Synovial reaction and concentrations of proteoglycan fragments in joint fluid after intraarticular knee injuries

In patients with pathology to cruciate ligaments, menisci and cartilage and in some patients with symptomatic knees without gross intraarticular changes, proteoglycan fragment concentrations in joint fluid and inflammatory reaction of the synovium were related to the cartilage condition. There was a weak positive correlation between increased concentrations of proteoglycan fragments in joint fluid and the degree of cartilage degeneration, indicating higher concentrations in knees with more advanced cartilage destruction, but there was no correlation to the synovial reaction at histological inspection. However, in most knees the synovial tissue was infiltrated by inflammatory cells. Symptomatic knees free from gross intraarticular pathology showed similar synovial changes and concentrations of proteoglycan fragments in joint fluid as knees with intraarticular pathology and obvious cartilage degeneration. The complex process of proteoglycan synthesis, release, degradation, and clearance from joint fluid apparently caused the weak or absent correlations between this marker protein and the degree of synovitis and arthrosis stage.     

The effect of formoterol inhalation on endurance performance in hypobaric conditions

INTRODUCTION: Inhaled beta2-agonists are important therapeutic agents for the treatment of exercise-induced asthma in athletes but are restricted by international antidoping regulations. PURPOSE: To investigate whether 18 mug of inhaled formoterol affects endurance performance during running at high altitudes until exhaustion among 20 nonasthmatic male athletes aged 21-35 yr. METHODS:: In a randomized, double-blind, placebo-controlled crossover study, the athletes performed one screening test and two similar performance tests. Each performance test consisted of 20 min of warm-up and a running test until exhaustion, which lasted 210-300 s in hypobaric conditions equal to 2000 m above sea level. Maximal oxygen consumption (VO2max) and peak ventilation (VEpeak) were measured during running, and pulmonary function was measured before and after exercise. The screening test was used to determine running speed on days 2 and 3, with inhaled formoterol or placebo in a randomized manner before exercise. VO2, VE, arterial oxyhemoglobin saturation (SPO2), and heart rate (HR) were measured during exercise, and maximum plasma lactate concentration was measured after exercise. RESULTS: Inhaled formoterol did not improve running time to exhaustion, VO2, VE, SPO2, or HR (P > 0.05) in hypobaric conditions compared with placebo, although formoterol significantly improved lung function (FEV1 and FEF50) 15 and 30 min before exercise and 3, 6, 10, and 15 min after exercise. CONCLUSIONS: Inhaled formoterol did not improve endurance performance in healthy nonasthmatic athletes at hypobaric conditions equal to 2000 m above sea level. Inhaled formoterol can thus be used by asthmatic athletes in sports under extreme conditions.     

Antioxidant restriction and oxidative stress in short-duration exhaustive exercise

PURPOSE: To determine the effect of dietary antioxidant restriction on oxidative stress, antioxidant defenses, and exercise performance in athletes. Oxidative stress has been shown to increase during exercise. To alleviate oxidative stress, a high intake of antioxidant rich foods or supplements may be required in trained athletes. METHODS: Plasma oxidative stress and antioxidant defenses were examined in 17 trained athletes who underwent two separate exercise tests. Before the initial exercise test participants followed their habitual (high) antioxidant (H-AO) diets. Then they followed a 2-wk restricted-antioxidant (R-AO) diet before the second exercise test. Blood was taken at rest, after submaximal and high-intensity exhaustive exercise, and after 1 h of recovery. RESULTS: The R-AO diet induced a threefold reduction in antioxidant intake when compared with habitual-antioxidant (H-AO) diets. F(2)-isoprostane concentration (marker of oxidative stress) was significantly higher after submaximal exercise (38%), exhaustion (45%), and 1 h of recovery (31%) when following the R-AO diet compared with the H-AO diet. Rate of perceived exertion was increased on the R-AO diet whilst exercise time to exhaustion was not affected. Total antioxidant capacity and circulating antioxidant concentrations, although not significantly different, tended to be lower when following the R-AO diet. CONCLUSION: Athletes regularly participating in up to 40 min of acute high-intensity exercise may require higher intakes of exogenous antioxidants to defend against increased oxidative stress during exercise, which can be met through an adequate intake of high-antioxidant foods. Thus, there seems no valid reason to recommend antioxidant supplements to athletes participating in acute high-intensity exercise events up to 40 min in duration, except in those known to be consuming a low-antioxidant diet for prolonged periods.     

