Sodium balance during U. S. football training in the heat: cramp-prone vs. reference players.

U. S. football players with a history of heat cramps were evaluated for the effect of physical training, sodium intake, and loss of sweat sodium on whole blood sodium concentration (BNa). Athletes (n=14 males, 24+/-1 y) were recruited and studied based on medical history, age, and position. The reference group (R, n=8 without a cramping history) and cramp-prone group (C, n=6, history of whole-body cramps associated with extensive sweat loss during exercise in the heat) were measured for body mass and BNa (ISTAT) before and after team training of 2.2 h in hot conditions (WBGT=29-32 degrees C). Intake and loss of fluid and sodium were also measured to determine respective acute balance. In R, BNa was stable pre- to post-training (138.9+/-1.8 to 139.0+/-2.0 mmol/L) while it tended to decline in C (137.8+/-2.3 to 135.7+/-4.9 mmol/L), and three subjects in C had BNa values below 135 mmol/L (131.7+/-2.9 mmol/L). C consumed a greater percentage of total fluid as water (p<0.05). Mean sweat sodium concentration was (52.6+/-29.2 mmol/L for C and 38.3+/-18.3 mmol/L for R (p>0.05). Compared to R, C tended to experience a decline in BNa and greater acute sodium imbalance. These changes may place cramp-prone players at greater risks for developing acute sodium deficits during training.

American College of Sports Medicine roundtable. The physiological and health effects of oral creatine supplementation.

Creatine (Cr) supplementation has become a common practice among professional, elite, collegiate, amateur, and recreational athletes with the expectation of enhancing exercise performance. Research indicates that Cr supplementation can increase muscle phosphocreatine (PCr) content, but not in all individuals. A high dose of 20 g x d(-1) that is common to many research studies is not necessary, as 3 g x d(-1) will achieve the same increase in PCr given time. Coincident ingestion of carbohydrate with Cr may increase muscle uptake; however, the procedure requires a large amount of carbohydrate. Exercise performance involving short periods of extremely powerful activity can be enhanced, especially during repeated bouts of activity. This is in keeping with the theoretical importance of an elevated PCr content in skeletal muscle. Cr supplementation does not increase maximal isometric strength, the rate of maximal force production, nor aerobic exercise performance. Most of the evidence has been obtained from healthy young adult male subjects with mixed athletic ability and training status. Less research information is available related to the alterations due to age and gender. Cr supplementation leads to weight gain within the first few days, likely due to water retention related to Cr uptake in the muscle. Cr supplementation is associated with an enhanced accrual of strength in strength-training programs, a response not independent from the initial weight gain, but may be related to a greater volume and intensity of training that can be achieved. There is no definitive evidence that Cr supplementation causes gastrointestinal, renal, and/or muscle cramping complications. The potential acute effects of high-dose Cr supplementation on body fluid balance has not been fully investigated, and ingestion of Cr before or during exercise is not recommended. There is evidence that medical use of Cr supplementation is warranted in certain patients (e.g.. neuromuscular disease); future research may establish its potential usefulness in other medical applications. Although Cr supplementation exhibits small but significant physiological and performance changes, the increases in performance are realized during very specific exercise conditions. This suggests that the apparent high expectations for performance enhancement, evident by the extensive use of Cr supplementation, are inordinate.

Blood volume: importance and adaptations to exercise training, environmental stresses, and trauma/sickness.

This paper reviews the influence of several perturbations (physical exercise, heat stress, terrestrial altitude, microgravity, and trauma/sickness) on adaptations of blood volume (BV), erythrocyte volume (EV), and plasma volume (PV). Exercise training can induce BV expansion: PV expansion usually occurs immediately, but EV expansion takes weeks. EV and PV expansion contribute to aerobic power improvements associated with exercise training. Repeated heat exposure induces PV expansion but does not alter EV. PV expansion does not improve thermoregulation, but EV expansion improves thermoregulation during exercise in the heat. Dehydration decreases PV (and increases plasma tonicity) which elevates heat strain and reduces exercise performance. High altitude exposure causes rapid (hours) plasma loss. During initial weeks at altitude, EV is unaffected, but a gradual expansion occurs with extended acclimatization. BV adjustments contribute, but are not key, to altitude acclimatization. Microgravity decreases PV and EV which contribute to orthostatic intolerance and decreased exercise capacity in astronauts. PV decreases may result from lower set points for total body water and central venous pressure, while EV decreases may result from increased erythrocyte destruction. Trauma, renal disease, and chronic diseases cause anemia from hemorrhage and immune activation which suppresses erythropoiesis. The re-establishment of EV is associated with healing, improved life quality, and exercise capabilities for these injured/sick persons.

