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PubMed1994

[Hepato-digestive disorders in athletic practice].

Gastrointestinal and liver disorders are often observed in high performance athletes, especially those training for the increasingly popular endurance sports including the marathon and the triathlon. The disorders often start with stress before competition or training, followed by dehydration during the event. Insufficient training is an aggravating factor as are certain environmental factors including hot climate, irregular terrain and high altitude. Athletes may also consume non-steroid anti-inflammatory drugs, for example after a minor bone lesion or joint sprain, in an attempt to maintain their highest level of performance. Gastric signs include epigastric pain known to be caused by ischaemic gastritis resulting from decreased splanchnic flow and increased vasoconstriction in the gastric mucosa. Gastrooesophageal reflux results from modifications in sphincter tone and gastric emptying. Drinking hyperosmolar liquids also plays a role. Abdominal pain, diarrhoea, melena and uncommonly ischaemic colitis are the main signs of colic disorders. Mesenteric ischaemia may occur due to lowered splanchnic blood supply (by as much as 80% in some cases). Mechanical trauma is another mechanism; in marathon runners the "caecal slap syndrome" is a repeated microtrauma of the caecum against a hypertrophied muscular wall. Waterborne infectious agents may also lead to colic lesions. Exertion heat stroke is an emergency situation which can cause multiple organ damage and usually occurs after long intense exercise, often, but not always in a hot environment. Uncompensated thermogenesis and excessive loss of water by perspiration leads to central hyperthermia and ischaemic hepatic necrosis. Fatal liver failure has been observed. More or less severe symptoms of gastrointestinal or hepatic disorders are observed in 30% of high performance athletes and the incidence may reach 40% in those who have trained insufficiently. Such disorders lead to reduced performance in 10% of these athletes.

Colonic Diseases↗
PubMed2002

Hydration testing of athletes.

Dehydration not only reduces athletic performance, but also places athletes at risk of health problems and even death. For athletes, monitoring hydration has significant value in maximising performance during training and competition. It also offers medical personnel the opportunity to reduce health risks in situations where athletes engage in intentional weight loss. Simple non-invasive techniques, including weight monitoring and urine tests, can provide useful information. Bioimpedance methods tend to be easy to use and fairly inexpensive, but generally lack the precision and accuracy necessary for hydration monitoring. Blood tests appear to be the most accurate monitoring method, but are impractical because of cost and invasiveness. Although future research is needed to determine which hydration tests are the most accurate, we encourage sports teams to develop and implement hydration monitoring protocols based on the currently available methods. Medical personnel can use this information to maximise their team's athletic performance and minimise heat- and dehydration-related health risks to athletes.

Body Weight↗
PubMed2006

Circadian variation in swim performance.

Previous findings of time-of-day differences in athletic performance could be confounded by diurnal fluctuations in environmental and behavioral "masking" factors (e.g., sleep, ambient temperature, and energy intake). The purpose of this study was to examine whether there is a circadian rhythm in swim performance that is independent of these masking factors. Experienced swimmers (n = 25) were assessed for 50-55 consecutive hours in the laboratory. The swimmers followed a 3-h "ultra-short" sleep-wake cycle, involving 1 h of sleep in darkness and 2 h of wakefulness in dim light, that was repeated throughout the observation. The protocol distributes behavioral and environmental masking factors equally across the 24-h period. Each swimmer was scheduled to perform six maximal-effort 200-m swim trials that were distributed equally across eight times of day (n = 147 trials). Each trial was separated by 9 h. A cosine fit of intra-aural temperature data established the time of the lowest body temperature (Tmin). Swim performances were z-transformed and compared across the eight times of day and across twelve 2-h intervals relative to Tmin. Analysis of covariance, controlling for trial number, revealed a significant (P < 0.001) pattern in swim performance relative to environmental and circadian times of day. Performance peaked 5-7 h before Tmin (approximately 2300) and was worst from 1 h before to 1 h after Tmin (approximately 0500). Mean swim performance was 169.5 s; circadian variation from peak to worst performance was 5.8 s. These data suggest a circadian rhythm in athletic performance independent of environmental and behavioral masking effects.

