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Coffee Cuts Liver Cancer Risk
And decaf reduces colorectal cancer risk, another study finds
By Kathleen Doheny
HealthDay Reporter
TUESDAY, Feb. 15 (HealthDay News) -- Coffee drinkers may have reason to smile: Daily coffee consumption seems to reduce the risk of liver cancer, a new study finds.
And drinking decaffeinated coffee seems to cut colorectal cancer risk, another study claims.
Both papers appear in the Feb. 16 issue of the Journal of the National Cancer Institute.
"We were surprised. We didn't expect the decaf findings," said Karin B. Michels, an associate professor of epidemiology at Harvard Medical School, and lead author of the study that looked at caffeine consumption and colorectal cancer risk.
The researchers were trying to confirm conflicting results from earlier studies, some finding that coffee reduced colorectal cancer risk and others revealing no effect. They evaluated data from two large studies, the Nurses' Health Study and the Health Professionals' Follow-up Study, together including more than 173,000 men and women. The goal was to look at the association between coffee, tea and caffeine consumption and the incidence of colorectal cancer.
They found no association between consumption of caffeinated coffee or tea and the incidence of colon or rectal cancer in either group. But they found that those who regularly drank two or more cups of decaffeinated coffee a day had about half the rate of rectal cancer as those who never drank decaf coffee.
It had been theorized that increased bowel motility [movements] from coffee consumption was "one of the most important mechanisms" in the reduction of cancer risk, said Michels. "We set out to confirm that, but we did not find an association between caffeine consumption and lower cancer risk."
It could be, she speculated, that decaffeinated coffee has an effect on bowel motility, but something in caffeine cancels out that effect.
The finding needs to be confirmed in other studies, Michels said, before any recommendation about coffee drinking can be made.
In the second study, Dr. Manami Inoue of the National Cancer Center in Tokyo and colleagues followed more than 90,000 middle-aged and elderly Japanese men and women for 10 years. They found that those who drank coffee daily or almost daily had half the risk of liver cancer, compared to those who did not drink coffee. They didn't differentiate between caffeinated or decaffeinated coffee, but noted that decaf coffee is rarely consumed in Japan.
The rate of liver cancer among those who never drank coffee was 547.2 cases per 100,000 people over a decade, but the rate among daily coffee drinkers was 214.6 cases per 100,000 over the same period.
"In our study, liver cancer risk significantly decreased with the amount of coffee consumed (compared with nondrinkers, 48 percent decrease with 1-2 cups per day; 52 percent decrease for 3-4 cups per day; 76 percent decrease for 5 cups per day)," Inoue said. "Our results are consistent with, but more pronounced than, those of previous case-control studies."
About 17,550 new cases of primary liver and bile duct cancers are expected to be diagnosed this year in the United States, according to the American Cancer Society. About 104,950 new cases of colon cancer and 40,340 of rectal cancer are expected to be diagnosed this year as well.
Dr. Michael J. Thun, head of epidemiological research for the American Cancer Society, said the two new studies are interesting, but the results shouldn't prompt any recommendations or changes in coffee-consumption habits.
"There isn't anything in these studies that would persuade people to give up or take up coffee drinking," Thun said, adding, "The liver finding is interesting, but needs to be replicated."
The finding that decaffeinated, but not regular, coffee reduced colorectal cancer risk is surprising to Thun, as it was to the study authors. "But it is important not to overinterpret," Thun said. Again, more research is needed to be sure the finding isn't a fluke, he added.
While the associations both bear more study, Thun said, "it's much too soon to go changing your diet."
More information
To learn more about cancers, visit the American Cancer Society (www.cancer.org ).
SOURCES: Karin B. Michels, Sc.D., associate professor, epidemiology, Harvard Medical School and Brigham and Women's Hospital, Boston; Manami Inoue, M.D., Ph.D., S.M., section head, epidemiology and prevention division, research center for cancer prevention and screening, National Cancer Center, Tokyo; Feb. 16, 2005, Journal of the National Cancer Institute
Copyright © 2005 ScoutNews LLC. All rights reserved.
Last updated 2/15/2005.
