Drinking guidelines for exercise: what evidence is there that athletes should drink "as much as tolerable", "to replace the weight lost during exercise" or "ad libitum"?

The most recent (1996) drinking guidelines of the American College of Sports Medicine (ACSM) propose that athletes should drink "as much as tolerable" during exercise. Since some individuals can tolerate rates of free water ingestion that exceed their rates of free water loss during exercise, this advice has caused some to overdrink leading to water retention, weight gain and, in a few, death from exercise-associated hyponatraemic encephalopathy. The new drinking guidelines of the International Olympic Committee (IOC), recently re-published in this Journal, continue to argue that athletes must drink enough to replace all their weight lost during exercise and to ingest sodium chloride since sodium is "the electrolyte most critical to performance and health". In this rebuttal to that Consensus Document, I argue that these new guidelines, like their predecessors, lack an adequate, scientifically proven evidence base. Nor have they been properly evaluated in appropriately controlled, randomized, prospective clinical trials. In particular, these new guidelines provide erroneous recommendations on five topics. If novel universal guidelines for fluid ingestion during exercise are to be promulgated by important international bodies including the IOC, they should first be properly evaluated in appropriately controlled, randomized, prospective clinical trials conducted under environmental and other conditions that match those found in "out-of-doors" exercise. This, and the potential influence of commercial interests on scientific independence and objectivity, are the two most important lessons to be learned from the premature adoption of those 1996 ACSM drinking guidelines that are not evidence-based. These concerns need to be addressed before the novel IOC guidelines are accepted uncritically. Otherwise the predictable consequences of the premature adoption of the 1996 ACSM guidelines will be repeated.     

Influence of pre-exercise glucose ingestion of two concentrations on paraplegic athletes

In this study, we assessed the influence that pre-exercise glucose ingestion of two concentrations has on the physiological responses of paraplegic athletes. Eight men with paraplegia ingested a drink containing 4% (low) or 11% (high) carbohydrate in a randomized double-blind crossover design, 20 min before exercise. The participants performed wheelchair exercise at 65% of peak oxygen uptake for 1 h followed by a 20 min performance test. During both trials, the physiological responses were similar and indicated steady-state exercise. At the onset of exercise, blood glucose concentrations in both trials increased after carbohydrate ingestion (P < 0.05) before returning to resting values after 20 min of exercise and there were no differences between trials. Free fatty acid concentrations increased from rest to 1 h of exercise in both trials, with a greater increase during the low carbohydrate trial that led to a difference in free fatty acids between trials at the end of the 1 h tests (P < 0.05). There was a tendency for the performance distances and power outputs achieved during the high carbohydrate trial to be greater than those achieved during the low carbohydrate trial (P= 0.08). In conclusion, when paraplegic athletes ingested low and high carbohydrate drinks before exercise, the decline in blood glucose concentrations was similar. The tendency for higher blood glucose concentrations, respiratory exchange ratios and power outputs and lower free fatty acid concentrations (P < 0.05) during the high carbohydrate trial suggests that a higher concentration of carbohydrate in a sports drink might be a better choice for paraplegic athletes.     

Fluid and electrolyte needs for training, competition, and recovery

Fluids and electrolytes (sodium) are consumed by athletes, or recommended to athletes, for a number of reasons, before, during, and after exercise. These reasons are generally to sustain total body water, as deficits (hypohydration) will increase cardiovascular and thermal strain and degrade aerobic performance. Vigorous exercise and warm/hot weather induce sweat production, which contains both water and electrolytes. Daily water (4-10 L) and sodium (3500-7000 mg) losses in active athletes during hot weather exposure can induce water and electrolyte deficits. Both water and sodium need to be replaced to re-establish "normal" total body water (euhydration). This replacement can be by normal eating and drinking practices if there is no urgency for recovery. But if rapid recovery (<24 h) is desired or severe hypohydration (>5% body mass) is encountered, aggressive drinking of fluids and consuming electrolytes should be encouraged to facilitate recovery for subsequent competition.     

