Microsoft word - conference report iaaf - peter res.doc
A consensus statement conference was organized by the IAAF to “help shape the priorities of the IAAF medical and anti-doping committee and of the IOC working group on nutrition over the next few years”. The conference was a follow up of the 1995 conference also held in Monaco.
A lot of progress in the field of sports nutrition has been made over the past 12 years, so it was decided to organize a new conference.
As the only representative from the IOC diploma in Sports Nutrition, I was asked to write a report on the conference. The report for my fellow students was to be both factual and about my personal experiences.
I have written down my expectations, experiences and summaries of the different topics. I have tried not to just copy the summary of what the author wrote, but more topics of special interest to me. I have incorporated topics from the manuscripts, from the presentations and from the discussions.
What a surprise it was to be invited for this conference. I was proud and happy to be offered such a great opportunity. I was very excited to be able to meet with all those people that I actually only knew from their publications. I was going to meet the people and faces behind the names.
I expected to get a lot of new information on the latest research and get to talk to the people who actually were responsible of the research and designed the studies. The process of getting to consensus is interesting.
I expected to get caught on every word that I would have written wrong in the paper I was co-author of, since it was going be read by the people that collected the data that the recommendations are based on.
So I was more aware of the importance of working evidence based than I was ever before.
It was great to meet those outstanding people from all over the world. The group was really well put together, with both practical and scientific input from different countries. Especially in formulating the consensus statement, there were some issues regarding formulation. For instance: training in the U.S.A. is often referred to as workout, while in the UK this would be a session, so we ended up using the word activity.
The data knowledge of the people who were there was amazing. And the capacity of reproducing details of whatever study relevant made me more aware of the necessity to not read abstracts only.
I found that, in general, people agreed on most topics. The consensus statement was to be finished in 4 hours and we ran a whole 1 minute late. According to Ron Maughan, this was a walkover, compared to previous consensus statements he was involved in.
Actually, I found the number of really new studies less than I would have expected before. On the other hand, we are privileged to be presented the latest research in our study. And science is a slowly progressing field. I guess one cannot expect great revolutions overnight. I do know more about everything that we don’t know yet.
Content of the conference
When I have to give one theme of the conference, it probably is “individualization”. The amount of energy, protein, carbohydrate, fat, micronutrients and water in the foods should all be eaten according to individual needs. The individual needs depend on age, sex, training stimuli, environmental factors, genetic factors. Ball park ranges can be given, but should be finalized to suit the individual by monitoring among other things: body composition, blood (iron) parameters, and sweat loss.
Nutrition for sprints
Although nutrition for sprints hasn’t received as much attention as distance running, nutrition can have a profound effect on recovery from training and competition, training adaptations and a power tot weight ratio. General recommendations for all sprinters are, at best, useless. Very specific guidelines cannot and should not be given for macronutrient intakes, only ranges. Individual needs should be considered.
Recommendations for use of specific foods to ward off drowsiness or to improve reaction time cannot be given at the time, because of a lack of data to either support or discard effects of nutrition on reaction time.
Foods and drinks on race day should be individually tested so that the chance of GI discomfort is minimized. Careful consideration of what not to eat is probably more important than what to eat.
Weight training is an important component of a sprinters training. It should be noted that an optimal mass does not equal a maximal mass. Changes is muscle mass will be induced by training plus nutrition. Protein balance does not become positive without provision of exogenous amino acid sources. This can be obtained from foods as well as it can be obtained from special sports products. A relatively small amount of exogenous amino acids results in positive protein balance, probably 10-15 gram of a mixed protein. Leucine does not seem to have an effect when enough carbohydrate and protein is provided. Weight training should never be done in glycogen depleted state, since there is evidence that this will reduce the maximal anabolic response.
