ABSTRACT
BACKGROUND: Referees' activity can be an instrument for training students with an impact on health-related physical fitness (PF). This study aimed to investigate the differences in PF and body composition between students without sports practice (G1), students with regular sports practice (G2), and student referees in team invasion games (G3). METHODS: This study followed a cross-sectional design. The sample comprised 45 male students between 14 and 20 years old (16.40 ± 1.85). Three groups (G1, G2, and G3) of 15 participants each were selected. PF was assessed by a 20 m shuttle run, change-of-direction test, and standing long jump. Body composition was determined by body mass index (BMI; kg/m2) and the percentage of body fat (%BF) predicted by skinfold. RESULTS: After controlling for age as a covariate, the block of variables used to characterize PF was statistically different between sports practice groups favoring student referees (p < 0.001; r = 0.26). Similar results were achieved for body composition (i.e., BMI and %BF) (p < 0.001; r = 0.17). However, when the dependent variables were evaluated separately, there were only differences between groups in %BF (p = 0.007; r = 0.21). Student referees had statistically significantly lower values than the remaining groups. CONCLUSION: Refereeing activity benefits PF related to health and performance, including body composition. This study confirms the benefits related to health in children and adolescents who are involved in refereeing activity.
ABSTRACT
The teaching of evolution was the subject of intense controversy in the United States in the first decades of the twentieth century. Both the validity of the theory and its ethical, political and religious implications were in dispute. This article analyzes a magazine intended to popularize science in this context, Evolution: a Journal of Nature (1927-1938). The objective is to demonstrate that the dynamics of the public circulation of knowledge represented by the magazine cannot be reduced to a process of simplification, eliminating details and exceptions of little use to the general public, but rather consisted of a complete adaptation, creatively connecting scientific knowledge to questions of great importance in the public arena.
O ensino de evolução foi objeto de intensa controvérsia nos EUA nas primeiras décadas do século XX. Em disputa, estava não apenas a validade da teoria, mas também a consideração de suas implicações éticas, políticas e religiosas. Este artigo analisa uma revista de popularização científica inserida nesse contexto, a Evolution: a Journal of Nature (1927-1938). O objetivo é demonstrar que a dinâmica de circulação pública do conhecimento representada pela revista não se resumiu a um processo de simplificação, eliminando detalhes e ressalvas pouco úteis ao público não especializado, mas antes consistiu em uma completa adaptação, confrontando criativamente o conhecimento científico com questões de grande importância na arena pública.
Subject(s)
Dissent and Disputes , Knowledge , Biological Evolution , Morals , United StatesABSTRACT
A low resting heart rate (HR) would be of great benefit in cardiovascular diseases. Ivabradine-a novel selective inhibitor of hyperpolarization-activated cyclic nucleotide gated (HCN) channels- has emerged as a promising HR lowering drug. Its effects on the autonomic HR control are little known. This study assessed the effects of chronic treatment with ivabradine on the modulatory, reflex and tonic cardiovascular autonomic control and on the renal sympathetic nerve activity (RSNA). Male Wistar rats were divided in 2 groups, receiving intraperitoneal injections of vehicle (VEH) or ivabradine (IVA) during 7 or 8 consecutive days. Rats were submitted to vessels cannulation to perform arterial blood pressure (AP) and HR recordings in freely moving rats. Time series of resting pulse interval and systolic AP were used to measure cardiovascular variability parameters. We also assessed the baroreflex, chemoreflex and the Bezold-Jarish reflex sensitivities. To better evaluate the effects of ivabradine on the autonomic control of the heart, we performed sympathetic and vagal autonomic blockade. As expected, ivabradine-treated rats showed a lower resting (VEH: 362 ± 16 bpm vs. IVA: 260 ± 14 bpm, p = 0.0005) and intrinsic HR (VEH: 369 ± 9 bpm vs. IVA: 326 ± 11 bpm, p = 0.0146). However, the chronic treatment with ivabradine did not change normalized HR spectral parameters LF (nu) (VEH: 24.2 ± 4.6 vs. IVA: 29.8 ± 6.4; p > 0.05); HF (nu) (VEH: 75.1 ± 3.7 vs. IVA: 69.2 ± 5.8; p > 0.05), any cardiovascular reflexes, neither the tonic autonomic control of the HR (tonic sympathovagal index; VEH: 0.91± 0.02 vs. IVA: 0.88 ± 0.03, p = 0.3494). We performed the AP, HR and RSNA recordings in urethane-anesthetized rats. The chronic treatment with ivabradine reduced the resting HR (VEH: 364 ± 12 bpm vs. IVA: 207 ± 11 bpm, p < 0.0001), without affecting RSNA (VEH: 117 ± 16 vs. IVA: 120 ± 9 spikes/s, p = 0.9100) and mean arterial pressure (VEH: 70 ± 4 vs. IVA: 77 ± 6 mmHg, p = 0.3293). Our results suggest that, in health rats, the long-term treatment with ivabradine directly reduces the HR without changing the RSNA modulation and the reflex and tonic autonomic control of the heart.