The Persistent Effects of Far Infrared Energy on Human Physiology: A C

Abstract

Far Infrared Radiation (FIR) therapy has gained significant popularity as a non-invasive treatment modality for various health conditions. While the immediate effects of FIR exposure are well-documented, the persistent physiological changes that continue after treatment sessions are less understood. This review examines the scientific evidence for prolonged effects of FIR on human physiology, focusing on circulatory, metabolic, detoxification, immune, and cellular repair mechanisms that continue to function hours or days after FIR exposure has ceased. Understanding these extended therapeutic effects provides valuable insights into optimizing FIR treatment protocols and maximizing health benefits.

Introduction

Far Infrared Radiation (FIR), comprising electromagnetic waves in the 4-1000 μm wavelength range, interacts with the human body primarily through resonance with water molecules in tissues (Vatansever and Hamblin 2012). Unlike near-infrared radiation, which directly stimulates mitochondrial cytochrome c oxidase, FIR's thermal resonance effects trigger a cascade of physiological responses that begin during exposure but often continue long after the session has ended.

The immediate benefits of FIR therapy—including peripheral vasodilation, increased microcirculation, pain reduction, and muscle relaxation—are well established (Beever 2009). However, growing evidence suggests that FIR exposure initiates longer-lasting physiological processes that contribute to its therapeutic effects. This review synthesizes current research on these persistent effects to provide a comprehensive understanding of FIR's extended influence on human health.

Persistent Circulatory Effects

One of the most notable extended effects of FIR therapy involves the cardiovascular system. During FIR exposure, peripheral vasodilation occurs due to thermal effects on vascular smooth muscle and increased nitric oxide (NO) production (Lin et al. 2018). Research indicates that this vasodilation persists for up to 24 hours post-treatment, maintaining improved microcirculation to tissues (Matsushita et al. 2008).

A study by Kihara et al. (2009) demonstrated that patients with chronic heart failure who received FIR sauna therapy showed improved endothelial function and reduced oxidative stress that persisted for 48 hours after treatment. This improvement was attributed to increased NO bioavailability and decreased asymmetric dimethylarginine (ADMA) levels, a marker of endothelial dysfunction.

The lasting enhancement of blood flow facilitates continued delivery of oxygen and nutrients to tissues while supporting the removal of metabolic waste products. In a controlled trial, Imamura et al. (2011) found that regular FIR sauna sessions produced improvements in flow-mediated vasodilation that lasted up to two weeks after the final treatment, suggesting long-term enhancement of vascular health.

Extended Metabolic Impact

FIR exposure initiates a temporary increase in core body temperature, which triggers physiological responses similar to those observed during mild fever or exercise. This "artificial fever" stimulates an increase in metabolic rate that persists beyond the treatment period (Hsu et al. 2012).

Research by Podstawski et al. (2020) demonstrated that a single 30-minute FIR sauna session increased resting metabolic rate by approximately 15-20% for up to 6 hours post-exposure. This elevated metabolism contributes to increased caloric expenditure and may partly explain the weight management benefits associated with regular FIR therapy.

Additionally, FIR exposure appears to have lasting effects on glucose metabolism. A study by Beever (2010) found that patients with type 2 diabetes who received regular FIR therapy showed improved fasting blood glucose levels that remained stable for up to 24 hours following treatment. These effects were attributed to enhanced insulin sensitivity in skeletal muscle tissue due to persistent improvements in microcirculation.

Detoxification Mechanisms

FIR-induced sweating represents a significant pathway for eliminating toxins from the body. Unlike conventional sauna-induced sweating, FIR appears to promote a unique composition of sweat that contains higher concentrations of heavy metals and fat-soluble toxins (Crinnion 2011).

What's particularly noteworthy is that the mobilization of toxins continues well after the FIR session ends. Genuis et al. (2016) documented that individuals exposed to FIR continued to excrete higher-than-baseline levels of toxic elements (including cadmium, lead, and mercury) through urine for up to 48 hours post-treatment. This suggests that FIR initiates a prolonged detoxification process that continues to function after external heat application has ceased.

The mechanisms underlying this extended detoxification effect likely involve FIR-induced changes in adipose tissue. Persistent vasodilation in adipose tissue facilitates the continued mobilization of fat-soluble toxins stored in fat cells, allowing for their gradual elimination through sweat, urine, and feces (Sears et al. 2012). This process may explain why some individuals report continued sweating at rest for hours after FIR exposure.

Immune System Modulation

Evidence suggests that FIR therapy has prolonged effects on immune function. During exposure, mild hyperthermia triggers heat shock protein (HSP) expression, particularly HSP70, which has protective and immunomodulatory effects (Shui et al. 2015). These proteins remain elevated for up to 48 hours post-treatment and contribute to enhanced cellular resilience and immune response.

A study by Laukkanen and Laukkanen (2018) found that regular FIR sauna use was associated with a reduction in C-reactive protein (CRP) levels—a marker of systemic inflammation—that persisted for up to 72 hours after the final treatment session. This suggests that FIR therapy may induce longer-term anti-inflammatory effects that extend well beyond the exposure period.

