Impact of Remote Ischemic Preconditioning Post-application Delay on Muscle Oxygenation during Subsequent Cycling Intervals

INTRODUCTION: Remote ischemic preconditioning (RIPC) involves brief, repeated bouts of manually-imposed blood flow restriction of the arms or legs. The alternating periods of occlusion and reperfusion lead to endothelial adaptations, capable of enhancing blood flow and oxygen delivery. PURPOSE: The aim of this study was to investigate the effect of a lower limb RIPC protocol, with either a 5-min or 45-min post-application delay, on muscle oxygen saturation within that same limb at rest and during short- duration intense cycling. METHODS: Subjects included recreationally aerobically trained college-aged students (23± 3 years, 173.5± 5.4 cm, 69.2± 4.0 kg, 15.2± 4.0 % BF, 2peak VO : 46.6± 1.1 mL•kg-1•min-1 at 215± 19 W). All subjects randomly completed four experimental trials: RIPC with 5-min delay, RIPC with 45-min delay, SHAM with 5-min delay, and SHAM with 45-min delay. For the RIPC conditions, each subject received 5-min of alternating-leg blood flow occlusion using a blood pressure cuff (220 mmHg) placed on the upper thighs for a total of 40 min. After a 5 or 45-min delay, the subjects completed 5, 1-min cycle sprints separated by 2 min of recovery. The SHAM conditions were identical to the RIPC, however, subjects laid supine for the same 40-min duration with alternating-leg cuff inflation to 20 mmHg. Muscle oxygen saturation was measured continuously using a portable NIRS-based sensor placed over the vastus lateralis (VL). RESULTS: RIPC decreased muscle oxygen saturation in the VL in a replicable manner (MD: 29.5± 13.4%, mean occlusion slope: -5.0± 2.4 %•min-1, mean reperfusion slope: 38.5± 22.4%•min-1) while SHAM conditions left muscle oxygen saturation largely unchanged (MD: 2.9± 1%). Mean VL oxygen saturation (RIPC45:71.9± 0.7%; RIPC5: 67.3± 1.7%; SHAM45: 72.0± 4.4%; SHAM5: 69.9± 3.0%) and preservation of muscle oxygen saturation (MD: RIPC45: -12.4± 6.2%; RIPC5: -14.4± 9.9%; SHAM45: -11.6± 6.4%; SHAM5: -13.0± 7.1%) during high intensity cycling intervals varied minutely between experimental conditions. CONCLUSIONS: The muscle oxygenation response during a standard occlusion/reperfusion protocol may lack assumed constancy. Furthermore, the use of RIPC and the length of the delay following RIPC did not greatly alter the muscle oxygenation response to repetitive high-intensity cycling intervals.