Aerobic exercise makes your heart pump faster, but an overworking heart actually makes you die faster. So is aerobic exercise helpful or harmful to your body?
In: Biology
You can die of all things. It’s all about the details. The heart is a dynamic organ, it grows and shrinks according to demand. If you have high blood pressure and it’s chronic (due to bad diet or genetics etc) your heart faces higher resistance when it pumps the blood and this is called a higher afterload. Due to the physical stress this places on the individual heart cells, the heart begins to grow bigger in order to adapt. When you have something like regular aerobic exercise you increase the metabolic rate of your body as you consume more oxygen, causing your heart to have to pump faster and so it adapts and gets stronger. When you do resistance exercise, you increase the afterload also causing adaptation. Physically the heart only senses so much but during all of these scenarios above many endocrine and other organs in your body are secreting a number of hormones and cytokines and your brain is sending certain signals. These biochemical signals provide a molecular context for the heart to know how to grow. That is why there are different kinds of adaptations. A pathological stimulus such as hypertension or stroke and so on induce a different change in the heart, for example, the geometric growth in the individual cells is different (they start depositing sarcomeres, the contractile units that actually create the force within each muscle cell, in series as opposed to in parallel), and this produces a different biophysical contractile profile. The heart cells don’t just grow in size to generate more force, the heart actually changes metabolically and electrically, amongst others. In a pathological growth for example, your heart shifts from getting 70% of its energy from fat to getting most of it from glucose. It starts to express genes not normally expressed, and this is usually triggered by reopening an old package, literally a suite of genes called the fetal gene program. Your heart actually reverts to how it was when you were an infant and begins to switch the contractile proteins to versions you used then. We don’t understand how it all works but we know this is beneficial in the short term but really bad in the long term. In physiological adaptation the heart grows in a completely different way, a healthy way in the short and long terms. So in short, under disease conditions your heart is pushed to adapt quickly and sharply and in a drastic way that protects it and the body from damage and this comes at the cost of long term damage if the disease is not fixed. Under healthy conditions your heart doesn’t go to such far lengths and grows slowly depositing new contractile units in an orderly fashion. But even in exercise, if you go too far, you begin to develop pathological changes. And this is well documented. So the best advice is keep a regular moderate exercise regime and you will be perfect.
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