Understanding the benefits of exercise physiology for POTS

When we talk about treatments for POTS, conversation often turns to hydration, salt, compression garments and medication. These are all important parts of the picture.

But exercise has emerged as one of the most evidence-backed long-term treatments for POTS — and the physiological reasons why are worth understanding.

This blog is a closer look at what changes inside the body when someone with POTS exercises consistently and thoughtfully. It is more technical than our usual posts, but we have tried to keep the language clear.

A quick recap of what POTS is doing

POTS — Postural Orthostatic Tachycardia Syndrome — is a form of dysautonomia. The autonomic nervous system, which quietly controls things like heart rate, blood pressure and blood vessel constriction, does not respond the way it should when you change position.

For many people, POTS appears to begin after a specific event — a viral illness (often a cold, flu, COVID or glandular fever), a period of significant stress, a surgery, an injury, a pregnancy, or sometimes a long stretch of bed rest. For others, there is no obvious trigger and symptoms build gradually. Both presentations are common.

Whatever the starting point, the underlying issue tends to look similar. When you stand up, around 500–800 ml of blood is pulled into your lower body by gravity. In a healthy autonomic response, blood vessels constrict to push that blood back up to the heart. In POTS, that vessel response is impaired, so less blood returns to the heart. To maintain blood pressure, heart rate rises — often by 30 beats per minute or more in adults, and 40 or more in adolescents.

This rise in heart rate is what gives POTS its name. But the tachycardia itself is the response, not the cause — and understanding that distinction matters, because it shapes how exercise can help.

Why stroke volume matters in POTS

To understand how exercise helps POTS, it helps to start with two terms: stroke volume and cardiac output.

Stroke volume is the amount of blood your heart pumps with each beat. In a typical healthy adult at rest, this is around 70 ml.

Cardiac output is the total amount of blood your heart pumps per minute. It is calculated by multiplying stroke volume by heart rate. So a person with a stroke volume of 70 ml and a resting heart rate of 70 beats per minute has a cardiac output of around 4,900 ml per minute — close to five litres.

Why this matters in POTS

In many people with POTS, stroke volume is reduced, particularly on standing. This can happen because:

→ Less blood is returning to the heart

→ The left ventricle does not fill as fully

→ The chamber size and contractile strength of the heart have reduced over time

The body still needs the same overall cardiac output to maintain brain and organ perfusion. When stroke volume drops, the only available compensation is for heart rate to increase — which is one of the main reasons heart rate rises so sharply when someone with POTS stands.

In other words: the tachycardia is the response, not the cause.

How exercise helps

Structured exercise can gradually increase stroke volume. Over time, this means:

→ The heart pumps more blood with each beat

→ The body needs less heart rate compensation to maintain cardiac output

→ Resting and standing heart rates can come down

This is one of the central goals of exercise prescription for POTS.

Blood volume and plasma expansion

Research has shown that many people with POTS have reduced blood volume — particularly reduced plasma volume. Plasma is the fluid part of blood that carries red cells, proteins and electrolytes.

Lower plasma volume means less blood is available for the heart to fill with and pump out. It is a structural contributor to the low stroke volume picture.

The encouraging finding is that plasma volume expansion is one of the fastest adaptations to consistent aerobic training. Within days to weeks of starting a paced exercise program, plasma volume can increase by around 10–20%. The mechanism involves the release of proteins like albumin, which draw fluid into the bloodstream from surrounding tissues.

This is one reason some POTS clients notice symptom improvement within the first few weeks of structured exercise — well before the larger cardiac adaptations have occurred. It is also why hydration and sodium intake are part of POTS care alongside exercise, supporting the same goal of maintaining adequate plasma volume.

The muscle pump and venous return

Blood does not return to the heart on its own. From the lower half of the body, it has to travel uphill, against gravity.

The body's mechanical solution for this is called the skeletal muscle pump. When muscles in the calves, thighs, glutes and core contract, they compress the veins running through them. Veins contain one-way valves, so each contraction effectively squeezes blood upward toward the heart.

Why this matters in POTS

In POTS, weakened lower-body muscles mean a weakened muscle pump. Less venous return means less blood reaching the heart, which means less stroke volume.

This is one reason POTS-aware exercise programs place real emphasis on lower-body strength training:

→ Glute bridges

→ Calf raises

→ Leg presses

These exercises are not only about general strength — they directly improve the mechanical efficiency of the circulatory system, particularly the return of blood from the lower body back to the heart.

