Evidence-Based Case for Aquatic Therapy in Postural Orthostatic Tachycardia Syndrome (POTS)

May 12 / Aquatic Therapy University

Aquatic therapy is not simply a “comfortable alternative” for patients with POTS. In many ways, it directly addresses the core physiological impairments that define the condition. The aquatic environment provides a rare combination of cardiovascular support, autonomic modulation, and exercise tolerance that is difficult to replicate on land.

Guideline Support

The 2015 Heart Rhythm Society (HRS) Expert Consensus Statement specifically recommends that initial exercise training for individuals with POTS “should be restricted to non-upright exercises including the use of rowing machines, recumbent cycles, and swimming to minimize orthostatic stress on the heart” (Sheldon et al., 2015).

In addition, structured progressive exercise carries a Class IIa recommendation as part of POTS management (Bryarly et al., 2019).

That recommendation matters. Because for many patients with POTS, the issue is not motivation. It is physiology. The body simply does not tolerate upright exercise well enough to participate consistently during the early stages of rehabilitation.

Water changes that equation.

Why Water Is Uniquely Suited for POTS

The primary mechanisms underlying POTS include:

  • cardiovascular deconditioning
  • reduced blood volume (hypovolemia)
  • excessive venous pooling
  • impaired venous return upon standing
  • exaggerated compensatory tachycardia

Aquatic immersion counteracts nearly every one of these mechanisms simultaneously (Fedorowski, 2019; Fu & Levine, 2018).

1. Hydrostatic Pressure Improves Venous Return

One of the most powerful effects of immersion is hydrostatic compression.

Head-out water immersion redistributes approximately 700 mL of blood into the thoracic cavity, increasing cardiac filling, stroke volume, and cardiac output. 

Heart volume may increase by approximately 180 mL, with cardiac output increasing by over 30% (Gauer, 1975).

In practical terms? The pool acts like a full-body circulatory assist device.

Patients who struggle to maintain blood flow to the heart during standing suddenly experience improved preload and more efficient circulation. The tachycardic “panic response” of the cardiovascular system becomes less necessary because the body is no longer fighting gravity alone.

2. Water Functions Like Full-Body Compression Garments

Compression garments are commonly recommended for POTS because they reduce venous pooling in the extremities.

Hydrostatic pressure does the same thing — but often more effectively and more uniformly.

Immersion compresses peripheral vasculature, reduces venous diameter, and improves spontaneous venous flow throughout the body (de Moraes Silva et al., 2023).

Unlike compression socks, however, the water does not stop at the knee.
The support is circumferential, dynamic, and proportional to immersion depth.

3. Aquatic Immersion Modulates the Autonomic Nervous System

Water immersion also produces measurable autonomic effects.

As immersion depth increases, central venous pressure rises and sympathetic nervous system activity decreases. Heart rate falls significantly during xiphoid-level immersion (Gabrielsen et al., 1993; Pendergast et al., 2015).

For a patient population characterized by autonomic overactivation, this is clinically meaningful.

Many patients describe the water as the first place they feel “normal” during exercise.

That statement is not merely emotional. It is physiological.

4. Water Removes the Orthostatic Challenge

Swimming and horizontal aquatic exercise eliminate much of the gravitational stress responsible for symptom provocation in POTS (Bryarly et al., 2019; Fu & Levine, 2018).

This allows patients to:
  • exercise longer
  • tolerate higher workloads
  • improve conditioning safely
  • participate before upright exercise becomes feasible

And perhaps most importantly…

…it allows success early in the rehabilitation process.

That matters because many POTS patients have experienced repeated exercise failure before referral to therapy.

Clinical Outcomes: Exercise Programs That Include Swimming

The exercise program developed by Fu and Levine incorporates swimming, rowing, and recumbent cycling as foundational “base training” activities. The outcomes reported from this approach are remarkable (Bryarly et al., 2019; Fu & Levine, 2018).