Caffeine ingestion during exercise to exhaustion in elite distance runners. Revision.

Caffeine is currently being used as an ergogenic aid by many athletes. The aim of this research was to determine whether a large dose of caffeine (10 mg.kg-1) taken immediately prior to the start of endurance exercise would have the desired effect of increasing endurance performance. Six males, who were not habitual caffeine users and who had performed at least two marathons, served as subjects in this experiment. They ran on a treadmill at a speed which had been calculated would elicit 75% of their VO2max for 45 minutes, after which time the speed was increased by two miles per hour till exhaustion. During the caffeine trial the athletes ran further than either the control or placebo conditions (p less than 0.05). Blood lactate values did not change across condition except for the final collection period which was significantly higher in the caffeine trial (p less than 0.05). As expected there was a significant time effect in all conditions (p less than 0.0001). Blood triglycerides after the start of the test were always higher in the caffeine condition but this was only significant at the 45 minute and end of exercise collection periods (p less than 0.05). The results suggest that endurance athletes can use caffeine just prior to exercise rather than one to three hours prior to exercise.     

The effect of BCAA supplementation upon the immune response of triathletes

INTRODUCTION: Intense long-duration exercise could lead to immune suppression through a decrease in the circulating level of plasma glutamine. The decrease in plasma glutamine concentration as a consequence of intense long-duration exercise was reversed, in some cases, by supplementing the diet of the athletes with branched-chain amino acids (BCAA). To better address this question, we have evaluated some blood parameters (lymphocyte proliferation, the level of plasma cytokines, plasma glutamine concentration, and in vitro production of cytokines by peripheral blood lymphocytes) before and after the S?o Paulo International Triathlon, as well as the incidence of symptoms of infections between the groups. METHODS: Twelve elite male triathletes of mean age 25.5 +/- 3.2 yr (ranging from 21.4 to 30.1 yr), weighing 74.16 +/- 3.9 kg, swam 1.5 km, cycled 40 km, and ran 10 km (Olympic triathlon) in the S?o Paulo International Triathlon held in April 1997 and April 1998. In both events, six athletes received BCAA and the others, placebo. RESULTs: Athletes from the BCAA group (BG) presented the same levels of plasma glutamine, before and after the trial, whereas those from the placebo group showed a reduction of 22.8% in plasma glutamine concentration after the competition. Changes in the proliferative response of peripheral blood lymphocytes were accompanied by a reduction in IL-1 production after exercise (22.2%), which was reversed by BCAA supplementation (20.3%), without changes in IL-2 production. DISCUSSION: The data obtained show that BCAA supplementation can reverse the reduction in serum glutamine concentration observed after prolonged intense exercise such as an Olympic triathlon. The decrease in plasma glutamine concentration is paralleled by an increased incidence of symptoms of infections that results in augmented proliferative response of lymphocytes cultivated in the absence of mitogens. The prevention of the lowering of plasma glutamine concentration allows an increased response of lymphocytes to ConA and LPS, as well as an increased production of IL-1 and 2, TNF-alpha, and IFN-gamma, possibly linked to the lower incidence of symptoms of infection (33.84%) reported by the supplemented athletes.     