Total protein needs are dependant on timing of ingestion, type of protein, other nutrients ingested and training stimuli. However, in no athlete there has been shown a higher need than 1.7 gram per kg body weight per day. This is probably the upper limit of protein needs. It should be noted that this requirement is measured in the most extreme activities, like Tour de France cycling. Most athletes do not need this amount. Many athletes consume this amount of protein already in their habitual diet, without the need to supplement. Supplements might be useful for convenience or accuracy of amounts ingested. Because of adaptive responses, a higher protein intake results in higher protein oxidation. If protein intake is reduced all of a sudden, the oxidation remains high for some time and the athlete risks shirt term negative protein balance.
Side effects of high protein intake have been largely overestimated. Risks reported in the literature include kidney damage and bone demineralization. Kidney damage has never been shown in otherwise healthy individuals. Bone consists of protein for a large part and in fact, bone collagen responds similarly to muscle proteins following ingestion of a protein source. However, there is no rationale for advocating protein intakes above 1.7 gram per kg body weight per day. Furthermore, high protein intake might compromise carbohydrate intake. Carbohydrate intake should be sufficient to maintain glycogen stores during periods of training and racing (~ 5 gram/kg body weight per day, but dependent on amount and intensity of training). There was discussion about post exercise protein breakdown. It was hypothesized that protein breakdown might not be a bad thing. It might have a role in muscle remodeling. Clearly, more research is needed.
Energy balance is just as, if not more, important for muscle hypertrophy than is protein intake.
Creatine can enhance power and increase muscle mass. The extra weight gain can potentially negatively impact performance. The most important effect seems to be that more work can be done during high intensity training programs. Data remain equivocal, but importantly, none of the available studies has reported impaired performance. Furthermore, some data indicate increased glycogen storage when carbohydrate is co-ingested with creatine.
Buffering agents such as bicarbonate and β-alanine are not recommended at the time for sprint events. Despite widely used in elite 400 meter runners, effects have rarely been shown under 1 minute of exercise. There is a rationale for increased training outputs, but adaptive responses might be compromised.
Nutrition for middle distance running
Middle distance running is at the cross roads of training stimuli. Rivaling almost the mileage of a marathon runner in the base training phase, training proceeds over the year to almost the high intensity training of a sprinter during race season.
The different phases of the periodized training regime require different amounts of energy and macronutrient content.
The presentation on middle distance running was build around the concept of periodization of both training and nutrition. Periodization is often applied as a relative high volume, low intensity base training towards a high intensity, low volume race season. Obviously, energy needs and relative carbohydrate needs to change according to the training phase. Towards racing season, likely, the total energy needs are not as high as during base training. However, because of intense training, the relative reliance on CHO use is higher. Also protein needs differ for different seasons. Recommended fat intake is a result of estimated total energy needs minus CHO and protein needs.
Several supplements can have a profound effect for the middle distance runner: caffeine, creatine and buffering agents such as bicarbonate and β-alanine. Buffering agents are an effective way to remain blood and intracellular pH. Much research has been done in the past on bicarbonate. In many studies this has been proven successful in events ranging from 1 to 15 minutes. Recently, studies have been done on β-alanine. Alanine combines with histidine to form carnosine. This is one of the few dipeptides in the muscle with the right dissociation curve to buffer the intramuscular fluid. Administration of alanine has been shown to improve the amount present in the cell. This can be used as an intracellular buffer. Similar small but significant performance benefits have been reported as for bicarbonate. A “chronic” supplementation of bicarbonate can be applied and has been proven successful in keeping blood bicarbonate elevated for several days. This protocol might be especially useful in persons prone to GI distress after acute bicarbonate loading. Bicarbonate and β-alanine can be interesting supplements for elite middle distance runners.
A warning should be given against the use of pseudo-ephedrine. Although the substance itself is not on the WADA-list, athletes can test positive for one of the metabolites.
The intensity of much of the training of a middle distance runner is done above 75% VO2max, so that carbohydrate should be the primary fuel. Furthermore, the weight training that is often done alongside relies heavily on anaerobic ATP production, with declines in muscle glycogen reported of 25-40% after a multiple set resistance exercise bout. Future studies should answer the present questions about optimal timing of different training stimuli and concurrent nutritional status.
