Ischaemic preconditioning blunts exercise-induced mitochondrial dysfunction, speeds oxygen uptake kinetics but does not alter severe-intensity exercise capacity.

Abstract

What is the central question of this study? Ischaemic preconditioning is a novel pre-exercise priming strategy. We asked whether ischaemic preconditioning would alter mitochondrial respiratory function and pulmonary oxygen uptake kinetics and improve severe-intensity exercise performance. What is the main finding and its importance? Ischaemic preconditioning expedited overall pulmonary oxygen uptake kinetics and appeared to prevent an increase in leak respiration, proportional to maximal electron transfer system and ADP-stimulated respiration, that was evoked by severe-intensity exercise in sham-control conditions. However, severe-intensity exercise performance was not improved. The results do not support ischaemic preconditioning as a pre-exercise strategy to improve exercise performance in recreationally active participants. We examined the effect of ischaemic preconditioning (IPC) on severe-intensity exercise performance, pulmonary oxygen uptake ( ) kinetics, skeletal muscle oxygenation (muscle tissue O2 saturation index) and mitochondrial respiration. Eight men underwent contralateral IPC (4×5min at 220mmHg) or sham-control (SHAM; 20mmHg) before performing a cycling time-to-exhaustion test (92% maximum aerobic power). Muscle (vastus lateralis) biopsies were obtained before IPC or SHAM and ∼1.5min postexercise. The time to exhaustion did not differ between SHAM and IPC (249±37vs. 240±32s; P=0.62). Pre- and postexercise ADP-stimulated (P) and maximal (E) mitochondrial respiration through protein complexes (C) I, II and IV did not differ (P>0.05). Complex I leak respiration was greater postexercise compared with baseline in SHAM, but not in IPC, when normalized to wet mass (P=0.01vs. P=0.19), mitochondrial content (citrate synthase activity, P=0.003vs. P=0.16; CI+IIP, P=0.03vs. P=0.23) and expressed relative to P (P=0.006vs. P=0.30) and E (P=0.004vs. P=0.26). The mean response time was faster (51.3±15.5vs. 63.7±14.5s; P=0.003), with a smaller slow component (270±105vs. 377±188mlmin-1 ; P=0.03), in IPC compared with SHAM. The muscle tissue O2 saturation index did not differ between trials (P>0.05). Ischaemic preconditioning expedited kinetics and appeared to prevent an increase in leak respiration through CI, when expressed proportional to E and P evoked by severe-intensity exercise, but did not improve exercise performance.