electronic media, regardless of whether for a fee or gratis without the prior written permission of Blogging Chiros, LLC.
When you suffer from joint or muscle pain, it is important to work on maintaining as much flexibility as possible. The more flexible you are, the less likely you will be to further injure yourself. One of the best ways to improve your flexibility is by stretching before you are active.
However, you need to warm up your muscles before you stretch. If you stretch first, you can actually injure yourself by pushing your joints too far. Spend a few minutes doing some light activity before you stretch. This can be as simple as a brisk walk or some basic calisthenics.
If you have been seeing a chiropractor, he or she may be able to recommend some stretches for you. Otherwise, you can use some of these basic techniques. There are two basic forms of stretching, static and dynamic.
Static Stretching vs. Dynamic Stretching
Static stretches involve holding a position for a certain period of time to loosen up your muscles. These tend to be what most people think of when they think about stretching. However, dynamic stretches are also important. With these, you move parts of your body to work on your flexibility.
Many of the most effective stretches for back pain can be done right at home. For example, lie on your back with your knees bent. Grasp one knee in both hands and pull it up towards your chest. Hold this position for 30 seconds and then lower the knee to the starting pose. Repeat with the other knee. You can also do both knees at the same time.
A similar stretch begins in the same position as the previous one. However, instead of lifting your knee to your chest, roll both legs to one side so that your knees are as close to the floor as possible. Hold this position for 10 seconds, and then roll to the other side.
Another common stretch recommended by many chiropractors comes from yoga, where it is known as the “cat pose.” Get down on the floor on your hands and knees, with your hands underneath your shoulders. First, let your abdomen drop down towards the floor. Then, reverse this movement by arching your back. Repeat this cycle three to five times.
More dynamic stretches can also be good for your muscle pain. Try doing handwalks to stretch your shoulders and abdominal muscles. Stand up straight and slowly lower your hands towards the floor. Walk your hands out in front of you until you are as far down as you can go. Then walk your hands back to the starting position.
A final stretch that can help your back muscles is known as the “scorpion.” Lie face-down and stretch your arms out to the sides. First, slowly move your right foot towards your left arm. Then, move your left foot towards your right arm. Make sure to move in a slow and controlled fashion.
When you are suffering from muscle or joint pain, it is a good idea to stretch both in the morning and the evening. By incorporating these exercises into your daily routine, you can avoid many common injuries.
If you need further instruction regarding stretches, please give us a call so that you can schedule an appointment with our Doctor of Chiropractic.
This article is copyrighted by Blogging Chiros LLC for its Doctor of Chiropractic members and may not be copied or duplicated in any manner including printed or electronic media, regardless of whether for a fee or gratis without the prior written permission of Blogging Chiros, LLC.
We usually talk of energy in general terms, as in �I don�t have a lot of energy today� or �You can feel the energy in the room.� But what really is energy? Where do we get the energy to move? How do we use it? How do we get more of it? Ultimately, what controls our movements? The three metabolic energy pathways are the�phosphagen system, glycolysis�and the�aerobic system.�How do they work, and what is their effect?
Albert Einstein, in his infinite wisdom, discovered that the total energy of an object is equal to the mass of the object multiplied by the square of the speed of light. His formula for atomic energy, E = mc2, has become the most recognized mathematical formula in the world. According to his equation, any change in the energy of an object causes a change in the mass of that object. The change in energy can come in many forms, including mechanical, thermal, electromagnetic, chemical, electrical or nuclear. Energy is all around us. The lights in your home, a microwave, a telephone, the sun; all transmit energy. Even though the solar energy that heats the earth is quite different from the energy used to run up a hill, energy, as the first law of thermodynamics tells us, can be neither created nor destroyed. It is simply changed from one form to another.
ATP Re-Synthesis
The energy for all physical activity comes from the conversion of high-energy phosphates (adenosine�triphosphate�ATP) to lower-energy phosphates (adenosine�diphosphate�ADP; adenosine�monophosphate�AMP; and inorganic phosphate, Pi). During this breakdown (hydrolysis) of ATP, which is a water-requiring process, a proton, energy and heat are produced: ATP + H2O ���ADP + Pi�+ H+�+ energy + heat. Since our muscles don�t store much ATP, we must constantly resynthesize it. The hydrolysis and resynthesis of ATP is thus a circular process�ATP is hydrolyzed into ADP and Pi, and then ADP and Pi�combine to resynthesize ATP. Alternatively, two ADP molecules can combine to produce ATP and AMP: ADP + ADP ���ATP + AMP.
Like many other animals, humans produce ATP through three metabolic pathways that consist of many enzyme-catalyzed chemical reactions: the phosphagen system, glycolysis and the aerobic system. Which pathway your clients use for the primary production of ATP depends on how quickly they need it and how much of it they need. Lifting heavy weights, for instance, requires energy much more quickly than jogging on the treadmill, necessitating the reliance on different energy systems. However, the production of ATP is never achieved by the exclusive use of one energy system, but rather by the coordinated response of all energy systems contributing to different degrees.
1. Phosphagen System
During short-term, intense activities, a large amount of power needs to be produced by the muscles, creating a high demand for ATP. The phosphagen system (also called the ATP-CP system) is the quickest way to resynthesize ATP (Robergs & Roberts 1997). Creatine phosphate (CP), which is stored in skeletal muscles, donates a phosphate to ADP to produce ATP: ADP + CP ���ATP + C. No carbohydrate or fat is used in this process; the regeneration of ATP comes solely from stored CP. Since this process does not need oxygen to resynthesize ATP, it is anaerobic, or oxygen-independent. As the fastest way to resynthesize ATP, the phosphagen system is the predominant energy system used for all-out exercise lasting up to about 10 seconds. However, since there is a limited amount of stored CP and ATP in skeletal muscles, fatigue occurs rapidly.
