An acute episode of exercise can 'train' the heart and protect it against future damage.
The results of the new research — led by Dick Thijssen, who is a professor of cardiovascular physiology and exercise at the Liverpool John Moores University in the United Kingdom — have been published in the journal JAMA Cardiology.
As Prof. Thijssen and colleagues explain, it is a widely accepted fact that exercise protects the heart over time. However, it is less known that it can also do so within hours, and that a single workout episode is enough to yield clinically significant benefits.
This under-appreciated advantage of exercise may be due to a phenomenon called ischemic, or cardiovascular, preconditioning.
The team explains the reasoning behind the theory of cardiovascular preconditioning: repeatedly exposing the heart to short, non-life-threatening episodes of ischemia — an inadequate supply of blood to the heart — makes the heart more resistant to a more serious, future ischemia episode.
The "paradox" of ischemic preconditioning is a concept first introduced in the mid-1980s, and it has been suggested that one of the ways to induce this cardioprotective effect is through exercise.
So, the review by Prof. Thijssen and colleagues aimed to examine the evidence for this theory in existing preclinical studies.
Protection through exercise preconditioning
The review found that between one and three workout sessions per week can provide "strong" protection for the heart.
Moreover, one single workout episode can provide cardioprotection for 2–3 hours, and even stronger and longer-lasting benefits emerge 24 hours after the exercise session has finished.
"Importantly," the authors write, "these associations are present on the first episode of exercise, with subsequent exercise sessions reactivating protective pathways and leading to ongoing beneficial effects."
This cardioprotective effect could be explained by ischemic preconditioning, write the researchers, given that an intense episode of exercise can have systematic effects such as inducing myocardial ischemia.
Although factors such as obesity and age may interfere with some of these immediate protective effects of exercise, regular training can restore these benefits. The authors explain:
"Taken together, cardioprotection through exercise preconditioning is a facile, inexpensive, and potent therapy that deserves greater recognition and further resources to establish the optimal dose."
"Nonetheless," they continue, "as is so often the case with the benefits of exercise, its prescription follows the cardinal rule: use it or lose it."
Prof. Thijssen comments on the results of the study, saying, "This is a key review summarizing how a single bout of exercise can have a clear impact in keeping the heart adequately supplied with blood."
"Firstly," he explains, "this means that one bout of exercise can cause clinically relevant protection against cardiovascular disease."
"Secondly," Prof. Thijssen continues, "this means that benefits of exercise are present, even in the absence of changes in risk factors. These are both important and powerful messages for all who want to take up exercise."
The team explains that the findings could be used to help cardiac patients through a procedure of so-called prehabilitation; an optimized dose of physical exercise in the days before a cardiac intervention may help to decrease in-hospital mortality and disease, they suggest.