The effect of a dietary nitrate supplementation in the form of a single shot of beetroot juice on static and dynamic apnoea performance

Introduction: The purpose of the present study was to assess the effects of acute nitrate (NO3-)-rich beetroot juice supplementation on peripheral oxygen saturation (SpO2), heart rate (HR), and pulmonary gas exchange during submaximal static and dynamic apnoea. Methods: Nine (six male, three female) trained apneists (age: 39.6 ± 8.2 years, stature: 170.4 ± 11.5cm, body mass: 72.0 ± 11.5 kg) performed three submaximal static apnoeas at 60%, 70% and 80% of the participant’s current reported personal best time, followed by three submaximal (~ 75% or personal best distance) dynamic apnoeas following the consumption of either a 140 ml concentrated NO3--rich beetroot juice (BRJ; 7.7 mmol NO3-) or a NO3--depleted placebo (PLA; 0.1 mmol NO3-) in double-blind randomised manner. HR and SpO2 were measured via fingertip pulse oximetry at the nadir, and online gas analysis was used to assess pulmonary oxygen uptake (V̇O2) during recovery following breath-holds. Results: There were no differences (P <0.05) between conditions for HR (PLA = 59 ± 11 bpm and BRJ = 61 ± 12 bpm), SpO2 (PLA = 83 ± 14% and BRJ = 84 ± 9%) or V̇O2 (PLA = 1.00 ± 0.22 L.min-1 and BRJ = 0.97 ± 0.27 L.min-1). Conclusion: The consumption of 7.7mmol of beetroot juice supplementation prior to a series of submaximal static and dynamic apnoeas did not induce a significant change in SpO2, HR and V̇O2, when compared to placebo. Therefore there is no apparent physiological response that may benefit free-divers as a result of the supplementation.