Optimization of oar blade design for improved performance in rowing

Abstract

The aim of the present study was to find a more optimal blade design for rowing performance than the Big Blade, which has been shown to be less than optimal for propulsion. As well as the Big Blade, a flat Big Blade, a flat rectangular blade, and a rectangular blade with the same curvature and projected area as the Big Blade were tested in a water flume to determine their fluid dynamic characteristics at the full range of angles at which the oar blade might present itself to the water. Similarities were observed between the flat Big Blade and rectangular blades. However, the curved rectangular blade generated significantly more lift in the angle range 0 – 90° than the curved Big Blade, although it was similar between 90 and 180°. This difference was attributed to the shape of the upper and lower edges of the blade and their influence on the fluid flow around the blade. Although the influence of oar blade design on boat speed was not investigated here, the significant increases in fluid force coefficients for the curved rectangular blade suggest that this new oar blade design could elicit a practically significant improvement in rowing performance.     

A fluid dynamic investigation of the Big Blade and Macon oar blade designs in rowing propulsion

Abstract

The purpose of this investigation was to examine the fluid dynamic characteristics of the two most commonly used oar blades: the Big Blade and the Macon. Scaled models of each blade, as well as a flat Big Blade, were tested in a water flume using a quasi-static method similar to that used in swimming and kayaking research. Measurement of the normal and tangential blade forces enabled lift and drag forces generated by the oar blades to be calculated over the full range of sweep angles observed during a rowing stroke. Lift and drag force coefficients were then calculated and compared between blades. The results showed that the Big Blade and Macon oar blades exhibited very similar characteristics. Hydraulic blade efficiency was not therefore found to be the reason for claims that the Big Blade could elicit a 2% improvement in performance over the Macon. The Big Blade was also shown to have similar characteristics to the flat plate when the angle of attack was below 90°, despite significant increases in the lift coefficient when the angle of attack increased above 90°. This result suggests that the Big Blade design may not be completely optimized over the whole stroke.     

不同剂量茶多糖补充对运动大鼠心肌、血清自由基代谢的影响

为了解不同剂量茶多糖补充对长期大负荷运动大鼠心肌、血清自由基代谢的影响,本研究通过建立灌服不同剂量茶多糖大鼠的长期大负荷游泳训练实验模型,测定大鼠心肌、血清的丙二醛(MDA)含量,超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)和过氧化氢酶(CAT)的活性。结果表明:与运动组相比,运动+茶多糖Ⅰ组、运动+茶多糖Ⅱ组和运动+茶多糖Ⅲ组心肌、血清的MDA含量明显下降,SOD、GSH-Px和CAT活性明显升高,且运动+茶多糖Ⅰ组与运动组间有极显著性差异(P<0.01),运动+茶多糖Ⅱ组和运动+茶多糖Ⅲ组与运动+茶多糖Ⅰ组间有极显著性差异(P<0.01),运动+茶多糖Ⅲ组与运动+茶多糖Ⅱ组间具有显著性差异(P<0.05),呈现一种剂量依赖性:茶多糖补充剂量越高,MDA下降越明显,SOD、GSH-Px和CAT活性升高越明显。提示茶多糖具有较强的抗自由基损伤和抗脂质过氧化的作用,长期服用茶多糖可以有效地减轻运动产生的内源性自由基对大鼠心血管系统的损伤,对大鼠心血管系统产生有效的保护作用。     

游泳耐力训练对高脂饮食大鼠肝组织自由基代谢及肝细胞凋亡的影响

目的：通过对8-12周游泳耐力训练前后大鼠肝组织SOD、MDA、线粒体膜电位以及肝细胞凋亡率的测定及分析,考察长期耐力训练对于高脂饮食诱导大鼠肝细胞凋亡的影响与机制,为运动预防NASH提供新的切入点。方法：采用SD雄性大鼠44只,适应性喂养1周后,随机分为6组：8周对照组、8周高脂组、8周高脂运动组、12周对照组、12周高脂组和12周高脂运动组。对照组给予普通饲料喂养,高脂组和高脂运动组给予高脂饲料喂养;对照组和高脂组不施加运动干预,高脂运动组大鼠于每日上午8～9时进行无负重游泳运动,每周5次。运动负荷为第1周每次游泳30min,第2周60min,第3周90min,然后以此运动量一直保持到12周结束。用流式细胞仪法检测8周和12周耐力训练后肝细胞自由基代谢、线粒体膜电位和细胞凋亡变化。结果：8周高脂运动组的肝细胞凋亡率显著高于高脂组（P〈0.05）,12周高脂运动组则显著低于高脂组（P〈0.05）;8周高脂运动组肝脏SOD显著高于高脂组（P〈0.05）,12周也显著高于高脂组（P〈0.05）;8周高脂运动组MDA显著低于高脂组（P〈0.05）,12周组非常显著低于高脂组（P〈0.01）;8周高脂运动组线粒体膜电位显著高于高脂组（P〈0.05）,12周组非常显著高于高脂组（P〈0.01）。结论：长期有氧耐力训练可以通过降低脂质过氧化物的生成和加速过氧化物的清除,提高肝脏的抗氧化能力,使肝细胞线粒体产生适应性改变,膜电位升高,最终抑制高脂饮食诱导NASH大鼠肝细胞凋亡率的显著升高。     

The effect of three surface conditions,speed and running experience on vertical acceleration of the tibia during running*

Research has focused on parameters that are associated with injury risk, e.g. vertical acceleration. These parameters can be influenced by running on different surfaces or at different running speeds, but the relationship between them is not completely clear. Understanding the relationship may result in training guidelines to reduce the injury risk. In this study, thirty-five participants with three different levels of running experience were recruited. Participants ran on three different surfaces (concrete, synthetic running track, and woodchip trail) at two different running speeds: a self-selected comfortable speed and a fixed speed of 3.06 m/s. Vertical acceleration of the lower leg was measured with an accelerometer. The vertical acceleration was significantly lower during running on the woodchip trail in comparison with the synthetic running track and the concrete, and significantly lower during running at lower speed in comparison with during running at higher speed on all surfaces. No significant differences in vertical acceleration were found between the three groups of runners at fixed speed. Higher self-selected speed due to higher performance level also did not result in higher vertical acceleration. These results may show that running on a woodchip trail and slowing down could reduce the injury risk at the tibia.