The endurance training in base training relies more on fat metabolism, and usually, energy expenditure is higher than in other phases. Absolute and relative contribution of fat can be highest in this period, but should probably only still be around 2 gram per kg body weight per day or around 30 percent of total energy.
Carbohydrate intake can remain around 7-10 gram per kg per day. Fewer total energy expenditure towards race season makes the relative contribution of carbohydrate higher towards this phase.
Protein needs increase with increased mileage and resistance training. Protein needs will never be more than 1.7 gram per kg body mass per day. Many athletes consume this amount of protein in their habitual diet, so there is no need for emphasis on extra protein intake.
Acute strategies to maximize glycogen recovery between sessions include taking 1.2 to 1.5 gram of carbohydrate per kg body mass per hour in the first 2 hours after training. There is still debate over whether inclusion of
protein can benefit recovery. Data show either no difference or enhanced protein balance, subsequent performance and muscle protein degradation markers. No negative effects of protein in a recovery meal have been reported. Inclusion of protein seems prudent at a dose of about 0.1 gram of essential amino acids per kg body mass after exercise. This would translate to about 14 gram of whole protein from milk. No difference has been shown between protein from foods or from supplements.
Nutrition for long distance running
Over history, long distance running has shown to be the front line of sport nutrition research and application. The introduction of carbo-loading in the late 1960 was one of the first well known nutrition strategies to enhance performance. Since then, the protocol of glycogen loading has been evolved into a 2-3 day protocol. Recently, supramaximal glycogen stores, comparable to the values previously reported, have been shown already after 36 hours. It seems that 2 days of high carbohydrate diet, together with a training taper is enough to maximally enhance glycogen stores.
Long distance runners are characterized by a high maximum oxygen uptake and very low levels of body fat, with minimal development of muscle in their arms and upper torso. Especially “hot weather” race winners tend to be small and light. Females usually have to push their body weight further from their natural shape than male runners. However, the penalty is also greater. Some athletes develop eating disorders, osteopenia and chronic menstrual dysfunction.
The carbohydrate needs are complex and multifactorial. There have been some studies that have shown benefits of training in a low glycogen state. However, there are some well described potential disadvantages of this strategy like increased risk of illness and injury, and reduced well being and capacity to train. Training in low glycogen state is not recommended at the time. Distance runners should follow established carbohydrate intake guidelines.
Protein requirement is elevated by long distance running, and can be maximally nearly twice the requirement of sedentary people (1.7 g/kg/d). Nitrogen balance can be influenced by timing of protein intake, with better maintenance of nitrogen balance when protein is consumed after exercise.
Fat adaptation has been researched extensively, but no positive performance outcomes have been shown. A reduction in the ability to perform high intensity exercise has been shown. Fat adaptation should not be undertaken by marathon runners.
Fluid and carbohydrate should be consumed with races of 60 min and longer. The concentration of carbohydrate can be varied between 4 and 8% according to priority of rehydrating of refueling. It is not recommended to give more than 60 grams per hour, although higher absorption rates have been reported with mixed carbohydrate forms. However, this study was done in cyclist and the overall impression is that higher intakes would cause GI distress in most individuals.
What was also noted is that the GI tract is highly adaptive and can get used to high carbohydrate and fluid intakes. This might be worth training, especially for marathon runners.
Iron deficiency often occurs in long distance runners. Although there does not seem to be a higher incidence than in the general population, iron deficiency can hinder performance and should be avoided. Regular screening of serum ferritin is warrented. Iron supplementation should only be commenced after diagnosis of low serum ferritin and/or low heamoglobin.
At the time there is no certainty about whether intra-muscular iron injections offer advantages over oral iron supplementation. There is a risk for anaphylactic shock and iron overload, so oral iron supplementation should be preferred.
The only supplement to have shown consistently beneficial effects on long distance running is caffeine in doses ranging from 3-7 mg/kg. 3-5 mg/kg have shown similar results as 7 mg/kg. Doses of 9 mg/kg actually hindered performance.
Multi-event, throwers, jumpers
A pyramid is used as a visual tool to show the importance of the different aspects of sport nutrition. The basis should be a healthy diet, the middle layer consist of nutrition around training and at the very top there is place for specific supplementation.
