• The effect of beetroot juice on intermittent shuttle running performance involving different numbers of directional changes

      Highton, Jamie; Francis, Ben (University of Chester, 2018-10-01)
      The aim of the study was to assess the effect of dietary nitrate (NO3-) supplementation on blood pressure and the physiological responses to submaximal shuttle running and performance during intermittent shuttle running involving different numbers of directional changes. Eight male recreational team sport athletes (age: 22.6 ± y, body mass: 79.4 ± 4.4 kg, stature: 179.4 ± 5.4 cm, predicted VO2max: 48.5 ± 4,1 ml·kg·-1·min·-1) completed submaximal shuttle running at 60% of their predetermined VO2peak and intermittent shuttle running to exhaustion over a 20 m course or a 10 m course involving more directional changes. Participants performed each protocol twice across four trials; once following the ingestion of NO3 - concentrated beetroot juice 2.5 h before exercise and once following the ingestion of NO3 - depleted beetroot juice. Oxygen uptake (VO2), heart rate (HR), rating of perceived exertion (RPE), blood lactate and time to exhaustion during intermittent shuttle running were assessed. Increasing the number of directional changes increased the VO2 and HR response to submaximal shuttle running (p < 0.05). However, NO3 - did not affect blood pressure, the physiological responses to submaximal exercise or performance during intermittent shuttle running (p > 0.05). These findings indicate that increasing the number of directional changes during shuttle running elevates the physiological and metabolic demand, but that NO3 - does not impact upon the physiological responses or performance during submaximal and intermittent shuttle running.