This article can be accessed directly at:
http://www.liverfacts.com/ms/news/524004/main.html
And decaf reduces colorectal cancer risk, another study finds
By Kathleen Doheny
HealthDay Reporter
TUESDAY, Feb. 15 (HealthDay News) -- Coffee drinkers may have reason to smile: Daily coffee consumption seems to reduce the risk of liver cancer, a new study finds.
And drinking decaffeinated coffee seems to cut colorectal cancer risk, another study claims.
Both papers appear in the Feb. 16 issue of the Journal of the National Cancer Institute.
"We were surprised. We didn't expect the decaf findings," said Karin B. Michels, an associate professor of epidemiology at Harvard Medical School, and lead author of the study that looked at caffeine consumption and colorectal cancer risk.
The researchers were trying to confirm conflicting results from earlier studies, some finding that coffee reduced colorectal cancer risk and others revealing no effect. They evaluated data from two large studies, the Nurses' Health Study and the Health Professionals' Follow-up Study, together including more than 173,000 men and women. The goal was to look at the association between coffee, tea and caffeine consumption and the incidence of colorectal cancer.
They found no association between consumption of caffeinated coffee or tea and the incidence of colon or rectal cancer in either group. But they found that those who regularly drank two or more cups of decaffeinated coffee a day had about half the rate of rectal cancer as those who never drank decaf coffee.
It had been theorized that increased bowel motility [movements] from coffee consumption was "one of the most important mechanisms" in the reduction of cancer risk, said Michels. "We set out to confirm that, but we did not find an association between caffeine consumption and lower cancer risk."
It could be, she speculated, that decaffeinated coffee has an effect on bowel motility, but something in caffeine cancels out that effect.
The finding needs to be confirmed in other studies, Michels said, before any recommendation about coffee drinking can be made.
In the second study, Dr. Manami Inoue of the National Cancer Center in Tokyo and colleagues followed more than 90,000 middle-aged and elderly Japanese men and women for 10 years. They found that those who drank coffee daily or almost daily had half the risk of liver cancer, compared to those who did not drink coffee. They didn't differentiate between caffeinated or decaffeinated coffee, but noted that decaf coffee is rarely consumed in Japan.
The rate of liver cancer among those who never drank coffee was 547.2 cases per 100,000 people over a decade, but the rate among daily coffee drinkers was 214.6 cases per 100,000 over the same period.
"In our study, liver cancer risk significantly decreased with the amount of coffee consumed (compared with nondrinkers, 48 percent decrease with 1-2 cups per day; 52 percent decrease for 3-4 cups per day; 76 percent decrease for 5 cups per day)," Inoue said. "Our results are consistent with, but more pronounced than, those of previous case-control studies."
About 17,550 new cases of primary liver and bile duct cancers are expected to be diagnosed this year in the United States, according to the American Cancer Society. About 104,950 new cases of colon cancer and 40,340 of rectal cancer are expected to be diagnosed this year as well.
Dr. Michael J. Thun, head of epidemiological research for the American Cancer Society, said the two new studies are interesting, but the results shouldn't prompt any recommendations or changes in coffee-consumption habits.
"There isn't anything in these studies that would persuade people to give up or take up coffee drinking," Thun said, adding, "The liver finding is interesting, but needs to be replicated."
The finding that decaffeinated, but not regular, coffee reduced colorectal cancer risk is surprising to Thun, as it was to the study authors. "But it is important not to overinterpret," Thun said. Again, more research is needed to be sure the finding isn't a fluke, he added.
While the associations both bear more study, Thun said, "it's much too soon to go changing your diet."
More information
To learn more about cancers, visit the American Cancer Society (www.cancer.org ).
SOURCES: Karin B. Michels, Sc.D., associate professor, epidemiology, Harvard Medical School and Brigham and Women's Hospital, Boston; Manami Inoue, M.D., Ph.D., S.M., section head, epidemiology and prevention division, research center for cancer prevention and screening, National Cancer Center, Tokyo; Feb. 16, 2005, Journal of the National Cancer Institute
Copyright © 2005 ScoutNews LLC. All rights reserved.
Last updated 2/15/2005.
This article can be accessed directly at:
http://www.liverfacts.com/ms/news/524004/main.html
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hier wat studies i.v.m koffie en training.
