Ischemic preconditioning of the muscle improves exercise performance but not maximal oxygen uptake in humans
ABSTRACT Brief episodes of nonlethal ischemia, commonly known as "ischemic preconditioning" (IP), are protective against cell injury induced by infarction. Moreover, muscle IP has been found capable of improving exercise performance. The aim of the study was the comparison of standard exercise performances carried out in normal conditions with those carried out following IP, achieved by brief muscle ischemia at rest (RIP) and after exercise (EIP). Seventeen physically active, healthy male subjects performed three incremental, randomly assigned maximal exercise tests on a cycle ergometer up to exhaustion. One was the reference (REF) test, whereas the others were performed after the RIP and EIP sessions. Total exercise time (TET), total work (TW), and maximal power output (W(max)), oxygen uptake (VO(2max)), and pulmonary ventilation (VE(max)) were assessed. Furthermore, impedance cardiography was used to measure maximal heart rate (HR(max)), stroke volume (SV(max)), and cardiac output (CO(max)). A subgroup of volunteers (n = 10) performed all-out tests to assess their anaerobic capacity. We found that both RIP and EIP protocols increased in a similar fashion TET, TW, W(max), VE(max), and HR(max) with respect to the REF test. In particular, W(max) increased by ∼ 4% in both preconditioning procedures. However, preconditioning sessions failed to increase traditionally measured variables such as VO(2max), SV(max,) CO(max), and anaerobic capacity(.) It was concluded that muscle IP improves performance without any difference between RIP and EIP procedures. The mechanism of this effect could be related to changes in fatigue perception.
[Show abstract] [Hide abstract]
- "For example, a faster induction of pulmonary O 2 dynamics induced by prior exercise results from cardiovascular activation in addition to skeletal muscle activation (Burnley et al. 2000; Gurd et al. 2005; Marles et al. 2007; Faisal et al. 2009). Compared with prior exercise, IPC did not have a beneficial effect on the cardiovascular response during exercise (de Groot et al. 2010; Crisafulli et al. 2011; Bailey et al. 2012a,b). In this study, the changes in HR during exercise was also unaffected by IPC. "
ABSTRACT: Ischemic preconditioning (IPC) improves maximal exercise performance. However, the potential mechanism(s) underlying the beneficial effects of IPC remain unknown. The dynamics of pulmonary oxygen uptake (VO2) and muscle deoxygenation during exercise is frequently used for assessing O2 supply and extraction. Thus, this study examined the effects of IPC on systemic and local O2 dynamics during the incremental step transitions from low- to moderate- and from moderate- to severe-intensity exercise. Fifteen healthy, male subjects were instructed to perform the work-to-work cycling exercise test, which was preceded by the control (no occlusion) or IPC (3 × 5 min, bilateral leg occlusion at >300 mmHg) treatments. The work-to-work test was performed by gradually increasing the exercise intensity as follows: low intensity at 30 W for 3 min, moderate intensity at 90% of the gas exchange threshold (GET) for 4 min, and severe intensity at 70% of the difference between the GET and VO2 peak until exhaustion. During the exercise test, the breath-by-breath pulmonary VO2 and near-infrared spectroscopy-derived muscle deoxygenation were continuously recorded. Exercise endurance during severe-intensity exercise was significantly enhanced by IPC. There were no significant differences in pulmonary VO2 dynamics between treatments. In contrast, muscle deoxygenation dynamics in the step transition from low- to moderate-intensity was significantly faster in IPC than in CON (27.2 ± 2.9 vs. 19.8 ± 0.9 sec, P < 0.05). The present findings showed that IPC accelerated muscle deoxygenation dynamics in moderate-intensity exercise and enhanced severe-intensity exercise endurance during work-to-work test. The IPC-induced effects may result from mitochondrial activation in skeletal muscle, as indicated by the accelerated O2 extraction. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.05/2015; 3(5). DOI:10.14814/phy2.12395
[Show abstract] [Hide abstract]
