A pulse is caused by a wave of pressure that radiates through your arteries each time the left ventricle of your heart contracts and pushes blood into the aorta. That single, forceful squeeze stretches the elastic wall of the aorta outward, and that stretch travels along your arterial walls like a ripple through a garden hose. By the time it reaches your wrist, about a meter from your heart, you can feel the artery briefly expand under your fingertips. That rhythmic expansion and relaxation is what you’re detecting when you check your pulse.
How the Heart Creates Each Beat
Your heart generates its own electrical signals. A cluster of cells in the upper right chamber (the sinoatrial node) fires a signal that spreads across the upper chambers, causing them to contract and push blood down into the lower chambers. A fraction of a second later, a second signal travels along the walls of the ventricles, causing them to contract and pump blood out of the heart. The left ventricle’s contraction is especially powerful because it needs to push blood into the aorta and out to the entire body.
This contraction phase is called systole, and it’s the origin of the pressure spike you feel as a pulse. The blood pressure reading you see as the top number (systolic pressure) reflects exactly this moment. Between beats, the ventricles relax and refill. That relaxation phase is diastole, and it’s the lower number in a blood pressure reading.
The Pressure Wave Travels Faster Than Blood
Here’s something that surprises most people: what you feel at your wrist is not the actual blood that just left your heart. The pressure wave moves through the arterial walls far faster than the blood itself flows. In a young person, the pulse wave travels through the aorta at about 5 meters per second. The blood itself moves at roughly 0.5 meters per second, about ten times slower. So when you feel a pulse at your wrist, you’re detecting the pressure ripple, not the arrival of fresh blood from the latest heartbeat.
This wave speed isn’t fixed throughout life. As arteries stiffen with age, the pulse wave can travel more than twice as fast as it did in youth. That faster wave actually changes the shape and strength of the pulse, which is one reason blood pressure tends to rise as people get older.
Why Artery Walls Matter
Your large arteries, especially the aorta, are elastic for a reason. When the left ventricle ejects blood, the aortic wall stretches outward to absorb that surge. Then, between heartbeats, the wall recoils inward, gently pushing the blood forward. This creates a smoother, more continuous flow of blood to your organs rather than the stop-and-start bursts that would happen if your arteries were rigid pipes.
Physiologists call this the Windkessel effect, named after an old German term for an air chamber used to smooth water flow. It’s the reason your tissues receive a steady supply of blood even though your heart pumps in discrete beats. When arteries lose their elasticity through aging or disease, they can no longer cushion the pressure surges as well. The gap between the highest and lowest pressure in each beat (called pulse pressure) widens, and the pulse feels stronger and more forceful. This is a hallmark of vascular aging and a contributor to high blood pressure.
What Determines Pulse Strength
The strength of the pulse you feel depends on several factors working together. The volume of blood ejected with each heartbeat (stroke volume) is a major one. A heart that pumps more blood per beat creates a bigger pressure wave. The speed of ejection matters too: a faster, more forceful contraction produces a sharper pulse. Together, increased blood flow and volume can account for a large portion of the difference in pulse pressure between people with normal and elevated blood pressure. One study in Hypertension found these two factors explained about 52% of the pulse pressure gap between groups.
Arterial stiffness plays the other key role. Stiffer arteries amplify the pressure wave, making the pulse more prominent. Peripheral resistance, the tightness of your smaller arteries, also affects how much pressure builds up in the system. A pulse can feel weak if blood volume is low (from dehydration, for example) or if the heart isn’t contracting forcefully.
How Your Nervous System Controls Pulse Rate
Your heart has a built-in pacemaker, but your nervous system constantly adjusts its firing rate to match what your body needs. Two competing branches handle this. The sympathetic nervous system speeds things up. When you’re stressed, exercising, or losing blood, sympathetic nerves release norepinephrine, which increases the rate of the heart’s pacemaker and strengthens each contraction. Your adrenal glands also release adrenaline into the bloodstream, amplifying the effect.
The parasympathetic nervous system, working through the vagus nerve, does the opposite. It slows the pacemaker’s discharge rate and reduces how quickly signals travel through the heart’s conduction system. At rest, parasympathetic activity dominates, which is why a calm, healthy adult typically has a resting pulse of 60 to 100 beats per minute. When you stand up suddenly, feel anxious, or start running, the balance shifts toward sympathetic activity within seconds, and your pulse quickens.
This push-and-pull happens continuously. A drop in blood pressure triggers more sympathetic activity and less parasympathetic activity, raising heart rate and tightening blood vessels to compensate. A rise in blood pressure does the reverse. It’s an automatic feedback loop that keeps blood flowing to your brain and organs.
Normal Resting Pulse by Age
Pulse rate varies significantly by age. Younger hearts are smaller and need to beat faster to circulate enough blood. Here are the standard ranges for resting heart rate:
- Newborns (0 to 1 month): 100 to 160 beats per minute
- Infants (1 to 12 months): 80 to 140
- Toddlers (1 to 3 years): 80 to 130
- Preschool (3 to 5 years): 80 to 110
- School age (6 to 12 years): 70 to 100
- Adolescents and adults: 60 to 100
Well-trained athletes often have resting rates below 60 because their hearts pump more blood per beat, so fewer beats are needed. A pulse consistently above or below these ranges at rest can signal an underlying issue worth investigating.
Where You Can Feel a Pulse
You can detect a pulse anywhere an artery runs close to the skin’s surface and over a firm structure like bone or tendon. The most common spot is the radial artery at the wrist, felt on the thumb side just below the base of the palm. The carotid pulse in the neck is another familiar one, often used during exercise because it’s easy to find.
The brachial pulse sits on the inner arm just above the elbow crease, between the bone on the inner side of the elbow and the biceps tendon. This is the artery a blood pressure cuff listens to. On the foot, the dorsalis pedis pulse can be felt on the top of the foot, near the big toe’s tendon, roughly a centimeter from a small bony bump. Checking foot pulses is particularly useful for assessing circulation in the legs.
How Wearable Devices Detect Your Pulse
Smartwatches and fitness trackers use a technique called photoplethysmography. A small LED on the back of the device shines light (usually green or infrared) into the skin of your wrist. A sensor next to it measures how much light bounces back. With each heartbeat, blood volume in the tiny vessels under the skin increases slightly, absorbing more light. Between beats, blood volume drops and more light reflects back. The device reads these fluctuations and calculates your heart rate from the pattern.
This is fundamentally the same thing you’re detecting with your fingertip when you feel a pulse manually: a rhythmic change in blood volume driven by the pressure wave from each heartbeat. The technology just uses light instead of touch.
When Pulse and Heartbeat Don’t Match
In some conditions, not every electrical heartbeat produces a strong enough contraction to send a detectable pulse wave to the wrist. The gap between the number of heartbeats and the number of pulses felt at the periphery is called a pulse deficit. It’s most commonly seen in atrial fibrillation, where the heart’s upper chambers quiver chaotically instead of contracting in an organized way. Some of those disorganized beats fail to fill the ventricle adequately, so when it contracts, there isn’t enough blood to generate a pressure wave you can feel. The result is an irregular pulse that seems to skip beats, even though electrical activity is still happening in the heart.