CUBA前八名部分运动员竞赛状态焦虑影响因素的研究

运用运动心理学有关理论对CUBA前八部分运动员竞赛状态焦虑的影响因素进行问卷调查。结果表明 :各因素的影响程度由大到小依次排列为“挫折”、“冲突”、“失误”、“比赛”、“自我概念”、“限制”、“实力”、“身体状态”。与此同时 ,针对这一特点提出高校教练员在赛中、赛前所要注意心理调控艺术及日常加强运动员心理适应能力训练的对策。     

老年运动补液的生理学机制研究

研究目的:为了解老年运动补液的生理学机制,强调补液在老年运动中所起的重要作用。研究方法:利用文献资料、逻辑分析等研究方法对以往研究进行归纳、演绎与分析。研究结果和结论:以经济、安全、有效为原则的最优补液是白开水,其次为蜂蜜水;而在经济条件和观念接受程度允许的前提下,运动饮料的补充效果最佳,并建议老年人慎用能量饮料;同时,老年运动补液要遵循"一总三分"原则,即要在"少量多次"总原则的基础上,针对运动前、中、后的不同时段分别按照,"未动即补"、"未渴及补"和"止动继补"的3个分原则进行科学合理的补液,以达到降低运动风险,提高锻炼效果的最终目的。     

The effects of substrate and fluid provision on thermoregulatory and metabolic responses to prolonged exercise in a hot environment

A high ambient temperature reduces the capacity to perform prolonged exercise. Total carbohydrate oxidation is less, and thus glycogen depletion is not limiting. Fluid ingestion in the heat should, therefore, focus on maintenance of hydration status rather than on substrate provision. Six healthy males cycled to exhaustion at 60% of maximum oxygen consumption (VO 2max ) with no drink, ingestion of a 15% carbohydrate-electrolyte drink (1.45 - 0.29 litres) or ingestion of a 2% carbohydrate-electrolyte drink (3.12 - 0.47 litres). The ambient temperature was 30.2 - 0.6°C (mean - s ), with a relative humidity of 71 - 1% and an air speed of approximately 0.7 m.s -1 on all trials. Weighted mean skin temperature, rectal temperature and heart rate were recorded and venous samples drawn for determination of plasma volume changes, blood metabolites, serum electrolytes and osmolality. Expired gas was collected to estimate rates of fuel oxidation. Exercise capacity was significantly ( P ? 0.05) different in all trials. The median (range) time to exhaustion was 70.9 min (39.4-97.4 min) in the no-drink trial, 84.0 min (62.7-145 min) in the 15% carbohydrate trial and 118 min (82.6-168 min) in the 2% carbohydrate trial. The 15% carbohydrate drink resulted in significantly ( P ? 0.05) elevated blood glucose and total carbohydrate oxidation compared with the no-drink trial. The 2% carbohydrate drink restored plasma volume to pre-exercise values by the end of exercise. No differences were observed in other thermoregulatory or cardiorespiratory responses between trials. These results suggest that fluid replacement with a large volume of a dilute carbohydrate drink is beneficial during exercise in the heat, but the precise mechanisms for the improved exercise capacity are unclear.     

Fluid ingestion and exercise hyperthermia: Implications for performance,thermoregulation, metabolism and the development of fatigue

The development of fatigue during exercise and the subsequent onset of exhaustion occur earlier in the heat than in cooler environments. The underlying mechanisms responsible for the premature development of fatigue in the heat have yet to be clearly identified. However, the proposed mechanisms include metabolic, cardiovascular and central nervous system perturbations, together with an elevated core temperature. Fluid ingestion is one of three strategies that have been shown to be successful in enhancing the performance of endurance exercise in the heat, with the other interventions being precooling and acclimatization. However, like the development of fatigue in the heat, the mechanisms by which fluid ingestion allows for improved exercise performance remain unclear. We propose that fluid ingestion enhances exercise performance in the heat by increasing the heat storage capacity of the body. We suggest that the thermoregulatory, metabolic and cardiovascular alterations that occur as a result of this increased heat storage capacity contribute to performance enhancement when fluid is ingested during exercise heat stress.     

