Preconditioning cardioprotection and exercise performance: a radical point of view

Moderate-Intensity Exercise Maintains Redox Homeostasis for Cardiovascular Health

It is well known that exercise is beneficial for cardiovascular health. Oxidative stress is the common pathological basis of many cardiovascular diseases. The overproduction of free radicals, both reactive oxygen species and reactive nitrogen species, can lead to redox imbalance and exacerbate oxidative damage to the cardiovascular system. Maintaining redox homeostasis and enhancing anti-oxidative capacity are critical mechanisms by which exercise protects against cardiovascular diseases. Moderate-intensity exercise is an effective means to maintain cardiovascular redox homeostasis. Moderate-intensity exercise reduces the risk of cardiovascular disease by improving mitochondrial function and anti-oxidative capacity. It also attenuates adverse cardiac remodeling and enhances cardiac function. This paper reviews the primary mechanisms of moderate-intensity exercise-mediated redox homeostasis in the cardiovascular system. Exploring the role of exercise-mediated redox homeostasis in the cardiovascular system is of great significance to the prevention and treatment of cardiovascular diseases.

Extracellular vesicles and cardiovascular system: Biomarkers and Cardioprotective Effectors

In the last few decades extracellular vesicles (EVs), which include exosomes and microvesicles, have attracted significant interest in cardiovascular pathophysiology due to their intrinsic properties. Indeed, EVs by transferring their cargo, which contains miRNA, DNA, proteins and lipids, were found effective in preventive and regenerative medicine and in protecting the heart against an array of pathological conditions, including myocardial infarction and arrhythmias. EVs can attenuate cellular senescence, inflammation and myocardial injury. Cardiovascular structures may be targeted by circulating EVs derived by extra-cardiac cells and platelets, as well by EVs locally released from all major cardiovascular cell types, including endothelial cells, cardiomyocytes, macrophages and fibroblasts. Yet, EVs of cardiovascular origin can be also transferred to distant tissues by circulation. Therefore, EVs have been proposed not only as promising diagnostic tools (early disease biomarkers), but also as therapeutics. This review focuses on the protective effects exerted by EVs, released by different cell types in the cardiovascular system. Physical exercise is considered as a natural mechanism of EV production involved in preventive medicine. Particular attention will be devoted to describe the impact of EVs in cardioprotection after ischemia/reperfusion injury.

Remote ischemic preconditioning increases accumulated oxygen deficit in middle-distance runners

The mediators underlying the putative benefits of remote ischemic preconditioning (IPC) on dynamic whole body exercise performance have not been widely investigated. Our objective was to test the hypothesis that remote IPC improves supramaximal exercise performance in National Collegiate Athletic Association (NCAA) Division I middle-distance runners by increasing accumulated oxygen deficit (AOD), an indicator of glycolytic capacity. A randomized sham-controlled crossover study was employed. Ten NCAA Division I middle-distance athletes [age: 21 ± 1 yr; maximal oxygen uptake (V̇o2max): 65 ± 7 ml·kg−1·min−1] completed three supramaximal running trials (baseline, after mock IPC, and with remote IPC) at 110% V̇o2max to exhaustion. Remote IPC was induced in the right arm with 4 × 5 min cycles of brachial artery ischemia with 5 min of reperfusion. Supramaximal AOD (ml/kg) was calculated as the difference between the theoretical oxygen demand required for the supramaximal running bout (linear regression extrapolated from ~12 × 5 min submaximal running stages) and the actual oxygen demand for these bouts. Remote IPC [122 ± 38 s, 95% confidence interval (CI): 94–150] increased ( P < 0.001) time to exhaustion 22% compared with baseline (99 ± 23 s, 95% CI: 82–116, P = 0.014) and sham (101 ± 30 s, 95% CI: 80–123, P = 0.001). In the presence of IPC, AOD was 47 ± 36 ml/kg (95% CI: 20.8–73.9), a 29% increase compared with baseline (36 ± 28 ml/kg, 95% CI: 16.3–56.9, P = 0.008) and sham (38 ± 32 ml/kg, 95% CI: 16.2–63.0, P = 0.024). Remote IPC considerably improved supramaximal exercise performance in NCAA Division I middle-distance athletes. Greater glycolytic capacity, as estimated by increased AOD, is a potential mediator for these performance improvements.

NEW & NOTEWORTHY Our novel findings indicate that ischemic preconditioning enhanced glycolytic exercise capacity, enabling National Collegiate Athletic Association (NCAA) middle-distance track athletes to run ~22 s longer before exhaustion compared with baseline and mock ischemic preconditioning. The increase in “all-out” performance appears to be due to increased accumulated oxygen deficit, an index of better supramaximal capacity. Of note, enhanced exercise performance was demonstrated in a specific group of in-competition NCAA elite athletes that has already undergone substantial training of the glycolytic energy systems.

No influence of ischemic preconditioning on running economy

PURPOSE

Many of the potential performance-enhancing properties of ischemic preconditioning suggest that the oxygen cost for a given endurance exercise workload will be reduced, thereby improving the economy of locomotion. The aim of this study was to identify whether ischemic preconditioning improves exercise economy in recreational runners.

METHODS

A randomized sham-controlled crossover study was employed in which 18 adults (age 27 ± 7 years; BMI 24.6 ± 3 kg/m²) completed two, incremental submaximal (65-85% VO_2max) treadmill running protocols (3 × 5 min stages from 7.2-14.5 km/h) coupled with indirect calorimetry to assess running economy following ischemic preconditioning (3 × 5 min bilateral upper thigh ischemia) and sham control. Running economy was expressed as mlO₂/kg/km and as the energy in kilocalories required to cover 1 km of horizontal distance (kcal/kg/km).

RESULTS

Ischemic preconditioning did not influence steady-state heart rate, oxygen consumption, minute ventilation, respiratory exchange ratio, energy expenditure, and blood lactate. Likewise, running economy was similar (P = 0.647) between the sham (from 201.6 ± 17.7 to 204.0 ± 16.1 mlO₂/kg/km) and ischemic preconditioning trials (from 202.8 ± 16.2 to 203.1 ± 15.6 mlO₂/kg/km). There was no influence (P = 0.21) of ischemic preconditioning on running economy expressed as the caloric unit cost (from 0.96 ± 0.12 to 1.01 ± 0.11 kcal/kg/km) compared with sham (from 1.00 ± 0.10 to 1.00 ± 0.08 kcal/kg/km).

CONCLUSIONS

The properties of ischemic preconditioning thought to affect exercise performance at vigorous to severe exercise intensities, which generate more extensive physiological challenge, are ineffective at submaximal workloads and, therefore, do not change running economy.

Exercise-induced cardiopulmonary arrest in a child with aortic stenosis

The beneficial effect of exercise restriction in preventing sudden cardiac death in children with aortic stenosis remains unclear. We report the case of a 15-year-old boy with congenital aortic stenosis who was resuscitated after sudden cardiac arrest during exercise. The case led to the new concept that exercise restriction may prevent not only unpredictable ventricular ischaemic events and associated arrhythmias but also progressive ventricular hypertrophy.