Coffee and Exercise
So, having said all this, can coffee improve your fitness? It does seem that the ingestion of caffeine can enhance exercise and sports performance, and this area of research has produced quite compelling results. In a landmark study by American doctor Dave Costill in the 1970s, a group of cyclists were able to ride for 21 minutes longer post-caffeine ingestion.
In fact, caffeine's efficacy as a performance-enhancing drug has led the International Olympic Committee to consider urinary levels of caffeine exceeding 12 micrograms/ml as worthy of a ban. You'd have to knock back eight cups of coffee to achieve such a target, however. Assuming you're not competing at the top level, a strong cup of coffee an hour before that fun run or charity bike ride might just help you through. Even if it isn't physiologically easier, studies have shown that people perceive their effort to be less intense after caffeine ingestion. In other words, you're trying as hard but you don't feel as if you are. However, caffeine can also dehydrate you, so don't overdo it and be sure to drink water regularly during your workouts.
So, these previous studies show that caffeine can boost your endurance, particularly during exercise lasting between thirty minutes and two hours. Because of its high caffeine content, many people drink coffee in the belief that it has the same effect. Unfortunately, it doesn't according to a recent study.
A Canadian research team compared the effects of coffee and caffeine on run time to exhaustion. A group of nine men took part in five trials. Sixty minutes before each run, the men took one of the following.
* Placebo (a "dummy" supplement).
* Caffeine capsules.
* De-caffeinated coffee.
* De-caffeinated coffee with caffeine added.
* Regular coffee.
Performance times were up to 10 minutes longer in subjects using the caffeine capsules. There were no differences in run times among the other trials.
These results are somewhat surprising, especially when you consider that caffeine absorption was similar during all three caffeine trials. The only explanation is that something in the coffee interferes with the effects of caffeine.
This isn't surprising, especially when you consider there are hundreds of compounds dissolved when coffee beans are roasted, ground and extracted in hot water. In fact, when one of these compounds was injected into rats, it actually slowed heart rate and lowered blood pressure.
The bottom line, then, is that if you plan to use caffeine to boost your exercise routines (particularly your endurance times), pure caffeine (such as in the form of capsules) might prove to be more beneficial than coffee.
Conclusion
Clearly, coffee has some health benefits, but also has very real risks and it’s role in the improvement of fitness levels is questionable. So, in light of these facts, I highly recommend being balanced to your approach to coffee ingestion as it relates to your health and fitness. One great way to achieve that balance is to follow the guidelines of the coffee diet and to enjoy your coffee in moderation while following a proper exercise routine. And, if you aren’t sure how to best do that, consult with a clinically certified nutritionist and/or fitness expert. After all, the longer we live, the longer we can enjoy coffee!
bron:http://www.ineedcoffee.com/03/coffeefitness/
Coffee and Exercise
So, having said all this, can coffee improve your fitness? It does seem that the ingestion of caffeine can enhance exercise and sports performance, and this area of research has produced quite compelling results. In a landmark study by American doctor Dave Costill in the 1970s, a group of cyclists were able to ride for 21 minutes longer post-caffeine ingestion.
In fact, caffeine's efficacy as a performance-enhancing drug has led the International Olympic Committee to consider urinary levels of caffeine exceeding 12 micrograms/ml as worthy of a ban. You'd have to knock back eight cups of coffee to achieve such a target, however. Assuming you're not competing at the top level, a strong cup of coffee an hour before that fun run or charity bike ride might just help you through. Even if it isn't physiologically easier, studies have shown that people perceive their effort to be less intense after caffeine ingestion. In other words, you're trying as hard but you don't feel as if you are. However, caffeine can also dehydrate you, so don't overdo it and be sure to drink water regularly during your workouts.
So, these previous studies show that caffeine can boost your endurance, particularly during exercise lasting between thirty minutes and two hours. Because of its high caffeine content, many people drink coffee in the belief that it has the same effect. Unfortunately, it doesn't according to a recent study.
A Canadian research team compared the effects of coffee and caffeine on run time to exhaustion. A group of nine men took part in five trials. Sixty minutes before each run, the men took one of the following.
* Placebo (a "dummy" supplement).
* Caffeine capsules.
* De-caffeinated coffee.
* De-caffeinated coffee with caffeine added.
* Regular coffee.
Performance times were up to 10 minutes longer in subjects using the caffeine capsules. There were no differences in run times among the other trials.
