Effect of New Zealand Blackcurrant Extract on Substrate Oxidation and Cycling Performance in Normobaric Hypoxia

Blackcurrant is high in anthocyanin content. We have shown enhanced whole-body fat oxidation and increased time trial performance during cycling, in addition to increased femoral artery diameter during a sustained submaximal isometric contraction of the m.quadriceps with intake of New Zealand blackcurrant (NZBC) extract in normobaric normoxia (Cook et al., 2015, 2017). The effect of blackcurrant on metabolic and physiological responses and performance during cycling in normobaric hypoxia are not known. PURPOSE: To examine the effect of NZBC extract on intensity-dependent physiological and metabolic responses and 16.1-km cycling time trial in trained cyclists in normobaric hypoxia. METHODS: The study used a double-blind randomized cross-over design. Eleven healthy men from cycling and triathlon clubs with at least 3 yrs experience and cycling 8-10 hr·wk−1 (age: 38±11 yrs, height: 179±4 cm, body mass: 76±8 kg, V̇O2max: 47±5 mL·kg−1·min−1, maximum power: 398±38 W, mean±SD) ingested NZBC extract (600 mg·day−1 containing 220 mg anthocyanins) or placebo (PL) for 7 days (washout 14 days). Participants performed bouts of 10 min at 45, 55 and 65% V̇O2max, using indirect calorimetry and blood sampling, followed by a 16.1 km timetrial on a SRM ergometer (SRM International, Germany). Participants were familiarized for the time-trial. All testing took place in a temperature controlled (15°C) normobaric hypoxic chamber set at an altitude of ~2500 m (15% FiO2) (TIS Services, Medstead, UK) in morning sessions. Data was analysed using paired t-tests. RESULTS: At each intensity, NZBC extract had no effect on metabolic and physiological responses (e.g. at 65% V̇O2max, heart rate - PL: 133±12, NZBC; 132±12 beats·min-1); fat oxidation - PL: 0.24±0.12, NZBC: 0.20±0.16 g·min-1; carbohydrate oxidation - PL: 2.34±0.42, NZBC: 2.48±0.35 g·min-1; lactate - PL: 1.37±0.45, NZBC: 1.56±0.57 mmol·L-1). No improvements in 16.1 km time-trial performance were observed (PL: 1685±92, NZBC: 1685±99 sec). CONCLUSION: Seven day intake of New Zealand blackcurrant extract does not change whole-body fat oxidation and 16.1 km time-trial performance during cycling in normobaric hypoxia.