Beetroot juice can boost men's stamina by making muscles more fuel-efficient, a study has found.The research, which was focused on men aged 19 to 38 cycling on exercise bikes, revealed that drinking half a litre of beetroot juice daily for a week enabled them to cycle 16 percent longer before getting tired out, reports The scientists found that drinking beetroot juice doubled the amount of nitrate in the blood of volunteers, and reduced the rate at which muscles used their main source of energy. The findings also revealed that beetroot juice helped muscles work more efficiently and lowered their oxygen uptake. Professor Andy Jones from the University of Exeter's School of Sport and Health Sciences who led the study, said: "Since our first study came out we have seen growing interest in the benefits of drinking beetroot juice in the world of professional sport. I expect this study to attract even more attention from athletes".