运动员在热环境训练时补充猕猴桃饮料效果的研究

<正> 运动员在热环境训练时,由于体内代谢和外界热环境的综合影响,可使机体受热致体温增高。外界气温接近人体皮肤温度时,排汗成为散热的主要途径。但大量排汗可引起身体脱水,血容量减少,并加重心脏血管和肾脏的负担。伴随出汗,体内无机盐和维生素的丢失,还能导致代谢紊乱,运动能力下降,严     

Utility of delayed gadolinium-enhanced MRI (dGEMRIC) for qualitative evaluation of articular cartilage of patellofemoral joint

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) was used for the measurement of relative proteoglycan depletion of articular cartilage in the patellofemoral (PF) joint following a proprietary protocol, which was compared with the X-ray images, proton density weighted MR images (PDWI) and arthroscopic findings. The study examined 30 knees. The ages ranged from 16 to 74 (average 40.3) years. The Gd-DTPA^2–containing contrast medium was used in a single dose. The subjects were made to exercise the knee joint for 10 min; and MR images were taken 2 h after intravenous injection of contrast medium. T1-calculated images were produced and the region of interest (ROI) was set as follows. (1) ROI1: entire articular cartilage in a slice through the center of the patella. (2) ROI2: low signal region in T1-calculated images, which were set in a blind fashion by two observers. (3) ROI3: articular cartilage on one side that includes ROI2 where low signal region were detected (medial or lateral). ROI3 was set to examine the contrast of ROI2 with surrounding articular cartilage. The average T1 values of ROI1 was 393.5±33.6 ms for radiographic grade 0 and 361.3±11.1 ms for grade I, which showed a significant difference (P=0.036). The T1 value of ROI2 was 351.6±28.2 ms for grade I, 361.9±38.3 ms for grade II, 362.1±67.7 ms for grade III, and 297.8±54.1 ms for grade IV according to arthroscopic Outerbridge classification. All cases, that demonstrated decrease of T1 values on dGEMRIC (ROI2), showed abnormal arthroscopic or direct viewing findings. The ratio (ROI3/ROI2) in cases of only slight damage classified as Outerbridge grade I (6 cases) was an average of 1.04±0.02 and was 1.0 or greater in all cases, thereby indicating well-defined contrast with the surrounding cartilage. The diagnosis of damage in articular cartilage was possible in all 16 cases with radiographic K–L grade I on dGEMRIC, while the intensity changes were not found in 10 of 16 cases on PDWI. The dGEMRIC with a single-dose would be useful on a diagnosis of the area demonstrating early relative proteoglycan depletion in the articular cartilage of the PF joint prior to any discernible changes in the subchondral bone on X-ray images and exceeds to plain MR images for examining deterioration of articular cartilage.     

Effect of carbohydrate ingestion on exercise endurance and metabolism after a 1-day fast

Fasting before an exercise event has been demonstrated to decrease endurance. The purpose of this study was to investigate whether this decrement in performance after fasting could be reversed by ingestion of a carbohydrate solution before and during exercise. Nine fit male subjects ran to exhaustion at approximately 70% VO2max in two counterbalanced trials. The subjects were fasted for 21 h before both trials, and the trials were arranged so that the subjects ingested either a carbohydrate (CHO) or placebo (PL) solution. Although ratings of perceived exertion were significantly lower in the CHO trial, there were no differences in endurance time to exhaustion in the two trials (102 +/- 8 min in the PL trial and 106 +/- 8 min in the CHO trial). There were no differences between trials for the VO2, heart rate, and blood lactate concentrations. As expected, the blood glucose and insulin concentrations were higher in the CHO trial. The respiratory exchange ratio was significantly higher in the CHO trial at 40 min of exercise and tended to be higher at all other times, suggesting a greater reliance on carbohydrate and less on fat as an energy source. This seemed to be confirmed by the significantly lower plasma glycerol concentration, which suggested less fat mobilization in the CHO trial. Ingestion of a glucose polymer solution increased carbohydrate utilization in fasted subjects, but exercise performance was not improved.     

