Caffeine

Contraindications of caffeine use—Systemic The medical considerations/contraindications included have been selected on the basis of their potential clinical significance. Risk versus benefit should be considered when the following medical problems exist

Anxiety disorders, including agoraphobia and panic attacks (increased risk of anxiety, nervousness, fear, nausea, palpitations, rapid heartbeat, restlessness, and trembling ) Cardiac disease, severe (high doses not recommended because of increased risk of tachycardia or extrasystoles, which may lead to heart failure ) Hepatic function impairment (half-life of caffeine may be prolonged, leading to toxic accumulation ) Hypertension or Insomnia (may be potentiated) Seizure disorders, in neonates (caution is recommended because seizures have been reported following toxic doses ) Sensitivity to caffeine or other xanthines

Caffeine is found in all of the following EXCEPT?

Creatine

Regulation of product labeling enables consumers to easily see the content of caffeine within they consume.

False

The ergogenic effects of caffeine are seen in both trained athletes and untrained individuals.

False

The ergogenic effects of caffeine supplementation are related to the dosage provided with a dosage of 6mg/kg producing greater benefits to performance than a 3mg/kg dose.

False

Which of the following is more applicable to actual sport performance?

Time trial performance

About Caffeine Common Name(s): Caffeine Category: HERBS Scientific Name(s): 1,3,7-trimethylxanthine

True

At higher doses (>15 mg/kg), caffeine can cause nervousness, insomnia, headaches, and unsteadiness.

True

At low doses (2-10 mg/kg), caffeine can cause increased alertness, less fatigue, reduced reaction time, increased ventilation, and poorer performance of some fine motor skills.

True

Caffeine also directly acts on muscle cells by enhancing the release of calcium from the sarcoplasmic reticulum in muscles cells, which improves muscle contraction.

True

Caffeine also has inconsistent effects on the cardiovascular system.

True

Caffeine can also sustain higher levels of energy and work potential for a longer period of time because it stimulates the nervous system by essentially blocking or holding back the activation threshold of neurons, which is what leads to a perception of fatigue.

True

Caffeine can cause a mild increase in urine output from the kidneys and dilation of the bronchi.

True

Caffeine causes the release of epinephrine from the adrenal glands, which causes lipolysis (break down of fat) in muscle and adipose tissues.

True

Caffeine has both central and peripheral effects in the body.

True

Caffeine is a crystal-like substance found in many beverages (coffee, tea, and cola), medications, and foods.

True

Caffeine is commonly consumed by people, including athletes, for various performance and or fitness related reasons.

True

Caffeine is quickly absorbed into the bloodstream and attains maximum values within 15 to 120 minutes of consumption.

True

Depending on where it acts in the body, caffeine can either raise or lower heart rate and cause blood vessels to constrict or dilate.

True

Enzymes in the liver breakdown caffeine, leaving very little to be cleared in urine.

True

For the most current information on the Recommended Dietary Allowances (RDAs) and Dietary Reference Intakes (DRIs) for all nutrients, please visit this section of the US Department of Agriculture's Food & Nutrition Information Center

True

In general, these and other studies show that a dose of caffeine ranging from 5 - 9 mg/kg bodyweight ingested 1 hour before submaximal exercise (75-85% VO2 max) produced significant increases (28%-156%) in exercise time to exhaustion.

True

In summary, there are three basic mechanisms by which caffeine may enhance athletic performance: By causing a shift in muscle substrate metabolism from carbohydrates to fats especially during the first 15 minutes of exercise when glycogenolysis is normally very high. This is basically stating that fat utilization for energy during moderate intensity exercise is increased after caffeine intake, particularly in the early stages of exercise, which also means that glycogenolysis (the breakdown of glycogen to glucose for energy) is spared early so that more glycogen is available for energy later in the training session. By stimulating the central nervous system via altering neurotransmitter function or increasing the recruitment of motor units because of a decrease in the activation threshold of neurons. This may be a factor in the decrease in perceived exertion that many studies found. Essentially, by decreasing the activation threshold of neurons, the caffeine is allowing the body to do the same work, but with a decreased perception of intensity and difficulty, which can lead to greater work potential. By a direct effect on skeletal muscle homeostasis (i.e. attenuation of the accumulation of potassium). Seeing as it has been established that the accumulation of potassium may be related to fatigue, attenuating (decreasing) the potassium accumulation may invariably lead to increased work load due to delayed fatigue.