Adult↗
PubMed1996

The relationship between jaw posture and muscular strength in sports dentistry: a reappraisal.

From the late 1970s until the early 1990s, there have been several reports of improved appendage muscle strength and athletic performance. Much of the criticism of using a mouthguard alone or in conjunction with a splint, such as a mandibular orthopedic repositioning appliance (MORA), to enhance athletic performance has been aimed at study designs, controls, periods of time, double blindness, and the placebo effect. Although it would appear that designing a study which pleases both clinician and researcher would be a difficult task, studies have been performed that do meet the "gold standard." The results favor the premise that jaw repositioning can enhance appendage muscular strength and athletic performance. Studies performed during the mid-1980s, and to which the scientific community refers to continually, on closer examination are flawed.

Bite Force↗
PubMed1995

Relationship of muscular strength to jaw posture in sports dentistry.

From the late 1970s until the early 1990s there have been several reports of improved appendage muscle strength and athletic performance. Much of the criticism of using a mouthguard alone or in conjunction with a splint, such as a mandibular orthopedic repositioning appliance (MORA), to enhance athletic performance has been aimed at study designs, controls, periods of time, double blindness and the placebo effect. Although it would appear that designing a study that would please both clinician and researcher would be a difficult task, studies have been performed that do meet the "gold standard"; and the results favor the premise that jaw repositioning can enhance appendage muscular strength and athletic performance. Previous studies performed in the mid-1980s, and to which the scientific community refers to continually, on closer examination are flawed.

Dentistry↗
PubMed1997

Impact of different sports and training on cardiac structure and function.

There is overwhelming evidence, particularly from echocardiography, that the heart of competitive athletes may differ from that of nonathletes, matched for age, gender, and body size. A larger left ventricular mass has been shown in athletes performing predominantly dynamic aerobic and anaerobic sports, in athletes engaged in static training, and in players of ball sports. Enlargement of the left ventricular internal diameter was most pronounced and reached about 10% in athletes performing predominantly dynamic sports; mainly strength training athletes had a lesser increase of the internal dimension, which was limited to 2.5%. Also the left ventricular wall appeared to be thickened in all types of athletes compared with controls. In sports with high dynamic and low static demands, wall thickness was proportionate or slightly disproportionate to the size of the internal diameter so that relative wall thickness was not different from controls or slightly increased (predominantly eccentric hypertrophy). In strength athletes, the disproportionate increase of wall thickness averaged about 12% (predominantly concentric hypertrophy). In sports with high dynamic and high static demands and requiring prolonged training, such as cycling, the increases of absolute and relative wall thickness reached 29% and 19% and were more pronounced than in runners (mixed hypertrophy). A plausible interpretation of these results is that the development of so-called eccentric or concentric left ventricular hypertrophy according to the type of sports cannot be regarded as an absolute or dichotomous concept because training regimens and sports activities are not exclusively dynamic or static and because the load on the heart is not purely of the volume or the pressure type. Most studies agree that left ventricular systolic and diastolic function is normal in the athlete at rest, whereas diastolic function seems to be enhanced in the exercising endurance athlete. The consistency of the results of studies on athletes in the competitive and the resting season, of training of sedentary subjects, and of spinal cord-injured patients suggests that variations in physical activity can alter left ventricular structure; genetic factors do not seem to be involved in the size of the left ventricular internal diameter but have to be taken into account to interpret wall thickness.

Adaptation, Physiological↗
PubMedDate not supplied

Gender and performance in athletics.

