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Researchers at The University of Auckland have shown for the first time that the mere presence of carbohydrate solution in the mouth immediately boosts muscle strength, even before it is swallowed.

The results suggest that a previously unknown neural pathway is activated when receptors in the mouth detect carbohydrate, stimulating parts of the brain that control muscle activity and producing an increase in muscle strength.

Previous research had shown that the presence of carbohydrate in the mouth can improve physical performance during prolonged activity, but the mechanism involved was not known and it was unclear whether a person must be fatigued for the effect to be seen.

“There appears to be a pathway in the brain that tells our muscles when energy is on the way,” says lead researcher Dr Nicholas Gant from the Department of Sport and Exercise Science.

“We have shown that carbohydrate in the mouth produces an immediate increase in neural drive to both fresh and fatigued muscle and that the size of the effect is unrelated to the amount of glucose in the blood or the extent of fatigue.”

The current research has been published in the journal Brain Research and has also captured the attention of New Scientist magazine.

In the first of two experiments, 16 healthy young men who had been doing biceps exercises for 11 minutes were given a carbohydrate solution to drink or an identically flavored energy-free placebo. Their biceps strength was measured before and immediately afterward, as was the activity of the brain pathway known to supply the biceps.

Around one second after swallowing the drink, neural activity increased by 30 percent and muscle strength two percent, with the effect lasting for around three minutes. The response was not related to the amount of glucose in the bloodstream or how fatigued the participants were.

“It might not sound like much, but a two percent increase in muscle strength is enormous, especially at the elite level. It’s the difference between winning an Olympic medal or not,” says co-author Dr Cathy Stinear.

As might be expected, a second boost in muscle strength was observed after 10 minutes when carbohydrate reached the bloodstream and muscles through digestion, but no additional boost in neural activity was seen at that time.

“Two quite distinct mechanisms are involved,” says Dr Stinear. “The first is the signal from the mouth via the brain that energy is about to be available and the second is when the carbohydrate actually reaches the muscles and provides that energy,” says Dr Stinear.

“The carbohydrate and placebo solutions used in the experiment were of identical flavor and sweetness, confirming that receptors in the mouth can process other sensory information aside from the basic taste qualities of food. The results suggest that detecting energy may be a sixth taste sense in humans,” says Dr Gant.

In the second experiment, 17 participants who had not been doing exercise and were not fatigued simply held one of the solutions in their mouths without swallowing. Measurements of the muscle between the thumb and index finger were taken while the muscle was either relaxed or active.

A similar, though smaller effect was observed as in the first experiment, with a nine percent increase in neural activity produced by the carbohydrate solution compared with placebo. This showed that the response is seen in both large powerful muscles and in smaller muscles responsible for fine hand movements.

“Together the results show that carbohydrate in the mouth activates the neural pathway whether or not muscles are fatigued. We were surprised by this, because we had expected that the response would be part of the brain’s sophisticated system for monitoring energy levels during exercise,” says Dr Stinear.

“Seeing the same effect in fresh muscle suggests that it’s more of a simple reflex – part of our basic wiring – and it appears that very ancient parts of the brain such as the brainstem are involved. Reflexive movements in response to touch, vision and hearing are well known but this is the first time that a reflex linking taste and muscle activity has been described,” she says.

Further research is required to determine the precise mechanisms involved and to learn more about the size of the effect on fresh versus fatigued muscle.

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Article adapted by MD Sports from original press release.
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Contact: Pauline Curtis
The University of Auckland

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Research News

Bethesda, MD – A visit to the meat counter at any supermarket is proof positive that a good number of Americans are avoiding carbohydrates and consuming high levels of protein and fat, in accordance with the Atkins diet. This carbohydrate-free, fat- and protein- rich diet is for those seeking immediate weight loss, which means most of us.But what do others, such as weight lifters and callisthenic enthusiasts, do about carbohydrates? Their goal is muscle preservation and strengthening, but for years, different theories have been offered about the effectiveness of carbohydrates in maintaining an appropriate muscle protein balance. A new study may lead to a truce in the debate at the nation’s gymnasiums, and those dedicated to resistance training may finally have an answer as to whether carbohydrates have a positive role in muscle development.

Background

Resistance exercise — also called strength training — increases muscle strength and mass, bone strength, and the body’s metabolism. The different methods for resistance training include free weights, weight machines, calisthenics and resistance tubing. When using free weights, dumbbells, and bars stacked with weight plates, you are responsible for both lifting the weight and determining and controlling your body position through the range of motion.