2. Glycolysis
Glycolysis is the predominant energy system used for all-out exercise lasting from 30 seconds to about 2 minutes and is the second-fastest way to resynthesize ATP. During glycolysis, carbohydrate�in the form of either blood glucose (sugar) or muscle glycogen (the stored form of glucose)�is broken down through a series of chemical reactions to form pyruvate (glycogen is first broken down into glucose through a process called�glycogenolysis). For every molecule of glucose broken down to pyruvate through glycolysis, two molecules of usable ATP are produced (Brooks et al. 2000). Thus, very little energy is produced through this pathway, but the trade-off is that you get the energy quickly. Once pyruvate is formed, it has two fates: conversion to lactate or conversion to a metabolic intermediary molecule called acetyl coenzyme A (acetyl-CoA), which enters the mitochondria for oxidation and the production of more ATP (Robergs & Roberts 1997). Conversion to lactate occurs when the demand for oxygen is greater than the supply (i.e., during anaerobic exercise). Conversely, when there is enough oxygen available to meet the muscles� needs (i.e., during aerobic exercise), pyruvate (via acetyl-CoA) enters the mitochondria and goes through aerobic metabolism.
When oxygen is not supplied fast enough to meet the muscles� needs (anaerobic glycolysis), there is an increase in hydrogen ions (which causes the muscle pH to decrease; a condition called acidosis) and other metabolites (ADP, Pi�and potassium ions). Acidosis and the accumulation of these other metabolites cause a number of problems inside the muscles, including inhibition of specific enzymes involved in metabolism and muscle contraction, inhibition of the release of calcium (the trigger for muscle contraction) from its storage site in muscles, and interference with the muscles� electrical charges (Enoka & Stuart 1992; Glaister 2005; McLester 1997). As a result of these changes, muscles lose their ability to contract effectively, and muscle force production and exercise intensity ultimately decrease.
3. Aerobic System
Since humans evolved for aerobic activities (Hochachka, Gunga & Kirsch 1998; Hochachka & Monge 2000), it�s not surprising that the aerobic system, which is dependent on oxygen, is the most complex of the three energy systems. The metabolic reactions that take place in the presence of oxygen are responsible for most of the cellular energy produced by the body. However, aerobic metabolism is the slowest way to resynthesize ATP. Oxygen, as the patriarch of metabolism, knows that it is worth the wait, as it controls the fate of endurance and is the sustenance of life. �I�m oxygen,� it says to the muscle, with more than a hint of superiority. �I can give you a lot of ATP, but you will have to wait for it.�
The aerobic system�which includes the�Krebs cycle�(also called the�citric acid cycle or TCA cycle) and the�electron transport chain�uses blood glucose, glycogen and fat as fuels to resynthesize ATP in the mitochondria of muscle cells (see the sidebar �Energy System Characteristics�). Given its location, the aerobic system is also called�mitochondrial respiration.�When using carbohydrate, glucose and glycogen are first metabolized through glycolysis, with the resulting pyruvate used to form acetyl-CoA, which enters the Krebs cycle. The electrons produced in the Krebs cycle are then transported through the electron transport chain, where ATP and water are produced (a process called�oxidative phosphorylation) (Robergs & Roberts 1997). Complete oxidation of glucose via glycolysis, the Krebs cycle and the electron transport chain produces 36 molecules of ATP for every molecule of glucose broken down (Robergs & Roberts 1997). Thus, the aerobic system produces 18 times more ATP than does anaerobic glycolysis from each glucose molecule.
Fat, which is stored as triglyceride in adipose tissue underneath the skin and within skeletal muscles (called�intramuscular triglyceride), is the other major fuel for the aerobic system, and is the largest store of energy in the body. When using fat, triglycerides are first broken down into free fatty acids and glycerol (a process called�lipolysis). The free fatty acids, which are composed of a long chain of carbon atoms, are transported to the muscle mitochondria, where the carbon atoms are used to produce acetyl-CoA (a process called�beta-oxidation).
Following acetyl-CoA formation, fat metabolism is identical to carbohydrate metabolism, with acetyl-CoA entering the Krebs cycle and the electrons being transported to the electron transport chain to form ATP and water. The oxidation of free fatty acids yields many more ATP molecules than the oxidation of glucose or glycogen. For example, the oxidation of the fatty acid palmitate produces 129 molecules of ATP (Brooks et al. 2000). No wonder clients can sustain an aerobic activity longer than an anaerobic one!
Understanding how energy is produced for physical activity is important when it comes to programming exercise at the proper intensity and duration for your clients. So the next time your clients get done with a workout and think, �I have a lot of energy,� you�ll know exactly where they got it.
Energy System Characteristics
Energy System Workouts
Have clients warm up and cool down before and after each workout.
Phosphagen System
An effective workout for this system is short, very fast sprints on the treadmill or bike lasting 5�15 seconds with 3�5 minutes of rest between each. The long rest periods allow for complete replenishment of creatine phosphate in the muscles so it can be reused for the next interval.
2 sets of 8 x 5 seconds at close to top speed with 3:00 passive rest and 5:00 rest between sets
5 x 10 seconds at close to top speed with 3:00�4:00 passive rest
Glycolysis
This system can be trained using fast intervals lasting 30 seconds to 2 minutes with an active-recovery period twice as long as the work period (1:2 work-to-rest ratio).
8�10 x 30 seconds fast with 1:00 active recovery
4 x 1:30 fast with 3:00 active recovery
Aerobic System
While the phosphagen system and glycolysis are best trained with intervals, because those metabolic systems are emphasized only during high-intensity activities, the aerobic system can be trained with both continuous exercise and intervals.
60 minutes at 70%�75% maximum heart rate
15- to 20-minute tempo workout at lactate threshold intensity (about 80%�85% maximum heart rate)
5 x 3:00 at 95%�100% maximum heart rate with 3:00 active recovery
Brooks, G.A., et al. 2000.�Exercise Physiology: Human Bioenergetics and Its Applications.Mountain View, CA: Mayfield.
Enoka, R.M., & Stuart, D.G. 1992. Neurobiology of muscle fatigue.�Journal of Applied Physiology, 72�(5), 1631�48.
Glaister, M. 2005. Multiple sprint work: Physiological responses, mechanisms of fatigue and the influence of aerobic fitness.�Sports Medicine, 35�(9), 757�77.
Hochachka, P.W., Gunga, H.C., & Kirsch, K. 1998. Our ancestral physiological phenotype: An adaptation for hypoxia tolerance and for endurance performance?�Proceedings of the National Academy of Sciences, 95,�1915�20.
Hochachka, P.W., & Monge, C. 2000. Evolution of human hypoxia tolerance physiology.�Advances in Experimental and Medical Biology, 475,�25�43.
