One reason we train aerobically is to condition our hearts. Aerobic exercise positively impacts heart health in a number of ways. In response to consistent aerobic training, your cardiovascular system becomes more efficient at pumping blood and oxygen to your muscles and tissues. In fact, it becomes so proficient that your resting heart rate drops. That’s a sign you’re getting more aerobically fit!
Aerobic exercise also improves how cells respond to insulin. That’s a good thing! Improvements in insulin sensitivity lower your risk for metabolic syndrome, type 2 diabetes, and heart disease. Plus, aerobic exercise has favorable effects on blood lipids, the fats that circulate in your blood. But that’s not all. Aerobic training can reduce your triglyceride level and raise HDL-cholesterol, the kind linked with protection against heart disease. Aerobic exercise also increases oxygen delivery to tissues, which helps with blood pressure control. That’s important since high blood pressure is a strong risk factor for heart disease.
Aerobic Exercise and Your Heart
As mentioned, when you train aerobically, your heart becomes a more efficient pump and better at delivering oxygen to tissues. Thanks to your heart’s newfound pumping ability, it can deliver more blood and oxygen with each heartbeat. We call this an increase in stroke volume and it’s a well-known benefit of aerobic exercise.
How DOES your heart become a better pump in response to aerobic exercise? The architecture of your heart actually changes and the left ventricle, the lower chamber on the left side of your heart becomes larger. This makes sense since this is the side of your heart that pumps blood to your muscles and tissue. The right ventricle sends blood back to the lungs and pushes against less resistance.
During the early stages of aerobic training, the left ventricle increases in size by dilating. The inside chamber of the ventricle becomes larger without an increase in wall thickness. But over time, the wall of the left ventricle also becomes thicker. A bigger chamber and thicker ventricle can pump blood more efficiently.
You also see thickening of the left ventricle in people who have heart disease and long-standing high blood pressure. So, unless your doctor knows you exercise, they might initially wonder whether you have heart problems. Ha! Tell them you’re trying to prevent them.
Exercise is good medicine for your heart. In fact, one study showed aerobic exercise can reverse some of the abnormal thickening of the left ventricle that people with chronic, untreated hypertension develop over time.
Resistance Training and Your Heart
Resistance training also changes the structure of your heart. In response to regular weight training, the wall of your left ventricle thickens in diameter BUT the inner chamber doesn’t dilate or become larger as with aerobic exercise. The reason your left ventricle thickens is your arteries clamp down when you lift a heavy weight. Tight arteries increase the resistance your heart has to pump against. A thicker ventricular wall is helpful because it can generate more force to push against extra resistance.
So, the way your heart changes in response to aerobic and resistance training differ. In one case, you’re getting enlargement AND thickening of the left ventricle (aerobic training) and the other your ventricle only becomes thicker (resistance training).
Is resistance training healthy for your heart? Although aerobic exercise has more established and direct benefits for heart health, resistance training may also indirectly benefit your heart. How? Resistance training increases insulin sensitivity. As your cells become more sensitive to insulin, it lowers your risk for metabolic syndrome, a significant risk factor for heart disease. Aerobic training AND resistance training improve how cells respond to insulin.
There’s strong evidence to suggest that aerobic exercise reduces blood pressure, but what impact does resistance training have on blood pressure readings? When you’re doing heavy resistance training, your blood pressure temporarily rises, sometimes to a significant degree. The rise in blood pressure will be higher if you hold your breath while lifting. That’s why it’s important to breathe when you lift!
Interestingly, some studies show you experience a greater drop in blood pressure after resistance training than after an aerobic workout. Also, research shows resistance training, especially dynamic resistance training, can lower your blood pressure long term, just as aerobic training can. In one study, researchers asked women with high blood pressure to weight train three times a week for four months. When they compared their blood pressure before and after training, the women experienced a 12% drop in systolic blood pressure and a 5% drop in diastolic.
Even the American Heart Association acknowledges that all exercise, including resistance training, is beneficial to heart health and encourages resistance training, under supervision, even for people with chronic diseases such as heart disease. If you have heart disease, talk to your doctor before starting any exercise program.
Your best bet, if you’re trying to lower your blood pressure, is to do more dynamic circuit training or alternate resistance training with aerobic exercise. Talk to your doctor before resistance training to make sure your blood pressures are under reasonable control since your blood pressure can rise while you’re actively lifting.
The Bottom Line
Aerobic exercise AND resistance exercise are good for your heart but they affect the architecture of your heart in different ways. Each has heart health benefits as well. There’s no reason why you can’t enjoy the health benefits of both. Why choose one over the other? Most people devote too much time to aerobic training and too little to resistance exercise. You need the latter for preserving muscle and bone health as you age. Exercise of all types is one of the best medicines there is – and it’s all natural.
References:
Medscape News and Perspective. “‘Athlete’s Heart’ Develops in Stages in Response to Exercise”
J Gerontol A Biol Sci Med Sci (2000) 55 (4): M245-M251. doi: 10.1093/gerona/55.4.M245.
Sports Med. 2008;38(1):69-90.
Prevention. “The Exercise For Better Blood Pressure”
Circulation. 2000; 101: 828-833 doi: 10.1161/01.CIR.101.7.82.
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