After a tough workout you may feel like your muscles are pumped up. They might feel harder than normal and look bigger in the mirror. That feeling can be exhilarating because you can actually feel and see your progress for a moment. However, that feeling usually subsides after a few hours when your muscles return to normal.
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Arnold Schwarzenegger, a famous bodybuilder and fitness pioneer, termed this feeling "the pump." Thankfully, you don't have to be an iconic bodybuilder to feel the sensation of the pump. It typically happens when you do high-rep weightlifting exercises.
"The pump" happens when your body sends blood to the muscle that you're working. Blood brings nutrients to the muscles to help them perform. When your workout is complete, you will notice that your muscles gradually return back to normal.
Increase In Blood
During exercise, your body must meet increased demands for oxygen-rich blood. If you perform a vigorous exercise, you may notice your heart rate increase. This occurs because your body sends more blood to the muscles being used in order for them to work properly. This is why you feel a pumped-up feeling in your legs rather than your arms after performing leg exercises.
Blood also carries substances like glycogen to your muscles. Glycogen is a simplified form of carbohydrate that your muscles can break down and use to fuel contractions. Creatine is another form of energy that your muscles use, although your body burns through it quickly.
While bringing fuel to the muscle is important, bringing waste products away from the muscle is equally as important. Blood pulls harmful waste products, like lactic acid and carbon dioxide, out of the muscle. If they accumulate it will make your muscle fatigue quickly.
Chasing the Pump
As you get stronger and progress in the weight room, you might find that the effect from "the pump" becomes more dramatic. That's because your muscles develop more capillaries as an adaptation to weightlifting.
Capillaries are a small network of blood vessels that create a web around your muscle and deliver blood. As you build more capillaries you will continue sending more blood to the muscle, increasing the effect of "the pump."
As "the pump" fades away, you might be disappointed in the way your muscles look. The difference can, in fact, be significant enough to make you notice. However, you're not losing any progress. This is just your body going back to normal.
When you complete your workout and rest, your body no longer needs to send an increased amount of blood to that region of the body. Therefore, you feel that your muscles have deflated because the increased amount of blood that led to the pumped-up effect is no longer present.
Blood leaves your muscles when the parasympathetic nervous system kicks into action. Your parasympathetic nervous system makes your body relax to kickstart the recovery process. It also draws blood away from your limbs and into your torso.
It's important for blood to leave the muscles so that it can help you do other things, like digest food. If your muscles were pumped up all the time, your body might have trouble maintaining its normal functions.
Be careful to avoid becoming obsessed with the feeling of "the pump." If you workout too often, trying to keep blood in your muscles, you can overwork your body and impede recovery.