The body’s net muscle protein balance (i.e., the difference between muscle protein synthesis and protein breakdown) generally remains negative in the recovery period after resistance exercise in the absence of nutrient intake, i.e., the muscle’s protein is breaking down complex chemical compounds to simpler ones. However, it has been demonstrated that infusion or ingestion of amino acids after resistance exercise stimulates muscle protein synthesis. Furthermore, as little as six grams of essential amino acids (EAA) alone effectively stimulates net protein synthesis after a strenuous resistance exercise session.

The body’s response to the six grams of EAA does not appear to differ when 35 grams of carbohydrates are added. This reflects the uncertainty of the independent effects of carbohydrates on muscle protein metabolism after resistance exercise. Additionally, it is unclear how carbohydrate intake causes changes of net protein balance between synthesis and breakdown and how it relates to changes in plasma insulin concentration.

Interpretation of the response of muscle protein to insulin is complicated by the fact that a systemic increase in insulin concentration causes a fall in plasma amino acid concentrations, and this reduced amino acid availability could potentially counteract a direct effect of insulin on synthesis. A past study found that the normal postexercise increase in muscle protein breakdown was slowed by insulin, thus improving net muscle protein balance. However, whereas local infusion of insulin may effectively isolate the effect of insulin per se, the response may differ from when insulin release is stimulated by ingestion of carbohydrates.

A New Study

Accordingly, a new study set out to investigate the independent effect of carbohydrate intake on muscle protein net balance during recovery from resistance exercise. The authors of “Effect Of Carbohydrate Intake on Net Muscle Protein Synthesis During Recovery from Resistance Exercise,” are Elisabet Børsheim, Melanie G. Cree, Kevin D. Tipton, Tabatha A. Elliott, Asle Aarsland, and Robert R. Wolfe, all from the Department of Surgery, Metabolism Unit, Shriners Hospitals for Children-Galveston, University of Texas Medical Branch, Galveston, TX. Their findings appeared in the February 2004 edition of the Journal of Applied Physiology. The journal is one of 14 peer-reviewed scientific journals published each month by the American Physiological Society (www.APS.org).

Methodology

Sixteen recreationally active and healthy subjects took part in the study. At least one week before an experiment, subjects were familiarized with the exercise protocol, and their one repetition maximum, a maximum weight possible with a leg extension, was determined. The subjects were assigned to one of two groups: carbohydrate group (CHO; n = 8) or placebo group (n = 8). Subjects were instructed not to exercise for at least 48 hours before an experiment, not to use tobacco or alcohol during the 24 h before an experiment, and not to make any changes in their dietary habits.

The two groups of eight subjects performed a resistance exercise bout (10 sets of eight repetitions of leg presses at 80 percent of one repetition maximum) before they rested in bed for four hours. One group (CHO) received a drink consisting of 100 grams of carbohydrates one hour after exercise; the placebo group received a noncaloric placebo drink. Leg amino acid metabolism was determined by infusion of 2H5- or 13C6-labeled phenylalanine, sampling from femoral artery and vein, and muscle biopsies from vastus lateralis, the lateral head of quadriceps muscle of anterior (extensor) compartment of thigh.

Results

Key findings of the study included: 

  • Plasma glucose concentration was significantly increased in the carbohydrate group until 210 min after intake of drink. 
  • Plasma concentration of insulin reflected the changes in glucose concentration. The drink intake did not affect arterial insulin concentration in the placebo group, whereas arterial insulin increased by several times after the drink in the CHO group. 
  • Arterial phenylalanine (a common amino acid in proteins) concentration did not change after intake of drink in the placebo group but decreased and stabilized in the CHO group. 
  • Net muscle protein balance between synthesis and breakdown did not change in the placebo group but improved in the CHO group during the second and third hour after the drink. The improved net balance in the CHO group was due primarily to a progressive decrease in muscle protein breakdown.

Conclusions

This study is the first to compare net muscle protein balance (protein synthesis minus breakdown) after carbohydrate ingestion with control after exercise. The principal finding was that intake of 100 grams of carbohydrates after resistance exercise improved muscle net protein balance.

The findings from this research demonstrate that carbohydrates intake alone can improve net protein balance between synthesis and breakdown. In this work, the gradual improvement in net muscle protein balance after carbohydrate intake was due principally to a progressive reduction in breakdown. However, the improvement was small compared with previous findings after intake of amino acids or amino acids and carbohydrates.

