Aerobic literally means ‘with oxygen.’ The use of oxygen in muscles while energy is generated. Aerobic activity generally refers to low/moderate intensity exercise.



Amino Acids are building blocks from which complete proteins are made. Whey protein contains isolated amino acids that help to repair muscle tissue. There are 22 amino acids from which proteins are constructed. Nine are essential (we must obtain them from our diet) and the remaining are non-essential (the body naturally produces them).



Anaerobic literally means ‘without oxygen.’ During anaerobic activity, muscles rely on reactions that do not require oxygen to create muscle contractions. Anaerobic activity generally refers to high-intensity exercise.



Anaerobic Threshold is the physiological point during exercise when lactic acid begins to accumulate in muscles. It’s also the level of effort at which reactions not requiring oxygen are predominantly utilized in order to create energy for muscle contractions. Sometimes called Lactate Threshold.



Arginine is an amino acid required for the production of nitric oxide, which helps to dilate blood vessels and regulate blood flow during exercise.



“BCAAs” refer to the three essential amino acids — leucine, valine, isoleucine. BCAA’s are metabolized in the muscle and help by preventing the breakdown of muscle tissue during and after exercise. Leucine, the most important amino acid, is critical in initiating the protein synthesis, the process through which your muscles rebuild and get stronger.



Beta Alanine is a precursor to Arginine, which acts as a muscle buffer to the acidic environment resulting from the accumulation of hydrogen ions during heavy training. As hydrogen ions accumulate, the surrounding environment becomes more acidic resulting in fatigue and the decline in exercise performance. Beta Alanine helps to reduce the level of acidity, thus preventing fatigue.



Bonking is when your body draws down its glycogen stores to the point of glycogen depletion. Effects include nausea, dizziness, and lack of power. Because an athlete’s body uses glucose as fuel during endurance exercise, athletes need to replace a significant amount of their calories with carbohydrates (anywhere between 30-90 grams per hour). Endurance activities cause the body to quickly burn through the its stored glycogen. When the body runs out, you bonk, and that’s why you need to replenish calories during exercise. Avoiding the bonk is why we created the first Energy Gel back in 1991. When you keep the glycogen pilot light burning and you stay hydrated, you cross the finish line.



Studies have found that caffeine can stimulate your central nervous system, which can decrease perception of pain or effort during exercise. It also enhances performance by increasing focus and concentration and by decreasing perceived effort during exercise. In addition to these effects, caffeine also has the ability to spare your glycogen stores, which helps you save your body’s fuel for later.



The body’s main store of calcium is on bone mass. Studies have reported no change in serum calcium concentration after a marathon. Calcium is included in GU products in the form of calcium carbonate, which has buffering properties to help reduce the level of acidity within the working muscle.



Calories are the units of energy value in foods. Carbohydrates contain 4 calories/gram; fats contain 9 calories/gram, and protein contains 4 calories/gram.

When you deplete your calorie stores during exercise, you quite literally run out of gas! This is what is often referred to ask bonking, and while it’s extremely detrimental to your athletic performance, it can also be danger as you lose cognitive abilities as well.



Carbohydrates are the sugars, starches and fibers found in fruits, grains, vegetables and milk products that are converted into blood glucose or blood sugar by your body to be used for energy. They typically make up around half of the daily caloric intake.



Carnosine is an intramuscular buffer made up of the amino acids beta-alanine and histidine. It is highly concentrated in muscle and brain tissues.



An acid found naturally in citrus fruits that can act as a preservative or a flavoring agent.



Dehydration occurs as a result of excess fluid loss during activity. Signs include fatigue, thirst, decreased urine output, etc.



Athletes experience dry mouth when bodily fluids are concentrated elsewhere in the body. The lack of fluids in the mouth cause the salivary glands to become dry, and it is especially common during long-distance activity in the heat.



Electrolytes are minerals in your body and blood that affect how your body functions, particularly during exercise. When you sweat, you lose electrolytes. And, as anyone who’s ever tasted her own sweat during a hard workout knows, sweat is salty. That’s because the primary electrolyte you lose when you sweat is sodium. Electrolytes help maintain fluid balance, prevent dehydration, and are also essential for muscle contractions.



Fat is a macromolecule containing nine calories per gram that is predominantly metabolized during low-moderate intensity exercise. It is not a primary fuel source during exercise, as it digests very slowly.



Fat-adaptation involves drastic carbohydrate restriction in conjunction with a supplement in fat consumption so as to utilize fat as the preferred source of fuel during exercise instead of carbohydrates. Studies show that this does not increase performance and may even impact physiological adaptations made from hard training.



Fat utilization refers to the body’s use of fat as a fuel source for muscles. This can predominantly occur during low to moderate exercise.



Fiber, a substance that is difficult to digest during exercise, is typically found in cereals, fruits, vegetables, legumes, and wheat. Fiber, particularly insoluble fiber, can contribute to bulk in the gut, which decreases the rate at which food particles are digested and absorbed into the bloodstream. The longer it takes for food particles to leave the gut, the slower energy is delivered to the working muscles to sustain activity.



Fructose is a simple carbohydrate that is found naturally in fruits. Too much fructose has been reported to contribute to stomach distress (gastric distress). It has a low glycemic index (GI), and when consumed in conjunction with maltodextrin, it has been shown to increase oxidation rates. Fructose utilizes a different transport mechanism than maltodextrin, which reduces the rate at which it competes for entry into the bloodstream and to the working muscles.

When the oxidation rate increases, more carbohydrates can be delivered to the working muscles. For example, when just glucose is consumed, approximately 30g of carbohydrates are utilized by the working muscles per hour. In contrast, when maltodextrin and fructose are consumed together, approximately 60g of carbohydrates can be utilized by the working muscles per hour.