Treatment of suspected heat illness.

1. Despite advances in the art and science of fluid balance, exertional heat illness -- even life-threatening heat stroke -- remains a threat for some athletes today. 2. Risk factors for heat illness include: being unacclimatized, unfit, or hypohydrated; certain illnesses or drugs; not drinking in long events; and a fast finishing pace. 3. Heat cramps typically occur in conditioned athletes who compete for hours in the sun. They can be prevented by increasing dietary salt and staying hydrated. 4. Early diagnosis of heat exhaustion can be vital. Early warning signs include: flushed face, hyperventilation, headache, dizziness, nausea, tingling arms, piloerection, chilliness, incoordination, and confusion. 5. Pitfalls in the diagnosis of heat illness include: confusion preventing self-diagnosis; the lack of trained spotters; rectal temperature not taken promptly; the problem of "seek not, find not;" and the mimicry of heat illness. 6. Heat stroke is a medical emergency. Mainstays of therapy include: emergency on-site cooling; intravenous fluids; treating hypoglycemia as needed; intravenous diazepam for seizures or severe cramping or shivering; and hospitalizing if response is slow or atypical. 7. The best treatment is prevention. Tips to avoiding heat illness include: rely not on thirst; drink on schedule; favor sports drinks; monitor weight; watch urine; shun caffeine and alcohol; key on meals for fluids and salt; stay cool when you can; and know the early warning signs of heat illness.

Exercise as disease detector.

Exercise is a well-known stress test for uncovering heart or lung disease, but it can also stress other organs and unmask a range of medical disorders. Practical case examples are given in seven areas: anemia, headache, hematuria, gastrointestinal problems, seizure, anhidrosis, and hypothyroidism. Recognizing the exercise-induced manifestations can lead to timely diagnoses that improve and save lives.

Ergogenic Aids: What Athletes Are Using-and Why.

Athletes at all levels explore ergogenic aids. Testosterone and growth hormone are still abused and difficult to detect. Single doses of albuterol or salmeterol do not seem ergogenic, but questions remain about prolonged dosing and about other beta2 agonists. Caffeine can be ergogenic for prolonged or brief exertion. Creatine supplementation is legal and in vogue among strength and power athletes. Not all studies agree, but creatine seems ergogenic for repeated brief bouts of intense exercise. Ergogenic aids pose vexing questions for athletes, physicians, and society.

Infectious mononucleosis: recognizing the condition, 'reactivating' the patient.

A two-step infection by the Epstein-Barr virus accounts for the characteristic features of infectious mononucleosis (IM). New serologic tests for viral antigens exist, but a rapid kit test for heterophil antibody usually suffices to confirm the diagnosis. General management is supportive only. Splenic rupture is very rare, almost never fatal if diagnosed early, and, in most cases, is probably best treated by splenectomy. Athletes tend to recover from IM faster than nonathletes. When the spleen returns to normal size, the athlete can return to contact sports, though it may take 3 to 6 months for an elite athlete to regain top form.

Overtraining: consequences and prevention.

Overtraining refers to prolonged fatigue and reduced performance despite increased training. Its roots include muscle damage, cytokine actions, the acute phase response, improper nutrition, mood disturbances, and diverse consequences of stress hormone responses. The clinical features are varied, non-specific, anecdotal and legion. No single test is diagnostic. The best treatment is prevention, which means (1) balancing training and rest, (2) monitoring mood, fatigue, symptoms and performance, (3) reducing distress and (4) ensuring optimal nutrition, especially total energy and carbohydrate intake.

Immunology and exercise. Physiology, pathophysiology, and implications for HIV infection.

This article covers the latest information on the immunologic changes of exercise as well as the effects of regular exercise on persons infected with HIV and the exercise recommendations for HIV-infected athletes. Included are discussions about psychoneuroimmunology and exercise-associated changes in immunity.

Circadian Rhythms.

In brief Active people watch their body clocks for health and performance advantages. Recent research on circadian rhythms suggests that exercising in the morning is safe, exercise at any time of day boosts mood, athletic performance peaks late in the day, athletes should train at the same time they will race, and jet lag may influence team sports.