The researchers conclude that intake of carbohydrates alone after resistance exercise will modestly improve the anabolic effect of exercise. However, amino acid intake is necessary for a maximal response, one desired by most participating in resistance exercise programs.

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Article adapted by Sports Performance Research from original press release.

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Contact: Donna Krupa

American Physiological Society 

Source: Journal of Applied Physiology. The journal is one of 14 peer-reviewed scientific journals published each month by the American Physiological Society (www.APS.org).

The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

Consuming caffeine, whether in coffee of soft drinks, has been shown to delay fatigue during prolonged exercise. Studies have shown, for example, that ingesting three to nine mg/kg of caffeine can increase the amount of exercise time to achieve by as much as 50 percent. How caffeine achieves this effect has not been fully determined.

Caffeine and the Central Nervous System (CNS) Study

No previous research effort has examined the possible direct central nervous system (CNS) effects of caffeine on fatigue during prolonged exercise. Now, a team of researchers from the University of South Carolina has hypothesized that the blockade of adenosine receptors by caffeine may be the most likely mechanism of CNS stimulation and delayed fatigue.

Their theory is based on the fact that adenosine is produced within the body and inhibits neuronal excitability and synapse transmission. Adenosine also inhibits the release of most brain excitatory neurotransmitters, particularly dopamine (DA), and may reduce DA synthesis. Decreases in dopamine (DA), along with increases in 5-HT (serotonin, which is generally associated with behavioral suppression), have been linked to central fatigue during exercise. In addition, adenosine has been shown to reduce arousal, induce sleep, and suppress spontaneous activity, which are all behaviors associated with increases in 5-HT.

The researchers’ hypothesis is the foundation of a new study to determine the effects of intracerebroventricular injection of caffeine and the adenosine A1 and A2 receptor agonist 5′-N-ethylcarboxamidoadenosine (NECA) on treadmill run time to fatigue in rats. NECA was chosen for the study because caffeine is a nonselective adenosine receptor antagonist, and it is not known which of the four subtypes of adenosine receptors may be involved in an effect of caffeine on fatigue. However, A2b and A3 receptors are relatively less active than A1 and A2a receptors under normal physiological conditions. If the researchers were correct, the CNS administration of caffeine will increase run time to fatigue, whereas NECA will reduce run time to fatigue. Furthermore, pretreatment with caffeine before NECA will weaken the fatigue-inducing effects of NECA.

The authors of “Central Nervous System Effects of Caffeine and Adenosine on Fatigue,” are J. Mark Davis, Zuowei Zhao, Howard S. Stock, Kristen A. Mehl, James Buggy, and Gregory A. Hand, all from the Schools of Public Health and Medicine, University of South Carolina, Columbia, SC. Their findings appear in the February 2003 edition of the American Journal of Physiology –Regulatory, Integrative and Comparative Physiology. The journal is one of 14 peer-reviewed publications produced monthly by the American Physiological Society (APS).

Methodology

Male Wistar rats, five weeks old and weighing 200-250 grams, were used in this study, and randomly assigned to intracerebroventricular or intraperitoneal injection groups. Rats were given two weeks of treadmill acclimation of running for 15 minutes a day. The treadmill speed was slowly increased from eight meters a minute, 7.5 percent grade at the beginning, progressing to 20 meters a minute at the end of the acclimation period. Gentle hand prodding and mild electric shock were combined to encourage the animals to run throughout the study.

After the first two weeks of acclimation, rats assigned to the intracerebroventricular group were anesthetized with pentobarbital sodium, and tubes were implanted bilaterally into the lateral ventricles. After seven days of recovery from surgery, the rats were again acclimated to treadmill running for another one to two weeks, until they were able to run easily for at least 15 minutes per day for 5 consecutive days at a speed of 20 meters a minute at a 7.5 percent grade. Animals that were unable to run at that pace were excluded.

Four drug treatments were used in the study: NECA, caffeine, caffeine plus NECA, and a vehicle solution (Normosol-R). The vehicle solution has been used as a control solution in other studies involving intracerebroventricular infusions of drugs and tissue microdialysis. In the CNS groups (n = 10), each rat was injected intracerebroventricularly with one of the four drugs (NECA, caffeine, caffeine plus NECA, or vehicle) in one testing session. The other drugs were then given in successive testing sessions at one-week intervals to allow full recovery from the exercise bout and washout of the drugs. On two days during the recovery period, all rats were exercised for 15 minutes to maintain acclimation to the treadmill protocol. All rats received all four-drug treatments in a randomized and counterbalanced design to minimize possible order effects.

