Louis
07-04-2010, 02:06 PM
Don't know if this particular story has come up here or not:
Story here (http://well.blogs.nytimes.com/2010/06/23/phys-ed-do-sport-bars-and-gels-provide-the-energy-of-sports-drinks/?ref=magazine)
June 23, 2010, 12:01 am
Phys Ed: Do Sport Bars and Gels Provide the Energy of Sports Drinks?
By GRETCHEN REYNOLDS
According to a study published this spring in the journal Medicine & Science in Sports & Exercise, people who exercise for more than about two hours at a time can benefit from sports drinks. Most of us know that, of course. The carbohydrates in the drinks provide immediate fuel, which allows our bodies to avoid dipping into its own energy stores, meaning that, theoretically, you can exercise longer or more intensively before running out of fuel. But few people, in practice, can or will drink enough calories during a long workout to benefit significantly, the study authors suggest. The volume of fluid needed is, to say the least, daunting. Achieving the ideal “carbohydrate-intake rates,” the authors write, requires toting and stomaching about a half gallon of a typical sports drink every hour. Good luck with that.
Instead, it seems to be common practice today, the researchers write, for many athletes to turn to more-concentrated and portable forms of carbohydrates, like sports bars and those frostinglike little packets of sports gels that are ubiquitous at running and cycling races. But to date no one has comprehensively studied whether, in fact, these carbohydrate alternatives are as effective as liquid calories. Do carbohydrates from solid or semisolid sources reach the bloodstream and straining muscles as quickly as those from fluids? Are they burned as effectively? Do they, in the process of being digested, cause what scientists delicately refer to as “gastrointestinal distress”?
To examine those questions, a group of Swiss and English scientists undertook an ambitious series of experiments recently, the results of which were published in Medicine & Science in Sports & Exercise (the official journal of the American College of Sports Medicine).
During the experiments, the scientists provided eight trained, male cyclists with either water, a sports drink, sports bars or gel packets. In each session, the cyclists rode moderately, at a pace equal to about 60 percent of their maximal oxygen capacities — strenuous but not excruciating — for three hours. Throughout, they received calorically matched amounts of the different types of carbohydrates or plain water, while scientists checked their blood-sugar levels and various other metabolic measures.
What the researchers found was that the carbohydrates from the gels and the sports bars were being metabolized as quickly and as efficiently as those from the sports drink. The experiments weren’t designed to test whether the various carbohydrates actually improved the riders’ performances, enabling them to ride longer and harder. But it did show that gels and bars were as effective as sports drinks at sparing the riders’ stored body fuel.
There were some differences between the carbs, of course. Bars, in particular, seemed to create dips in dietary-carbohydrate usage. At certain points, especially early in the rides, the riders who were eating bars burned about 15 percent less dietary carbohydrates than the riders who were drinking sports drinks. This finding could imply that, at those moments, the riders were burning more of their bodily fuel stores. But by the end of the three-hour rides, the overall dietary-carbohydrate usage was virtually identical between those swallowing sports drinks and those eating bars; and both groups had burned far less stored bodily fuel than the riders drinking water. “I would conclude that the bar provided the same amount of energy in a very similar fashion” as the sports drink, says Asker Jeukendrup, director of the Human Performance lab at the University of Birmingham in England and senior author of the studies, who also is an accomplished triathlete. “I think the fact that at some time points there was a small difference is more a statistical effect than a physiological one.”
From a practical standpoint, another of the studies’ findings may be almost as important. In the gel and bar experiments, none of the riders reported any gastrointestinal distress. The cyclists receiving sports drinks also felt fine. Everyone’s stomachs and related organs remained undisturbed.
The studies do have some limitations. For one, the experiments were financed in part by Nestlé, which owns PowerBar, a company that makes bars, gels and sports drinks. But, says Dr. Jeukendrup, “the majority of the research was done before Nestle started funding some of this work.”
The scientists also used sports drinks, bars and gels that were sweetened with a combination of the carbohydrates glucose and fructose, in a 2-to-1 ratio, which, Mr. Jeukendrup says, provides the “most energy.” Few mass-market sports-nutritional products contain that precise carbohydrate mix, however. To find the most-comparable products, read labels carefully. Glucose often is listed as “maltodextrin.” High fructose corn syrup, although questioned in some nutritional contexts, “contains both glucose and fructose,” Mr. Jeukendrup says, and may be useful in sports products. Be wary of products that contain only fructose. “Fructose on its own can cause gastrointestinal distress,” Mr. Jeukendrup says.
As for just how much of the various foods or drinks you need, that’s “not an easy question to answer,” Mr. Jeukendrup says. It depends on the length of your session. If you’re exercising for an hour or less, “the amount of carbohydrates you need are minimal,” he says. If, on the other hand, you’ll be working out for more than two hours, “you may want to increase your carbohydrates to about 60 grams per hour,” the equivalent of about one bar and a gel; or two and a half gels; or a half liter of a sports drink plus a gel packet or some other combination thereof. “When you engage in endurance exercise of 2.5 hours or longer,” Mr. Jeukendrup adds, “I would recommend a higher intake (up to 90 grams per hour),” making sure to find drinks or bars that utilize both glucose and fructose.
Finally, what about skipping carbohydrates altogether during exercise, in hopes of losing weight? Science, sadly, discourages this idea. You’re likely to run out of energy and stop exercising earlier, Mr. Jeukendrup says, so the net effect would be fewer calories burned. The calories from a sports drink, gel or bar “may help you to maintain the exercise intensity and increase overall energy expenditure,” Mr. Jeukendrup says, equaling more benefit in the long run.
