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Infrared Saunas vs. Exercise in Women: Research Literature Review

woman relaxing in infrared indoor sauna

Jessica Carlos |

Table of Contents

Introduction to the study

Throughout history, practices such as saunas, steam rooms, and hot springs have been embraced for promoting health and wellness. Health experts highly recommend exercise due to its numerous benefits, anti-inflammatory, anti-aging effects, and its role in disease prevention. Clinical advantages of regular sauna usage, deficient humidity forms like Finnish and infrared saunas, are primarily seen in enhancing cardiovascular disease (CVD) [?] outcomes. For instance, using a Finnish sauna at least four times a week has shown a 63% reduction in sudden cardiac death and a 40% drop in all-cause mortality in men [1], strikingly close to the benefits of regular exercise.

The benefits of both saunas and exercises are believed to stem from several common physiological mechanisms, including the enhancement of endothelium-dependent vascular dilation, decreased arterial stiffness, modulations in the autonomic nervous system, alterations in inflammatory markers and lipid profiles, and blood pressure reduction [2].

Modern non-invasive metrics like arterial stiffness and heart rate variability (HRV) [?] are emerging as reliable clinical indicators for CVD. Arterial stiffness is a biomarker for vascular aging and provides a more dynamic understanding of blood vessel changes than resting blood pressure [3]. Meanwhile, HRV, which can be assessed in both time and frequency domains, indicates the heart's response to the autonomic nervous system. A higher HRV denotes a better adaptive response of the cardiovascular system to mental or physical stress [4].

While there have been studies comparing the effects of thermal therapy and exercise on arterial stiffness and HRV, most of these have concentrated on men and have utilized either passive water-based heating methods or humid/dry saunas [5]. There's a need for more comprehensive research incorporating female participants, using crossover designs, having sufficient washout periods, and integrating control groups or interventions.

This study was formulated to delve deeper into the physiological outcomes of infrared sauna bathing, especially looking into clinical markers of CVD, which have been more extensively researched in relation to exercise. The trial, conducted on premenopausal women, juxtaposed thermal responses, arterial stiffness, and HRV during infrared sauna, exercise, or controlled resting interventions. The hypothesis was that the infrared sauna and exercise would induce comparable thermal and cardiovascular-related responses when set against the control.

The Blueprint: Study Design Explained

is an infrared sauna similar to exercising inforgraphic

The Quest Begins

Dr. Joy Hussain wasn't just embarking on another research project; she was diving deep into the mysterious terrains of how our bodies respond to infrared saunas and exercise. The vehicle for this exploration? A meticulous, randomized, controlled crossover trial [?] - a gold standard in research methodologies. This method ensures that each participant experiences every condition, creating an even playing field for results. Following the CONSORT 2010 guidelines and the 2019 updates, Dr. Hussain designed a tripartite study: a controlled setting, a physical exertion session, and the centerpiece, the infrared sauna session.

Given the importance of establishing a baseline, every participant's journey started with the control session, after which they plunged into the randomized world of exercise and sauna sessions. Set against the backdrop of the Queensland Academy of Sport in Brisbane, this study spanned from August 2019 to March 2020. But, like a twist in a novel, the worldwide pandemic pressed pause on this intriguing journey in mid-March 2020.

Who Were The Participants?

Dr. Hussain's recruitment efforts stretched across the digital expanse of social media and branched into public advertisements. But joining this study wasn't an open call. Stringent criteria, from age and health factors to lifestyle habits, ensured a uniform pool of participants. The bar was set high:

  • Be a premenopausal woman above 18.
  • Be relatively new to saunas.
  • Maintain a standard Body Mass Index (BMI).
  • Be clear of chronic medications, barring hormonal contraceptives.

Some medical conditions, like atrial fibrillation [?], were automatic deal-breakers.

Anchored in Ethics

Scientific endeavors are only complete with a robust ethical framework. Dr. Hussain ensured that every participant was not just a test subject but an informed and consenting participant. The study enhanced its ethical credentials by obtaining an official registration with the ANZCTR.

