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Ketogenic Diets Maybe · Ketogenic Diets No · Eating Disorders in Males  · Fatigue Fracas · Sit-Up Put-Down · Practice Strategy

     The Ferret was nosing around the gym recently and overheard a couple of well-cut guys enthusing about a new craze called cyclical ketogenic dieting. On the principle that sport scientists can sometimes trail the field in performance enhancement, The Ferret asked Lyle McDonald, who is writing a book on the subject, to argue the case for these diets.
     The word ketogenic refers to the fact that your liver makes ketones from fat as an alternative source of fuel, when you run short of carbohydrate. In the past few years, there has been a renewed interest in low-carbohydrate or ketogenic diets. For athletes (especially bodybuilders), the latest approach is to alternate five or six days of low-carbohydrate dieting with one or two days of carbohydrate loading. It's sometimes referred to as cyclical ketogenic dieting. Books promoting it have been written by Dr Mauro DiPasquale (The Anabolic Diet) and Daniel Duchaine (Bodyopus).
      As might be expected, these diets have met with a great deal of criticism. While there is no published research specifically on the cyclical approach, research on ketogenic diets with athletes shows that they could be more beneficial than the usual high-carb diets. Carbohydrate loading is also a tried-and-true strategy for endurance athletes. There may be a synergistic effect from combining the two approaches, but it's mere guesswork at this point. Periodized training seems to work, so why shouldn't periodized dieting?

For reviews of ketogenic metabolism, see:
McGarry, J.D. et. al. (1989). Regulation of ketogenesis and the renaissance of carnitine palmitoyltransferase. Diabetes/Metabolism Reviews, 5, 271-284.
Mitchell, G.A. et al. (1995). Medical aspects of ketone body metabolism. Clinical & Investigative Medicine, 18(3), 193-216.
For a review of glycogen supercompensation, see:
Pascoe, D.D. and Gladden, L.B. (1996). Muscle glycogen resynthesis after short term, high intensity exercise and resistance exercise. Sports Medicine, 21, 98-118.
Contributed by
Lyle McDonald

     When this issue was aired on the Sportscience list recently, Tom McCullough summed up the case against ketogenic and other unusual diets. Here's his view.
     Weight control is a very big issue for most Americans. At any given time 25% of men and 44% of women are trying to shed unwanted pounds. It's easy to see how the weight loss industry has become so profitable, pulling in nearly $27 billion yearly, most often at the expense of consumers who are looking for a fast and easy way to shed excess fat. Most of these diets do not work. Some are actually harmful and peddle blatant misinformation. Worse, we have become overrun with unethical salesman who use science and pseudo-science to dupe us into believing in their magic. Worse yet, athletes can be very gullible people! Our search for that elusive extra edge means that we often fall prey to those who deal in myths.
     The most recent fad in diets is the high fat (65-70% of calories) or ketogenic diet such as Bodyopus. Many assume that if we take in high percentages of dietary fat, we will be able to increase the amount of fat we burn and boost the amount of muscle we put on. All without quite as much diligence in the gym.
     So what do the experts advise we do to protect ourselves from the purveyors of snake oil and magic diet formulas? Dr. Andrew Coggan of the University of Texas Medical Branch, Galveston, Texas, advises: "Ask yourself, is somebody trying to sell me something, for example a product, book, or system? Is the claim or product being promoted as revolutionary, with sweeping and widespread benefits?" Ellen Coleman, R.D., M.A., M.P.H. says: "The athlete should beware if: 1) the claim sounds too good to be true; 2) the suspected quack encourages distrust of reputable health professionals such as medical doctors, exercise physiologists, and registered dietitians; 3) a preponderance of case histories, testimonials, and subjective evidence are used to justify exaggerated claims." Dr. Lawrence Spriet of the University of Guelph, Ontario, Canada, adds: "I would further recommend staying away from some of the fad magazines and books that abound in today's society. Rather, look more to the science and educational materials that contain opinions of several researchers in a particular area."
     To lose weight, you have to eat less calories than you burn. We should all be aware that there are no quick fixes, no magic foods, and no magic nutrient ratios!

Dietary fat and physical activity: fueling the controversy. (1996). Gatorade Sport Science Institute Round Table #25, 7(3). Link to this article at the GSSI site.
Contributed by
Tom McCullough.

     Eating disorders are not just a female problem. Eight percent of elite male athletes in Norway suffer from some type of eating disorder, according to research just completed by two masters students at the Norwegian University of Sport in Oslo. Over 900 national class male athletes participated in the study, making it the largest, and perhaps only, national study of eating disorders among elite male athletes. Included among those who reported suffering from eating disorders were international gold medalists in Olympic, World Championship and World Cup events. Laxatives, diuretics, and diet pills are just some of the preparations that athletes reported using to reduce or control weight. In the sports of boxing, karate, wrestling and judo, 82% of the athletes had used these extraordinary weight control methods. Sixteen percent of athletes in rock climbing and ski jumping had symptoms of eating disorders, according to project leader Jorunn Sundgot Borgen. Least affected among the elite were athletes in team sports (soccer, handball).

