There are two categories of exercise that many people have heard of: anaerobic and aerobic. Weight training is associated with anaerobic, which is a type of exercise that doesn’t require as much oxygen. Aerobic requires more oxygen and is associated with distance running and other forms of cardio.
Heart health is associated with aerobic exercise, but that’s partially a myth. Lifting weights and doing other strength exercises is also helpful for your heart, but less than cardio.
When you lift weights, your muscles get stronger and bigger. They also store more energy for later and grow blood vessels to increase blood flow. All of these adaptations make your muscles stronger and give them better endurance. That way, you can lift more weights or do more reps.
If you start distance running, you’ll notice that your first few workouts are tough. You could feel sluggish, have a hard time catching your breath, and want to stop. Eventually, you start to feel better and running will get easier.
Part of the reason for your improvement in cardio activities is actually muscle growth. Running makes your legs stronger and more muscular. Rowing makes your back, arms, and legs more muscular. However, that’s not the only reason why cardio feels easier as you do it more.
To get better at cardio, your cardiovascular system has to adapt. A big change happens at the heart. However, your heart doesn’t simply become “stronger.” It gets more efficient.
The heart muscle is different from the muscles in your biceps. It’s not supposed to get any bigger. That’s because your heart has to fill with blood, and if it gets too thick, not enough blood gets in. So, it gets “stronger” by stretching more and contracting harder.
Let’s say that you can pump one cup of blood per heartbeat. Your heart pumps away as you exercise harder and harder, but eventually, it can’t keep up with your body. So, if it can’t beat faster, it has to beat more efficiently. The heart stretches to fill with more blood, so it doesn’t have to beat faster. This is known as “stroke volume.”
Tracking your heart rate is interesting because it should actually get lower over time as your heart gets more efficient. Or, at a given heart rate, you can run faster and for longer. Perhaps instead of saying someone has a “strong heart,” we should say they have a stretchy heart.