Fluid ingestion and exercise hyperthermia: implications for performance, thermoregulation, metabolism and the development of fatigue

The development of fatigue during exercise and the subsequent onset of exhaustion occur earlier in the heat than in cooler environments. The underlying mechanisms responsible for the premature development of fatigue in the heat have yet to be clearly identified. However, the proposed mechanisms include metabolic, cardiovascular and central nervous system perturbations, together with an elevated core temperature. Fluid ingestion is one of three strategies that have been shown to be successful in enhancing the performance of endurance exercise in the heat, with the other interventions being precooling and acclimatization. However, like the development of fatigue in the heat, the mechanisms by which fluid ingestion allows for improved exercise performance remain unclear. We propose that fluid ingestion enhances exercise performance in the heat by increasing the heat storage capacity of the body. We suggest that the thermoregulatory, metabolic and cardiovascular alterations that occur as a result of this increased heat storage capacity contribute to performance enhancement when fluid is ingested during exercise heat stress.     

Ramadan fasting and the goals of sports nutrition around exercise

Ramadan fasting, involving abstinence from fluid and food from sunrise to sundown, results in prolonged periods without nutrient intake and inflexibility with the timing of eating and drinking over the day. Dietary choices may also change due to special eating rituals. Although nutrition guidelines are specific to the sport, to the periodized training and competition calendar, and to the individual, many promote the consumption of carbohydrate and fluid before and during exercise, and consumption of protein, carbohydrate, and fluids soon after the session is completed. Failing to meet overall nutritional needs, or to provide specific nutritional support to a session of exercise, is likely to impair acute performance and reduce the effectiveness of training or recovery. Muslim athletes who fast during Ramadan should use overnight opportunities to consume foods and drinks that can supply the nutrients needed to promote performance, adaptation, and recovery in their sports. Because of the benefits of being able to consume at least some of these nutrients before, during or after an exercise session, the schedule of exercise should be shifted where possible to the beginning or end of the day, or during the evening when some nutritional support can be provided.     

权利抑或特权：奥运会参赛权法律性质辨析——平昌冬奥会俄罗斯运动员及辅助人员体育仲裁案例述评

俄罗斯国家奥委会遭国际奥委会(IOC)暂停成员资格,导致很多无辜运动员无法参加平昌冬奥会,国际体育仲裁院(CAS)平昌冬奥会特别仲裁机构处理的数起案件均涉及俄罗斯运动员的参赛资格问题。俄罗斯运动员在仲裁程序中败诉的主要原因是《奥林匹克宪章》规定:奥运会是IOC的专属财产、任何人不拥有参加奥运会的所谓权利、IOC可以拒绝任何人参赛而无须出具理由。IOC运用对奥运会的专属权利,无正当合理理由拒绝符合参赛条件的俄罗斯清白运动员参赛,有构成垄断的嫌疑。符合参赛选拔条件、且不存在禁止性限制因素(如兴奋剂禁赛处罚在身)的清白运动员参加奥运会,是他们的权利,而不是IOC赋予他们的特权。切实保护运动员参赛权利是各国法院和国际体育仲裁院在处理体育参赛资格案件中的一贯立场,平昌冬奥会仲裁庭的实践过于保守。奥林匹克运动体育善治的改革,要求必须对《奥林匹克宪章》进行修改,最大限度地保护运动员的参赛权利,实现《运动员权利与义务宣言》的宗旨。     

The effects of substrate and fluid provision on thermoregulatory and metabolic responses to prolonged exercise in a hot environment

A high ambient temperature reduces the capacity to perform prolonged exercise. Total carbohydrate oxidation is less, and thus glycogen depletion is not limiting. Fluid ingestion in the heat should, therefore, focus on maintenance of hydration status rather than on substrate provision. Six healthy males cycled to exhaustion at 60% of maximum oxygen consumption (VO2max) with no drink, ingestion of a 15% carbohydrate-electrolyte drink (1.45+/-0.29 litres) or ingestion of a 2% carbohydrate-electrolyte drink (3.12+/-0.47 litres). The ambient temperature was 30.2+/-0.6 degrees C (mean +/- s), with a relative humidity of 71+/-1% and an air speed of approximately 0.7 m x s(-1) on all trials. Weighted mean skin temperature, rectal temperature and heart rate were recorded and venous samples drawn for determination of plasma volume changes, blood metabolites, serum electrolytes and osmolality. Expired gas was collected to estimate rates of fuel oxidation. Exercise capacity was significantly (P < 0.05) different in all trials. The median (range) time to exhaustion was 70.9 min (39.4-97.4 min) in the no-drink trial, 84.0 min (62.7-145 min) in the 15% carbohydrate trial and 118 min (82.6-168 min) in the 2% carbohydrate trial. The 15% carbohydrate drink resulted in significantly (P < 0.05) elevated blood glucose and total carbohydrate oxidation compared with the no-drink trial. The 2% carbohydrate drink restored plasma volume to pre-exercise values by the end of exercise. No differences were observed in other thermoregulatory or cardiorespiratory responses between trials. These results suggest that fluid replacement with a large volume of a dilute carbohydrate drink is beneficial during exercise in the heat, but the precise mechanisms for the improved exercise capacity are unclear.     