McLester, J.R. 1997. Muscle contraction and fatigue: The role of adenosine 5′-diphosphate and inorganic phosphate.�Sports Medicine, 23�(5), 287�305.
Robergs, R.A. & Roberts, S.O. 1997.�Exercise Physiology: Exercise, Performance, and Clinical Applications.�Boston: William C. Brown.
Nutrition�Abstract: A number of factors contribute to success in sport, and diet is a key component. An athlete�s dietary requirements depend on several aspects, including the sport, the athlete�s goals, the environment, and practical issues. The importance of individualized dietary advice has been increasingly recognized, including day-to-day dietary advice and specific advice before, during, and after training and/or competition. Athletes use a range of dietary strategies to improve performance, with maximizing glycogen stores a key strategy for many. Carbohydrate intake during exercise maintains high levels of carbohydrate oxidation, prevents hypoglycemia, and has a positive effect on the central nervous system. Recent research has focused on athletes training with low carbohydrate availability to enhance metabolic adaptations, but whether this leads to an improvement in performance is unclear. The benefits of protein intake throughout the day following exercise are now well recognized. Athletes should aim to maintain adequate levels of hydration, and they should minimize fluid losses during exercise to no more than 2% of their body weight. Supplement use is widespread in athletes, with recent interest in the beneficial effects of nitrate, beta-alanine, and vitamin D on performance. However, an unregulated supplement industry and inadvertent contamination of supplements with banned substances increases the risk of a positive doping result. Although the availability of nutrition information for athletes varies, athletes will bene t from the advice of a registered dietician or nutritionist.
Introduction To The Importance & Influence Of Nutrition On Exercise
Nutrition is increasingly recognized as a key component of optimal sporting performance, with both the science and practice of sports nutrition developing rapidly.1 Recent studies have found that a planned scientific nutritional strategy (consisting of fluid, carbohydrate, sodium, and caffeine) compared with a self-chosen nutritional strategy helped non-elite runners complete a marathon run faster2 and trained cyclists complete a time trial faster.3 Whereas training has the greatest potential to increase performance, it has been estimated that consumption of a carbohydrate�electrolyte drink or relatively low doses of caffeine may improve a 40 km cycling time trial performance by 32�42 and 55�84 seconds, respectively.4
Evidence supports a range of dietary strategies in enhancing sports performance. It is likely that combining several strategies will be of greater bene t than one strategy in isolation.5 Dietary strategies to enhance performance include optimizing intakes of macronutrients, micronutrients, and fluids, including their composition and spacing throughout the day. The importance of individualized or personalized dietary advice�is becoming increasingly recognized,6 with dietary strategies varying according to the individual athlete�s sport, personal goals, and practicalities (eg, food preferences). �Athlete� includes individuals competing in a range of sport types, such as strength and power (eg, weight-lifting), team (eg, football), and endurance (eg, marathon running). The use of dietary supplements can enhance performance, provided these are used appropriately. This manuscript provides an overview of dietary strategies used by athletes, the efficacy of these strategies, availability of nutrition information to athletes, and risks associated with dietary supplement intake.
Review Of Diet Strategies Employed By Athletes
Maximizing Muscle Glycogen Stores Prior To Exercise
Carbohydrate loading aims to maximize an athlete�s muscle glycogen stores prior to endurance exercise lasting longer than 90 minutes. Benefits include delayed onset of fatigue (approximately 20%) and improvement in performance of 2%�3%.7 Initial protocols involved a depletion phase (3 days of intense training and low carbohydrate intake) followed by a loading phase (3 days of reduced training and high carbo- hydrate intake).8,9 Further research showed muscle glycogen concentrations could be enhanced to a similar level without the glycogen-depletion phase,10 and more recently, that 24 hours may be sufficient to maximize glycogen stores.11,12 Current recommendations suggest that for sustained or intermittent exercise longer than 90 minutes, athletes should consume 10�12 g of carbohydrate per kg of body mass (BM) per day in the 36�48 hours prior to exercise.13
There appears to be no advantage to increasing pre- exercise muscle glycogen content for moderate-intensity cycling or running of 60�90 minutes, as signi cant levels of glycogen remain in the muscle following exercise.7 For exercise shorter than 90 minutes, 7�12 g of carbohydrate/kg of BM should be consumed during the 24 hours preceding.13 Some14,15 but not all16 studies have shown enhanced performance of intermittent high-intensity exercise of 60�90 minutes with carbohydrate loading.
Carbohydrate eaten in the hours prior to exercise (com- pared with an overnight fast) has been shown to increase muscle glycogen stores and carbohydrate oxidation,17 extend cycle time to exhaustion,5 and improve exercise performance.5,18 Specific recommendations for exercise of longer than 60 minutes include 1�4 g of carbohydrate/kg of BM in the 1�4 hours prior.13 Most studies have not found improvements in performance from consuming low glycemic�index (GI) foods prior to exercise.19 Any metabolic or performance effects from low GI foods appear to be attenuated when carbohydrate is consumed during exercise.20,21
Carbohydrate Intake During The Event
Carbohydrate ingestion has been shown to improve performance in events lasting approximately 1 hour.6 A growing body of evidence also demonstrates beneficial effects of a carbohydrate mouth rinse on performance.22 It is thought that receptors in the oral cavity signal to the central nervous system to positively modify motor output.23
In longer events, carbohydrate improves performance primarily by preventing hypoglycemia and maintaining high levels of carbohydrate oxidation.6 The rate of exogenous carbohydrate oxidation is limited by the small intestine�s ability to absorb carbohydrate.6 Glucose is absorbed by the sodium- dependent transporter (SGLT1), which becomes saturated with an intake of approximately 1 g/minute. The simultaneous ingestion of fructose (absorbed via glucose transporter 5�[GLUT5]), enables oxidation rates of approximately 1.3 g/minute,24 with performance benefits apparent in the third hour of exercise.6 Recommendations reflect this, with 90 g of carbohydrate from multiple sources recommended for events longer than 2.5 hours, and 60 g of carbohydrate from either single or multiple sources recommended for exercise of 2�3 hours� duration (Table 1). For slower athletes exercising at a lower intensity,�carbohydrate requirements will be less due to lower carbohydrate oxidation.6 Daily training with high carbohydrate availability has been shown to increase exogenous carbohydrate oxidation rates.25
The �Train-Low, Compete-High� Approach
The �train-low, compete-high� concept is training with low carbohydrate availability to promote adaptations such as�enhanced activation of cell-signaling pathways, increased mitochondrial enzyme content and activity, enhanced lipid oxidation rates, and hence improved exercise capacity.26 However, there is no clear evidence that performance is improved with this approach.27 For example, when highly trained cyclists were separated into once-daily (train-high) or twice-daily (train-low) training sessions, increases in resting muscle glycogen content were seen in the low-carbohydrate- availability group, along with other selected training adaptations.28 However, performance in a 1-hour time trial after 3 weeks of training was no different between groups. Other research has produced similar results.29 Different strategies have been suggested (eg, training after an overnight fast, training twice per day, restricting carbohydrate during recovery),26 but further research is needed to establish optimal dietary periodization plans.27
Fat As A Fuel During Endurance Exercise
There has been a recent resurgence of interest in fat as a fuel, particularly for ultra endurance exercise. A high-carbohydrate strategy inhibits fat utilization during exercise,30 which may not be beneficial due to the abundance of energy stored in the body as fat. Creating an environment that optimizes fat oxidation potentially occurs when dietary carbohydrate is reduced to a level that promotes ketosis.31 However, this strategy may impair performance of high-intensity activity, by contributing to a reduction in pyruvate dehydrogenase activity and glycogenolysis. 32 The lack of performance benefits seen in studies investigating �high-fat� diets may be attributed to inadequate carbohydrate restriction and time for adaptation.31 Research into the performance effects of high fat diets continues.