Results
The major findings of this study revealed that:

  • CNS administration of caffeine at a dose of 200 µg/rat (0.6 mg/kg), which is much less than the effective dose given peripherally (6 mg/kg), does increase treadmill run time to fatigue in rats by approximately 60 percent;
  • the same dose of caffeine given peripherally (intraperitoneally) is ineffective.
  • the results supported the researchers’ hypothesis that intracerebroventricular CNS administration of the selective adenosine A1 and A2 receptor agonist NECA significantly reduced run time to fatigue, whereas intracerebroventricular caffeine increased run time to fatigue.
  • inhibitory effects of NECA on run time to fatigue were also reversed by intracerebroventricular pretreatment with caffeine, suggesting that the ergogenic effects of intracerebroventricular caffeine are mediated through blockade of the adenosine receptors.
  • CNS administration of the adenosine receptor agonist NECA inhibited treadmill run time to fatigue and spontaneous locomotor activity in rats.
  • pretreatment with caffeine blocked the inhibitory effects of NECA on exercise performance, although not on spontaneous behavioral activity.
  • peripheral (intraperitoneal) administration of the same drugs at the same doses had no effect on treadmill run time to fatigue.

Conclusions

These results indicate that caffeine can act specifically within the CNS to delay fatigue, at least in part by blocking adenosine receptors. Because caffeine easily crosses the BBB, these results also suggest that the CNS also plays an important role in the ergogenic effect of caffeine ingestion.

The precise independent contribution of caffeine at the central (behavioral) and peripheral (metabolic) levels awaits further research. The researchers argue that some interaction at both levels is likely.

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Article adapted by MD Only Sports Weblog from original press release.
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Contact: Donna Krupa
American Physiological Society

Source: February 2003 edition of the American Journal of Physiology– Regulatory, Integrative and Comparative Physiology

The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

Although it’s too soon to recommend dropping by Starbucks before hitting the gym, a new study suggests that caffeine can help reduce the post-workout soreness that discourages some people from exercising.In a study to be published in the February issue of The Journal of Pain, a team of University of Georgia researchers finds that moderate doses of caffeine, roughly equivalent to two cups of coffee, cut post-workout muscle pain by up to 48 percent in a small sample of volunteers.

Lead author Victor Maridakis, a researcher in the department of kinesiology at the UGA College of Education, said the findings may be particularly relevant to people new to exercise, since they tend to experience the most soreness.

“If you can use caffeine to reduce the pain, it may make it easier to transition from that first week into a much longer exercise program,” he said.

Maridakis and his colleagues studied nine female college students who were not regular caffeine users and did not engage in regular resistance training. One and two days after an exercise session that caused moderate muscle soreness, the volunteers took either caffeine or a placebo and performed two different quadriceps (thigh) exercises, one designed to produce a maximal force, the other designed to generate a sub-maximal force. Those that consumed caffeine one-hour before the maximum force test had a 48 percent reduction in pain compared to the placebo group, while those that took caffeine before the sub-maximal test reported a 26 percent reduction in pain.

Caffeine has long been known to increase alertness and endurance, and a 2003 study led by UGA professor Patrick O’Connor found that caffeine reduces thigh pain during moderate-intensity cycling. O’Connor, who along with professors Kevin McCully and the late Gary Dudley co-authored the current study, explained that caffeine likely works by blocking the body’s receptors for adenosine, a chemical released in response to inflammation.

Despite the positive findings in the study, the researchers say there are some caveats. First, the results may not be applicable to regular caffeine users, since they may be less sensitive to caffeine’s effect. The researchers chose to study women to get a definitive answer in at least one sex, but men may respond differently to caffeine. And the small sample size of nine volunteers means that the study will have to be replicated with a larger study.

O’Connor said that despite these limitations, caffeine appears to be more effective in relieving post-workout muscle pain than several commonly used drugs. Previous studies have found that the pain reliever naproxen (the active ingredient in Aleve) produced a 30 percent reduction in soreness. Aspirin produced a 25 percent reduction, and ibuprofen has produced inconsistent results.

“A lot of times what people use for muscle pain is aspirin or ibuprofen, but caffeine seems to work better than those drugs, at least among women whose daily caffeine consumption is low,” O’Connor said.