Differences in self-regulatory skills among talented athletes: The significance of competitive level and type of sport

Abstract

Research has shown that talented athletes outscore their mainstream peers on the basis of self-regulation. Although valuable, this does not tell us more about the distinction between good athletes and the best, which is a prerequisite in talent development. Therefore, we examined the self-regulatory skills of 222 male and female talented athletes aged 12–16 years as a function of competitive sport level (junior international or junior national athletes) and type of sport (individual or team sports). Multivariate analyses of covariance in combination with a discriminant function analysis revealed that “reflection” distinguishes between athletes at the highest levels of excellence. Furthermore, athletes playing individual sports had higher scores on “planning” and “effort” than team sport athletes, highlighting the importance of differences between types of sport. In conclusion, we emphasize the importance of reflection as a self-regulatory skill. Reflection facilitates the development of sport-specific characteristics, which may vary by type of sport. This means that an advanced sense of reflection may help talented athletes to acquire desirable characteristics during their “talent” years to ultimately reach adult elite levels of competition.     

Nutritional strategies for promoting fat utilization and delaying the onset of fatigue during prolonged exercise

Carbohydrate ingestion before and during endurance exercise delays the onset of fatigue (reduced power output). Therefore, endurance athletes are recommended to ingest diets high in carbohydrate (70% of total energy) during competition and training. However, increasing the availability of plasma free fatty acids has been shown to slow the rate of muscle and liver glycogen depletion by promoting the utilization of fat. Ingested fat, in the form of long-chain (C 16-22 ) triacylglycerols, is largely unavailable during acute exercise, but medium-chain (C 8-10 ) triacylglycerols are rapidly absorbed and oxidized. We have shown that the ingestion of medium-chain triacylglycerols in combination with carbohydrate spares muscle carbohydrate stores during 2 h of submaximal (< 70% VO 2 peak) cycling exercise, and improves 40 km time-trial performance. These data suggest that by combining carbohydrate and medium-chain triacylglycerols as a pre-exercise supplement and as a nutritional supplement during exercise, fat oxidation will be enhanced, and endogenous carbohydrate will be spared. We have also examined the chronic metabolic adaptations and effects on substrate utilization and endurance performance when athletes ingest a diet that is high in fat (> 70% by energy). Dietary fat adaptation for a period of at least 2-4 weeks has resulted in a nearly two-fold increase in resistance to fatigue during prolonged, low- to moderate-intensity cycling (< 70% VO 2 peak). Moreover, preliminary studies suggest that mean cycling 20 km time-trial performance following prolonged submaximal exercise is enhanced by 80 s after dietary fat adaptation and 3 days of carbohydrate loading. Thus the relative contribution of fuel substrate to prolonged endurance activity may be modified by training, pre-exercise feeding, habitual diet, or by artificially altering the hormonal milieu or the availability of circulating fuels. The time course and dose-response of these effects on maximizing the oxidative contribution of fat for exercise metabolism and in exercise performance have not been systematically studied during moderate- to high-intensity exercise in humans.     

Energy availability in athletes

This review updates and complements the review of energy balance and body composition in the Proceedings of the 2003 IOC Consensus Conference on Sports Nutrition. It argues that the concept of energy availability is more useful than the concept of energy balance for managing the diets of athletes. It then summarizes recent reports of the existence, aetiologies, and clinical consequences of low energy availability in athletes. This is followed by a review of recent research on the failure of appetite to increase ad libitum energy intake in compensation for exercise energy expenditure. The review closes by summarizing the implications of this research for managing the diets of athletes.     

