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Consumption of nitric oxide precursors only via consumption of whole foods, juices, concentrates or plant extracts. Studies must explicitly state the food source(s) of these compounds.
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Differences in bioavailability between food and synthetic sources.
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Foods could not be consumed in combination with other (non-nitric oxide precursor) foods/supplements that may influence endurance exercise performance (e.g. caffeine) unless the comparator group also contains these components. Such interventions will be included in the qualitative synthesis only.
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Confounds the ability to infer the effect of increasing intake of nitric-oxide precursors.
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Report an external (or externally derived) measure of maximal endurance exercise performance in a test of at least two minutes durations.
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Maximise the contribution of the aerobic energy system to exercise performance and thus provide a measure of endurance exercise performance.
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Intermittent-type performance tests required a work duration of at least two minutes and could not have between-repetition recovery intervals of >60 secs
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Maximise the contribution of the aerobic energy system to exercise performance and thus provide a measure of endurance exercise performance.
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Performance tests conducted in normobaric, normoxic and temperate conditions.
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Variant conditions may influence the function of the nitric oxide pathway and the effects of nitric oxide-related supplementation
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Where performance tests were acutely repeated (e.g. repeated time trials), only data from the initial performance test were considered eligible.
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Performance in subsequent trial(s) may be confounded by initial performance and factors which influence recovery.
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Study sample participants aged 18-65 years
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Exclude adolescent and older adult populations due to age-based differences in vascular function and oxidative stress
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