The effect of nitrate supplementation on sport performance: High intensity intermittent performance in recreational athletes

Oral ingestion of nitrate (NO3-) in the form of both nitrate salts and
concentrated red beetroot juice has been shown to significantly lower blood
pressure at rest and to improve exercise performance during cycle time trials.
Furthermore, a positive exercise performance effect of nitrate ingestion has
been observed in recreational athletes during intermittent exercise. However,
this was achieved after acute supplementation with a substantial dose of
dietary nitrate. Whether similar ergogenic effects of nitrate supplementation
can be achieved with a more conventional 6-day nitrate supplementation protocol
with a lower daily dose remains to be established. Based on the gaps in current
literature, our main goal will be to gain further insight into the effects of a
6-day nitrate supplementation protocol on high intensity intermittent exercise
performance in recreational athletes.

The objective of the current study is to assess the effect of 6-day dietary
nitrate ingestion on high intensity intermittent sports performance in
recreational soccer players.

This study is a double-blind, randomized cross-over placebo controlled study.
Over a 3 week period, 1 day every 2 weeks, subjects will be requested to
perform an intermittent exercise performance test (Yo-Yo IR1 test). In the 5
days leading up to the exercise test, subjects will be asked to consume 1 dose
of the supplement ( nitrate or placebo) daily and a last dose on the test day.

6 days of supplementation with 6x 800-1000 mg (800-1000 mg/day) nitrate in the
form of 140 mL concentrated red beetroot juice, or 6x 140 mL nitrate-depleted
concentrated red beetroot juice (placebo), separated by a 1 week wash out
period.

Subjects will be required to report to the laboratory for a total of 4 visits
(i.e. including screening and familiarization visits). On test days, subjects
will be asked to fill out a questionnaire on the gastro-intestinal tolerance
before commencing with the intermittent exercise test. A venous blood sample
will also be collected as a pre-exercise measurements through the use of a
venipuncture in a forearm vein. Subjects will also be asked to provide a sample
of unstimulated saliva during the same time point. After the pre-exercise
measurements and a standardized warm-up, subjects will be required to perform
an intermittent exercise test (Yo-Yo IR1 test). Prior to the familiarization
test, subjects will be asked to record their diet and activity for 36 h and
refrain from strenuous physical exercise or labour for the 24 h preceding the
visit. They will be asked to replicate their food intake and refrain from
exercise for the 36 h and 24 h respectively, prior to the 2 subsequent trial
visits. Subjects will also be asked to avoid alcohol for 24 h and caffeine for
12 h preceding each trial day, and to have their final standardized meal and
drink (except for water), 3 h prior to performing the intermittent exercise
test on the evening of a test day. The subjects will be asked to fill out a
medical questionnaire at the screening. The risks that are associated with
participating in this study are low. The dose of concentrated red beetroot
juice used in the current study has been administered in multiple clinical and
exercise studies. No adverse events were reported, except for reports of mild
headache (which may or may not be associated with the intake of nitrate). The
long term effects of nitrate ingestion still need to be fully investigated. The
use of nitrate rich beverages has however been described to lead to mild
gastrointestinal distress (bloating, belching) in some cases. Performing a
venipuncture can result in a small risk of fainting or developing a hematoma
when the needle is subsequently removed. This risk is very small due to the
fact that the blood draw will be done by well trained and experienced staff
members. For the intermittent exercise test, the potential risks and
discomforts inherent to the exercise testing procedure during each visit are
minimal and are similar to those associated with any form of strenuous physical
activity including fatigue, fainting, abnormal blood pressure etc.