Nutrition: Protein
While protein consumption prior to and during endurance and resistance exercise has been shown to enhance rates of muscle protein synthesis (MPS), a recent review found protein ingestion alongside carbohydrate during exercise does not improve time�trial performance when compared with the ingestion of adequate amounts of carbohydrate alone.33
Fluid And Electrolytes
The purpose of fluid consumption during exercise is primarily to maintain hydration and thermoregulation, thereby benefiting performance. Evidence is emerging on increased risk of oxidative stress with dehydration.34 Fluid consumption prior to exercise is recommended to ensure that the athlete is well-hydrated prior to commencing exercise.35 In addition,�carefully planned hyperhydration ( fluid overloading) prior to an event may reset fluid balance and increase fluid retention, and consequently improve heat tolerance.36 However, fluid overloading may increase the risk of hyponatremia 37 and impact negatively on performance due to feelings of fullness and the need to urinate.
Hydration requirements are closely linked to sweat loss, which is highly variable (0.5�2.0 L/hour) and dependent on type and duration of exercise, ambient temperature, and athletes� individual characteristics.35 Sodium losses linked to high temperature can be substantial, and in events of long duration or in hot temperatures, sodium must be replaced along with fluid to reduce risk of hyponatremia. 35
It has long been suggested that fluid losses greater than 2% of BM can impair performance,35 but there is controversy over the recommendation that athletes maintain BM by fluid ingestion throughout an event.37 Well-trained athletes who �drink to thirst� have been found to lose as much as 3.1% of BM with no impairment of performance in ultra-endurance events.38 Ambient temperature is important, and a review illustrated that exercise performance was preserved if loss was restricted to 1.8% and 3.2% of BM in hot and temperate conditions, respectively.39
Dietary Supplementation: Nitrates, Beta-Alanine & Vitamin D
Performance supplements shown to enhance performance include caffeine, beetroot juice, beta-alanine (BA), creatine, and bicarbonate.40 Comprehensive reviews on other supplements including caffeine, creatine, and bicarbonate can be found elsewhere.41 In recent years, research has focused on the role of nitrate, BA, and vitamin D and performance. Nitrate is most commonly provided as sodium nitrate or beetroot juice.42 Dietary nitrates are reduced (in mouth and stomach) to nitrites, and then to nitric oxide. During exercise, nitric oxide potentially influences skeletal muscle function through regulation of blood ow and glucose homeostasis, as well as mitochondrial respiration.43 During endurance exercise, nitrate supplementation has been shown to increase exercise efficiency (4%�5% reduction in VO at a steady attenuate oxidative stress.42 Similarly, a 4.2% improvement in performance was shown in a test designed to simulate a football game.44
BA is a precursor of carnosine, which is thought to have a number of performance-enhancing functions including the reduction of acidosis, regulation of calcium, and antioxidant properties.45 Supplementation with BA has been shown to�2�state; 0.9% improvement in time trials), reduce fatigue, and�augment intracellular carnosine concentration.45 A systematic review concluded that BA may increase power output and working capacity and decrease feelings of fatigue, but that there are still questions about safety. The authors suggest caution in the use of BA as an ergogenic aid.46
Vitamin D is essential for the maintenance of bone health and control of calcium homeostasis, but is also important for muscle strength,47,48 regulation of the immune system,49 and cardiovascular health.50 Thus inadequate vitamin D status has potential implications for the overall health of athletes and performance. A recent review found that the vitamin D status of most athletes reflects that of the population in their locality, with lower levels in winter, and athletes who train predominantly indoors are at greater risk of deficiency.51 There are no dietary vitamin D recommendations for athletes; however, for muscle function, bone health, and avoidance of respiratory infections, current evidence supports maintenance of serum 25-hydroxy vitamin D (circulating form) concentrations of 80�100 nmol/L.51
Diets Specific For Post Exercise
Recovery from a bout of exercise is integral to the athlete�s training regimen. Without adequate recovery of carbohydrate, protein, fluids, and electrolytes, beneficial adaptations and performance may be hampered.