Ergolytic drugs in medicine and sports.

Just as drugs that enhance exercise capacity and/or athletic performance are often called "ergogenic," drugs that impair these functions can be termed "ergolytic." Today's athletes hear too much about the former and too little about the latter. Ergolytic drugs used today by certain athletes include alcohol, marijuana, smokeless tobacco, cocaine, antihypertensives, eye drops, and diuretics. Some antidepressants, too, can be ergolytic, as well as some antihistamines and other common drugs--even caffeine--in some settings, for some people. Internists can help their fitness-minded patients by educating them about ergolytic drugs and by tailoring their management to foster peak performance at work and play.

Infection, Immunity, and Exercise.

In brief How-and if-exercise alters immunity is open to debate. Research centers on changes in the number and function of granulocytes and lymphocytes and in levels of immunoglobulins. In general, these immune changes are mixed, mild, and brief. Clinical studies are inconclusive and fraught with confounders, especially the impact of psychological stress. Whether exercise enhances immunity or impairs it may, in fact, depend on whether the exercise is a joy or a stress.

Sickle Cell Trait, Heroic Exercise, and Fatal Collapse.

In brief Although sickle cell trait is generally benign and consistent with peak athleticism, it poses a small risk of gross hematuria and splenic infarction at altitude. More alarming is the growing evidence that, in some people with sickle cell trait, maximal exercise-especially in hot weather or when new at altitude-can evoke a life-threatening syndrome of sickling, fulminant rhabdomyolysis, lactic acidosis, collapse, acute renal failure, and hyperkalemia. More than 30 such cases are described, along with practical tips for recognition and prevention.

Sports anemia, iron supplements, and blood doping.

1) Athletes tend to have lower hemoglobin concentrations than sedentary counterparts. This has been called sports anemia, a misnomer. 2) Sports anemia is a false anemia and a beneficial adaptation to aerobic exercise, caused by an expanded plasma volume that dilutes red blood cells. 3) Athletes, however, can also develop true anemia, most commonly caused by iron deficiency. True anemia curbs athletic performance, but nonanemic iron deficiency does not. 4) Iron supplements are useful for women endurance athletes who repeatedly develop iron deficiency anemia despite dietary advice. 5) Some endurance athletes today are blood doping by abusing recombinant human erythropoietin (rEPO). They risk dying to win.

Hematuria in a young recreational runner.

A 27-year-old recreational jogger developed gross hematuria following a 2-mile run. Evaluation revealed a transitional cell carcinoma of the bladder. Etiologies for pigmenturia and the pathogenesis of exertional hematuria are reviewed. The need to exclude other causes of hematuria before attributing the finding to exercise is emphasized.

Exercise and arthritis. The hematology of inactivity.

Arthritis tends to promote inactivity, and inactivity tends to promote an unhealthful constellation of blood abnormalities that increases the risk of heart attack and stroke. The hematology of inactivity comprises the following: low plasma volume, high hematocrit, high plasma fibrinogen, elevated blood viscosity, increased platelet aggregability, and diminished fibrinolysis. Regular exercise reverses all these adverse blood changes and, thereby, helps prevent heart attack and stroke. Simply put, exercise "improves" the blood, making it flow more easily and clot less readily. This "healthy hematology of exercisers" is one more reason why prudent exercise is as vital for patients with arthritis as it is for the rest of us.

Hematuria-A Diagnostic Challenge.

In brief Athletes are prone to hematuria from diverse causes, and proper diagnosis hinges on a careful history, physical examination, and urinalysis, as well as on judicious use of screening tests, imaging studies, and cystoscopy. Using six illustrative cases, this article covers the adult athlete with hematuria: real and false, normal and abnormal, microscopic and gross. It focuses on when and how to evaluate hematuria, and offers practical tips on management.

Does Running Cause Osteoarthritis?

In brief: This review of the literature on exercise and arthritis considers the relevant epidemiologic and experimental studies of animals and humans, with a focus on the relationship between running and osteoarthritis. The cause of osteoarthritis-the most common joint disease in the United States-remains unknown. The incidence of the disease increases with age and eventually afflicts most people-athletes and nonathletes alike-to some extent: Almost everyone has some pathologic abnormality in the weight-bearing joints by age 40 or 50; by age 75 at least 85% of all people have diagnosable osteoarthritis. However, there is no conclusive evidence that running causes the disease; in fact, running may actually slow the functional aspects of musculoskeletal aging.