体育仲裁院（CAS）“奥委会规则”裁决述评

为了更进一步打击服用兴奋剂的行为,保持奥林匹克运动的纯洁性,国际奥委会执行委员会根据《奥林匹克宪章》的规定制定了＂奥委会规则＂。美国奥委会和国际奥委会之间因为服用兴奋剂禁赛处罚而不能在一段时间内参加奥运会的规则争议提交体育仲裁院（CAS）仲裁,CAS裁决运动员被禁赛期满后就有资格参加奥运会,否则就是对运动员的双重惩罚,违反基本的＂一事不再理＂原则,国际奥委会应对有关规则进行修改。该裁决维护了运动员参加奥运会的基本权益,也有利于反兴奋剂规则的全球统一化。     

The influence of serial feeding of drinks at different temperatures on thermoregulatory responses during cycling

In this study, we examined thermoregulatory responses to ingestion of separate aliquots of drinks at different temperatures during low-intensity exercise in conditions of moderate heat stress. Eight men cycled at 50% (s = 3) of their peak oxygen uptake (VO2peak) for 90 min (dry bulb temperature: 25.3 degrees C, s = 0.5; relative humidity: 60%, s = 5). Four 400-ml aliquots of flavoured water at 10 degrees C (cold), 37 degrees C (warm) or 50 degrees C (hot) were ingested after 30, 45, 60, and 75 min of exercise. Immediately after the 90 min of exercise, participants cycled at 95% VO2peak to exhaustion to assess exercise capacity. There were no differences between trials in rectal temperature at the end of the 90 min of exercise (cold: 38.11 degrees C, s = 0.30; warm: 38.10 degrees C, s = 0.33; hot: 38.21 degrees C, s = 0.30; P = 0.765). Mean skin temperature between 30 and 90 min tended to be influenced by drink temperature (cold: 34.49 degrees C, s = 0.64; warm: 34.53 degrees C, s = 0.69; hot: 34.71 degrees C, s = 0.48; P = 0.091). Mean heart rate from 30 to 90 min was higher in the hot trial (129 beats . min(-1), s = 7; P < 0.05) than on the cold (124 beats . min(-1), s = 9) and warm trials (126 beats . min(-1), s = 8). Ratings of thermal sensation were higher on the hot trial than on the cold trial at 35 and 50 min (P < 0.05). Exercise capacity was similar between trials (P = 0.963). The heat load and debt induced by periodic drinking resulted in similar body temperatures during low-intensity exercise in conditions of moderate heat stress due to appropriate thermoregulatory reflexes.     

A Response to Petrie's Note on Statistical Analysis of Attitude Scale Scores

Abstract

On four separate occasions resting, fasted adults ingested 10 oz of a cola-flavored soft drink containing either 0, 22.5, 35, or 150 mg caffeine. Heart rate, blood pressure, and plasma free fatty acid (FFA) and glucose values were obtained before and at 15, 30, 60, 90, 120, 180 and 360 min after the feeding. All urine was collected during the 6 hr following ingestion and was later assayed for total catecholamine (CA) content. Urine volume and total CA excretion increased as the amount of caffeine ingested increased. Only the 150 mg solution resulted in significant increases (over control) in 6 hr CA output, or FFA concentration and mean arterial pressure early after the feeding. The 150 mg drink also maintained blood glucose at pre–ingestion levels for the entire course of the experiment. The moderate increase in circulating FFA following ingestion of a commercially available cola (22 to 35 mg caffeine/bottle) is similar to the change seen in resting, nonfed subjects. These data suggest that ingestion of caffeine in an amount typically found in a single bottle of cola drink does not increase factors associated with coronary risk, nor will it have a positive influence on parameters associated with enhanced athletic performance, should those same changes occur during exercise.     

