Biomedical subjects

Renata Rebello Mendes

Publications and source records attributed to Renata Rebello Mendes.

3 recordsLinked to original sources

PubMed2006

[Neuroendocrine and nutritional aspects of overtraining].

The overtraining syndrome is characterized by an excessive training that results in several adverse effects the main of which being the decay in performance. Its incidence among elite athletes has been experiencing a significant increase lately, which prompted a rush of interest in the search for efficient measures to prevent and treat this condition. It is necessary, however, to clarify possible mechanisms involved in the development of overtraining. Several hypothesis are being proposed, such as a greater activation of both the autonomic nervous system and the hypothalamic-pituitary-adrenal axis, and suppression of the hypothalamic-pituitary-gonadal axis. On the contrary, some studies suggest that the modulation of such systems is but a consequence of the overtraining syndrome and not its cause. Thus, recent hypothesis related to cytokine release, to central fatigue, to depletion of muscle and liver glycogen, and to a reduction in glutamine availability during physical activity are being raised.

Cytokines↗

PubMed2004

Effects of creatine supplementation on the performance and body composition of competitive swimmers.

The objective of this study was to determine the effect of creatine supplementation on performance and body composition of swimmers. Eighteen swimmers were evaluated in terms of post-performance lactate accumulation, body composition, creatine and creatinine excretion, and serum creatinine concentrations before and after creatine or placebo supplementation. No significant differences were observed in the marks obtained in swimming tests after supplementation, although lactate concentrations were higher in placebo group during this period. In the creatine-supplemented group, urinary creatine, creatinine, and body mass, lean mass and body water were significantly increased, but no significant difference in muscle or bone mass was observed. These results suggest that creatine supplementation cannot be considered to be an ergogenic supplement ensuring improved performance and muscle mass gain in swimmers.

Adolescent↗

PubMed2002

[Creatine: the nutritional supplement for exercise - current concepts].

Creatine, a natural nutrient found in animal foods, is alleged to be an effective nutritional ergogenic aid to enhance sport or exercise performance. It may be formed in kidney and liver from arginina and glicina. Creatine may be delivered to the muscle, where it may combine readily with phosphate to form creatine phosphate, a high-energy phosphagen in the ATP-CP system, and is stored. The ATP-CP energy system is important for rapid energy production, such as in speed and power events. Approximately 120 g of creatine is found in a 70 kg male, 95% in the skeletal muscle. Total creatine exists in muscle as both free creatine (40%) and phosphocreatine (60%). It is only recently that a concerted effort has been undertaken to investigate its potential ergogenic effect relative to sport or exercise performance. It does appear that oral creatine monohydrate may increase muscle total creatine, including both free and phosphocreatine. Many, but not all studies suggest that creatine supplementation may enhance performance in high intensity, short-term exercise task that are dependent primarily on the ATP-CP energy system, particularly on laboratory test involving repeated exercise bouts with limited recovery time between repetitions. Short-term creatine supplementation appears to increase body mass, although the initial increase is most likely water associated with the osmotic effect of increased intramuscular total creatine. Chronic creatine supplementation in conjunction with physical training involving resistance exercise may increase muscle mass. However, confirmatory research data are needed. Creatine supplementation up to 8 weeks, with high doses, has not been associated with major health risks; with low doses, it was demonstrated that in 5 years period supplementation, there are no adverse effects. The decision to use creatine as a mean to enhance sport performance is left to the description to the individual athlete.

Creatine↗