Lower limb ischemic preconditioning combined with dietary nitrate supplementation does not influence time-trial performance in well-trained cyclists

Objectives: Dietary nitrate (NO3-) supplementation and ischaemic preconditioning (IPC) can independently improve exercise performance. The purpose of this study was to explore whether NO3- supplementation, ingested prior to an IPC protocol, could synergistically enhance parameters of exercise. Design: Double-blind randomized crossover trial. Methods: Ten competitive male cyclists (age 34 +/- 6 years, body mass 78.9 +/- 4.9 kg, VO2peak 55 +/- 4 mL kg min(-1)) completed an incremental exercise test followed by three cycling trials comprising a square- wave submaximal component and a 16.1 km time-trial. Oxygen uptake (VO2) and muscle oxygenation kinetics were measured throughout. The baseline (BASE) trial was conducted without any dietary intervention or IPC. In the remaining two trials, participants received 3 x 5 min bouts of lower limb bilateral IPC prior to exercise. Participants ingested NO3- rich gel (NIT + IPC) 90 min prior to testing in one trial and a low NO3- placebo in the other (PLA + IPC). Plasma NO3- and nitrite (NO2-) were measured immediately before and after application of IPC. Results: Plasma [NO3-] and [NO2-] were higher before and after IPC in NIT+ IPC compared to BASE (P< 0.001) but did not differ between BASE and PLA + IPC. There were no differences in VO2 kinetics or muscle oxygenation parameters between trials (all P> 0.4). Performance in the time-trial was similar between trials (BASE 1343 +/- 72 s, PLA + IPC 1350 +/- 75 s, NIT+ IPC 1346 +/- 83 s, P = 0.98). Conclusions: Pre-exercise IPC did not improve sub-maximal exercise or performance measures, either alone or in combination with dietary NO3- supplementation. (C) 2019 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.