Cardiac remodeling

With consistent training over around three months, the heart muscle itself adapts. The left ventricle (the main pumping chamber) becomes slightly larger and stronger:

→ Chamber size increases (end-diastolic volume rises)

→ The walls of the ventricle strengthen

→ Each contraction becomes more forceful

This adaptation is called eccentric hypertrophy. It is the healthy, adaptive response to endurance training, and is distinct from the cardiac changes seen in disease.

The research behind this

Much of what we know about cardiac remodeling in POTS comes from work led by Dr Benjamin Levine at the University of Texas Southwestern. His team showed that POTS patients who completed a structured three-month exercise program had measurable increases in:

→ Left ventricular mass

→ End-diastolic volume

→ Stroke volume

These changes were accompanied by reduced standing heart rates and improved orthostatic tolerance.

This research is the basis of what is now widely known as the Levine Protocol — a graduated exercise program that starts recumbent, progresses slowly to upright, and runs lower-body strength training in parallel.

The autonomic nervous system

Alongside cardiac changes, consistent exercise also influences the autonomic nervous system — the system most directly involved in POTS. Two adaptations tend to occur over time.

Baroreflex sensitivity

The baroreflex is the body's automatic adjustment of heart rate and blood vessel tone in response to changes in blood pressure. In POTS, baroreflex responses are often blunted, and consistent exercise tends to improve baroreflex sensitivity over months.

Heart rate variability (HRV)

HRV is the small variation in time between heartbeats. It reflects the balance between sympathetic (activating) and parasympathetic (calming) nervous system activity, and lower HRV often suggests sympathetic dominance — a common finding in POTS.

Training tends to nudge HRV upward over time, reflecting improved autonomic balance. These changes are slower than blood volume or cardiac adaptations, but they are real, and they continue to develop with sustained training.

The deconditioning cycle that often follows

POTS itself is not caused by deconditioning. The underlying autonomic dysfunction comes first.

But once symptoms make standing, walking and exertion difficult, activity levels naturally drop. Over weeks and months, that drop in activity has consequences of its own — and these can quietly add a second layer on top of the original POTS picture:

→ Heart muscle becomes smaller and less efficient

→ Plasma volume drops further

→ Leg, glute and core muscles weaken, reducing the muscle pump

→ Autonomic regulation becomes less responsive

Each item in this list makes the others worse, creating a downward cycle where the body feels less and less capable of upright activity over time. This is not a moral failing or a sign of not trying hard enough — it is the predictable response of a body protecting itself from symptoms.

The encouraging news is that exercise can reverse this cycle when prescribed well. The same body that adapted downwards can adapt upwards, and the physiological changes described in the sections above are exactly what targeted exercise begins to undo.

What this looks like in a structured program

Translating the physiology into a workable plan is where exercise physiology earns its place. A POTS-aware program typically includes:

→ Posture-first programming — starting in positions where gravity is not a challenge (recumbent bike, rowing, swimming)

→ Inverted progression — adding duration before intensity, and intensity before upright posture

→ Lower-body strength as a non-negotiable

→ Heart rate guidance — usually working within individualised zones, often not above 75% of maximum

→ Symptom-led adaptation — adjusting the plan in response to flare days

→ Parallel hydration and sodium support

Over three to six months of consistent work, these elements produce meaningful change. Many clients describe a quiet but real shift — standing tasks that used to be exhausting become more manageable, post-exertion crashes ease, and daily functional capacity expands.

Why exercise prescription matters

Generic exercise advice can make POTS worse, not better. This is not because clinicians do not care — it is because standard prescription assumptions, like "start with 30 minutes of cardio most days", do not fit a body whose orthostatic tolerance, blood volume and autonomic regulation all need rebuilding.

An exercise physiologist with POTS experience can:

→ Read your individual picture — heart rate trends, symptom patterns, medication interactions

→ Monitor heart rate and blood pressure during sessions and adjust the dose in real time

→ Adapt the program around flare days, life events and progression

→ Work alongside your cardiologist or GP

POTS recovery is a long process. Most people need six to twelve months of consistent work before adaptations have fully landed, and having a clinician walking alongside you during that time often makes the difference between a plan that holds and one that gets abandoned.

How CardioCare Clinic can help

At CardioCare Clinic in Bondi Junction, we regularly work with people living with POTS and dysautonomia, both in-clinic and via telehealth across Australia.

Sophie is an Accredited Exercise Physiologist (ESSA), an ASAR-accredited Cardiac Sonographer, and a member of the Australian POTS Foundation. She has clinical experience in diagnostics as well as supporting people with POTS to build exercise capacity in a gradual, symptom-aware and sustainable way.

If you are looking for an exercise plan that respects the physiology of POTS — and a clinician who understands that progress often takes time, patience and careful progression — we would be glad to hear from you.