These results are somewhat surprising, especially when you consider that caffeine absorption was similar during all three caffeine trials. The only explanation is that something in the coffee interferes with the effects of caffeine.
This isn't surprising, especially when you consider there are hundreds of compounds dissolved when coffee beans are roasted, ground and extracted in hot water. In fact, when one of these compounds was injected into rats, it actually slowed heart rate and lowered blood pressure.
The bottom line, then, is that if you plan to use caffeine to boost your exercise routines (particularly your endurance times), pure caffeine (such as in the form of capsules) might prove to be more beneficial than coffee.
Conclusion
Clearly, coffee has some health benefits, but also has very real risks and it’s role in the improvement of fitness levels is questionable. So, in light of these facts, I highly recommend being balanced to your approach to coffee ingestion as it relates to your health and fitness. One great way to achieve that balance is to follow the guidelines of the coffee diet and to enjoy your coffee in moderation while following a proper exercise routine. And, if you aren’t sure how to best do that, consult with a clinically certified nutritionist and/or fitness expert. After all, the longer we live, the longer we can enjoy coffee!
bron:http://www.ineedcoffee.com/03/coffeefitness/
teh_pwnerer
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volgende:
Exercise plays a part in all our lives whether we are playing the
occasional game of football with the children, using exercise to help fight
the battle of the bulge, or, if we are elite athletes, amazing all around us
with the kind of breathtaking performances we saw at Athens this summer.
Caffeine is part of the naturally occurring group of stimulants found in leaves, nuts and seeds of a number of plants. Common dietary sources include coffee, tea, chocolate and a variety of soft drinks and sports drinks. The caffeine content of various foodstuffs is given below.
Table 1. Caffeine content of various foodstuffs
Foodstuff Serving size Caffeine content (mg)
Coffee* 150 ml 50-120
Tea* 150 ml 15-50
Chocolate Drink** 250 ml 10
Milk Chocolate** 50g 40
Caffeinated Soft Drinks 330 ml 40-100
(from Maughan 1999)
* Values for coffee and tea vary widely depending on the source and
method of preparation.
** In addition to caffeine, chocolate contains theobromine, which has an insignificant effect compared to caffeine.
So what is the effect of caffeine on different types of exercise?
Although the mechanism whereby caffeine may aid performance is not fully understood, there is substantial research that concludes that caffeine does improve physical performance. Its effect also appears to be widespread across a diverse variety of sports and exercises. Studies have also been wide ranging and have included well-trained athletes and relatively sedentary individuals of both coïtuses and different age groups.
One of the most comprehensive and recent reviews (Doherty and Smith 2004) looked at 39 published studies. Of these, 21 involved endurance exercise, 12 used short duration and high-intensity exercise and the remaining 6 used a graded exercise test. Including all these data, caffeine improved performance by 12.4%, relative to the placebo trials and this was shown to greatest effect in those who undertook exercise for a longer duration at any one time.
There are also a number of studies that show the beneficial effects of drinking coffee and/or caffeine ingestion on high intensity exercise. These include improved performance on a 1500 m run (Wiles 1992) and Anselme (1992) showed that anaerobic power in a cycling test was improved by the ingestion of the equivalent of two cups (250mg) of caffeinated coffee. Cycling was also the sport studied more recently by Bell (2001) when caffeine (5mg/kg) was shown to improve performance in a high intensity cycling test.
The beneficial effect has also been demonstrated in swimming trials. Collomp (1992) showed that in a swimming test (2x100m) there was improved performance after ingestion of 250 mg of caffeine.
What is the effective amount of caffeine?
Recent studies used small amounts of caffeine (1-2mg/kg). In many studies, coffee was used whilst others have used caffeine. However, they all show that small amounts of caffeine are effective in improving exercise performance significantly and these smaller amounts, as little as 90mg caffeine, are not associated with any unwanted side effects.
Caffeine and fluid requirements
The diuretic effect of caffeine is often over stressed, particularly in situations where dehydration is a major issue. This affects particularly competitions held in hot, humid climates where the risk of dehydration is high and is more important for endurance athletes where dehydration has a greater effect on performance.