It is recommended that athletes have a plan for competition day. This plan should be practiced in training. After the competition there should be a debriefing to evaluate and improve the nutrition plan.
Nutrition for throwers, jumpers and combined events athletes
Limited studies have assessed the nutrition al needs of jumpers, throwers or combined events athletes. Extrapolation of data from exercise protocols that mimic that of these events should be used to come to specific recommendations.
Goals for nutrition during training phase include 1) meeting energy needs, 2) timing of consumption of adequate fluid and electrolyte before, during and after exercise to ensure proper hydration, 3) timing consumption of carbohydrate intake , 4) timing consumption of adequate protein intake, 5) consuming effective and safe nutritional and dietary supplements and ergogenic aids.
Micronutrient intake should meet at least DRI. Data on both intake and needs of jumpers, throwers and combined event athletes are scarce, so it is hard to make conclusions.
Adequate hydration can be achieved by taking about 500 ml of cool fluid about two hours before exercise. The nature of events often allows athletes to consume fluid in between attempts. As is also stated in the hydration chapter, athletes should be warned not to overconsume fluid so that they gain weight. On the contrary, athletes might benefit from slight dehydration in jumping events. This is often seen in practice. There is some rationale behind this, but data showing definite performance improvement are lacking at the time. If chosen, deliberate dehydration should be practiced in training, never be more than 3% body weight and should be closely monitored. Heat cramps are associated with dehydration, so individuals prone to heat cramps should not dehydrate.
After competition, athletes should adequately rehydrate and refuel.
Supplements that can be of value to throwers, jumpers and combined event athletes are caffeine, bicarbonate (for 800 or 1500 meter in the heptathlon / pentathlon), and creatine. Supplement use should be monitored closely and be checked for doping contamination.
Tools should be developed to facilitate the translation of research findings in to practice.
Physique and body weight
People have very different genetics. Some events require low amounts of body fat and success is only likely within a relatively small range of body shapes and sizes. Genetics vary in a continuum between naturally very lean and virtually impossible to achieve weight goals.
International competitors in different events have different physiques. For instance, 400 meter runners are the tallest of all track runners. Tall people have an advantage with high jumping because they have a higher centre of gravity. Different physique characteristics, like power to weight ratio, limb length, energy expenditure and heat exchange, all have impact on performance. Some characteristics, like height, cannot be changed, others, like weight and body fat can be manipulated by diet and training.
Reducing weight should be done with a high carbohydrate diet, to support training and glycogen recovery. Nutrient density should be high and energy intake should never drop below 30 kcal or 125 kJ / kg fat free mass. A lower energy density (energy / g food) of the diet is advised as well.
Reduced carbohydrate diets are very popular in the general population and also in the athlete community. Studies have shown improved weight loss compared to low-fat diets, but never included athletes. The well described advantages of sufficient carbohydrate in athletes probably will negate possible positive effects of low-carbohydrate diet weight loss. However, carbohydrate intake advice should be individualized and not be interpreted as eating an unlimited amount of carbohydrate. Carbohydrate intake should not be under 5 gram/kg/d.
Athletes should be advised a basic diet and foods should be attached to training. This way, a more accurate diet can be prescribed. Also, the athlete knows how much to consume on rest days, when injured or when in transition phase. The extra food can be given per hour of exercise.
Low GI diets can have effect for athletes who want to lose weight. A possible negative effect is reduced glycogen resynthesis.
Protein is the most satiating of all macronutrients. Protein also induces the highest thermogenesis. Protein needs are higher on a energy restricted diet. Therefore, a relatively high protein intake can have a role in an energy restricted diet. However, if protein intake becomes too high, carbohydrate intake might be compromised.
Dairy intake has effect on body composition. Different mechanisms have been proposed. The calcium forms fatty acid soaps from the triglycerides and some is excreted. Conjugated linolic acid might have a role and other mechanisms have been proposed, but more research needs to be done to elucidate the mechanism.
