Exercise and its benefits on heart health are, of course, well documented. But there are some cases where vigorous exercise can actually be deadly.

[ECG machine]Share on Pinterest
New research investigates instances where extreme activity can be detrimental to the heart.

Normally, maintaining fitness through exercise helps keep a multitude of diseases at bay.

The proven benefits of exercise include a reduction in the risk of developing type 2 diabetes, hypertension, osteoporosis and colon cancer.

Added to that list are more obvious benefits: reduction in weight, lowered blood pressure and a drop in low-density lipoprotein (LDL), or “bad,” cholesterol.

The effect of a single exercise program on any one of the above risk factors might be small, but when the effect is taken as a whole and combined with good nutrition, the positive implications on general health are vast.

However, Dr. Jeffrey Towbin and his team at the Cincinnati Children’s Hospital Medical Center have recently been investigating situations when endurance exercise can have severe consequences.

The study, published in the American Journal of Physiology – Heart and Circulatory Physiology, investigated the effects of endurance exercise on arrhythmogenic ventricular cardiomyopathy.

Arrhythmogenic ventricular cardiomyopathy (AVC) is a rare disorder, but also the most common condition to cause sudden cardiac death during a bout of intense exercise. Most worryingly, it can be asymptomatic until the point of a major cardiac collapse.

AVC is a genetic disorder that affects the structural integrity of the heart wall.

Cells within the heart wall are linked together by proteins called desmosomes. When under duress – during intense exercise, for instance – the heart wall can become overstretched. The desmosome links are responsible for keeping the structure of the heart wall intact.

Desmosomes consist of various protein building blocks. In AVC, there are defects in one or more of these desmosome proteins. The faulty components prevent desmosomes from successfully holding the heart wall together.

In an AVC patient, during exercise, the heart cell links give way allowing gaps to form between cells. Scar tissue, in turn, forms between the cells. This scar tissue further weakens the heart’s ability to hold up under fire.

One of the vital constituents of desmosomes is the protein, desmoplakin. Previous studies using mice with mutated forms of desmoplakin have shown the mice develop similar symptoms to human AVC.

In the present study, Dr. Towbin’s team investigated the effect of vigorous exercise on these particular mice. The team found that endurance exercise brought on a significantly earlier onset of AVC symptoms.

Interestingly, the team managed to measure the desmosomes faults quite early on via biological markers. They noticed early signs of AVC before any cardiac symptoms presented. This is important because AVC is notoriously difficult to diagnose in its early phase; this particular finding could, therefore, be clinically useful in the future.

The changes in the heart wall in AVC are often patchy to begin with, making it difficult to detect via ECG. AVC patients’ ECG readouts do not necessarily show any changes in the early phase, or they produce readings that could signal a number of different conditions.

Early outward symptoms of AVC are equally difficult to place – for instance, palpitations or light-headedness are early signs of AVC but could also be the fault of any number of disorders.

A biological marker that could act as an early warning could save lives.

Dr Towbin’s investigations threw out another intriguing finding. During exercise, the team noticed significant changes in the Wnt-beta-catenin pathway.

The Wnt-beta-catenin pathway is involved in promoting the growth of new cells and preventing the deposition of fat. This offers a potential mechanism of the increase in AVC’s development seen during intense exercise.

Although the Wnt-beta-catenin pathway finding is only tentative, it gives researchers a new angle from which to approach research into AVC.

It seems AVC may be slowly letting down its guard. Future research now looks set to discover the mechanisms at play and potentially design new tests for its early detection.

Medical News Today recently discussed the potential of a pill that offers the same benefits as exercise.