A Glimpse into the Sessions

  • Control Session: This was the calm before the storm. Participants settled into a serene environment, calibrated at 77°F (25°C), spanning three 15-minute segments.
  • Exercise Session: Participants shifted gears, hopping onto cycles and pushing their limits through aerobic sessions punctuated by short breathers. The target? Ensuring heart rates pulsed at 55–70% of their maximum capacity.
  • Sauna Session: The pièce de résistance! Participants submerged themselves into the warm embrace of a full-spectrum infrared sauna, with temperatures soaring to a snug 140°F (60°C).

Metrics and Measurements

Dr. Hussain's team had an arsenal of tools:

  • Vital Signs and Thermal Metrics stretched from weighing scales to heartbeats, painting a comprehensive physiological picture.
  • Blood Pressure and Pulse Wave Analysis: The SphygmoCor XCEL delved deep, unveiling the subtleties of blood pressure and more.
  • Heart Rate Variability (HRV): Capturing the heart's rhythmic dance was essential—the Zephyr™ bioharness3, the chosen choreographer, recorded continuous 10-minute segments that reflected heart and breathing patterns.

On their designated session days, participants arrived in a state of preparation, having adhered to a precise set of guidelines. Their comfort and well-being were paramount: hydration, safety checks, and post-session feedback mechanisms were meticulously implemented.

Crunching the Numbers

A question often lingering in such endeavors is, "How many participants make the data reliable?" For Dr. Hussain's study, the magic number, after rigorous power analysis, was 9. Once this treasure trove of data was amassed, it was systematically arranged in Microsoft Excel and subsequently dissected using the cutting-edge IBM SPSS Statistics 26.0.

As the pages of Dr. Joy Hussain's research study unfurl, readers and researchers alike are impatient. The lingering query? What secrets did the infrared sauna whisper to the world?

A Deep Dive into the Findings

deep dive into the findings

Who Stepped Forward?

Venturing into the unknown can be daunting, yet from an initial group of 37 potential participants, 10 intrepid women embarked on this scientific journey. They committed from start to finish, and impressively, no participant abandoned the study. The research was conducted in a controlled indoor environment. The setting mirrored a mild, temperate day, with temperatures averaging a cozy 77.72°F (25.4°C) and only a slight variation of 0.9°F (0.9°C). The air retained a moderate moisture level, reflecting a 50% humidity.

Staying Hydrated

Water. It's the lifeblood of every physiological process, and in studies involving saunas and exercise, its importance is amplified tenfold. Throughout this scientific expedition, ensuring participants remained adequately hydrated. The results? Everyone stood up to the challenge, maintaining hydration levels that would make any researcher proud.

Thermal Responses

"How hot should a sauna be?" is a common question that comes to mind when we think of saunas. And in this study, the impact of this heat was palpable, especially in the context of tympanic temperatures [?]. Like a thermometer rising on a sunny day, sauna sessions witnessed a consistent temperature uptrend, overshadowing control and exercise interventions. However, nature always throws curveballs in a somewhat unexpected turn of events; skin temperatures slightly dipped during both sauna and exercise activities, with the back being the focal point of this cooling sensation.

Respiratory Responses

The rhythm of our breath is an intricate dance shaped by our activities. As anticipated, exercise sessions accelerated this rhythm, causing participants to take faster, deeper breaths. In stark contrast, the sauna's effect mirrored that of the control group, maintaining a steady respiratory pace. And for those with concerns about the crucial oxygen saturation levels, the study offered comforting news: no alarming fluctuations were observed.

Cardiovascular Responses:

Our heart, that tireless drummer, sets the pace for our body. As expected, exercise sessions accelerated its beats, showcasing a marked increase in rhythm compared to the sedate control. But, in the match-up between sauna sessions and either exercise or control, the differences blurred. The scoreboard showed near-identical results. Meanwhile, a whisper of change was observed in systolic blood pressure [?] post-sauna and exercise sessions, suggesting a mild decrease. But this whisper didn't shout loud enough to be deemed statistically significant.