Muscle Glycogen Synthesis
Consuming carbohydrates immediately post exercise to coincide with the initial rapid phase of glycogen synthesis has been used as a strategy to maximize rates of muscle glycogen synthesis. An early study found delaying feeding by 2 hours after glycogen-depleting cycling exercise reduced glycogen synthesis rates.52 However the importance of this early enhanced rate of glycogen synthesis has been questioned in the context of extended recovery periods with sufficient carbohydrate consumption. Enhancing the rate of glycogen synthesis with immediate carbohydrate consumption after exercise appears most relevant when the next exercise session is within 8 hours of the first.53,54 Feeding frequency is also irrelevant with extended recovery; by 24 hours post exercise, consumption of carbohydrate as four large meals or 16 small snacks had comparable effects on muscle glycogen storage.55
With less than 8 hours between exercise sessions, it is recommended that for maximal glycogen synthesis, 1.0�1.2 g/kg/hour is consumed for the first 4 hours, followed by resumption of daily carbohydrate requirements.13 Additional protein has been shown to enhance glycogen�synthesis rates when carbohydrate intake is suboptimal.56 The consumption of moderate to high GI foods post exercise is recommended;13 however, when either a high-GI or low-GI meal was consumed after glycogen-depleting exercise, no performance differences were seen in a 5 km cycling time trial 3 hours later.57
Muscle Protein Synthesis
An acute bout of intense endurance or resistance exercise can induce a transient increase in protein turnover, and, until feeding, protein balance remains negative. Protein consumption after exercise enhances MPS and net protein balance,58 predominantly by increasing mitochondrial protein fraction with endurance training, and myofibrillar protein fraction with resistance training.59
Only a few studies have investigated the effect of timing of protein intake post exercise. No significant difference in MPS was observed over 4 hours post exercise when a mixture of essential amino acids and sucrose was fed 1 hour versus 3 hours after resistance exercise.60 Conversely, when a protein and carbohydrate supplement was provided immediately versus 3 hours after cycling exercise, leg protein synthesis increased threefold over 3 hours.61 A meta-analysis found timed post exercise protein intake becomes less important with longer recovery periods and adequate protein intake,62 at least for resistance training.
Dose�response studies suggest approximately 20 g of high-quality protein is sufficient to maximize MPS at rest,63 following resistance,63,64 and after high-intensity aerobic exercise.65 Rate of MPS has been found to approximately triple 45�90 minutes after protein consumption at rest, and then return to baseline levels, even with continued availability of circulating essential amino acids (termed the �muscle full� effect).66 Since exercise-induced protein synthesis is elevated for 24�48 hours following resistance exercise67and 24�28 hours following high-intensity aerobic exercise,68 and feeding protein post exercise has an additive effect,58,64 then multiple feedings over the day post exercise might maximize muscle growth. In fact, feeding 20 g of whey protein every 3 hours was subsequently found to maximally stimulate muscle myofibrillar protein synthesis following resistance exercise.69,70
In resistance training, where post exercise intake of protein was balanced by protein intake later in the day, increased adaptation of muscle hypertrophy resulted in equivocal strength performance effects.71,72 Most studies have not found a subsequent bene t to aerobic performance with post exercise protein consumption.73,74 However, in two�well controlled studies in which post exercise protein intake was balanced by protein intake later in the day, improvements were seen in cycling time to exhaustion75 and in cycling sprint performance.76
Fluids And Electrolyte Balance
Fluid and electrolyte replacement after exercise can be achieved through resuming normal hydration practices. However, when euhydration is needed within 24 hours or substantial body weight has been lost (.5% of BM), a more structured response may be warranted to replace fluids and electrolytes.77
Availability Of Nutritional Information To Athletes At Varying Levels
The availability of nutrition information for athletes varies. Younger or recreational athletes are more likely to receive generalized nutritional information of poorer quality from individuals such as coaches.78 Elite athletes are more likely to have access to specialized sports-nutrition input from qualified professionals. A range of sports science and medicine support systems are in place in different countries to assist elite athletes,1 and nutrition is a key component of these services. Some countries have nutrition programs embedded within sports institutes (eg, Australia) or alternatively have National Olympic Committees that support nutrition programs (eg, United States of America).1 However, not all athletes at the elite level have access to sports-nutrition services. This may be due to financial constraints of the sport, geographical issues, and a lack of recognition of the value of a sports-nutrition service.78
Athletes eat several times per day, with snacks contributing to energy requirements.79 Dietary intake differs across sports, with endurance athletes more likely to achieve energy and carbohydrate requirements compared to athletes in weight-conscious sports.79 A review found daily intakes of carbohydrate were 7.6 g/kg and 5.7 g/kg of BM for male and female endurance athletes, respectively.80 Ten elite Kenyan runners met macronutrient recommendations but not guide- lines for fluid intake.81 A review of fluid strategies showed a wide variability of intake across sports, with several factors influencing intake, many outside the athlete�s control.82
Nutrition information may be delivered to athletes by a range of people (dietitians, nutritionists, medical practitioners, sports scientists, coaches, trainers) and from a variety of sources (nutrition education programs, sporting magazines, the media and Internet).83 Of concern is the provision of�nutrition advice from outside various professional�s scope of practice. For example, in Australia 88% of registered exercise professionals provided nutrition advice, despite many not having adequate nutrition training.84 A study of Canadian high-performance athletes from 34 sports found physicians ranked eighth and dietitians, 16th as choice of source of dietary supplement information.85
Risks Of Contravening The Doping Regulations
Supplement use is widespread in athletes.86,87 For example, 87.5% of elite athletes in Australia used dietary supplements88 and 87% of Canadian high-performance athletes took dietary supplements within the past 6 months85 (Table 2). It is difficult to compare studies due to differences in the criteria used to define dietary supplements, variations in assessing supplement intake, and disparities in the populations studied.85
Athletes take supplements for many reasons, including for proposed performance benefits, for prevention or treatment of a nutrient deficiency, for convenience, or due to fear of �missing out� by not taking a particular supplement.41
The potential benefits (eg, improved performance) of taking a dietary supplement must outweigh the risks.86,87 There are few permitted dietary supplements available that have an ergogenic effect.87,89 Dietary supplementation cannot compensate for poor food choices.87 Other concerns include lack of efficacy, safety issues (toxicity, medical concerns), negative nutrient interactions, unpleasant side effects, ethical issues, financial expense, and lack of quality control.41,86,87 Of major concern, is the consumption of prohibited substances by the World Anti-Doping Agency (WADA).