A comparison of women's and men's performance in swimming, running, and skating is made based on available world record data. The ratio of women's to men's record times is analyzed as a time series, and the asymptotic value of this ratio is discussed in the context of a model. "Rate of improvement curves" are defined over time and by event in a given sport and are compared across gender. The relationship of record time to event distance is estimated and also analyzed across event and gender boundaries. We make three conclusions: 1. The rate of improvement for women has been extraordinary and is larger for longer distance vents. 2. Law-like relations emerge for record times and event lengths. These relations have interesting physical interpretations when examined for various sports. 3. The male physiology is more suited to anaerobic strength events while, given increased access and participation, women can be expected to be more on a par with men in some long-distance aerobic events.

Cross-Sectional Studies↗
PubMed1987

Adverse effects of anabolic steroids in athletes.

The effects of anabolic steroid use on athletic performance and the adverse effects associated with the use of anabolic steroids are reviewed. Anabolic steroids increase protein synthesis in skeletal muscles and reverse catabolic processes. Because of these properties, some athletes use anabolic steroids in an attempt to improve their athletic performance. However, studies indicate that increases in muscle mass and strength during anabolic steroid administration are observed only in athletes who already are weight-trained and who continue intensive training while maintaining high-protein, high-calorie diets. Adverse effects attributed to anabolic steroid use occur frequently. Serious adverse effects include hepatic and endocrine dysfunction; cardiovascular and behavioral changes also are reported. Some of the adverse effects associated with the use of these agents are irreversible, particularly in women. The use of anabolic steroids to improve athletic performance has become prevalent. However, the reported benefits are tempered by numerous adverse reactions.

Aggression↗
PubMed2004

Shoulder MR arthrography: which patient group benefits most?

OBJECTIVE: We sought to compare the diagnostic accuracy of conventional MRI versus MR arthrography of the shoulder in the assessment of high-performance athletes (professional baseball players) and to compare our findings in these patients with the conventional MRI and MR arthrographic findings in an age-matched control group of nonprofessional athletes. MATERIALS AND METHODS: Conventional MRI and MR arthrographic examinations of the shoulder in 20 consecutive professional baseball players with shoulder pain were reviewed retrospectively by two musculoskeletal radiologists in consensus. These interpretations were compared with retrospective consensus interpretations of conventional MRI and MR arthrographic examinations of the shoulder obtained in a control group of 50 consecutive nonprofessional athletes with shoulder pain. MR images were assessed for full- or partial-thickness supraspinatus tendon tears, superior labral anteroposterior (SLAP) tears, and anterior or posterior labral tears. RESULTS: In the 20 consecutive professional athlete patients, two full-thickness and six partial-thickness undersurface supraspinatus tendon tears were seen on MR arthrography but not seen on conventional MRI as well as six SLAP tears, two anterior labral tears, and one posterior labral tear. Three patients had both SLAP tears and full- or partial-thickness supraspinatus tendon tears. Of 14 patients with findings on MR arthrography that were not seen on MRI, 11 had arthroscopic correlation. In all 11, arthroscopic findings confirmed findings on MR arthrography. In the group of 50 nonprofessional athlete patients, five had additional findings on MR arthrography not seen on conventional MRI: two anterior labral tears, two partial-thickness supraspinatus tendon tears, and two SLAP tears. One patient had both a partial-thickness supraspinatus tendon tear and a SLAP tear seen on MR arthrography. The five patients with additional findings on MR arthrography had arthroscopy. In all five, arthroscopic findings confirmed the findings on MR arthrography. CONCLUSION: MR arthrography is considerably more sensitive for detection of partial-thickness supraspinatus tears and labral tears than conventional MRI. MR arthrography showed injuries in addition to those seen on conventional MRI in 14 of 20 patients in the high-performance athlete group. These results suggest high-performance athletes may be a subgroup of patients for whom MR arthrography yields considerably more diagnostic information than conventional MRI.

Adolescent↗
PubMed2004

The optimal training load for the development of muscular power.