Story here (http://well.blogs.nytimes.com/2010/06/23/phys-ed-do-sport-bars-and-gels-provide-the-energy-of-sports-drinks/?ref=magazine)
June 23, 2010, 12:01 am
Phys Ed: Do Sport Bars and Gels Provide the Energy of Sports Drinks?
By GRETCHEN REYNOLDS
According to a study published this spring in the journal Medicine & Science in Sports & Exercise, people who exercise for more than about two hours at a time can benefit from sports drinks. Most of us know that, of course. The carbohydrates in the drinks provide immediate fuel, which allows our bodies to avoid dipping into its own energy stores, meaning that, theoretically, you can exercise longer or more intensively before running out of fuel. But few people, in practice, can or will drink enough calories during a long workout to benefit significantly, the study authors suggest. The volume of fluid needed is, to say the least, daunting. Achieving the ideal “carbohydrate-intake rates,” the authors write, requires toting and stomaching about a half gallon of a typical sports drink every hour. Good luck with that.
Instead, it seems to be common practice today, the researchers write, for many athletes to turn to more-concentrated and portable forms of carbohydrates, like sports bars and those frostinglike little packets of sports gels that are ubiquitous at running and cycling races. But to date no one has comprehensively studied whether, in fact, these carbohydrate alternatives are as effective as liquid calories. Do carbohydrates from solid or semisolid sources reach the bloodstream and straining muscles as quickly as those from fluids? Are they burned as effectively? Do they, in the process of being digested, cause what scientists delicately refer to as “gastrointestinal distress”?
To examine those questions, a group of Swiss and English scientists undertook an ambitious series of experiments recently, the results of which were published in Medicine & Science in Sports & Exercise (the official journal of the American College of Sports Medicine).
During the experiments, the scientists provided eight trained, male cyclists with either water, a sports drink, sports bars or gel packets. In each session, the cyclists rode moderately, at a pace equal to about 60 percent of their maximal oxygen capacities — strenuous but not excruciating — for three hours. Throughout, they received calorically matched amounts of the different types of carbohydrates or plain water, while scientists checked their blood-sugar levels and various other metabolic measures.
What the researchers found was that the carbohydrates from the gels and the sports bars were being metabolized as quickly and as efficiently as those from the sports drink. The experiments weren’t designed to test whether the various carbohydrates actually improved the riders’ performances, enabling them to ride longer and harder. But it did show that gels and bars were as effective as sports drinks at sparing the riders’ stored body fuel.
There were some differences between the carbs, of course. Bars, in particular, seemed to create dips in dietary-carbohydrate usage. At certain points, especially early in the rides, the riders who were eating bars burned about 15 percent less dietary carbohydrates than the riders who were drinking sports drinks. This finding could imply that, at those moments, the riders were burning more of their bodily fuel stores. But by the end of the three-hour rides, the overall dietary-carbohydrate usage was virtually identical between those swallowing sports drinks and those eating bars; and both groups had burned far less stored bodily fuel than the riders drinking water. “I would conclude that the bar provided the same amount of energy in a very similar fashion” as the sports drink, says Asker Jeukendrup, director of the Human Performance lab at the University of Birmingham in England and senior author of the studies, who also is an accomplished triathlete. “I think the fact that at some time points there was a small difference is more a statistical effect than a physiological one.”
From a practical standpoint, another of the studies’ findings may be almost as important. In the gel and bar experiments, none of the riders reported any gastrointestinal distress. The cyclists receiving sports drinks also felt fine. Everyone’s stomachs and related organs remained undisturbed.
The studies do have some limitations. For one, the experiments were financed in part by Nestlé, which owns PowerBar, a company that makes bars, gels and sports drinks. But, says Dr. Jeukendrup, “the majority of the research was done before Nestle started funding some of this work.”
The scientists also used sports drinks, bars and gels that were sweetened with a combination of the carbohydrates glucose and fructose, in a 2-to-1 ratio, which, Mr. Jeukendrup says, provides the “most energy.” Few mass-market sports-nutritional products contain that precise carbohydrate mix, however. To find the most-comparable products, read labels carefully. Glucose often is listed as “maltodextrin.” High fructose corn syrup, although questioned in some nutritional contexts, “contains both glucose and fructose,” Mr. Jeukendrup says, and may be useful in sports products. Be wary of products that contain only fructose. “Fructose on its own can cause gastrointestinal distress,” Mr. Jeukendrup says.
As for just how much of the various foods or drinks you need, that’s “not an easy question to answer,” Mr. Jeukendrup says. It depends on the length of your session. If you’re exercising for an hour or less, “the amount of carbohydrates you need are minimal,” he says. If, on the other hand, you’ll be working out for more than two hours, “you may want to increase your carbohydrates to about 60 grams per hour,” the equivalent of about one bar and a gel; or two and a half gels; or a half liter of a sports drink plus a gel packet or some other combination thereof. “When you engage in endurance exercise of 2.5 hours or longer,” Mr. Jeukendrup adds, “I would recommend a higher intake (up to 90 grams per hour),” making sure to find drinks or bars that utilize both glucose and fructose.
Finally, what about skipping carbohydrates altogether during exercise, in hopes of losing weight? Science, sadly, discourages this idea. You’re likely to run out of energy and stop exercising earlier, Mr. Jeukendrup says, so the net effect would be fewer calories burned. The calories from a sports drink, gel or bar “may help you to maintain the exercise intensity and increase overall energy expenditure,” Mr. Jeukendrup says, equaling more benefit in the long run.