Inadequate regulation in the supplement industry (com- pounded by widespread Internet sales) makes it difficult for athletes to choose supplements wisely.41,86,87 In 2000�2001, a study of 634 different supplements from 13 countries found that 94 (14.8%) contained undeclared steroids, banned by WADA.90 Many contaminated supplements were routinely used by athletes (eg, vitamin and mineral supplements).86 Several studies have confirmed these findings. 41,86,89
A positive drug test in an athlete can occur with even a minute quantity of a banned substance.41,87 WADA maintains a �strict liability� policy, whereby every athlete is responsible for any substance found in their body regardless of how it got there.41,86,87,89 The World Anti-Doping Code (January 1, 2015) does recognize the issue of contaminated supplements.91 Whereas the code upholds the principle of strict liability, athletes may receive a lesser ban if they can��show �no significant fault� to demonstrate they did not intend to cheat. The updated code imposes longer bans on those who cheat intentionally, includes athlete support personnel (eg, coaches, medical staff), and has an increased focus on anti-doping education.91,99
In an effort to educate athletes about sports-supplement use, the Australian Institute of Sport�s sports-supplement program categorizes supplements according to evidence�of efficacy in performance and risk of doping outcome.40 Category A supplements have sound evidence for use and include sports foods, medical supplements, and performance supplements. Category D supplements should not be used by athletes, as they are banned or are at high risk for contamination. These include stimulants, pro-hormones and hormone boosters, growth hormone releasers, peptides, glycerol, and colostrum.40
Conclusion
Athletes are always looking for an edge to improve their performance, and there are a range of dietary strategies available. Nonetheless, dietary recommendations should be individualized for each athlete and their sport and provided by an appropriately qualified professional to ensure optimal performance. Dietary supplements should be used with caution and as part of an overall nutrition and performance plan.
Disclosure
The authors report no conflicts of interest in this work.
Kathryn L Beck1 Jasmine S Thomson2 Richard J Swift1 Pamela R von Hurst1
1School of Food and Nutrition, Massey institute of Food Science and Technology, College of Health, Massey University Albany, Auckland, 2School of Food and Nutrition, Massey institute of Food Science and Technology, College of Health, Massey University Manawatu, Palmerston North, New Zealand
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References:
1. Burke LM, Meyer NL, Pearce J. National nutritional programs for the
2012 London Olympic Games: A systematic approach by three different
countries. In: van Loon LJC, Meeusen R, editors. Limits of Human
Endurance. Nestle Nutrition Institute Workshop Series, volume 76.
Vevey, Switzerland: Nestec Ltd; 2013:103�120.
2. Hansen EA, Emanuelsen A, Gertsen RM, S�rensen SSR. Improved
marathon performance by in-race nutritional strategy intervention.
Int J Sport Nutr Exerc Metab. 2014;24(6):645�655.
3. Hottenrott K, Hass E, Kraus M, Neumann G, Steiner M, Knechtle B.
A scientific nutrition strategy improves time trial performance by ?6%
when compared with a self-chosen nutrition strategy in trained cyclists:
a randomized cross-over study. Appl Physiol Nutr Metab. 2012;
37(4):637�645.
4. Jeukendrup AE, Martin J. Improving cycling performance: how should
we spend our time and money. Sports Med. 2001;31(7):559�569.
5. Wright DA, Sherman WM, Dernbach AR. Carbohydrate feedings
before, during, or in combination improve cycling endurance
performance. J Appl Physiol (1985). 1991;71(3):1082�1088.
6. Jeukendrup A. A step towards personalized sports nutrition: carbohydrate
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7. Hawley JA, Schabort EJ, Noakes TD, Dennis SC. Carbohydrateloading
and exercise performance. An update. Sports Med. 1997;24(2):
73�81.
8. Bergstr�m J, Hermansen L, Hultman E, Saltin B. Diet, muscle glycogen
and physical performance. Acta Physiol Scand. 1967;71(2):140�150.
9. Karlsson J, Saltin B. Diet, muscle glycogen, and endurance performance.
J Appl Physiol. 1971;31(2):203�206.
10. Sherman WM, Costill DL, Fink WJ, Miller JM. Effect of exercise-diet
manipulation on muscle glycogen and its subsequent utilization during
performance. Int J Sports Med. 1981;2(2):114�118.
11. Bussau VA, Fairchild TJ, Rao A, Steele P, Fournier PA. Carbohydrate
loading in human muscle: an improved 1 day protocol. Eur J Appl
Physiol. 2002;87(3):290�295.
12. Fairchild TJ, Fletcher S, Steele P, Goodman C, Dawson B, Fournier PA.
Rapid carbohydrate loading after a short bout of near maximal-intensity
exercise. Med Sci Sports Exerc. 2002;34(6):980�986.
13. Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for
training and competition. J Sports Sci. 2011;29 Suppl 1:S17�S27.
14. Raman A, Macdermid PW, M�ndel T, Mann M, Stannard SR. The
effects of carbohydrate loading 48 hours before a simulated squash
match. Int J Sport Nutr Exerc Metab. 2014;24(2):157�165.
15. Balsom PD, Wood K, Olsson P, Ekblom B. Carbohydrate intake and
multiple sprint sports: with special reference to football (soccer). Int J
Sports Med. 1999;20(1):48�52.
16. Abt G, Zhou S, Weatherby R. The effect of a high-carbohydrate diet
on the skill performance of midfield soccer players after intermittent
treadmill exercise. J Sci Med Sport. 1998;1(4):203�212.
17. Coyle EF, Coggan AR, Hemmert MK, Lowe RC, Walters TJ. Substrate
usage during prolonged exercise following a preexercise meal. J Appl
Physiol (1985). 1985;59(2):429�433.
18. Neufer PD, Costill DL, Flynn MG, Kirwan JP, Mitchell JB, Houmard J.
Improvements in exercise performance: effects of carbohydrate feedings
and diet. J Appl Physiol (1985). 1987;62(3):983�988.
19. Burke LM, Collier GR, Hargreaves M. Glycemic index � a new tool
in sport nutrition? Int J Sport Nutr. 1998;8(4):401�415.
20. Burke LM, Claassen A, Hawley JA, Noakes TD. Carbohydrate intake
during prolonged cycling minimizes effect of glycemic index of preexercise
meal. J Appl Physiol (1985). 1998;85(6):2220�2226.
21. Wong SH, Chan OW, Chen YJ, Hu HL, Lam CW, Chung PK. Effect of
preexercise glycemic-index meal on running when CHO-electrolyte
solution is consumed during exercise. Int J Sport Nutr Exerc Metab.
2009;19(3):222�242.
22. Burke LM, Maughan RJ. The Governor has a sweet tooth � mouth
sensing of nutrients to enhance sports performance. Eur J Sport Sci.
2015;15(1):29�40.