This refers to the natural process of eliminating stomach contents. A specific type of carbohydrate can influence the gastric emptying rate. For example, when maltodextrin and fructose are consumed together, gastric emptying rate increases versus consuming an equivalent amount of only glucose.



A nutrition plan doesn’t do any good if your stomach is too upset to eat, and ginger can help prevent nausea during exercise.



Glutamine is an amino acid that may help with immune function. Long periods of heavy training can reduce glutamine levels in the blood; therefore, supplementing with glutamine may help to prevent suppression of the immune response.



A mixture of proteins found in wheat, rye and barley.



The rate at which a carbohydrates increases blood sugar level in the two hours following ingestion. Maltodextrin is a high-glycemic carbohydrate and fructose is a low-glycemic carbohydrate.



Main storage form of glucose in the body found in the liver and muscle.



A serious electrolyte disorder that occurs when the level of sodium in your blood is abnormally low, which is the result of excessive salt loss or excessive water intake.



Iron is an essential mineral found in hemoglobin and carries oxygen throughout our bodies. When your muscles contract, they use oxygen to maintain normal cell function. This is why your breathing intensifies as you work harder!



Lactic acid is naturally formed in the body during exercise when oxygen levels are low. It’s used for energy when carbohydrates are broken down in the body during exercise.

The accumulation of lactic acid during exercise results in the burning sensation you feel in your muscles after intense activity. As lactic acid levels increase, so does your feeling of fatigue. If intensity level decreases, lactic acid can be converted into fuel during exercise.



At approximately 2% of sweat sodium content, magnesium is a low abundance electrolyte in sweat. Maximal magnesium losses in sweat may approach 30mg/hour at high sweat rates, so supplementing at 15mg/hour during exercise will help prevent those losses. (A word of caution—magnesium can be a laxative at high doses).



Maltodextrin is a complex carbohydrate made from cornstarch that composes a chain of glucose units. When broken down into single glucose molecules, it delivers energy to the working muscles at a faster rate than fructose. Like fructose, it needs to be transported across the small intestine and into the bloodstream. It does this with the help of a transport mechanism that does not compete with fructose, making it a superior carbohydrate option in sports nutrition products.



Mental fatigue is caused by continual mental effort or attention on a specific task.



Muscle cramping can occur as a result of skeletal/muscle overload, fatigue, and excessive sweating. One possible cause of muscle cramping is that muscles fatigue increases the excitability of the muscle fibers, and this alters the impact neurons have on the muscle itself.



Exhaustive endurance exercise cause damage from increased muscle work generated by high mechanical forces. Damage can continue even after you’re done exercising. Branched-chain amino acids are metabolized directly in the muscle and help to prevent further muscle tissue damage both during and after exercise. The addition of whey protein after exercise further encourages the repair of muscle tissue damage.



According to the FDA, the term natural means that nothing artificial or synthetic (including all color additives regardless of source) has been included in or added to a specific food source.



The concentration of a solution expressed as the total number of solute particles per kilogram. The osmolality of a product is associated with gastric emptying rate. The higher the osmolality, the slower the gastric emptying rate, and vice versa.



Oxidation is the combination of oxygen with other molecules. The rate of oxidation effects how much oxygen is available for use by working muscle. For instance, maltodextrin is oxidized at a high rate whereas fructose is oxidized at a low rate.



An electrolyte or mineral found in your bloodstream that is lost through sweat during exercise.



Whey protein isolate (used in GU Recovery Drink Mix) helps promote muscle recovery and reduces muscle protein breakdown.

Whey protein contains all nine essential amino acids and isolates contain an even higher concentration of the branched-chain amino acids. Though dietary protein contains many of these amino acids, meat proteins come with significant amounts of fat and cholesterol, depending on the type of meat, that slows digestion. Vegetables are a great source of protein as well; however, they do not contain all essential nine amino acids. Whey protein is not intended to replace normal dietary protein, but it does serve as an effective post exercise supplement because it’s easily digestible and delivers increased levels of the amino acids that facilitate muscle tissue repair.



As it relates to exercise, replenish means to restore levels of carbohydrates in the form of glycogen and protein levels in the form of amino acids.



Sodium (the primary electrolyte lost in sweat) and potassium help maintain water balance and aid in optimum hydration. Maintaining water balance is essential to making sure your blood flows efficiently, which can in turn help you deliver oxygen to your muscles faster. When your water balance is off, you can lose muscle power.



The formation of chemical compounds from simpler compounds. For example, protein synthesis occurs as a result of amino acids combining to form a protein.



To taper means to gradually diminish. In endurance sports, this generally refers to the week or two before a competition when an athlete decreases training load in preparation for an upcoming race.



An amino acid that is found in high concentrations in the heart. It helps promote normal contractile functioning of the heart.



A bright, yellow, aromatic powder used for flavoring and coloring that may help to decrease inflammation.



Vasodilation refers to the widening of blood vessels which decreases blood pressure.



B6 helps prevent nausea, so you can stick to your race plan.



A fat-soluble vitamin that helps to increase intestinal absorption of calcium, iron, magnesium, phosphate, and zinc.



VO2 max is the measure of the maximum volume of oxygen you can use during aerobic exercise. It’s measured in millimeters per kilogram of body weight per minute (mL/Kg/min).



A measure of electrical power expressed in watts.



A complete protein that contains enriched essential amino acids, including branched-chain amino acids. Whey protein isolate contains 50-75% more leucine, the essential amino acid to kick-start protein synthesis.



White Tea is the least processed of all teas, and it is a source of caffeine and antioxidants.