内侧副韧带切断合并半月板部分切除对大鼠膝关节软骨、滑膜和细胞因子的影响

目的:观察内侧副韧带切断合并半月板部分切除对大鼠膝关节软骨、滑膜和关节液中细胞因子的影响。方法:20只SD大鼠,行内侧副韧带切断和内侧半月板部分切除术,分别在术后第1、2、3、4和5周各处死4只大鼠并取材;另备4只作为正常对照。组织学观察其关节软骨和滑膜的变化,酶联免疫吸附法(ELISA)测定关节液中细胞因子白细胞介素-1β(IL-1β)和肿瘤坏死因子-α(TNF-α)表达。结果:膝关节内侧副韧带切断和部分半月板切除后,大鼠关节液中IL-1β和TNF-α表达显著增高,TNF-α在术后第1周时、IL-1β在术后第2周时达到峰值,然后逐渐下降,第5周时仍显著高于正常对照水平。术后第1周,关节软骨丢失,软骨层变薄;软骨细胞减少,排列层次紊乱,有簇聚现象;蛋白多糖分泌减少,表面的软骨组织甲苯胺蓝染色失染。第2周,软骨继续退变,表面软骨纤维化,软骨下骨硬化,部分侵入软骨层,蛋白多糖进一步丢失,甲苯胺蓝染色失染严重。从第3周开始,正常的软骨细胞基本消失,呈纤维样变,软骨下骨硬化;髓腔融合、开放、纤维化,呈现晚期骨性关节炎的改变。滑膜细胞从术后第1周开始增生,炎细胞浸润;第2周滑膜炎症加重,并有血管增生;第3周滑膜已出现明显的纤维化改变。结论:内侧副韧带切断伴内侧半月板部分切除后,大鼠膝关节呈现骨性关节炎的改变,关节液中IL-1β和TNF-α表达显著增高。     

Effects of a proposed challenge on effort sense and cardiorespiratory responses during exercise.

PURPOSE: Highly trained endurance athletes train and race at relatively high intensities and are often confronted with challenges throughout a running event. The purpose of this study was to examine the effects of the anticipation of a proposed challenge on effort sense, heart rate (HR), ventilation ([dotVE), and ventilatory equivalent VE/VO2), a measure of ventilatory efficiency. METHODS: Highly trained endurance athletes (VO2max = 68.46 +/- 1.47 mL x kg(-1) x min(-1) ran two sessions at approximately 75% of VO2max for 35 min in a control condition and a proposed challenge condition. During the control condition, the subjects ran on a treadmill while simultaneously viewing a video depicting a runner exercising at 75% of VO2max and were told the run would continue at a speed that elicited 75% of VO2max. During the proposed challenge condition, subjects completed the same exercise protocol but viewed a video of a struggling runner and were told that the treadmill speed would be increased to "an extremely difficult" 95% of VO2max matching the intensity of the runner on the video. However, after data assessment at 17 min, subjects were told that the treadmill was malfunctioning and the treadmill speed could not be altered. The same intensity was maintained in both conditions. RPE, HR, VE, and VE/VO2 were assessed during the treadmill runs at 10, 17, 25, and 35 min. RESULTS: The effects of the manipulation were represented by a significant increase in state anxiety immediately following the video proposing the 95% challenge. RPE, HR, and VE increased similarly under both conditions, while VE/VO2 did not change. CONCLUSION: These findings suggest that for highly trained endurance athletes, anticipation of proposed challenge during running does not influence cardiorespiratory responses; thus these athletes demonstrate a "physiologically toughened" response.     

Interaction between gastrocnemius muscle weakness and moderate exercise deteriorates joint integrity in rat knee

The aim of this study was to determine the effect on the knee joint of the interaction between ankle muscle weakness and moderate exercise. Gastrocnemius muscle weakness was induced by intramuscular injection of botulinum toxin type A (BTX) in rats. Low‐speed treadmill running (12 m/min for 60 min) was applied for 6 weeks in rats with and without BTX. Untreated animals were used as controls. After BTX injection, the gastrocnemius muscle weakness was confirmed by 3‐D motion analysis in kinematic features of the hindlimb during locomotion as an increased maximal dorsiflexion angle during the stance phase. Serum biomarker analysis by enzyme‐linked immunosorbent assay revealed that low‐speed running decreased the catabolic effect on type II collagen. However, the inhibition of catabolism induced by running exercise was significantly counteracted by BTX injection. In addition, thinning of the cartilage layer and a reduction in the chondrocyte density was also found in the tibial plateau of the knee in the BTX‐injected rats after running for 6 weeks. These data suggest that moderate exercise have a positive effect on joint homeostasis. However, ankle muscle weakness may alter the mechanical environment of the knee and impair the integrity of joint cartilage with moderate exercise.     