Muscular power is considered one of the main determinants of athletic performance that require the explosive production of force such as throwing and jumping. Various training methods have been suggested to improve muscular power and dynamic athletic performance. Although various acute training valuables (e.g., sets, repetitions, rest intervals) could be manipulated, the training loads used are some of the most important factors that determine the training stimuli and the consequent training adaptations. Many research results showed that the use of different training loads elicits the different training adaptations and further indicated the load- and velocity-specific adaptations in muscular-power development. Using the optimal loads at which mechanical power output occurs has been recommended, especially to enhance maximum muscular power. Additionally, introducing periodization and combined training approach into resistance-training programs may further facilitate muscular-power development and enhance a wide variety of athletic performances.

Humans↗
PubMed1993

Nutritional practices of elite athletes. Practical recommendations.

The nutritional intake of elite athletes is a critical determinant of their athletic performance and ability to compete both physically and mentally. However, their demanding training and travel schedules in addition to a possible lack of nutritional knowledge may prohibit them from maintaining an optimal dietary intake. Sound scientific data about the nutritional habits of elite athletes are limited and, therefore, it is not clear as to whether elite athletes are following nutritional recommendations and maintaining nutritionally sound diets. This review takes a comprehensive look at 22 recent dietary intake studies, including 50 groups of elite athletes. The time period for food record collection ranged from 3 to 7 days except for 2 studies which collected records for 21 and 22 days. Energy intakes of > 50 kcal/kg/day for male athletes who train for > 90 min/day and 45 to 50 kcal/kg/day for female athletes training for > 90 min/day are recommended. Bodyweight should be monitored frequently as a check on calorie intake. With a sufficient calorie intake (1.2 to 2.0 kg/kg/day) protein supplementation is not necessary. Ingested carbohydrate stored as glycogen serves as the primary fuel for muscle performance. Athletes in training should consume 70% of total calories as carbohydrate. Athletes on low energy diets (< 2200 kcal/day) should have a diet of < 25% fat, and athletes with large energy needs should consume 30% fat in their diet. In general, fat intakes should be reduced and carbohydrate intakes increased. Athletes should also restrict alcohol intake during training and competition periods. Athletes with low calorie intakes should consume foods with high contents of iron, calcium, magnesium, zinc and vitamin B12. Athletes with high calorie intakes should consume foods that are naturally high in or fortified with B-group vitamins. Fluid, electrolyte and energy supplementation is desirable to support circulatory, metabolic and thermoregulatory functions. There is no special food that will help elite athletes perform better; the most important aspect of the diet of elite athletes is that it follows the basic guidelines for healthy eating.

Adult↗
PubMed2004

Sex differences in perceived importance of hamstring stretching among high school athletes.

Adolescent athletes completed a hamstring stretching technique and opinion survey and were measured for hamstring extensibility during preparticipation examination. Hamstring muscle group stretching practices, extensibility, and perception of importance to injury prevention, athletic performance, warming-up, cooling down, and coaches were contrasted by sex. As expected, girls displayed greater hamstring muscle group flexibility than boys. Boys and girls reported similar hamstring stretch repetitions and stretch duration. Boys scored hamstring stretching as being more important to improved athletic performance and to their coaches than did girls. Differences were not evident between groups for prevention of injury, warm-up, or cool-down. The lower perception of hamstring stretching importance for improving athletic performance and a lesser perception of hamstring stretching importance to their coaches suggests that adolescent female athletes and their coaches may not fully understand the value of static hamstring stretching. Modified hamstring stretching technique may selectively increase hamstring extensibility among girls without contributing to increasing capsuloligamentous knee joint laxity.

Adolescent↗
PubMed2005

Judgments of the fairness of using performance enhancing drugs.

Undergraduates (total N=185) were asked about performance-affecting drugs. Some drugs supposedly affected athletic performance, others memory, and other attention. Some improved performance for anyone who took them, others for the top 10% of performers, others for the bottom 10%, and finally, yet other drugs worked only on the bottom 10% who also showed physical abnormalities. Participants were asked about the fairness of allowing the drug to be used, about banning it, and about whether predictions of future performance based on testing with or without the drug were better. The study found that participants appreciated the "interaction effect," that they felt it was less unfair to allow the drug if it affected the bottom 10% than if it affected everyone, and they were more eager to have the drug banned if it affected everyone. Participants were least tolerant of drugs that affected athletic performance and most tolerant of those that affected attention.