Contributed by Stephen Seiler, translated from a report written in the Norwegian newspaper Verdens Gang.

     If you set out too fast in an endurance event, what finally forces you to slow down: your mind or your body? Does a ghost in the machine call the shots, or is the muscle machine maxed out? Most sport scientists assume that your machine runs out of steam first. They believe that the ability of your heart to pump blood to your muscles sets your speed in the event. Go too fast and your muscles will fatigue, because they can't get all the oxygen they need. And when your muscles fatigue, your effort goes up to max, to try to keep your speed up.
     Tim Noakes of the Sports Science Institute of South Africa thinks it might be the other way around. He says you might reach maximum effort well before your muscles flag, because unrestricted all-out exercise is potentially lethal. He made this controversial claim at the 1996 meeting of the American College of Sports Medicine. His talk was published last year, with a strong rebuttal by members of the establishment. The debate has continued recently on the Sportscience mailing list.
      In one sense, Noakes has to be right. Push too hard and you really can hurt yourself, so the unpleasant feeling of fatigue is one way the mind protects the body. But what's responsible for that feeling? Is it the muscles giving out, or does something else say whoa?
     The evidence for something else is indirect: instances of climbers at altitude, athletes, and diseased patients quitting exercise tests when it looks like their muscles have headroom for more push. But do the muscles of an athlete really have anything left at maximum effort? To answer that, you have to set up arcane experiments with electrical stimulation of muscles before, during, and after fatiguing exercise. The definitive experiment hasn't been done yet.
     Meanwhile it's clear that your muscles do get weaker as the event drags on. It's also clear that getting extra oxygen to your muscles speeds you up--that's how the banned drug erythropoietin (EPO) seems to work. And if you take oxygen away, you slow down--that's why smoking is bad for endurance athletes. These and other observations point to muscle as the primary site of fatigue.
     Sounds all very academic, but there are practical implications. Find the site of fatigue, figure out what's going on there, and you might be onto new ways to enhance performance.

Noakes, T. D. (1997). Challenging beliefs: ex Africa semper aliquid novi. Medicine & Science in Sports and Exercise, 29, 571-590.
Bassett, D.R. & Howley, E.T. (1997). Maximal oxygen-uptake - classical versus contemporary viewpoints. Medicine & Science in Sports and Exercise, 29, 591-603.
    To view the relevant messages on the Sportscience list, go to our
search form, put "limit or fatigue" in the Subject line of the form, and set the dates from Jan 27 to whenever.
Contributed by
Will Hopkins.

      Key items in health-related fitness assessments are bent-knee sit-ups to test abdominal strength and the sit-and-reach test of hamstring flexibility. But a recent study of nearly 3000 adults found no worthwhile relation between scores in these tests and low-back pain (Jackson et al., 1998). A sore back should have produced a bad score, so the tests are no good for studies of back pain. But the real disappointment is that good abdominal strength and hamstring flexibility don't seem to protect you from back pain. Should The Ferret stop doing sit-ups and toe-touches, or is more research needed?

Jackson, A.W., Morrow, J.R., Brill, P.A., Kohl, H.W., Gordon, N.F., & Blair, S.N. (1998). Relations of sit-up and sit-and-reach tests to low back pain in adults. Journal of Orthopaedic and Sports Physical Therapy, 27, 22- 26.
Contributed by
Duane Knudson.

     It's hardly news now, but a study published back in 1994 caught The Ferret's eye lately. It seems that repeating the same drill many times in succession may not be the most effective skill-practice strategy. During competition, athletes have to execute a skill in different ways and in different contexts, so it seems sensible to practice the skills in situations that are similar to those encountered in the game itself. The study supported that idea.
     In the study, collegiate baseball players got more out of extra batting practice when different pitches were presented in a random order. So instead of five curve balls in a row, then five fast balls and so on, the order varied: a fast ball, a slider, two curve balls, then another slider... The baseball players who got pitches in random order improved 57% on solid hits, while the players who received pitches in sequence improved only 25%. A control group doing normal training improved only 6%. These data are compelling, because improvements in performance are usually small for experienced performers.
     More research is needed to see if the skill level of the performer is important. For example, beginners may benefit more from lots of repetitions of the same skill than from a mixture of skills.

Hall, K.G., Domingues, D.A., & Cavazos, R. (1994). Contextual interference effects with skilled baseball players. Perceptual and Motor Skills, 78, 835-841.
Contributed by
Trish Shewokis. · · Homepage · Copyright ©1998
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