Surface anthropometry is recommended as the most practical and safe method to assess and track changes in body composition. When measuring skinfolds, it is advised to give a confidence interval. This shows the athlete a more realistic figure.
The female athlete triad
The female athlete triad consists of three interrelated health problems: amenorrhea, eating disorders and osteoporosis. New research shows that each component can occur on a continuum.
In healthy young adults, energy balance occurs at an energy availability of about 45 kcal (188 kJ) per kg fat free mass per day. When energy availability drops below 30 kcal (125 kJ)/kg FFM/day, the body suppresses reproductive function, bone turnover and other physiological processes. Energy availability of amenorrheic athletes has been shown consistently under 30 kcal/kg FFM/day.
Low energy availability can be caused by eating disorders. Eating disorders are life-threatening clinical mental illnesses that require medical and psychiatric treatment. Commercial products for estimating energy intake, energy expenditure, and fat free mass can be used for calculating energy availability. For most athletes, energy availability should be in the range of 30-45 kcal /kg FFM/day for weight loss and around 45 kcal/kg FFM/day for weight maintenance and above for growth and glycogen loading.
Clinical menstrual disorders are easy to detect, subclinical menstrual disorders are not that obvious. The underlying etiology is often uncertain. Medical tests are required to have a proper diagnosis of etiology and to provide adequate treatment.
Gynecological age (years since menarche) is a strong predictor of amenorrhea: the prevalence of amenorrhea was found to be 9% among marathon runners who were older than 15 years of gynecological age and 67% among those who were younger.
Bone strength and the risk of fracture depend not only on bone mineral but also on bone protein. Nevertheless, osteoporosis is diagnosed on the basis of bone mineral density (BMD) alone. To estimate bone fracture risk in premenopausal women is hard because of many confounding factors.
Amenorrheic athletes report fewer intake of total energy, protein and fat and higher intake of fibre. Micronutrient deficiency occurs more often in amenorrheic athletes than in eumenorrheic athletes. Problems occur most
frequently in energy nutrients, blood nutrients and bone building nutrients. Deficiency in calcium and iron are most common. Use of a broad spectrum low dose multi-vitamin/mineral supplement might be warrented.
IN addition to the three main health consequences of the triad, other health problems can occur. Growth might be impaired, but catch-up growth has been shown in elite gymnasts. Delayed menarche has been shown in lean dancers. Low availability of fuels suppresses reproductive function. Stress fractures occur more often in amenorrheic athletes.
Screening for disorders of the triad should include a menstrual history, physical activity history and current activity level, diet history and current dietary behavior in relationship to weight and sport expectations, and family history, especially mothers age of menarche.
Treatment should consist of improving energy availability. This can be done by increasing energy intake or reducing energy expenditure.
Youth in athletics
Adequate nutrition for youth athletes is important to enhance sports performance, avoid injury, and to ensure optimal growth, maturation and bone health. Of particular importance for youth athletes is meeting energy demands for growth and for exercise. Needs of protein per kg bodyweight, and calcium are increased. Youth have been shown to have a higher fat utilization than adults. Dehydration is more detrimental to children than to adults.
Carbohydrate intake should be enough to replenish glycogen stores. It is unclear whether glycogen supercompensation has similar effects in children as in adults. Fat intake should be according to general health guidelines, with about 35% of energy coming from fat, with less than 10% coming from saturated fats. Protein intake should be higher than for non-athletic peers. An intake of about 1.4 g/ kg/d is advised.
Iron deficiency is a common problem in adolescents. Dietary iron intake and bio-availability should be optimized. Blood parameters should be monitored and corrected if necessary. Calcium intake of 1300 mg is recommended for children from 9-18 years to achieve net calcium balance. Athletes should be screened for low intakes of especially iron and calcium.
Even mild dehydration (as little as 1-2% body weight) should be avoided since it impairs performance. Dehydration has more profound effects in youth athletes than in adults. Adding flavor, sodium and carbohydrate to a rehydration solution improves voluntary fluid ingestion and will aid absorption. Young athletes should be encouraged to drink to compensate for sweat loss.
