Nitric oxide (NO) has been identified as an important biological messenger involved in a number of physiological processes and is produced from L-arginine and molecular oxygen by NO-synthases or the more recently identified nitrate to nitrite to NO pathway. Dietary nitrate can be found in green leafy vegetables and is particularly abundant in beetroot and has been shown to be a potential ergogenic agent. The nitrate to nitrite to NO pathway has been shown to be involved in a number of physiological processes that could account for the improved exercise response following nitrate ingestion. However, the benefits of nitrate as an ergogenic aid have been shown to be effected by numerous factors that can influence its efficacy. These include age, training level, dosage and the mode, duration and intensity of the exercise.~Research with healthy younger moderately trained adults has repeatedly shown that ingestion of dietary nitrate can reduce the oxygen cost of submaximal exercise and improve exercise performance during high intensity exercise; whereas research with younger more highly trained endurance athletes is equivocal, since some studies have failed to demonstrate an improvement in exercise performance following nitrate ingestion.~The effects of nitrate have also been shown to be influenced by age. It has been documented that there are alterations in NO metabolism in older adults thought to result from impairment of the NO-synthases pathway. The investigators have shown that consumption of a supplement high in nitrate, such as beetroot juice, leads to elevated plasma nitrite levels and may help restore NO metabolism in older adults; whereas a diet high in nitrate without supplementation was insufficient at increasing plasma nitrite levels. The investigators research, along with that of others has shown nitrate supplementation to have positive effects in older adults with chronic diseases. However, research examining the effects of dietary nitrate on exercise performance in healthy older adults is scarce. Presently, it is unclear as to whether nitrate supplementation is beneficial to exercise performance in older adults and there is no data examining the effect of nitrate supplementation on exercise performance in active older adults. Therefore, the purpose of this study is to examine the effect of chronic nitrate supplementation on exercise performance in active higher functioning older adults.
Research with young healthy individuals has shown that beetroot juice beverages that contain large amounts of nitrate can improve exercise performance. Currently, it is not know whether the consumption of beetroot juice beverages high in nitrate can improve exercise performance in higher functioning middle- to older-aged adults. Therefore, the purpose of this study is to compare the effect of two different beetroot juice beverages (one high in nitrate and one low in nitrate) on exercise performance in middle- to older-aged adults.