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BMJ Open Sport Exerc Med. 2019 Aug 7;5(1):e000560. doi: 10.1136/bmjsem-2019-000560. eCollection 2019.

Effects of almond, dried grape and dried cranberry consumption on endurance exercise performance, recovery and psychomotor speed: protocol of a randomised controlled trial.

Author information

School of Health Science, University of South Australia, Adelaide, South Australia, Australia.
School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, Australia.



Foods rich in nutrients, such as nitrate, nitrite, L-arginine and polyphenols, can promote the synthesis of nitric oxide (NO), which may induce ergogenic effects on endurance exercise performance. Thus, consuming foods rich in these components, such as almonds, dried grapes and dried cranberries (AGC), may improve athletic performance. Additionally, the antioxidant properties of these foods may reduce oxidative damage induced by intense exercise, thus improving recovery and reducing fatigue from strenuous physical training. Improvements in NO synthesis may also promote cerebral blood flow, which may improve cognitive function.

Methods and analysis:

Ninety-six trained male cyclists or triathletes will be randomised to consume ~2550 kJ of either a mixture of AGC or a comparator snack food (oat bar) for 4 weeks during an overreaching endurance training protocol comprised of a 2-week heavy training phase, followed by a 2-week taper. The primary outcome is endurance exercise performance (5 min time-trial performance) and secondary outcomes include markers of NO synthesis (plasma and urinary nitrites and nitrates), muscle damage (serum creatine kinase and lactate dehydrogenase), oxidative stress (F2-isoprostanes), endurance exercise function (exercise efficiency, submaximal oxygen consumption and substrate utilisation), markers of internal training load (subjective well-being, rating of perceived exertion, maximal rate of heart rate increase and peak heart rate) and psychomotor speed (choice reaction time).


This study will evaluate whether consuming AGC improves endurance exercise performance, recovery and psychomotor speed across an endurance training programme, and evaluate the mechanisms responsible for any improvement.

Trial registration number:



cognitive function; dried fruit; exercise performance; nitric oxide; recovery; tree nuts

Conflict of interest statement

Competing interests: This study is funded by a grant from the International Nut and Dried Fruit Council Foundation, although they have not and will not be involved in the collection, analysis and interpretation of data, or the preparation or submission of the article for publication. JB invented the rHRI technology that will be used in this study. The rHRI technology has been patented by the University of South Australia and JB has assigned all the rights of this technology to the University. AC has previously provided consultancy services to Nuts For Life, an Australian initiative established to provide information about the health effects of tree nuts.

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