Pulse Wave Analysis Responses

The arterial narrative is complex, and the Augmentation Index (AIx75) [?] attempted to tell its tale. Initial readings hinted a possible increase in arterial stiffness following exercise and sauna sessions compared to the control. However, these preliminary findings treaded on thin ice, calling for more rigorous statistical scrutiny. The Central Augmented Pressure (AugPress), on the other hand, maintained its stoic consistency throughout.

HRV Responses

In cardiac studies, the Zephyr™ bioharness3 emerges as a critical tool. Armed with this device, Dr. Hussain's team delved deep into the heart's rhythmic nuances, exploring heart rate variability across different scenarios. The outcome? A symphony of consistency, irrespective of whether the environment was that of a sauna, exercise, or control.

infrared sauna as exercise_results

TOP: Tympanic temperature measurements were taken from 10 subjects over time with different interventions. There was a significant increase in temperature with the infrared sauna compared to control (+1.05°C) and exercise (+0.79°C) at time points 15, 30, and 45 minutes.

MIDDLE: Skin temperature measurements from the back of 10 subjects showed significant decreases between exercise and control (-0.84°C) and sauna and control (-0.48°C) at certain time points. A difference between sauna and exercise was noted but only at the 15-minute mark.

BOTTOM: Respiratory rate measurements from 10 subjects over time revealed significant increases between exercise and control (+7.66 breaths/min) and exercise and infrared sauna (+6.66 breaths/min) at specific intervals.

Not Without Its Hitches: Adverse Events

While the majority of the participants breezed through, three of them did hit some bumps. Post-exercise, one participant felt the unsettling grip of nausea and dizziness. Another grappled with an irksome bicycle seat irritation during the exercise, which fortunately found resolution with a simple seat tweak. The sauna session wasn't without its drama, either. A participant experienced dizziness post-session, which escalated into a migraine headache later in the day, resolving only with some much-needed rest.

The sauna and exercise interventions undeniably influenced certain physiological parameters. However, it wasn't without its share of minor hiccups, as evidenced by the experiences of a few participants.

Unpacking the Research

 infrared sauna or exercise woman exercising

A Quick Recap of the Study's Objective

Dr. Joy Hussain's research focused on understanding how infrared sauna (IR) sessions influenced the physiological markers in ten healthy women. For a well-rounded understanding, she juxtaposed these outcomes against those from moderate-intensity exercise and simple resting periods. What's especially noteworthy is the crossover design employed: each woman acted as her control, eliminating inter-participant variation.

Main Takeaways from the Study

Core Insights from Tympanic Temperature (Ttymp)

Dr. Hussain's analysis unveiled a notable rise in tympanic temperature, which is a proxy for our core body temperature, during and after the infrared sauna sessions. This rise was more evident when juxtaposed with results from the exercise and control phases. Such an outcome is not entirely surprising, as it resonates with existing data on passive heating techniques. A fascinating observation was the consistent impact of the sauna on body temperature, even when participants were at different stages of their menstrual cycles - a factor known to influence body temperature.

The Skin's Narrative

While the core temperature readings provided some expected results, the skin had a unique story. Specific regions, namely the back, wrists, and forehead, registered a drop in temperature, especially during exercise sessions. The big question then arises: Why this cooling effect? Heavy sweating, especially pronounced during sauna sessions, is the primary factor behind this phenomenon.

Breath and Pace - Diving into Respiratory Rate (RR)

As participants pushed their physical limits with exercise, their respiratory rate quickened. This heightened pace was distinctly faster than recorded during the sauna and control scenarios.