There is no evidence of growth retardation in athletics. Growth retardation has been shown in female gymnasts, but even in that population, catch-up growth was reported during periods of rest or decreased training.
Supplements should not be taken under the age of 18. In general, not much is known about long term health consequences of supplement use in youth. However, it is recognized that supplements are used by youth athletes. Care should be taken that when youth athletes insist on using supplements, knowledgeable health professionals assist in choosing the type, brand and dosage of supplements.
Fluid needs for training and competition in athletes
Hydration status affects performance. Different events have different fluid needs.
General guidelines for all events are to ensure euhydration by consuming about 500 ml of fluid with sodium or sodium containing foods 2 hours before exercise.
In the hours after exercise, 150% of water lost should be provided to adequately rehydrate. A scale can be used to estimate sweat losses.
Competition hydration plans should be practiced during training.
The main concern for sprints is that pre-race activities and warm-up will result in a sub-optimal hydration status. Also training in a warm environment or wearing heavy clothing can result in dehydration. There might be some advantage in commencing a race somewhat dehydrated, since this can influence power to weight ratio positively. However, no more than 2-3% body weight should be lost. A higher degree of dehydration will negatively impact performance.
Middle and long distance runners should always start their training and races euhydrated. Starting from about 10k, there is rationale for consuming drinks during exercise. This drink should not have high energy density or osmolality. General guidelines for fluid replacement will be meaningless, since individual sweat rate and sweat sodium content is vastly different.
In the jumping events, no clear effect of mild dehydration has been found. If hypohydration does not reduce muscle force production or power then jumping performance may be improved with hypohydration. However, systematic research is required to investigate this.
There is no rationale for throwers to commence their competition hypohydrated. Accuracy, but not speed, of cricket bowlers were worse after dehydration. Throwers should aim to stay euhydrated, but beware not to overdrink during the long hours on the track.
Multi-event athletes should aim to start their completion euhydrated and try to keep within 2% body weight loss during the day. Fluid can be ingested between attempts or between events. Athletes should be aware not to overdrink, so that body weight is gained during the day. Sodium should be ingested as well in the form of sodium containing fluids or in the form of sodium containing foods. Recovery of body water losses after the first day of a multi-event competition may be one of the recovery priorities for many of these athletes.
Fatigue and illness
IL-6 can have profound negative effects on performance, fatigue and sleep quality. Low glycogen and other training and life stressors can elevate IL-6. IL-6 can be the anti-inflammatory trigger.
Recommendations to keep immunity high include: maintain energy equilibrium, keep CHO stores high, have moderate amount of fat in the diet, stay wel hydrated. Use of vitamin C and γ-tocopherol is equivocal, with some positive findings. However, it should be noted that anti-oxidants might dampen the training adaptation.
In spite of many possible markers of overtraining, a good psychological test still seems to be the most accurate measure of overtraining.
Adequate nutrition before, during and after training and competition is a key element of maintaining health and to ward off early fatigue and possible immunosuppression. A period of immunosuppression after an intense exercise bout is inevitable and can last up to 72 hour. However, it can be attenuated by proper nutrition.
The cytokine IL-6 seems to play a central role in acquired immunity. IL-6 is considered the “switch” from innate to acquired immunity. IL-6 can only be active when bound to the receptors IL-6R and gp130. It is therefore important to not only look at levels of IL-6, but also at levels of IL-6R and gp130.
IL-6 seems to serve as an energy sensor: low glycogen levels prior to exercise elevate IL-6 compared to placebo controls and CHO feeding during exercise attenuates IL-6 release. When IL-6 was administered prior to exercise, it induced an increased sensation of psychological and physical fatigue, possibly through central mechanisms.
Ensuring adequate glycogen and delaying depletion of glycogen is clearly a key goal for athletic events.
Overtraining is defined as an accumulation of training stress and/or non-training stress, which results in long-term (weeks and months) decrement in performance. Overtraining also relates to an increased incidence of infections, persistent sore muscles and general malaise and disturbed sleep. The etiology of the syndrome is complex and
the existence has even been challenged. Chronic stress can cause elevated IL-6 levels, which in turn can cause a disturbed balance in T-helper cells. This will lead to increased susceptibility to viral infections.