Potent inhibition of cartilage biosynthesis by coincubation with joint capsule through an IL-1-independent pathway

The reason for the increased risk for development of osteoarthritis (OA) after acute joint trauma is not well understood, but the mechanically injured cartilage may be more susceptible to degradative mediators secreted by other tissues in the joint. To establish a model for such interactions, we coincubated bovine cartilage tissue explants together with normal joint capsule and found a profound (∼70%) reduction in cartilage proteoglycan biosynthesis. This reduction is due to release by the joint capsule of a heat-labile and non-toxic factor. Surprisingly, while cultured synovium is a canonical source of interleukin-1 (IL-1), blockade either by soluble IL-1 type II receptor (sIL-1r) or IL-1 receptor antagonist (IL-1RA) had no effect. Combined blockade of IL-1 and tumor necrosis factor α (TNF-α) also had no effect. To support the clinical relevance of the findings, we harvested joint capsule from post-mortem human knees. Human joint capsule from a normal adult knee also released a substance that caused an ∼40% decrease in cartilage proteoglycan biosynthesis. Furthermore, this inhibition was not affected by IL-1 blockade with either sIL-1r or IL-1RA. These results suggest that joint capsule tissue from a normal knee joint can release an uncharacterized cytokine that potently inhibits cartilage biosynthetic activity by an IL-1- and TNF-independent pathway.     

Exercise-induced effects on growth hormone levels are associated with ghrelin changes only in presence of prolonged exercise bouts in male athletes

AIM: The aim of this study was to evaluate growth hormone (GH) and ghrelin levels in response to physical exercise in athletes. METHODS: Two different exercise workloads were administered in two different groups of athletes. Group A athletes (19 males, 18 females; mean age +/- standard deviation: 25+/-6.7 years), performing a 60-90 min training session at approximately 80% of VO2max, were sampled for GH and ghrelin determinations before and immediately at the end of a training session on-the-field. Group B athletes (4 males; mean age: 28.2+/-7.2 years) performed two consecutive 30-min cycling sessions at 80% of individual VO2max at different time intervals between bouts (2 and 6 h) in two different days. GH and ghrelin concentrations were determined in blood samples collected at 15-min intervals during exercise and following 1 h of recovery. RESULTS: In group A athletes, GH levels increased after the training session (P<0.0001), with no differences between males and females. In male athletes, ghrelin levels significantly decreased after the training session (from 1 506.4+/-859 to 1 254.8+/-661.7 pg/mL, P<0.05), while no significant changes were found in females. No correlations were observed between GH and ghrelin levels at rest and after training. In group B athletes, GH levels significantly increased after the first exercise bouts (peak: 26.8+/-11.2 and 17.3+/-3.5 ng/mL, respectively), while the pattern of GH response was different after the second bout of exercise performed at 2-h or 6-h interval. In fact, peak GH concentration in response to the second bout (4.3+/-1.6 ng/mL) was lower (P<0.01) than that of the first bout when the interval elapsed was only 2 h, while a recovery of GH responsiveness was evident after the 6-h interval between the two exercise bouts (11.9+/-3.3 ng/mL). As far as ghrelin levels are concerned, no significant changes were observed during and after the two exercise bouts performed at the different time intervals. CONCLUSION: GH responses to prolonged exercise bouts (60-90 min) are associated with changes in ghrelin levels only in male athletes, while repeated exercise bouts of lower duration (30 min), capable to determine marked GH responses, are divorced from changes in ghrelin concentrations.     

