Validation of Ischemic Preconditioning for Skeletal Muscle: Combined by Dietary Nitrate

Abstract

The ischemic preconditioning phenomenon was introduced in a study that demonstrated that repetitions of short-term ischemia and reperfusion of coronary arteries could reduce the myocardial damage following prolonged ischemia （direct effect）．Moreover, it was later demonstrated that the ischemic preconditioning of coronary arteries also protects remote cardiac tissue that is not directly exposed to ischemic preconditioning （remote effect）．Because of the intermittent nature of the blood flow during intense muscle actions, it was proposed that ischemic preconditioning prior to exercise could increase muscular performance. Although most of the exercise studies employed an ischemic preconditioning protocol involving four cycles of 5-min circulatory occlusion followed by a 5-min reperfusion period, the optimal number of repetitions of ischemic preconditioning remained unclear. First, we examined the effective repetition numbers （from one to four） of direct and remote ischemic preconditioning in lower leg on exercise performance and fatigability. Contrary to previous reports, the results showed that any repetition of ischemic preconditioning did not affect the maximum strength and fatigability in knee extension. Concerning those negative results, we examined effects of ischemic preconditioning in a practical exercise of repeated-jump and combined ischemic preconditioning with dietary nitrate （donor of nitric oxide）．However, we could not demonstrate significant effects of ischemic preconditioning on exercise performance and muscle damage even with dietary nitrate.