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

Abstract

ObjectivesDietary 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. DesignDouble-blind randomized crossover trial. MethodsTen competitive male cyclists (age 34±6years, body mass 78.9±4.9kg, V⋅O2peak 55±4 mLkgmin−1) completed an incremental exercise test followed by three cycling trials comprising a square-wave submaximal component and a 16.1km time-trial. Oxygen uptake (V⋅O2) 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 3×5min bouts of lower limb bilateral IPC prior to exercise. Participants ingested NO3−-rich gel (NIT+IPC) 90min 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. ResultsPlasma [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 V⋅O2 kinetics or muscle oxygenation parameters between trials (all P>0.4). Performance in the time-trial was similar between trials (BASE 1343±72s, PLA+IPC 1350±75s, NIT+IPC 1346±83s, P=0.98). ConclusionsPre-exercise IPC did not improve sub-maximal exercise or performance measures, either alone or in combination with dietary NO3− supplementation.