Desempenho da potência anaeróbia em atletas de elite do mountain bike submetidos à suplementação aguda com creatina

Unaltered R-R interval variability and bradycardia in cyclists as compared with non-athletes

PURPOSE

To test whether elite mountain bikers display a cardiac autonomic modulation pattern that is distinctive from that of active non-athletes.

BACKGROUND

The relationship between autonomic adaptation and bradycardia during physical exercise, including high-performance sports such as the mountain biking, remains to be elucidated.

METHODS

Twelve elite mountain bikers and 11 matched non-athletes controls were evaluated for time- and frequency-domain heart rate variability based on a 5-min ECG R-R intervals series obtained in both the supine and the orthostatic positions. Oxygen uptake and pulse rate were obtained at ventilatory thresholds and peak effort during an incremental cardiopulmonary exercise test. Significance of differences between medians (25th, 75th percentiles) from the two groups was evaluated by the Mann-Whitney test at p ≤ 0.05.

RESULTS

Athletes had lower heart rate [50 (47, 59) versus 63 (60, 69) bpm; p = 0.0004] and higher cardiopulmonary performance than controls [70.9 (64.6, 74.4) versus 47.7 (41.0, 51.9) mL (kg min)(-1); p = 0.01]. No statistical difference was found in heart rate variability in the group of athletes (p = 0.17-0.97), except for trend toward having lower coefficient of variation and low-frequency absolute power indices both in supine position (p = 0.06).

CONCLUSIONS

Bradycardia and higher oxygen uptake were found in association with unaltered cardiac autonomic modulation in elite mountain bikers athletes in supine and orthostatic positions, compared to active non-athletes. This bradycardia was not dependent on distinctive resting autonomic modulation. Intrinsic adaptation of sinus node and/or a peculiar state of autonomic adaptation to this exercise can be possible mechanisms.

Suplementação com creatina associada ao treinamento resistido não altera as funções renal e hepática

A creatina é o suplemento nutricional mais popular utilizado para melhorar o desempenho em atividades que envolvem exercícios de curta duração e alta intensidade. Porém, as possíveis intercorrências advindas do seu uso não estão totalmente elucidadas. O objetivo do estudo foi avaliar os efeitos de duas dosagens de suplementação com creatina nas funções renal e hepática de adultos saudáveis durante oito semanas de treinamento de musculação. Exames bioquímicos foram realizados em 35 praticantes de musculação distribuídos aleatoriamente em três grupos, placebo (PLA, n = 12), creatina (CRE1, n = 12) e creatina 2 (CRE2, n = 11), antes e após oito semanas de treinamento com exercícios resistidos. Em desenho duplo-cego, os voluntários foram suplementados (20g/dia) com creatina (CRE1 e CRE2) ou placebo (PLA) por sete dias e nos 53 dias subsequentes com 0,03g/kg de massa corporal de creatina (CRE1) e placebo (PLA) e com 5g/dia o grupo CRE2. Não houve intervenção na composição de suas dietas, que foram registradas e analisadas. Os resultados dos exames bioquímicos realizados permaneceram dentro das faixas de normalidade. Os valores de creatinina aumentaram 12,2% no grupo CRE1 e 9,0%, no CRE2, enquanto que no grupo PLA diminuiu 4,7%, entretanto, esses valores não ultrapassaram os índices de normalidade. Os valores dos exames da função hepática diminuíram em quase todas as frações, em todos os tratamentos, contudo, sem significância estatística. Conclui-se que a suplementação com creatina nas dosagens utilizadas (0,03g/kg e 5g/dia) para indivíduos saudáveis por oito semanas não altera a função hepática ou renal, sendo assim, nas condições deste estudo, foi considerada segura.

The locomotor system as seen in Brazilian scientific journals: a mini review

OBJECTIVE

To make recent selected publications on the locomotor system available to the readership of Clinics.

METHOD

A general survey of articles published in selected Brazilian journals was inspected and 91 articles were critically analyzed. They were categorized and briefly described. A final summary of themes is reproduced here.

RESULTS

Papers fall into two main categories: articular and muscular pathology and therapeutics; medical sports. A number of papers are not classifiable under these headings.

CONCLUSION

The locomotor system has been extensively analyzed and discussed in the Brazilian scientific press in recent years. Not surprisingly, knee and ankle pathology, soccer and running are dominant themes.