Effect of carbohydrate ingestion during cycling exercise on affective valence and activation in recreational exercisers

Carbohydrate (CHO) ingestion enhances “feel-good” responses during acute exercise but no study has examined the effect of regular ingestion of CHO on affective valence. We investigated the effect of CHO ingestion on perceptual responses and perceived work intensity of individual exercise sessions throughout a 10-week cycling (“spin”) exercise intervention. We also assessed whether any changes in affect and/or perceived work intensity would influence health and fitness parameters. Twelve recreational exercisers (46 ± 9 years; nine females and three males) were randomly allocated to either CHO (7.5% CHO; 5 mL · kg^?1 per exercise session; n = 6; CHO) or placebo (0% CHO, taste- and volume-matched solution; n = 6; PLA) groups. Participants exercised 2 × 45-min per week, over a 10-week intervention period. Perceptual measures of exertion (RPE), affect (feeling scale, FS) and activation (felt arousal scale, FAS) were assessed after each exercise session. The FAS ratings increased over time in CHO but decreased throughout the intervention in PLA (P = 0.03). There were no differences in heart rate (P = 0.70), RPE (P = 0.05) and FS (P = 0.84) between trials. Furthermore, no changes in health and fitness parameters were observed over time or between groups. CHO ingestion enhanced ratings of activation in recreational exercisers throughout a 10-week cycling intervention.     

The demands of the extra-time period of soccer: A systematic review

ObjectiveSoccer match-play is typically contested over 90 min; however, in some cup and tournament scenarios, when matches are tied, they proceed to an additional 30 min, which is termed “extra-time” (ET). This systematic review sought to appraise the literature available on 120-min of soccer-specific exercise, with a view to identifying practical recommendations and future research opportunities.MethodsThe review was conducted according to the PRISMA guidelines. Independent researchers performed a systematic search of PubMed, CINAHL, and PsycINFO in May 2019, with the following keywords entered in various combinations: “soccer”, “football”, “extra-time”, “extra time”, “extratime”, “120 minutes”, “120 min”, “additional 30 minutes”, and “additional 30 min”.ResultsThe search yielded an initial 73 articles. Following the screening process, 11 articles were accepted for analyses. Articles were subsequently organized into the following 5 categories: movement demands of ET, performance responses to ET, physiological and neuromuscular response during ET, nutritional interventions, and recovery and ET. The results highlighted that during competitive match-play, players cover 5%–12% less distance relative to match duration (i.e., meters per minute) during ET compared to the preceding 90 min. Reductions in technical performance (i.e., shot speed, number of passes and dribbles) were also observed during ET. Additionally, carbohydrate provision may attenuate and improve dribbling performance during ET. Moreover, objective and subjective measures of recovery may be further compromised following ET when compared to 90 min.ConclusionAdditional investigations are warranted to further substantiate these findings and identify interventions to improve performance during ET.     

Nutritional needs of elite endurance athletes. Part I: Carbohydrate and fluid requirements

Abstract

Both carbohydrate depletion and dehydration have been shown to decrease performance whilst severe dehydration can also cause adverse health effects. Therefore carbohydrate and fluid requirements are increased with exercise. Ingestion of 200–300?g of CHO 3–4?h prior to exercise is an effective strategy in order to meet daily CHO demands and increase CHO availability during the subsequent exercise period. There is little evidence that CHO during the hour immediately prior to exercise has adverse effects such as rebound hypoglycaemia. CHO ingestion during exercise has been shown to improve performance as measured by enhanced work output or decreased exercise time to complete a fixed amount of work. Recent studies have demonstrated that exogenous CHO oxidation rates can be increased by ingesting combinations of CHO that use different intestinal CHO transporters. After exercise maximal muscle glycogen re-synthesis rates can be achieved by ingesting CHO at a rate of ～1.2?g/kg/h, in relatively frequent (e.g., 15–30?min) intervals for up to 5?h following exercise. Protein amino acid mixtures may increase glycogen synthesis further but only if relatively small amounts of CHO are ingested.

Hypohydration and hyperthermia alone have negative effects on performance but their combination is particularly serious, both in terms of performance and health. Dehydration can be prevented by fluid ingestion pre exercise and during exercise. Because of large individual differences it is difficult to individualise the advice. Perhaps the best guidance for athletes is to weigh themselves to assess fluid losses during training and racing and limit weight losses to 1% during exercise lasting longer than 1.5?h. Excessive fluid intake has been associated with hyponatremia. Post exercise the volume of fluid ingested and sodium intake are important determinants of rehydration.