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.

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.

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.

The Anemias of Athletes.

In brief: Diagnosing anemia in athletes is complicated, because athletes normally have lower hemoglobin and serum ferritin concentrations than nonathletes. This dilutional pseudoanemia-a beneficial adaptation that enhances athletic performance-needs no treatment. Athletes can also develop true anemia from iron deficiency and/or footstrike hemolysis. True anemia can be treated with iron supplements and diet modification to increase absorbable iron; footstrike hemolysis can be minimized by paying attention to body weight, gait, shoes, and terrain. The widespread notion that depletion of iron stores without anemia limits performance is probably wrong, but even very mild iron deficiency anemia impairs maximal performance. The physician who recognizes and manages the diverse anemias of athletes performs a vital service.

Clinical and laboratory observations on serum folate-binding protein.

We studied the effect of serum folate-binding protein (FBP) on folate radioassays and the relationship of the serum level of unsaturated FBP to the serum folate level in various clinical states. Our modification of a heat-extracted radioassay was compared to a whole serum radioassay. Our results confirmed the existence of elevated serum levels of unsaturated FBP in some normal subjects, in some women taking oral contraceptives, and in most patients with uremia. Elevated levels of unsaturated FBP will produce falsely low results in folate radioassay unless the FBP has been destroyed by heat, as was done in the modified radioassay here presented. In normal and uremic subjects, serum folate and unsaturated FBP levels tended to correlate, whereas in patients taking large doses of folic acid the level of unsaturated FBP fell as the level of serum folate rose.

PIP: Clinical and laboratory observations on serum folate-binding protein (FBP) are reported. The effect of serum FBP on folate radioassays and the relationship of the serum level of unsaturated FBP to the serum folate level in various clinical states was studied. A comparison of a heat-extracted radioassay, a whole serum radioassay and the Lactobacillus casei assay was made, and all correlated well with each other. The existence of elevated serum levels of unsaturated FBP in some normal subjects, in some women taking oral contraceptives and in most patients with uremia (p less than .01) was confirmed. Elevated levels of unsaturated FBP produce falsely low results in folate radioassay unless the FBP has been destroyed by heat. Serum folate and unsaturated FBP levels tended to correlate in normal and uremic subjects whereas in subjects taking large doses of folic acid the level of unsaturated FBP fell as the level of serum folate rose.