Athletes competing in these conditions are often advised to increase their intake of fluid but also advised to avoid tea and coffee because of their mild diuretic effect. Current research, however, shows that, not only is this mild diuretic effect insignificant during exercise (Armstrong, 2002), but the negative effects caused by cutting such drinks from the diet may be more damaging (Maughan and Griffin, 2003). Conclusions from published studies show that intakes of less than 300mg caffeine a day will not affect levels of body's fluids.
Conclusion
In many of these studies, where performance was improved by the ingestion of caffeine or drinking coffee, there was the also the additional benefit of an associated reduction in the sensation of fatigue.
Given the various initiatives aimed at promoting physical activity to improve health, anything that encourages participation by reducing the discomfort and fatigue most people feel when exercising, has enormous potential implications for improving public health. Caffeine, in the form of coffee or as a pure ingredient, has that ability.
bron:[Link niet meer beschikbaar]
Exercise plays a part in all our lives whether we are playing the
occasional game of football with the children, using exercise to help fight
the battle of the bulge, or, if we are elite athletes, amazing all around us
with the kind of breathtaking performances we saw at Athens this summer.
Caffeine is part of the naturally occurring group of stimulants found in leaves, nuts and seeds of a number of plants. Common dietary sources include coffee, tea, chocolate and a variety of soft drinks and sports drinks. The caffeine content of various foodstuffs is given below.
Table 1. Caffeine content of various foodstuffs
Foodstuff Serving size Caffeine content (mg)
Coffee* 150 ml 50-120
Tea* 150 ml 15-50
Chocolate Drink** 250 ml 10
Milk Chocolate** 50g 40
Caffeinated Soft Drinks 330 ml 40-100
(from Maughan 1999)
* Values for coffee and tea vary widely depending on the source and
method of preparation.
** In addition to caffeine, chocolate contains theobromine, which has an insignificant effect compared to caffeine.
So what is the effect of caffeine on different types of exercise?
Although the mechanism whereby caffeine may aid performance is not fully understood, there is substantial research that concludes that caffeine does improve physical performance. Its effect also appears to be widespread across a diverse variety of sports and exercises. Studies have also been wide ranging and have included well-trained athletes and relatively sedentary individuals of both coïtuses and different age groups.
One of the most comprehensive and recent reviews (Doherty and Smith 2004) looked at 39 published studies. Of these, 21 involved endurance exercise, 12 used short duration and high-intensity exercise and the remaining 6 used a graded exercise test. Including all these data, caffeine improved performance by 12.4%, relative to the placebo trials and this was shown to greatest effect in those who undertook exercise for a longer duration at any one time.
There are also a number of studies that show the beneficial effects of drinking coffee and/or caffeine ingestion on high intensity exercise. These include improved performance on a 1500 m run (Wiles 1992) and Anselme (1992) showed that anaerobic power in a cycling test was improved by the ingestion of the equivalent of two cups (250mg) of caffeinated coffee. Cycling was also the sport studied more recently by Bell (2001) when caffeine (5mg/kg) was shown to improve performance in a high intensity cycling test.
The beneficial effect has also been demonstrated in swimming trials. Collomp (1992) showed that in a swimming test (2x100m) there was improved performance after ingestion of 250 mg of caffeine.
What is the effective amount of caffeine?
Recent studies used small amounts of caffeine (1-2mg/kg). In many studies, coffee was used whilst others have used caffeine. However, they all show that small amounts of caffeine are effective in improving exercise performance significantly and these smaller amounts, as little as 90mg caffeine, are not associated with any unwanted side effects.
Caffeine and fluid requirements
The diuretic effect of caffeine is often over stressed, particularly in situations where dehydration is a major issue. This affects particularly competitions held in hot, humid climates where the risk of dehydration is high and is more important for endurance athletes where dehydration has a greater effect on performance.
Athletes competing in these conditions are often advised to increase their intake of fluid but also advised to avoid tea and coffee because of their mild diuretic effect. Current research, however, shows that, not only is this mild diuretic effect insignificant during exercise (Armstrong, 2002), but the negative effects caused by cutting such drinks from the diet may be more damaging (Maughan and Griffin, 2003). Conclusions from published studies show that intakes of less than 300mg caffeine a day will not affect levels of body's fluids.
Conclusion
In many of these studies, where performance was improved by the ingestion of caffeine or drinking coffee, there was the also the additional benefit of an associated reduction in the sensation of fatigue.