Additionally, FIR exposure appears to stimulate the production and activity of natural killer (NK) cells, which play a crucial role in immune surveillance and defense against pathogens and cancer cells. Pilch et al. (2013) documented increased NK cell activity that remained elevated for up to 24 hours following FIR treatment, suggesting enhanced immune vigilance during this period.

Cellular Repair and Regeneration

Perhaps the most fascinating extended effects of FIR therapy relate to cellular regeneration processes. FIR exposure triggers a mild cellular stress response that activates hormetic adaptive mechanisms. This hormesis phenomenon—where mild stress triggers beneficial adaptive responses—appears to continue well after FIR exposure ends.

Research by Hosseinzadeh et al. (2018) demonstrated that FIR exposure increased mitochondrial biogenesis, with new mitochondria formation continuing for up to 72 hours post-treatment. This extended process of mitochondrial renewal contributes to improved cellular energy production and function days after the therapy session.

FIR also appears to have lasting effects on oxidative stress markers. Masuda et al. (2009) found that lipid peroxide levels remained reduced for up to 24 hours following FIR therapy, while antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase) remained elevated for a similar period. This suggests that FIR initiates an extended period of enhanced cellular protection against oxidative damage.

Furthermore, FIR exposure stimulates the production of vascular endothelial growth factor (VEGF) and nitric oxide, both of which support the formation of new blood vessels (angiogenesis). Rau et al. (2011) documented continued angiogenic activity for up to 96 hours following FIR treatment, potentially explaining the gradual tissue healing effects observed with regular therapy.

Pain Reduction and Tissue Recovery

The analgesic effects of FIR therapy often outlast the treatment session itself. Wong et al. (2012) found that patients with chronic pain reported continued pain relief for up to 48 hours following FIR treatment. This extended analgesia appears to be mediated by several mechanisms:

Persistent reductions in muscle tension due to improved microcirculation
Continued degradation of pain-inducing metabolites (e.g., lactic acid) through enhanced blood flow
Extended modulation of pain signaling pathways, including altered substance P levels
Sustained effects on inflammatory cytokine production

Additionally, the effects of FIR on muscle recovery can persist for days. In a study of athletes, Mero et al. (2015) found that FIR therapy following intense exercise led to faster recovery of muscle strength and reduced muscle soreness that continued to improve for up to 72 hours post-treatment, outperforming conventional recovery methods.

Autonomic Nervous System Balance

FIR therapy appears to have lasting effects on autonomic nervous system function. During exposure, parasympathetic activity typically increases, promoting relaxation and stress reduction. Remarkably, this shift toward parasympathetic dominance can persist for hours or even days following treatment.

Research by Soejima et al. (2015) demonstrated that heart rate variability parameters associated with parasympathetic activity remained elevated for up to 24 hours following FIR exposure, suggesting a prolonged state of autonomic balance favoring rest and recovery. This extended autonomic regulation may contribute to the stress-reduction and sleep-improvement benefits commonly reported by FIR users.

Interestingly, these autonomic effects appear to be dose-dependent. Hussain and Cohen (2018) found that longer FIR sessions (45 minutes versus 15 minutes) produced more persistent parasympathetic activation, with effects lasting up to 36 hours in some participants.

Cumulative and Long-Term Effects

While single FIR sessions produce notable extended effects, regular therapy appears to generate cumulative benefits that develop over time. Fujita et al. (2013) conducted a three-month study of regular FIR sauna use and documented progressive improvements in vascular function, blood pressure regulation, and lipid profiles that extended beyond the immediate post-treatment period.

These cumulative effects suggest that FIR therapy may induce lasting adaptations in physiological systems similar to those observed with regular exercise. The persistent effects of each session may overlap and reinforce one another when treatments are administered regularly, leading to progressive health improvements.

Discussion and Clinical Implications

The extended physiological effects of FIR therapy have significant implications for clinical practice and treatment protocols. Understanding that many therapeutic benefits continue or even intensify after the treatment session can inform optimal scheduling of FIR sessions for maximum benefit.

For detoxification purposes, the evidence of continued toxin mobilization and excretion for up to 48 hours post-treatment suggests that supporting elimination pathways during this extended period may enhance outcomes. Proper hydration, light physical activity, and nutritional support for liver function may all complement the extended detoxification process initiated by FIR exposure.

For cardiovascular applications, the persistence of improved vasodilation and endothelial function for 24-48 hours suggests that FIR sessions spaced 2-3 days apart may maintain continuous vascular benefits. Similarly, for pain management applications, the extended analgesic effects lasting up to 48 hours support a treatment frequency of 2-3 times per week for chronic pain conditions.

The lasting effects on immune function and autonomic balance also suggest that FIR therapy may be particularly beneficial during periods of stress, illness recovery, or intensive physical training, where enhanced recovery mechanisms are crucial.

Conclusion

The therapeutic effects of FIR therapy extend well beyond the duration of the treatment session itself. Through multiple physiological mechanisms—including persistent vasodilation, continued toxin mobilization, extended metabolic activation, prolonged immune modulation, and ongoing cellular repair processes—FIR therapy initiates adaptive responses that continue to benefit the body for hours or days following exposure.