A Deep Dive into Cardiovascular Dynamics

While heart matters always intrigue, the findings from this study regarding heart rate variability, blood pressure, and arterial stiffness were somewhat subdued. There were no groundbreaking shifts across the different interventions. A few postulations for these findings include:

  • The relatively gentle intensity of the interventions.
  • The control scenario may have inadvertently had similar health benefits as the other interventions.
  • The unique participant demographic for this study. It's crucial to remember that most previous studies predominantly featured male participants or those with specific health vulnerabilities.
Thermoregulation and the Intricacies of Oxygen Metabolism

There's a captivating dance between thermoregulation and oxygen metabolism at the cellular level. This study hinted at different regulatory mechanisms in play, especially considering the varying respiratory patterns witnessed during exercise and sauna sessions. All this, despite both scenarios inducing comparable temperature responses.

Deciphering Heart Rate Variability (HRV)

Heart rate variability, or HRV, is a crucial metric in such studies. However, drawing parallels with past research was a challenging endeavor. This is mainly attributed to past studies' inconsistent methodology, particularly regarding the inclusion of control groups and the specifics of sauna protocols.

Strengths vs. Limitations

Strengths: The standout? The crossover design, with each participant being their control. It's a solid approach, especially as 'normal range' values for arterial stiffness and HRV are still being pinned down.

Limitations: Over eight months, the study may not have accounted for the influence of seasonal changes. The variability in the time intervals between interventions for each participant and the limitation of only holding sessions in the morning also affect the results. These elements could skew results. Also, more monitoring post-intervention could have missed some essential physiological insights.

What's the Next Step?

next steps research

Dr. Hussain's diligent research has offered insights and opened doors to new avenues of exploration in the realm of passive heat studies. It's become evident that more than a one-size-fits-all approach is needed. Every thermal intervention, be it an infrared sauna or another modality, has distinct physiological responses. Dr. Hussain's revelations beckon the research community to employ a more granulated approach. Instead of solely focusing on traditional physiological markers, there's a clarion call to include the intricate maze of metabolic and enzymatic reactions in our body. This multidimensional lens will offer a more comprehensive perspective on how thermal treatments impact health. Here's what Dr. Hussain says:

"The infrared sauna exposure of our study reproduced some of the thermoregulatory but not all the hemodynamic or ANS-associated results found with other passive heat studies. This highlights the need for a more nuanced approach to evaluating clinical studies of passive heat, by not assuming all forms of thermal heat therapy will have equivalent cardiovascular or metabolic effects, especially regarding women. Measuring metabolic and enzymatic parameters along with sweating rate and other systemic physiological measurements in clinical studies will also guide further understanding of mechanistic differences. Clarifying such distinctions in the future will help to determine which passive heat activities are most beneficial for specific health-related outcomes, especially CVD-related outcomes." - Dr. Joy Hussain, PhD

Final Reflections

Navigating through Dr. Hussain's research, it becomes clear that infrared saunas etch their narrative in health benefits. While they induce specific healthful adaptations via thermoregulation, they chart a path distinct from traditional exercise. They don't replicate the cardiovascular, respiratory, or nuanced dance of the autonomic nervous system responses that exercise invokes. This differentiation is crucial for anyone considering wellness regimes. The sauna isn't a substitute for that morning jog or gym session; it's a complementary experience. So, when the warmth of an infrared sauna envelopes you, let Dr. Hussain's insights be your guide. Embrace the sauna's embrace, knowing its influence on your body is a unique tapestry of benefits, distinct from any other modality!

About Dr. Joy Hussain

dr. joy hussain cover photo

Dr. Joy serves as the Clinical Director for Health with Joy Pty Ltd, a cutting-edge medical practice in Brisbane, Australia, that intertwines wearables, wellness, and science-backed sauna therapies. In 2021, she achieved her PhD from RMIT University, focusing on the health benefits of regular sweating and sauna use. Her groundbreaking research delved into the potential of human sweat analysis through metabolomics. At present, she's channeling her knowledge to shape sauna-centric protocols for lifestyle medical purposes, targeting areas like cardiovascular disease prevention, cardiac rehabilitation, and alleviating postmenopausal hot flush symptoms. Beyond her primary roles, Dr. Joy actively engages with nearly 1K enthusiasts on her 'Sauna Science' Facebook group.