Analysis of Variance↗
PubMed1990

[Performance of athletes exercising in ozone polluted air].

The literature on the performance of those exercising in air containing ozone was examined. The action of ozone is mediated by muscarinic receptors and others of unknown nature localized, apparently, over the respiratory epithelium of gaseous transport. Due to its action on those receptors the inspiratory phase of the pulmonary ventilation is reduced in an effect associated with pain and, simultaneously, the resistance to the pass of air is increased. If exercise increases ventilation to 90 or more liters per minute the effective dose of ozone increases potentiating its effect on the inspiration and the resistance. The potentiated reduction of the inspiratory phase and the associated pain (a) strongly antagonize the ventilatory effort of exercise and (b) reduced the capacity of response to the increase in resistance with augmented inspirations. In this way an important decrease in performance appears.

Air Pollutants↗
PubMedDate not supplied

Nutritional considerations for vegetarian athletes.

With the growing interest in the potential health benefits of plant-based diets, it is relevant to consider whether vegetarian dietary practices could influence athletic performance. Accordingly, this review examines whether nutrients that may differ between vegetarian and omnivorous diets could affect physical performance. We also describe recent studies that attempt to assess the effects of a vegetarian diet on performance and comment on other nutritional aspects of vegetarianism of relevance to athletes. Although well-controlled long-term studies assessing the effects of vegetarian diets on athletes have not been conducted, the following observations can be made: 1) well-planned, appropriately supplemented vegetarian diets appear to effectively support athletic performance; 2) provided protein intakes are adequate to meet needs for total nitrogen and the essential amino acids, plant and animal protein sources appear to provide equivalent support to athletic training and performance; 3) vegetarians (particularly women) are at increased risk for non-anemic iron deficiency, which may limit endurance performance; and 4) as a group, vegetarians have lower mean muscle creatine concentrations than do omnivores, and this may affect supramaximal exercise performance. Because their initial muscle creatine concentrations are lower, vegetarians are likely to experience greater performance increments after creatine loading in activities that rely on the adenosine triphosphate/phosphocreatine system. 5) Coaches and trainers should be aware that some athletes may adopt a vegetarian diet as a strategy for weight control. Accordingly, the possibility of a disordered eating pattern should be investigated if a vegetarian diet is accompanied by unwarranted weight loss.

Adolescent↗
PubMed2003

Effects of dietary fat on muscle substrates, metabolism, and performance in athletes.

INTRODUCTION: The present investigation aimed at identifying differences in muscle structural composition, substrate selection, and performance capacity in highly trained endurance athletes as a consequence of consuming a high-fat or a low-fat diet. METHODS: Eleven duathletes ingested high-fat (53% fat; HF) or high-carbohydrate diets (17% fat; LF) for 5 wk in a randomized crossover design. RESULTS: In m. vastus lateralis, oxidative capacity estimated as volume of mitochondria per volume of muscle fiber (HF: 9.86 +/- 0.36 vs LF: 9.79 +/- 0.52%, mean +/- SE) was not different after the two diet periods. Intramyocellular lipid (IMCL) was significantly increased after HF compared with LF (1.54 +/- 0.27% vs 0.69 +/- 0.09%, P = 0.0076). Glycogen content was lower after HF than after LF, but this difference was not statistically significant (487.8 +/- 38.2 vs 534.4 +/- 32.6 mmol x kg-1 dry weight, P = 0.2454). Maximal power and [OV0312]O(2max) (63.6 +/- 0.9 vs 63.9 +/- 1.2 mL O(2) x min-1 x kg-1 on HF and LF) during an incremental exercise test to exhaustion were not different between the two diet periods. Total work output during a 20-min all-out time trial (298 +/- 6 vs 297 +/- 7 W) on a bicycle ergometer as well as half-marathon running time (80 min 12 s +/- 86 s vs 80 min 24 s +/- 82 s) were not different between HF and LF. Blood lactate concentrations and respiratory exchange ratios (RER) were significantly lower after HF than after LF at rest and during all submaximal exercise loads. CONCLUSIONS: Muscle glycogen stores were maintained after a 5-wk high-fat diet period whereas IMCL content was more than doubled. Endurance performance capacity was maintained at moderate to high-exercise intensities with a significantly larger contribution of lipids to total energy turnover.