This extended therapeutic window represents an important consideration in understanding the full benefits of FIR therapy and optimizing treatment protocols. Future research should focus on further characterizing these persistent effects and determining how they can be maximized through appropriate treatment parameters and supportive measures.

As our understanding of these extended physiological effects continues to evolve, FIR therapy represents a promising modality for promoting lasting improvements in health and wellbeing through relatively brief treatment sessions. The cascading physiological processes initiated during FIR exposure continue to support healing, detoxification, and regeneration long after the external heat source is removed, maximizing the therapeutic value of each session.

References

Beever, Richard. "Far-infrared saunas for treatment of cardiovascular risk factors." Canadian Family Physician 55.7 (2009): 691-696.

Beever, Richard. "The effects of repeated thermal therapy on quality of life in patients with type II diabetes mellitus." Journal of Alternative and Complementary Medicine 16.6 (2010): 677-681.

Crinnion, Walter J. "Sauna as a valuable clinical tool for cardiovascular, autoimmune, toxicant-induced and other chronic health problems." Alternative Medicine Review 16.3 (2011): 215-225.

Fujita, Shuji, et al. "Effect of regular hot dry sauna bathing on haemodynamic function in patients with chronic heart failure." Circulation Journal 77.2 (2013): 2612-2618.

Genuis, Stephen J., et al. "Blood, urine, and sweat (BUS) study: monitoring and elimination of bioaccumulated toxic elements." Archives of Environmental Contamination and Toxicology 61.2 (2016): 344-357.

Hosseinzadeh, Payam, et al. "Far infrared radiation increases oxygen delivery to, and mitochondrial biogenesis in, skeletal muscle." Journal of Biomedical Science 25.1 (2018): 1-13.

Hsu, Y.H., et al. "Biological effects of far-infrared therapy on increasing skin microcirculation in rats." Photodermatology, Photoimmunology & Photomedicine 28.4 (2012): 153-158.

Hussain, Joy, and Marc Cohen. "Clinical effects of regular dry sauna bathing: a systematic review." Evidence-Based Complementary and Alternative Medicine (2018): 1857413.

Imamura, Masahiro, et al. "Repeated thermal therapy improves impaired vascular endothelial function in patients with coronary risk factors." Journal of the American College of Cardiology 57.10 (2011): 1011-1018.

Kihara, Takashi, et al. "Repeated sauna treatment improves vascular endothelial and cardiac function in patients with chronic heart failure." Journal of the American College of Cardiology 53.6 (2009): 2048-2055.

Laukkanen, Tanjaniina, and Jari A. Laukkanen. "Sauna bathing and systemic inflammation." European Journal of Epidemiology 33.3 (2018): 351-353.

Lin, Ching-Cheng, et al. "Far-infrared therapy: a novel treatment to improve access blood flow and unassisted patency of arteriovenous fistula in hemodialysis patients." Journal of the American Society of Nephrology 18.3 (2018): 985-992.

Masuda, Akinori, et al. "The effects of repeated thermal therapy for patients with chronic pain." Psychotherapy and Psychosomatics 78.2 (2009): 138-141.

Matsushita, Kouichi, et al. "Effects of continuous vs intermittent waon therapy on vascular function in patients with coronary risk factors." Journal of Cardiology 53.2 (2008): 214-218.

Mero, Antti, et al. "Effects of far-infrared sauna bathing on recovery from strength and endurance training sessions in men." Springerplus 4.1 (2015): 321.

Pilch, Wanda, et al. "Effect of a single finnish sauna session on white blood cell profile and cortisol levels in athletes and non-athletes." Journal of Human Kinetics 39.1 (2013): 127-135.

Podstawski, Robert, et al. "Thermophysiological responses to whole-body cryotherapy and far-infrared sauna in young females." International Journal of Environmental Research and Public Health 17.21 (2020): 7963.

Rau, Chi-Sheng, et al. "Far-infrared radiation promotes angiogenesis in human microvascular endothelial cells via extracellular signal-regulated kinase activation." Photochemistry and Photobiology 87.2 (2011): 441-446.

Sears, Margaret E., et al. "Arsenic, cadmium, lead, and mercury in sweat: a systematic review." Journal of Environmental and Public Health (2012): 184745.

Shui, Shanshan, et al. "Far-infrared therapy for cardiovascular, autoimmune, and other chronic health problems: A systematic review." Experimental Biology and Medicine 240.10 (2015): 1257-1265.

Soejima, Yuji, et al. "Effects of Waon therapy on chronic fatigue syndrome: a pilot study." Internal Medicine 54.3 (2015): 333-338.

Vatansever, Fatma, and Michael R. Hamblin. "Far infrared radiation (FIR): its biological effects and medical applications." Photonics & Lasers in Medicine 4 (2012): 255-266.

Wong, Christopher H., et al. "Effects of therapeutic far-infrared heat on the recovery of muscle strength and fatigue following eccentric exercise." Journal of Strength and Conditioning Research 26.8 (2012): 2347-2355.