乳酸代谢新探

目前在运动生理及其代谢领域中一个最显著的观念性革命是对乳酸代谢的新认识.过去乳酸一直被视为运动中缺氧代谢即糖酵解过程中的终产物,并在体内积蓄而引起机体疲劳和氧债形成.然而目前的研究资料却与之截然不同:乳酸的产生、     

No effect of fluid intake on neutrophil responses to prolonged cycling

Ingesting carbohydrate beverages during prolonged exercise is associated with fewer numbers of circulating neutrophils and attenuated neutrophil functional responses, yet there is little information about the effect of fluid intake alone on immune responses to prolonged exercise. The aim of this study was to examine the influence of regular fluid ingestion compared with no fluid ingestion on plasma cortisol, circulating neutrophil and lipopolysaccharide (LPS)-stimulated neutrophil degranulation responses to prolonged cycling. In a randomized design, nine recreationally active males cycled for 2 h at 65% VO2max on two occasions with either fluid ingestion (lemon-flavoured water, fluid trial) before and during the exercise, or with no fluid intake at all (no fluid trial). Venous blood samples were obtained at rest, immediately after exercise and 1 h after exercise. Immediately after exercise, the plasma cortisol concentration was significantly higher in the no fluid trial than in the fluid trial (592 +/- 62 vs 670 +/- 63 nmol x l(-1), P < 0.05). Circulating numbers of neutrophils increased 4.5-fold (P < 0.01) and LPS-stimulated elastase release per neutrophil decreased 34 +/- 7% (P < 0.01) immediately after exercise; there were no differences between trials. These results suggest that in ambient environmental conditions, fluid ingestion alone has a negligible effect on circulating neutrophil and LPS-stimulated neutrophil degranulation responses to prolonged exercise.     

Time - motion analysis of professional rugby union players during match-play

The aim of this study was to quantify the movement patterns of various playing positions during professional rugby union match-play, such that the relative importance of aerobic and anaerobic energy pathways to performance could be estimated. Video analysis was conducted of individual players (n=29) from the Otago Highlanders during six "Super 12" representative fixtures. Each movement was coded as one of six speeds of locomotion (standing still, walking, jogging, cruising, sprinting, and utility), three states of non-running intensive exertion (rucking/mauling, tackling, and scrummaging), and three discrete activities (kicking, jumping, passing). The results indicated significant demands on all energy systems in all playing positions, yet implied a greater reliance on anaerobic glycolytic metabolism in forwards, due primarily to their regular involvement in non-running intense activities such as rucking, mauling, scrummaging, and tackling. Positional group comparisons indicated that while the greatest differences existed between forwards and backs, each positional group had its own unique demands. Front row forwards were mostly involved in activities involving gaining/retaining possession, back row forwards tended to play more of a pseudo back-line role, performing less rucking/mauling than front row forwards, yet being more involved in aspects of broken play such as sprinting and tackling. While outside backs tended to specialize in the running aspects of play, inside backs tended to show greater involvement in confrontational aspects of play such as rucking/mauling and tackling. These results suggest that rugby training and fitness testing should be tailored specifically to positional groups rather than simply differentiating between forwards and backs.