Mood alteration from treadmill running and its relationship to beta-endorphin, corticotropin, and growth hormone

We examined the effects of running on mood alteration in males and females and its relationship to changes in beta-endorphin (B-EN), corticotropin (ACTH), and growth hormone (GH). Thirteen males and ten females ran on a treadmill for 30 min at 80% of previously determined maximum heart rate. Five plasma samples were obtained through an indwelling catheter before exercise (-30 and 0 min), during exercise (15 min), at exercise completion (+30 min), and after 30 min of recovery (R30); the Profile of Mood States (POMS) inventory was administered at -30 and +30. Composite mood improved after the run for both males and females withput concomitant rise in B-EN. For males but not females, an increase in mood was associated with lower B-EN (r = 0.65) and ACTH (r = 0.65) and this relationship was also significant prior to exercise for B-EN (r = 0.74) and ACTH (r = 0.81). It appears that an increase in peripheral beta-endorphin concentration may not be a major contributor to improved mood in response to exercise, but is an indicator of negative mood in males.     

High-impact athletics after knee articular cartilage repair: a prospective evaluation of the microfracture technique

BACKGROUND: Knee articular cartilage injuries in athletes present a therapeutic challenge and have been identified as an important cause of permanent disability because of the high mechanical joint stresses in athletes. PURPOSE: To determine whether microfracture treatment of knee articular cartilage injuries can return athletes to high-impact sports and to identify the factors that affect the ability to return to athletic activity. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Thirty-two athletes who regularly participated in high-impact, pivoting sports before articular cartilage injury were treated with microfracture for single articular cartilage lesions of the knee. Functional outcome was prospectively evaluated with a minimum 2-year follow-up by subjective rating, activity-based outcome scores, and the ability for postoperative participation in high-impact, pivoting sports. RESULTS: At last follow-up, 66% of athletes reported good or excellent results. Activity of daily living, Marx activity rating scale, and Tegner activity scores increased significantly after microfracture. After an initial improvement, score decreases were observed in 47% of athletes. Forty-four percent of athletes were able to regularly participate in high-impact, pivoting sports, 57% of these at the preoperative level. Return to high-impact sports was significantly higher in athletes with age <40 years, lesion size <200 mm(2), preoperative symptoms <12 months, and no prior surgical intervention. CONCLUSION: Microfracture is an effective first-line treatment to return young athletes with short symptomatic intervals and small articular cartilage lesions of the knee back to high-impact athletics.     

补充巧克力对长时间中等度运动休闲跑步后恢复的影响

目的：研究运动前补充巧克力对运动引起的生理和代谢变化及恢复的影响。方法：１２名１８～２０岁男性休闲跑步自愿者作为受试实验对象,采用交叉设计,每名受试者参加两次试验,在跑步机上跑步１小时,运动中心率保持在１４８～１５０次／分。结果：运动前补充５６ｇ巧克力１５分钟后,血糖水平显著升高（５．４２±０．８３ｍｍｏｌ／Ｌ）并且在运动结束及其后的３０分钟仍保持在相当高的水平（４．９２±０．５７ｍｍｏｌ／Ｌ）,而补充安慰剂的对照组在运动后血糖水平低（３．９７±０．３７ｍｍｏｌ／Ｌ）,停止运动３０分钟后血糖低于正常水平（３．８４±０．３１ｍｍｏｌ／Ｌ）。血浆自由脂肪酸、血乳酸、血浆尿素氮水平以及自我感觉疲劳程度（ＲＰＥ）等结果均表明运动前补充巧克力提供运动和运动后恢复所必要的条件均有益。     

运动对血浆心钠素影响的初步探讨

本文通过观察中长跑运动员极限运动下血浆心钠素的变化,探索运动对心脏内分泌的影响。实验结果提示了运动时由于血液动力学和神经生化变化引起血浆心钠素增加,有训练运动员极限运动后心钠素明显增加,与良好的心脏功能和运动能力有关。     