Adult↗
PubMed1998

The effect of glycerol and desmopressin on exercise performance and hydration in triathletes.

BACKGROUND: Hydration is an important determinant of athletic performance, and glycerol-containing solutions have been demonstrated to produce a state of hyperhydration. Secretions of arginine vasopressin (AVP) and/or other renal mechanisms may account for reduced urine output following glycerol ingestion. This study examined the effect of glycerol and the AVP analog desmopressin (DDAVP) on hydration and exercise performance in triathletes ingesting routine volumes of prerace fluids. METHODS: Eight male triathletes ages 19 to 43 participated. After determination of their VO(2peak), each athlete completed a strenuous exercise protocol three times involving 60 min of exercise at 70% VO(2peak) followed immediately by an incremental increase in workload every 2 min until exhaustion. RESULTS: Pretreatment with 1 gxkg(-1) glycerol or 20 microgram of DDAVP intranasally failed to produce hyperhydration or any enhancement of athletic performance. There was a significant difference in reduction in body mass between DDAVP and control (P < 0.05) but no change in sweat volume. No physiologically relevant differences in plasma sodium, renin, or hemoglobin were seen with either active agent. Plasma osmolality did have a different time course in response to exercise following glycerol (P < 0.03) owing to a smaller incremental increase. Urine osmolality was also raised at baseline following glycerol (P < 0.05). Responses to exercise of plasma AVP, cortisol, and indices of carbohydrate metabolism were similar, although AVP was elevated following DDAVP administration (P < 0.01) owing to assay cross-reactivity. CONCLUSION: Although maintaining adequate hydration remains important for the endurance athlete, the routine use of either glycerol of DDAVP before athletic training or competition in a thermoneutral environment does not seem to confer any advantage over conventional fluid replacement.

Adult↗
PubMed2000

Comparison of physiological strain and muscular performance of athletes during two intermittent running exercises at the velocity associated with VO2max.

The purpose of this study was to examine physiological strain and muscular performance responses of well trained athletes during two intermittent running exercise protocols at the velocity associated with VO2max. Ten national level middle-distance runners (VO2max 69.4+/-5.1; mean+/-SD) performed in random order two 28 min treadmill running exercises: 14 bouts of 60 s runs with 60 s rest (IR60) and 7 bouts of 120 s runs with 120 s rest between each run (IR120). During IR120 peak oxygen uptake (12%), peak heart rate (3%) and peak blood lactate (79%) were significantly higher than during IR60 (P< 0.001) and almost the same as in the VO2max test. In IR120 the relative aerobic energy release calculated on the basis of the accumulated oxygen deficit during the running bouts was significantly higher than in IR60 (81.5+/-2.7 vs. 70.2+/-2.6%, P<0.001) likewise the sum oxygen consumption during the 14 min running (P< 0.001), while during the 14 min recovery it was as much lower (P < 0.001). There were no changes either during or between the IR60 and IR120 protocols with regard to the muscular performance parameters, stride length or height of maximal vertical jumps. In conclusion, during intermittent running at the velocity associated with VO2max doubling the duration of work and rest bouts from 60 s to 120s increased the physiological strain of well trained athletes to the same level as at exhaustion in the VO2max test but the muscular performance variables were not influenced.

Adult↗