At present, there is no clear guidance on the cause, the identification or the remedy of the overtraining syndrome.
Different deficiencies have an effect on fatigue and immune system. Energy deficiency can cause a reduction in memory T cells. Elevated fatty acid availability may decrease immune function by increasing the amount of prostaglandin. Too little fat in the diet can cause immunosuppression as well.
Often knowledge of athletes concerning sports nutrition is not good and very much influenced by the supplement industry. Advertorials are often seen as a good source of information. In general, the supplement industry is better in communicating their message than are scientists.
The science on supplements is very limited. Absence of efficiency ≠ absence of proof of efficiency.
Athletes should be warned against indiscriminate use of supplements. The risk of contamination of supplements with substances that are on the WADA list is very real. Some dishonest producers put substances like ephedrine in their supplements to make it work. Other supplements are cross-contaminated because doping substances have been produced in the same production line.
It is reassuring that only 4% of elite athletes buy supplements online. This is where most contaminated supplements are sold. However, buying supplements in a regular store is by no means a guarantee that the supplement is doping free.
Even a disclaimer on the label offers no guarantee. It should be concluded that there is no such thing as a risk-free supplement. However, risk can be minimized by buying from reputable manufacturers. Use only supplements with at least some scientific evidence. In Germany and The Netherlands, the doping authorities have made a list of checked product-batch combinations. This offers athletes the best risk reduction. Hopefully, other countries will implement a system alike.
It is recognized that because of limitations in research design it is very hard to prove if a strategy or supplement works. “No proven effect” is not the same as “proven no effect”. There might be an effect that cannot be detected by present research methodology.
Innovations in training
The “train low, compete high” paradigm of glycogen levels was challenged by a new study that show no benefit of training in low glycogen state 50% of the training-units in trained athletes in a real life setting instead of fixed amount of work with leg kicking. Although some genes involved in training adaptations were enhanced after training in the low glycogen state, this does not mean athletes should adopt the habit of training in low glycogen state. This would have deleterious effects on immune system, recovery of training and the ability to train hard and would be possible risk factor for overtraining.
Training in a low glycogen state is not recommended for strength training, with a proven negative effect on gene expression.
It was noted that in practice, many top athletes do their early morning run in the fasted state.
Athletes are advised to consume about 10 grams of protein in the early (<3h) phase of recovery to improve net protein balance. Some discussion took place about the role of muscle catabolism after exercise and that there might be some rationale for not dampening the catabolism as is done by adding extra protein. No effect of extra protein on muscle glycogen is to be expected when ample CHO is provided. The addition of protein in a CHO
drink during exercise remains equivocal. It seems that when enough carbohydrate is provided, the addition of protein is futile. There is no well accepted mechanism by which the added protein can have an ergogenic effect.
Athletes should have their blood iron parameters measured about 1 month before their training camp. In case of deficiency, iron stores can be replenished before take-off. No iron supplementation should be given without an indication of deficiency.
The anorexic effect of altitude can have a negative effect on energy balance. Strategies to improve energy intake include increasing meal frequency, and decrease protein intake. Protein is highly satiating and induces more thermogenesis than the other macronutrients. Therefore, low protein intake can enhance energy intake. Negative protein balance is worsened by an energy deficit. Increasing meal frequency is advised. Oxidative stress is enhanced in altitude training. There might be some rationale for the use of extra anti-oxidants. Foods that contain anti-oxidants are advised. The use of supplements remains controversial, since it might inhibit training adaptation, and act as pro-oxidant in high dosages. Athletes should not use bicarbonate at altitude, since it might induce acute mountain sickness. Altitude exposure induces higher fluid losses. This should be balanced by a higher fluid and sodium intake. The role of omega-3 fatty acids remains equivocal.
Nutrition for travel
Travel across time zones (jet-lag) can have a profound effect on sleep, digestion, well-being and performance.