23. Gant N, Stinear CM, Byblow WD. Carbohydrate in the mouth immediately
facilitates motor output. Brain Res. 2010;1350:151�158.
24. Jentjens RL, Moseley L, Waring RH, Harding LK, Jeukendrup AE.
Oxidation of combined ingestion of glucose and fructose during
exercise. J Appl Physiol (1985). 2004;96(4):1277�1284.
25. Cox GR, Clark SA, Cox AJ, et al. Daily training with high carbohydrate
availability increases exogenous carbohydrate oxidation during endurance
cycling. J Appl Physiol (1985). 2010;109(1):126�134.
26. Bartlett JD, Hawley JA, Morton JP. Carbohydrate availability and
exercise training adaptation: too much of a good thing? Eur J Sport
Sci. 2015;15(1):3�12.
27. Burke LM. Fueling strategies to optimize performance: training high
or training low? Scand J Med Sci Sports. 2010;20 Suppl 2:48�58.
28. Yeo WK, Paton CD, Garnham AP, Burke LM, Carey AL, Hawley JA.
Skeletal muscle adaptation and performance responses to once a day
versus twice every second day endurance training regimens. J Appl
Physiol (1985). 2008;105(5):1462�1470.
29. Morton JP, Croft L, Bartlett JD, et al. Reduced carbohydrate availability
does not modulate training-induced heat shock protein adaptations but
does upregulate oxidative enzyme activity in human skeletal muscle.
J Appl Physiol (1985). 2009;106(5):1513�1521.
30. Horowitz JF, Mora-Rodriguez R, Byerley LO, Coyle EF. Lipolytic suppression
following carbohydrate ingestion limits fat oxidation during
exercise. Am J Physiol. 1997;273(4 Pt 1):E768�E775.
31. Volek JS, Noakes T, Phinney SD. Rethinking fat as a fuel for endurance
exercise. Eur J Sport Sci. 2015;15(1):13�20.
32. Stellingwerff T, Spriet LL, Watt MJ, et al. Decreased PDH activation
and glycogenolysis during exercise following fat adaptation
with carbohydrate restoration. Am J Physiol Endocrinol Metab.
2006;290(2):E380�E388.
33. van Loon LJ. Is there a need for protein ingestion during exercise?
Sports Med. 2014;44 Suppl 1:S105�S111.
34. Hillman AR, Turner MC, Peart DJ, et al. A comparison of hyperhydration
versus ad libitum fluid intake strategies on measures of
oxidative stress, thermoregulation, and performance. Res Sports Med.
2013;21(4):305�317.
35. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ,
Stachenfeld NS; American College of Sports Medicine. American
College of Sports Medicine position stand. Exercise and fluid
replacement. Med Sci Sports Exerc. 2007;39(2):377�390.
36. Kristal-Boneh E, Glusman JG, Shitrit R, Chaemovitz C, Cassuto Y.
Physical performance and heat tolerance after chronic water loading and
heat acclimation. Aviat Space Environ Med. 1995;66(8):733�738.
37. Noakes TD. Drinking guidelines for exercise: what evidence is there that
athletes should drink �as much as tolerable�, �to replace the weight lost
during exercise� or �ad libitum�? J Sports Sci. 2007;25(7):781�796.
38. Hoffman MD, Stuempfle KJ. Hydration strategies, weight change
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#4: Avoid Overexertion
#4: Beware Of Little Critters
We usually talk of energy in general terms, as in �I don�t have a lot of energy today� or �You can feel the energy in the room.� But what really is energy? Where do we get the energy to move? How do we use it? How do we get more of it? Ultimately, what controls our movements? The three metabolic energy pathways are the�phosphagen system, glycolysis�and the�aerobic system.�How do they work, and what is their effect?
The energy for all physical activity comes from the conversion of high-energy phosphates (adenosine�triphosphate�ATP) to lower-energy phosphates (adenosine�diphosphate�ADP; adenosine�monophosphate�AMP; and inorganic phosphate, Pi). During this breakdown (hydrolysis) of ATP, which is a water-requiring process, a proton, energy and heat are produced: ATP + H2O ���ADP + Pi�+ H+�+ energy + heat. Since our muscles don�t store much ATP, we must constantly resynthesize it. The hydrolysis and resynthesis of ATP is thus a circular process�ATP is hydrolyzed into ADP and Pi, and then ADP and Pi�combine to resynthesize ATP. Alternatively, two ADP molecules can combine to produce ATP and AMP: ADP + ADP ���ATP + AMP.
During short-term, intense activities, a large amount of power needs to be produced by the muscles, creating a high demand for ATP. The phosphagen system (also called the ATP-CP system) is the quickest way to resynthesize ATP (Robergs & Roberts 1997). Creatine phosphate (CP), which is stored in skeletal muscles, donates a phosphate to ADP to produce ATP: ADP + CP ���ATP + C. No carbohydrate or fat is used in this process; the regeneration of ATP comes solely from stored CP. Since this process does not need oxygen to resynthesize ATP, it is anaerobic, or oxygen-independent. As the fastest way to resynthesize ATP, the phosphagen system is the predominant energy system used for all-out exercise lasting up to about 10 seconds. However, since there is a limited amount of stored CP and ATP in skeletal muscles, fatigue occurs rapidly.
Glycolysis is the predominant energy system used for all-out 
Since humans evolved for aerobic activities (Hochachka, Gunga & Kirsch 1998; Hochachka & Monge 2000), it�s not surprising that the aerobic system, which is dependent on oxygen, is the most complex of the three energy systems. The metabolic reactions that take place in the presence of oxygen are responsible for most of the cellular energy produced by the body. However, aerobic metabolism is the slowest way to resynthesize ATP. Oxygen, as the patriarch of metabolism, knows that it is worth the wait, as it controls the fate of endurance and is the sustenance of life. �I�m oxygen,� it says to the muscle, with more than a hint of superiority. �I can give you a lot of ATP, but you will have to wait for it.�
Fat, which is stored as triglyceride in adipose tissue underneath the skin and within skeletal muscles (called�intramuscular triglyceride), is the other major fuel for the aerobic system, and is the largest store of energy in the body. When using fat, triglycerides are first broken down into free fatty acids and glycerol (a process called�lipolysis). The free fatty acids, which are composed of a long chain of carbon atoms, are transported to the muscle mitochondria, where the carbon atoms are used to produce acetyl-CoA (a process called�beta-oxidation).