- "It should be noted that in the present study IPC exerted no significant effect on average, total or peak power. In cyclists exercising supra-maximally for approximately 120 s no beneficial effect of IPC was realised in terms of exercise time or power output (Crisafulli et al., 2011). In studies examining the effect of IPC on swimmers and cyclists however exercise duration was substantially longer than that which has been reported for team sports (Spencer et al., 2005), a sporting population from which the current cohort was drawn. "
ABSTRACT: This study investigated whether ischemic preconditioning (IPC) in a trained population affected repeated sprint performance. A secondary aim was to assess responses according to gender. Sixteen (nine females and seven males) well trained team sport athletes took part in a randomised crossover study design. Participants underwent an IPC and placebo treatment involving three periods of 5 min occlusion applied unilaterally (3 × 5 min occlusion to each leg) at either 220 mmHg or 50 mmHg. Each period of occlusion was followed by 5 min reperfusion. Following treatment 5 × 6 s maximal effort sprints were undertaken on a cycle ergometer against 7.5% body mass, each interspersed by 24 s recovery. Measured parameters included peak power, total power, percentage decrement, post-exercise blood lactate and ratings of perceived exertion. Nor within subject main effect for IPC was observed, neither was there an interaction effect with gender. Effect sizes were trivial (ES < 0.2) with the exception of a moderate (ES < 1.2) change in post-exercise blood lactate in the female cohort (1.6 ± 0.4 mmol−1 lower following IPC). Results suggest no benefit to team sport players in utilising IPC as a means of enhancing repeated sprint performance. A lower blood lactate response in female participants following IPC may suggest improved blood flow through vasodilation.Journal of Sports Sciences 12/2014; 33(11). DOI:10.1080/02640414.2014.988741 · 2.10 Impact Factor
[Show abstract] [Hide abstract]
- "Others have used lowpressure control conditions in which the blood pressure cuff is only inflated to 10–20 mm Hg (Jean-St-Michel et al. 2011; Bailey et al. 2012a, 2012b), but we chose not to employ this technique in the current study because it is easily distinguished from IPC and it is unknown if it induces any ischemic responses that would confound the study (Foster et al. 2011). Finally, while the size of the subject pool of the current study (n = 15) is similar to those used by previous IPC and exercise studies (n = 8 to 23) (de Groot et al. 2010; Crisafulli et al. 2011; Foster et al. 2011; Jean-St-Michel et al. 2011; Bailey et al. 2012a, 2012b), it was insufficient to detect some of the small effects of IPC on W peak , cardiovascular hemodynamics, and SpO 2 . With our measured effect size of 0.2 and power of 0.41, we calculated that we would have required a sample size of 22 subjects to find a significant effect of IPC on W peak at HA. "
ABSTRACT: Ischemic preconditioning (IPC) may improve blood flow and oxygen delivery to tissues, including skeletal muscle, and has the potential to improve intense aerobic exercise performance, especially that which results in arterial hypoxemia. The aim of the study was to determine the effects of IPC of the legs on peak exercise capacity (Wpeak), submaximal and peak cardiovascular hemodynamics, and peripheral capillary oxygen saturation (SpO2) in trained males at sea level (SL) and simulated high altitude (HA; 13.3% FIO2, ∼3650 m). Fifteen highly trained male cyclists and triathletes completed 2 Wpeak tests (SL and HA) and 4 experimental exercise trials (10 min at 55% altitude-specific Wpeak then increasing by 30 W every 2 min until exhaustion) with and without IPC. HA resulted in significant arterial hypoxemia during exercise compared with SL (73% ± 6% vs. 93% ± 4% SpO2, p < 0.001) that was associated with 21% lower Wpeak values. IPC did not significantly improve Wpeak at SL or HA. Additionally, IPC failed to improve cardiovascular hemodynamics or SpO2 during submaximal exercise or at Wpeak. In conclusion, IPC performed 45 min prior to exercise does not improve Wpeak or systemic oxygen delivery during submaximal or peak exercise at SL or HA. Future studies must examine the influence of IPC on local factors, such as working limb blood flow, oxygen delivery, and arteriovenous oxygen difference as well as whether the effectiveness of IPC is altered by the volume of muscle made ischemic, the timing prior to exercise, and high altitude acclimatization.Applied Physiology Nutrition and Metabolism 09/2014; 40(1):1-7. DOI:10.1139/apnm-2014-0080 · 2.23 Impact Factor