Her professional credentials span certifications in Family Medicine, Medical Acupuncture, and Remote Telemedicine.

You can learn more about Dr. Joy Hussain's research at: https://healthwithjoy.com.au/research (We highly recommend)

Contact Information & Socials

Key Words & Phrases

Cardiovascular Disease (CVD): Cardiovascular Disease (CVD) refers to a range of conditions affecting the heart and blood vessels, including coronary heart disease, cerebrovascular disease, and conditions resulting from blood clots or structural deformities from birth. Heart attacks and strokes, common CVD events, arise from obstructions in blood vessels, often due to fatty build-ups or clot formations (World Health Organization).

Heart Rate Variability (HRV): Heart rate variability refers to the subtle variations in the time intervals between consecutive heartbeats. While these variations may require specialized equipment to detect, they can signal potential health concerns, ranging from cardiac disorders to mental health challenges such as anxiety and depression (Cleveland Clinic).

Controlled Crossover Trial: A controlled crossover trial is a study design where participants are randomly assigned to sequences of treatments given consecutively. For example, in a basic AB/BA model, subjects receive treatment A followed by treatment B, or the reverse. This design enables comparing a patient's response to both treatments, which can lead to more precise results by eliminating patient variation (National Library of Medicine).

Atrial fibrillation (AFib): Atrial fibrillation (AFib) is an irregular heart rhythm where the heart's upper chambers beat chaotically and out of sync with the lower chambers. This condition increases the risk of blood clots, stroke, and other heart complications, often requiring treatments like medications or electric shock therapy. AFib can be associated with a related rhythm problem called atrial flutter (Mayo Clinic).

Tympanic temperature: Tympanic temperature is measured by placing a tiny sensor directly against the ear canal's tympanic membrane (Science Direct).

Systolic Blood Pressure: Systolic blood pressure (SBP) refers to the higher value in blood pressure readings, representing the force exerted on artery walls when the heart contracts. An elevation in SBP is a better predictor of cardiovascular disease than diastolic blood pressure. It is determined by the heart's pumping efficiency and the elasticity of arterial walls. Especially in older individuals, an increased SBP is prevalent and indicative of stiffer arteries (National Library of Medicine).

Augmentation Index (AIx75): The Augmentation Index (AIx) gauges the rigidity of the systemic arteries using the pressure waveform from the ascending aorta (National Library of Medicine).

Reference to Original Study

Joy N. Hussain, Marc M. Cohen, Nitin Mantri, Cindy J. O’Malley, Ronda F. Greaves, "Infrared sauna as exercise-mimetic? Physiological responses to infrared sauna vs exercise in healthy women: A randomized controlled crossover trial", Complementary Therapies in Medicine, Volume 64, 2022, 102798, ISSN 0965- 299.

Other References

[1] Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna
bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med.
2015;175(4):542–548.

[2] Jari A. Laukkanen, Tanjaniina Laukkanen, Setor K. Kunutsor, Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence, Mayo Clinic Proceedings, Volume 93, Issue 8, 2018, Pages 1111-1121, ISSN 0025-6196.

[3] Pierre Boutouyrie , Rosa-Maria Bruno, The Clinical Significance and Application of Vascular Stiffness Measurements, American Journal of Hypertension, Volume 32, Issue 1, January 2019, Pages 4–11.

[4] Billman GE, Huikuri HV, Sacha J, Trimmel K. An introduction to heart rate variability: methodological considerations and clinical applications. Front Physiol. 2015 Feb 25;6:55. doi: 10.3389/fphys.2015.00055. PMID: 25762937; PMCID: PMC4340167.

[5] Lee E, Laukkanen T, Kunutsor SK, Khan H, Willeit P, Zaccardi F, Laukkanen JA. Sauna exposure leads to improved arterial compliance: Findings from a non-randomised experimental study. Eur J Prev Cardiol. 2018 Jan;25(2):130-138. doi: 10.1177/2047487317737629. Epub 2017 Oct 19. PMID: 29048215.

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