Nutrition is increasingly recognized as a key component of optimal sporting performance, with both the science and practice of sports nutrition developing rapidly.1 Recent studies have found that a planned scientific nutritional strategy (consisting of fluid, carbohydrate, sodium, and caffeine) compared with a self-chosen nutritional strategy helped non-elite runners complete a marathon run faster2 and trained cyclists complete a time trial faster.3 Whereas training has the greatest potential to increase performance, it has been estimated that consumption of a carbohydrate�electrolyte drink or relatively low doses of caffeine may improve a 40 km cycling time trial performance by 32�42 and 55�84 seconds, respectively.4
Carbohydrate ingestion has been shown to improve performance in events lasting approximately 1 hour.6 A growing body of evidence also demonstrates beneficial effects of a carbohydrate mouth rinse on performance.22 It is thought that receptors in the oral cavity signal to the central nervous system to positively modify motor output.23
The �train-low, compete-high� concept is training with low carbohydrate availability to promote adaptations such as�enhanced activation of cell-signaling pathways, increased mitochondrial enzyme content and activity, enhanced lipid oxidation rates, and hence improved exercise capacity.26 However, there is no clear evidence that performance is improved with this approach.27 For example, when highly trained cyclists were separated into once-daily (train-high) or twice-daily (train-low) training sessions, increases in resting muscle glycogen content were seen in the low-carbohydrate- availability group, along with other selected training adaptations.28 However, performance in a 1-hour time trial after 3 weeks of training was no different between groups. Other research has produced similar results.29 Different strategies have been suggested (eg, training after an overnight fast, training twice per day, restricting carbohydrate during recovery),26 but further research is needed to establish optimal dietary periodization plans.27
There has been a recent resurgence of interest in fat as a fuel, particularly for ultra endurance exercise. A high-carbohydrate strategy inhibits fat utilization during exercise,30 which may not be beneficial due to the abundance of energy stored in the body as fat. Creating an environment that optimizes fat oxidation potentially occurs when dietary carbohydrate is reduced to a level that promotes ketosis.31 However, this strategy may impair performance of high-intensity activity, by contributing to a reduction in pyruvate dehydrogenase activity and glycogenolysis. 32 The lack of performance benefits seen in studies investigating �high-fat� diets may be attributed to inadequate carbohydrate restriction and time for adaptation.31 Research into the performance effects of high fat diets continues.
While protein consumption prior to and during endurance and resistance exercise has been shown to enhance rates of muscle protein synthesis (MPS), a recent review found protein ingestion alongside carbohydrate during exercise does not improve time�trial performance when compared with the ingestion of adequate amounts of carbohydrate alone.33
The purpose of fluid consumption during exercise is primarily to maintain hydration and thermoregulation, thereby benefiting performance. Evidence is emerging on increased risk of oxidative stress with dehydration.34 Fluid consumption prior to exercise is recommended to ensure that the athlete is well-hydrated prior to commencing exercise.35 In addition,�carefully planned hyperhydration ( fluid overloading) prior to an event may reset fluid balance and increase fluid retention, and consequently improve heat tolerance.36 However, fluid overloading may increase the risk of hyponatremia 37 and impact negatively on performance due to feelings of fullness and the need to urinate.
Performance supplements shown to enhance performance include caffeine, beetroot juice, beta-alanine (BA), creatine, and bicarbonate.40 Comprehensive reviews on other supplements including caffeine, creatine, and bicarbonate can be found elsewhere.41 In recent years, research has focused on the role of nitrate, BA, and vitamin D and performance. Nitrate is most commonly provided as sodium nitrate or beetroot juice.42 Dietary nitrates are reduced (in mouth and stomach) to nitrites, and then to nitric oxide. During exercise, nitric oxide potentially influences skeletal muscle function through regulation of blood ow and glucose homeostasis, as well as mitochondrial respiration.43 During endurance exercise, nitrate supplementation has been shown to increase exercise efficiency (4%�5% reduction in VO at a steady attenuate oxidative stress.42 Similarly, a 4.2% improvement in performance was shown in a test designed to simulate a football game.44
Consuming carbohydrates immediately 
An acute bout of intense endurance or resistance exercise can induce a transient increase in protein turnover, and, until feeding, protein balance remains negative. Protein consumption after exercise enhances MPS and net protein balance,58 predominantly by increasing mitochondrial protein fraction with endurance training, and myofibrillar protein fraction with resistance training.59
Fluid and electrolyte replacement after exercise can be achieved through resuming normal hydration practices. However, when euhydration is needed within 24 hours or substantial body weight has been lost (.5% of BM), a more structured response may be warranted to replace fluids and electrolytes.77
The availability of nutrition information for athletes varies. Younger or recreational athletes are more likely to receive generalized nutritional information of poorer quality from individuals such as coaches.78 Elite athletes are more likely to have access to specialized sports-nutrition input from qualified professionals. A range of sports science and medicine support systems are in place in different countries to assist elite athletes,1 and nutrition is a key component of these services. Some countries have nutrition programs embedded within sports institutes (eg, Australia) or alternatively have National Olympic Committees that support nutrition programs (eg, United States of America).1 However, not all athletes at the elite level have access to sports-nutrition services. This may be due to financial constraints of the sport, geographical issues, and a lack of recognition of the value of a sports-nutrition service.78
Supplement use is widespread in athletes.86,87 For example, 87.5% of elite athletes in Australia used dietary supplements88 and 87% of Canadian high-performance athletes took dietary supplements within the past 6 months85 (Table 2). It is difficult to compare studies due to differences in the criteria used to define dietary supplements, variations in assessing supplement intake, and disparities in the populations studied.85
A positive drug test in an athlete can occur with even a minute quantity of a banned substance.41,87 WADA maintains a �strict liability� policy, whereby every athlete is responsible for any substance found in their body regardless of how it got there.41,86,87,89 The World Anti-Doping Code (January 1, 2015) does recognize the issue of contaminated supplements.91 Whereas the code upholds the principle of strict liability, athletes may receive a lesser ban if they can��show �no significant fault� to demonstrate they did not intend to cheat. The updated code imposes longer bans on those who cheat intentionally, includes athlete support personnel (eg, coaches, medical staff), and has an increased focus on anti-doping education.91,99