MRI demonstration of hypertrophic articular cartilage repair in osteoarthritis

Transection of the anterior cruciate ligament in the dog produces changes in the unstable joint typical of osteoarthritis, although full-thickness cartilage ulceration is rare. Information concerning the late fate of the cartilage after transection is meager. In the present study magnetic resonance imaging (MRI) was used to evaluate cartilage abnormalities 3 years after transection. Plain radiographs of the osteoarthritic and contralateral knees were obtained serially. MRI was performed 3 years after anterior cruciate ligament transection, at which time all three animals exhibited knee instability. Radiographs of the osteoarthritic knees showed osteophytes and subchondral sclerosis with progression between 2 and 3 years. On MRI, articular cartilage margins in the knee were indistinct, and the cartilage was thicker than that in the contralateral knee (maximum difference= 2.7 mm). This increase in thickness is consistent with biochemical data from dogs killed up to 64 weeks after creation of knee instability, which showed marked increases in cartilage bulk and in proteoglycan synthesis and concentration. The findings emphasize that increased matrix synthesis after anterior cruciate ligament transection leads to functional cartilage repair sustained even in the presence of persistent alteration of joint mechanics.     

Joint Position Statement: nutrition and athletic performance. American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada

It is the position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine that physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition. These organizations recommend appropriate selection of food and fluids, timing of intake, and supplement choices for optimal health and exercise performance. This position paper reviews the current scientific data related to the energy needs of athletes, assessment of body composition, strategies for weight change, the nutrient and fluid needs of athletes, special nutrient needs during training, the use of supplements and nutritional ergogenic aids, and the nutrition recommendations for vegetarian athletes. During times of high physical activity, energy and macronutrient needs-especially carbohydrate and protein intake-must be met in order to maintain body weight, replenish glycogen stores, and provide adequate protein for building and repair of tissue. Fat intake should be adequate to provide the essential fatty acids and fat-soluble vitamins, as well as to help provide adequate energy for weight maintenance. Overall, diets should provide moderate amounts of energy from fat (20% to 25% of energy); however, there appears to be no health or performance benefit to consuming a diet containing less than 15% of energy from fat. Body weight and composition can affect exercise performance, but should not be used as the sole criterion for sports performance; daily weigh-ins are discouraged. Consuming adequate food and fluid before, during, and after exercise can help maintain blood glucose during exercise, maximize exercise performance, and improve recovery time. Athletes should be well-hydrated before beginning to exercise; athletes should also drink enough fluid during and after exercise to balance fluid losses. Consumption of sport drinks containing carbohydrates and electrolytes during exercise will provide fuel for the muscles, help maintain blood glucose and the thirst mechanism, and decrease the risk of dehydration or hyponatremia. Athletes will not need vitamin and mineral supplements if adequate energy to maintain body weight is consumed from a variety of foods. However, supplements may be required by athletes who restrict energy intake, use severe weight-loss practices, eliminate one or more food groups from their diet, or consume high-carbohydrate diets with low micronutrient density. Nutritional ergogenic aids should be used with caution, and only after careful evaluation of the product for safety, efficacy, potency, and whether or not it is a banned or illegal substance. Nutrition advice, by a qualified nutrition expert, should only be provided after carefully reviewing the athlete's health, diet, supplement and drug use, and energy requirements.     

Caffeine in sport. Influence of endurance exercise on the urinary caffeine concentration.

This study was conducted to evaluate the influence of excessive sweating during long-distance running on the urinary concentration of caffeine after the intake of a large amount of caffeine. Nine endurance-trained athletes participated in a randomised cross-over study in which 450 mg caffeine were taken with and without exercise. Exercise consisted of running for 30 min on a treadmill at 75% of maximum heart rate, one hour after intake of caffeine. This endurance exercise caused a decrease in the urine flow as well as in the amount of caffeine excreted in urine. The combined effect of both these decreases is that the concentrations of caffeine detected in urine were similar with and without exercise. The maximum caffeine concentration detected in any urine sample was 11.9 micrograms/ml without exercise and 10.4 micrograms/ml with exercise. It can be concluded that excessive sweating during long-distance running did not enhance the urinary caffeine concentration.