Given the various initiatives aimed at promoting physical activity to improve health, anything that encourages participation by reducing the discomfort and fatigue most people feel when exercising, has enormous potential implications for improving public health. Caffeine, in the form of coffee or as a pure ingredient, has that ability.
bron:[Link niet meer beschikbaar]
teh_pwnerer
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The Downside of Caffeine
Despite coffee/caffeine's positive effects on psychological states and performance, there are numerous documented risks that must considered when consuming caffeine, whether for performance-enhancing effects or simply as a part of daily dietary consumption.
Caffeine stimulates the central nervous system and can produce restlessness, headaches, and irritability. Caffeine also elevates your heart rate and blood pressure. Over the long-term as your body gets used to caffeine, it requires higher amounts to get the same effects. Certainly, having your body in a state of hormonal emergency all day long isn't very healthy.
Caffeine is also a diuretic and causes a loss of fluid, which then leads to a dehydrating effect. This is obviously not conducive to fitness activities such as resistance training, as fluid is needed for the transfer of nutrients to facilitate muscular growth. It is also important when considering the further loss of fluid while exercising in hot environments.
Perhaps the most important long-term problem is the effect of caffeine on sleep. The half-life of caffeine in the body is about 6 hours. If you drink a big cup of coffee with 200 mg of caffeine at 4PM, at 10PM you still have about 100mg in your body. By 4AM, you still have 50mg floating in your system. Even though you may be able to sleep, you may not be able to obtain the restful benefits of deep sleep. What's worse, the cycle continues as you may use more and more caffeine in hopes of counteracting this deficit.
bron:http://www.topendsports.com/nutrition/coffee.htm
Despite coffee/caffeine's positive effects on psychological states and performance, there are numerous documented risks that must considered when consuming caffeine, whether for performance-enhancing effects or simply as a part of daily dietary consumption.
Caffeine stimulates the central nervous system and can produce restlessness, headaches, and irritability. Caffeine also elevates your heart rate and blood pressure. Over the long-term as your body gets used to caffeine, it requires higher amounts to get the same effects. Certainly, having your body in a state of hormonal emergency all day long isn't very healthy.
Caffeine is also a diuretic and causes a loss of fluid, which then leads to a dehydrating effect. This is obviously not conducive to fitness activities such as resistance training, as fluid is needed for the transfer of nutrients to facilitate muscular growth. It is also important when considering the further loss of fluid while exercising in hot environments.
Perhaps the most important long-term problem is the effect of caffeine on sleep. The half-life of caffeine in the body is about 6 hours. If you drink a big cup of coffee with 200 mg of caffeine at 4PM, at 10PM you still have about 100mg in your body. By 4AM, you still have 50mg floating in your system. Even though you may be able to sleep, you may not be able to obtain the restful benefits of deep sleep. What's worse, the cycle continues as you may use more and more caffeine in hopes of counteracting this deficit.
bron:http://www.topendsports.com/nutrition/coffee.htm
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conclusie
1. Caffeine might reduce the rate of muscle-glycogen consumption during the first 15 minutes of exercise. As a result, there would be more glycogen in the muscles during later stages of exertion, prolonging endurance(4).
2. Caffeine may lower perceived exertion, making strenuous efforts feel easier. Some investigations have demonstrated that individuals routinely rate specific intensities of exercise as more comfortable if they have caffeine in their systems.
3. Caffeine may produce an adrenaline-like effect, stimulating more calcium to rush inside muscle cells during contractions, thus boosting the potential strength and power of muscular activity.
bron:http://www.pponline.co.uk/encyc/0652.htm
1. Caffeine might reduce the rate of muscle-glycogen consumption during the first 15 minutes of exercise. As a result, there would be more glycogen in the muscles during later stages of exertion, prolonging endurance(4).
2. Caffeine may lower perceived exertion, making strenuous efforts feel easier. Some investigations have demonstrated that individuals routinely rate specific intensities of exercise as more comfortable if they have caffeine in their systems.
3. Caffeine may produce an adrenaline-like effect, stimulating more calcium to rush inside muscle cells during contractions, thus boosting the potential strength and power of muscular activity.
bron:http://www.pponline.co.uk/encyc/0652.htm