Still, the researchers recommend that people use caution when using caffeine before a workout. For some people, too much caffeine can produce side effects such as jitteriness, heart palpitations and sleep disturbances.

“It can reduce pain,” Maridakis said, “but you have to apply some common sense and not go overboard.”

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Article adapted by MD Only Sports Weblog from original press release.
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Contact: Sam Fahmy
University of Georgia

The serious athlete knows better than to rely just on a famous cereal to provide additional energy in preparation of a sporting event. Supplements have assumed an important role in today’s training regimen. Some – such as anabolic steroids — have been deemed illegal by most sports authorities. Others – such as caffeine and creatine — are controversial yet presently allowed.Background
Caffeine, the primary ingredient of coffee, is used as a central nervous system stimulant, diuretic, circulatory and respiratory stimulant, and as an adjunct in the treatment of headaches. Evidence shows that caffeine intensifies muscle contractions, masks the discomfort of physical exertion, and even speeds up the use of the muscles’ short-term fuel stores. Some exercise physiologists believe that caffeine might improve performance by increasing fat oxidation and conserving muscle glycogen.

Creatine is used by athletes to increase lean body mass and improve performance in single and repetitive high-intensity, short-duration exercise tasks such as weightlifting, sprinting, and cycling. It is a popular nutritional supplement that is used by physically active people – from recreational exercisers to Olympic and professional athletes. According to a recent survey, 28 percent of athletes in an NCAA Division IA program reported using creatine. The creatine that is normally present in human muscle may come from two potential sources: dietary (animal flesh) and internally manufactured.

The purpose of creatine supplementation is to increase either total creatine stores or phosphocreatine (PCr) stores within muscle. Supplementation increases the rate of resynthesis of creatine phosphate following exercise. Various studies have shown increased muscle PCr levels after supplementing with 20-30 grams of creatine monohydrate daily.

Creatine supplementation has also been known to shorten relaxation time during intermittent maximal iosometric muscle contraction. This shortened time, coupled with a creatine loaded muscle facilitates calcium absorption into the sarcoplasmic reticulum (the endoplasmic reticulum of skeletal and cardiac muscle). However, some believe that caffeine intake enhances calcium release from the sarcoplasmic reticulum.

The Study
This has lead a research team from Belgium to suggest that the combined effects of creatine and caffeine supplementation may be counterproductive to creatine’s effect on muscle relaxation time. The authors of the study, “Opposite Actions of Caffeine and Creatine on Muscle Relaxation Time in Humans” are P. Hespel, B. Op ‘T Eijnde, and M. Van Leemputte, all from the Department of Kinesiology, Katholieke Universiteit Leuven, Leuven, Belgium. Their findings appear in the February 2002 edition of the Journal of Applied Physiology.

Methodology
Ten physical education students (nine men and one woman) participated in the study. They were told to abstain from medication and caffeine intake one week prior to the experiment. The subjects were additionally asked to avoid changes in their level of physical activity and diet during the 25-week duration of the study. In this double blind experiment, the subjects performed the exercise test before and after creatine supplementation, short-term caffeine intake, creatine supplementation in the short term, acute caffeine intake, or a placebo.

This study required the random assignment of the students into five experimental protocols, each lasting eight days. Three elements were measured during an experiment consisting of 30 intermittent contractions of quadriceps entailing two seconds of stimulation and two seconds of rest. Measurements included maximum torque (Tmax), contraction time (CT) from 0.25 to 0.75 of Tmax, and relaxation time (RT) from 0.75 to 0.25 of max.

Results
Key findings of this study included:

· a confirmation of the fact that oral creatine supplementation shortens muscle relaxation time in humans: relation time was reduced by five percent and was significantly shorter than after the placebo;

· discovery that the intake of caffeine, combined with a daily creatine supplement, counteracted the beneficial effects of creatine intake on relaxation time and fatigue enhanced this inhibitory effect; and

· the observation that caffeine reduces the functional capacity of sacroplasmic reticulum calcium ATPase.

Conclusion The researchers believe that the findings from this experiment offer indirect evidence that suggests that facilitation of muscle relaxation may be important to the ergogenic action of creatine supplementation as well as power production during sprint exercises.

However, for the athlete in training, the key finding is that sustained caffeine intake, over a three-day period, negates the benefits of creatine supplements.

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Article adapted by MD Only Sports Weblog from original press release.
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Contact: Donna Krupa
American Physiological Society