True

In the central nervous system caffeine affects parts of the brain and the spinal cord, while in the periphery it affects organs and tissues.

True

Increased lipolysis in fat cells occurs because caffeine reduces the inhibitory influence of adenosine on lipolysis, thus increasing lipolysis.

True

Lastly, caffeine has shown to decrease potassium accumulation, which as it states above may be related to fatigue, therefore once again delaying the perception of exhaustion, and increasing work load potential.

True

Many people believe that the requirements for athletes involved in heavy training are higher than the requirements for the rest of the population. While this may be true, there is no scientific evidence to support this hypothesis, and most nutrition experts/professionals agree that to correct deficiencies and/or to maintain optimal body functioning, the nutrient requirements for athletes do not exceed 200% of the recommendations (DRI, RDA, ESADDI, or otherwise) already established.

True

Most studies on the effects of caffeine on performance have examined its effects on submaximal continuous and intermittent endurance exercise on a treadmill or a cycle ergometer. Most of the studies using other exercise modalities examine time to exhaustion at a given intensity.

True

On a cellular level, caffeine inhibits adenosine, causing increased urine excretion, stimulation of the central nervous system, increased lipolysis in fat cells (adipocytes) and increased gastric secretion.

True

Previously certain levels of caffeine were prohibited in competition. It was removed from the prohibited list in 2004 and placed on the monitoring list. It could be returned to the prohibited list in the future. Urinary caffeine levels can depend on the caffeine dose, bodyweight, body composition (fat content), rate of caffeine metabolism in the liver, the timeframe during which the caffeine was ingested, hydration, exercise time, and other individual variables.

True

Proposed Effect(s) of caffeine:* also falls under the category of stimulant, alkaloid and methylxanthine * increases endurance performance, spares glycogen, increases lipid oxidation, enhances neuromuscular function, and attenuates plasma potassium levels during exercise

True

The effects of caffeine on exercise performance are controversial, with some studies finding an enhancing effect and others finding no effect at all.

True

The most researched and widely acknowledged mechanism of caffeine is by glycogen sparing via increased fat utilization, thus allowing the athlete to exercise longer at a given submaximal intensity. Other mechanisms include increased catecholamine release, increased calcium release from muscle cells, and reduced perception of effort.

True

The negative effects of acute caffeine ingestion include sleep disturbances, diuresis (which can lead to dehydration), unsteadiness, gastrointestinal distress, and possible increases in blood pressure. The negative effects of chronic caffeine ingestion include withdrawal headaches, heart palpitations, and increased serum cholesterol. While it is difficult to achieve a lethal dose of caffeine by consuming coffee, tea or caffeinated sodas, deaths through the use of caffeine tablets have been reported.

True

The research presented above states in most simple terms that caffeine can be effective in exercise by using more fat for energy than carbohydrates (glycogen), particularly at the beginning of exercise when normally, glycogen is the body's primary fuel source.

True

The short-term effects of caffeine on endurance and sprint performance have been studied in-depth, however the results of these studies remain controversial and inconclusive.

True

There are risks associated with caffeine supplementation and there are dietary alternatives.

True

There is no DRI, RDA, or ESADDI for caffeine.

True

There is no recommended daily intake for caffeine.

True

Through the blood, caffeine is spread to many tissues in the body, including the brain.

Trye

Which of the following are likely mechanisms of caffeine's effects

antagonism of adenosine receptors

Which of the following is true regarding true regarding caffeine's effect on carbohydrate metabolism?

caffeine ingestion results in an increased rate of skeletal muscle glycogenolysis

Which of the following concerning caffeine intake and exercise appears to be supported by recent research

enhanced oxidation of lipids/fats inhibition of carbohydrate oxidation no influence on muscle glycogen use **a & c**

Caffeine has little to no effect on heart rate ______

for chronic caffeine consumers

There appear to be some individuals that are not as responsive as others with regards to caffeine. This is related to?

genotype

Chronic caffeine intake _____.

has no effect on systolic blood pressure

Side effects of caffeine include all of the following EXCEPT?

lowered respiratory rate

Caffeine intake results in an improved exercise time to exhaustion for?

non-caffeine users to a greater extend than caffeine users

Maximal concentrations of caffeine are found in the blood following ________ of ingestion

45-60 minutes

A 100-400mg dose of caffeine has been show to result in a?

3-16% increase in resting metabolic rate