Reported improvements include:
  • increased VO₂ max
  • improved stroke volume
  • increased blood volume
  • improved baroreflex function
  • improved autonomic circulatory control
  • increased left ventricular mass and end-diastolic volume

Most notably:
The majority of patients completing the 3-month program no longer met diagnostic criteria for POTS (Bryarly et al., 2019).

Even more compelling, exercise training outperformed propranolol in restoring upright hemodynamics and improving quality of life (Bryarly et al., 2019).

That is a profound statement about the power of appropriately dosed physiological retraining.

The Hidden Superpower of Aquatic Therapy: Adherence

One of the greatest barriers in POTS rehabilitation is not designing the exercise program.

It is getting patients to stay in it long enough for physiological adaptation to occur.

Patients with POTS often abandon exercise because upright activity worsens symptoms during the early stages of conditioning (Bryarly et al., 2019).

Aquatic therapy reduces this barrier substantially.

The buoyancy, hydrostatic support, and symptom reduction associated with immersion decrease perceived exertion and orthostatic discomfort, improving tolerance during the critical early weeks of rehabilitation (Bryarly et al., 2019; Fu & Levine, 2018).

Clinically, this is huge. Because the “best exercise program” is not the one that looks impressive on paper. It is the one the patient can actually survive long enough to benefit from.

Clinical Summary

Aquatic therapy for POTS is supported by:

explicit Heart Rhythm Society exercise recommendations
  • strong hemodynamic and autonomic physiological rationale
  • exercise trials demonstrating remission-level outcomes
  • improved tolerance compared to upright land exercise
  • enhanced adherence during early rehabilitation
  • For many patients with POTS, the pool is not merely a modified environment.

It is the first environment where exercise becomes physiologically accessible again.

References

  • Bryarly, M., Phillips, L. T., Fu, Q., Vernino, S., & Levine, B. D. (2019). Postural orthostatic tachycardia syndrome: JACC focus seminar. Journal of the American College of Cardiology, 73(10), 1207–1228. https://doi.org/10.1016/j.jacc.2018.11.059
  • de Moraes Silva, M. A., Nakano, L. C., Cisneros, L. L., & Miranda, F. (2023). Balneotherapy for chronic venous insufficiency. Cochrane Database of Systematic Reviews, (1), CD013085. https://doi.org/10.1002/14651858.CD013085.pub3
  • Fedorowski, A. (2019). Postural orthostatic tachycardia syndrome: Clinical presentation, aetiology and management. Journal of Internal Medicine, 285(4), 352–366. https://doi.org/10.1111/joim.12852
  • Fu, Q., & Levine, B. D. (2018). Exercise and non-pharmacological treatment of POTS. Autonomic Neuroscience: Basic and Clinical, 215, 20–27. https://doi.org/10.1016/j.autneu.2018.07.001
  • Gabrielsen, A., Johansen, L. B., & Norsk, P. (1993). Central cardiovascular pressures during graded water immersion in humans. Journal of Applied Physiology, 75(2), 581–585. https://doi.org/10.1152/jappl.1993.75.2.581
  • Gauer, O. H. (1975). Recent advances in the physiology of whole body immersion. Acta Astronautica, 2(1–2), 31–39. https://doi.org/10.1016/0094-5765(75)90040-5
  • Pendergast, D. R., Moon, R. E., Krasney, J. J., Held, H. E., & Zamparo, P. (2015). Human physiology in an aquatic environment. Comprehensive Physiology, 5(4), 1705–1750. https://doi.org/10.1002/cphy.c140018
  • Sheldon, R. S., Grubb, B. P., Olshansky, B., Shen, W.-K., Calkins, H., Brignole, M., … Raj, S. R. (2015). 2015 Heart Rhythm Society expert consensus statement on the diagnosis and treatment of postural tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope. Heart Rhythm, 12(6), e41–e63. https://doi.org/10.1016/j.hrthm.2015.03.029