It is easier to travel westbound than eastbound, since our biological rhythm in “free-running” conditions spans about 25 hours. Pharmacological approaches are not being recommended for athletes, emphasis should be laid on behavioural strategies. Athletes should strive to arrive in the new time zone well in advance of their event. Pre-adjustment to the new time zone can be commenced before departure by going to bed either early for eastbound flights or late for westbound flights. Light and exercise can have influence on the circadian rhythm.
The influence of diet remains equivocal. Adequate timing of meals, adjusted to the new time zone, can have an effect. At this time, timing seems much more important than macronutrient content of the meals.
Athletes are prone to dehydration because a lot of fluid is lost just by breathing the dry air in the airplane. An estimate of 15-20 cl per hour should be acceptable. Habitual coffee consumers can take coffee in moderation. Alcohol should be avoided. Athletes should be encouraged to bring their own food supplies to compensate for the menu provided by the airline that is often low in volume and fibre. Exposure to light or avoidance to light can be a powerful adjustment to the new time zone. Training can have effect for adjustment, but seems to be more powerful for phase delay (eastbound) than for phase advance (westbound).
Caffeine is often used, but the effects are ambivalent: it reduces daytime sleepiness, but also impairs recovery time. Sleeping agents are often advocated. Because the right timing of intake difficult, the advantages are equivocal.
Athletes possibly face several challenges at the destination of travel. Changed environmental factors, like heat or altitude, reduced or enhanced (all you can eat buffets) access to foods, eating from fastfood restaurants or other facilities not tailored to the needs of the athletes, reduced hygiene standards, all make it difficult for athletes to eat a healthy diet. Meal plans and timing should be organized in advance. Portable and non-perishable foods can be taken along to replace important items that otherwise would be missing. A broad spectrum, low dose multi-vitamin/mineral supplement can be given to compensate for restricted intake of nutrient rich foods.
As many as 60% of athletes who travel international y develop diarrhea. Athletic performance may be affected during the attack and for some time afterwards. Athletes should avoid high risk foods and avoid tap water, even for brushing teeth. Personal hygiene, especially washing hands before meals, is important to lower the risk of diarrhea. Treatment of diarrhea is symptomatic in most cases. Fluid and electrolyte should be replaced. A bland diet low in fat and avoiding dairy and alcohol is recommended. If the condition is severe or persists for more than 48 hours antibiotics may be required.
Well chosen foods will help athletes train hard, reduce risk of illness and injury, and achieve performance goals. General recommendations can be made, but these should be implemented on a case by case basis, according to the athlete’s stage of maturation, sex, periodisation phase, training program and competition goals.
All nutrition goals can be met by regular food choices. However, specific sports foods can be convenient around training to get the right amount and combination of nutrients.
Individualized eating and hydration plans for training and competition can help an athlete to reach nutrition goals. Always practice competition plans in training.
The science of sport nutrition is generally very limited in its capacity to show significant performance benefits. In general, differences of about 2 percent can be proven significantly different, while in real life a performance difference of 0,04% was the difference between 1st and 5th in the 2003 London Marathon.
Luckily, sport nutrition guidelines generally follow public health guidelines. It should therefore not be problem to get the guidelines endorsed by governmental bodies.
Good food choices will contribute to health, enjoyment of life and to success in athletics.
Persons using assistive technology may not be able to fully access information in this file. For assistance, e-mail firstname.lastname@example.org. Include the Web site and filename in your message. 4. SCREENING BASELINE VISIT 4.1 INTRODUCTION Consistent with the philosophy and design of a large study, screening activities performed during the Baseline Visits have been kept streamlined. Screening a
Brazilian Journal of Probability and Statistics (2001), 15, pp. 201–220. SURVIVAL ANALYSIS: PARAMETRICS TOSEMIPARAMETRICS TO PHARMACOGENOMICSPranab K. SenDepartments of Biostatistics and Statistics, University of North Carolinaat Chapel Hill, USA. Email: email@example.comSummarySurvival analysis with genesis in biometry and reliability analysis evolved withstatistical modeling and analysis o