Stroke volume increases when your heart fills with more blood between beats, contracts with greater force, or pumps against less resistance in your blood vessels. A typical resting stroke volume for an untrained adult is around 60 to 80 milliliters per beat, while elite endurance athletes can exceed 150 milliliters per beat. The gap between those numbers is largely explained by training adaptations, blood volume, and hydration status, all of which you can influence.
The Three Factors That Control Stroke Volume
Every change in stroke volume traces back to three variables: preload, contractility, and afterload. Preload is how much blood fills your heart’s left ventricle before it contracts. The more it fills (within a healthy range), the more forcefully the muscle fibers stretch and snap back, pushing out a larger volume of blood. This is the Frank-Starling mechanism, and it’s the primary way your body raises stroke volume during exercise.
Contractility is the raw squeezing power of the heart muscle itself. During physical activity, stress hormones like norepinephrine bind to receptors on heart muscle cells and trigger a surge of calcium inside them, which ramps up the force of each contraction. This shifts the heart’s performance curve upward so that even at the same filling volume, each beat ejects more blood.
Afterload is the resistance the heart pumps against, largely determined by blood pressure and arterial stiffness. High afterload makes it harder for the ventricle to empty, which reduces stroke volume. People with long-standing high blood pressure, for example, typically have a lower stroke volume because the heart has to work against stiffer, narrower arteries. Reducing afterload, through exercise, weight management, or blood pressure control, lets the heart eject blood more efficiently.
Aerobic Training Is the Primary Driver
Consistent endurance exercise is the single most effective way to increase stroke volume over time. It works on multiple fronts simultaneously: the left ventricle gradually enlarges, allowing it to hold more blood before each beat; the heart wall thickens slightly, improving contractile force; and resting blood pressure tends to drop, lowering afterload. A study tracking elite female runners over 16 months of expanded training found progressive increases in left ventricular end-diastolic volume of about 7 milliliters per square meter of body surface area, confirming that the heart physically remodels in response to sustained aerobic work.
These adaptations explain why trained athletes have a lower resting heart rate. Their larger, more powerful ventricles pump the same total blood flow in fewer beats. At rest, the ejection fraction (the percentage of blood expelled each beat) actually decreases slightly in endurance athletes, not because their hearts are weaker, but because the ventricle has grown large enough that it doesn’t need to empty as completely to meet the body’s resting demand.
How long does this take? Structural cardiac remodeling is a slow process. Research on previously sedentary individuals showed that meaningful increases in left ventricular mass and end-diastolic volume required about one year of consistent endurance training. You’ll experience functional improvements in cardiac output within weeks, driven largely by plasma volume expansion and improved contractility, but the physical enlargement of the heart chamber takes many months of steady work.
Training Intensity Matters
Higher-intensity aerobic exercise creates a stronger stimulus for cardiac adaptation than easy, low-effort sessions. Intervals that push your heart rate to 85 to 95 percent of maximum force the ventricle to fill and empty at high volumes repeatedly, which is a potent trigger for remodeling. Think tempo runs, cycling intervals, rowing pieces, or swimming sets with structured rest.
That said, moderate-intensity continuous training (like a 45-minute jog at a conversational pace) still drives stroke volume improvements, particularly in people who are currently sedentary or lightly active. A practical approach combines both: two or three moderate sessions per week for aerobic base, plus one or two higher-intensity interval sessions to maximize the cardiac stimulus. The total weekly volume of aerobic exercise is what matters most for long-term heart chamber growth.
Blood Volume and Hydration
About half the difference in stroke volume between untrained and highly trained individuals comes down to blood volume. Trained endurance athletes carry significantly more plasma (the liquid portion of blood), which increases venous return to the heart, stretches the ventricle more during filling, and raises stroke volume through the Frank-Starling mechanism. In one study, when researchers artificially expanded blood volume in untrained men by roughly 400 milliliters using an intravenous solution, stroke volume jumped 11 percent during upright exercise. Further expansion beyond that 400 milliliters produced no additional benefit, suggesting there’s a ceiling to how much extra fluid the heart can use.
Even after matching blood volume between trained and untrained subjects, the trained group still had a 15 percent higher stroke volume, along with lower blood pressure and less vascular resistance. This confirms that blood volume expansion is only part of the story. The structural and functional adaptations of the heart itself account for the rest.
The practical takeaway: stay well hydrated, especially during exercise in the heat. Dehydration of around 3.5 percent of body mass reduces the volume of blood filling the left ventricle by 30 to 33 milliliters and drops stroke volume by 21 to 22 milliliters. Your heart rate climbs to compensate, but cardiac output still falls. Replacing fluids during prolonged exercise restores roughly half of that lost stroke volume and keeps heart rate from spiking as dramatically. For day-to-day training, arriving at workouts properly hydrated protects the stroke volume gains you’re building over time.
Resistance Training Has Limited Impact
Strength training produces a different pattern of cardiac adaptation than endurance work. Heavy lifting sharply increases blood pressure during each rep, which exposes the heart to high afterload. Over time, this can thicken the ventricular walls without significantly enlarging the chamber’s internal volume. Most research on resistance-trained athletes shows increases in left ventricular wall thickness and mass but no meaningful increase in the chamber volume that drives stroke volume.
That doesn’t mean strength training is irrelevant. It can modestly improve ejection fraction, and it supports overall cardiovascular health through blood pressure management, improved body composition, and better metabolic function. But if your primary goal is a larger stroke volume, aerobic training is the direct path. Resistance training works best as a complement, not a substitute.
Nutrition and Supplements
Despite popular interest in dietary nitrates (commonly consumed as beetroot juice) for cardiovascular performance, the evidence for a direct effect on stroke volume is weak. A controlled study measuring cardiac output and stroke volume every one to two hours for six hours after beetroot juice consumption found no change in stroke volume, cardiac output, or heart rate compared to placebo. This was consistent with previous research.
Beetroot juice may still improve exercise performance through other pathways, particularly by reducing the oxygen cost of submaximal exercise, but it does not appear to increase stroke volume acutely or chronically. No widely available supplement has strong evidence for directly raising stroke volume. The meaningful levers remain training, hydration, and managing blood pressure.
Putting It Together
Increasing stroke volume is primarily an exercise adaptation. The most effective approach combines regular aerobic training (at least three to five sessions per week, mixing moderate and high-intensity efforts), adequate hydration before and during exercise, and attention to blood pressure management over the long term. Expect functional improvements in the first several weeks as your blood volume expands and your heart’s contractile response improves. Structural changes to the heart chamber, the kind that meaningfully raise your resting and peak stroke volume, develop over months to a year of consistent work.
The resting heart rate drop that accompanies these changes is the simplest way to track progress without specialized equipment. As your stroke volume rises, your heart needs fewer beats per minute to circulate the same volume of blood. A gradually declining resting heart rate over weeks and months is a reliable sign that your heart is pumping more effectively with each beat.