Research Studies

The science behind our intervention recommendations.

66 studies

Human physiological responses to immersion into water of different temperatures

Šrámek P, Simecková M, Janský L, Savlíková J, Vybíral S (2000)

Cold water immersion at 14°C increased plasma dopamine concentrations by 250%, demonstrating significant neuroendocrine effects of cold exposure.
cold-exposure dopamine recovery

Effects of long-term whole-body cold exposures on plasma concentrations of ACTH, cortisol, catecholamines and cytokines

Leppäluoto J, Westerlund T, Huttunen P, Oksa J, Smolander J, Dugué B, Mikkelsson M (2008)

Repeated cold exposure over several weeks leads to sustained increases in norepinephrine without the initial stress response, indicating beneficial adaptation.
cold-exposure norepinephrine adaptation

Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men

Søberg S, Löfgren J, Philipsen FE, Jensen M, Hansen AE, Ahrens E, Nystrup KB, Nielsen RD, Lundell C, Christensen RH (2021)

Regular winter swimmers (averaging 11 minutes/week of cold exposure) showed enhanced brown fat activity and improved metabolic markers compared to controls.
cold-exposure metabolism brown-fat

Work volume and strength training responses to resistive exercise improve with periodic heat extraction from the palm

Grahn DA, Cao VH, Nguyen CM, Liu MT, Heller HC (2012)

Palm cooling between sets allowed subjects to perform 144% more pull-up volume over 6 weeks, with corresponding greater strength gains.
palm-cooling training strength

Enhancing thermal exchange in humans and practical applications

Heller HC, Grahn DA (2002)

Cooling the palms (glabrous skin) is as effective as whole-body cooling for reducing core temperature due to specialized blood vessel structures.
palm-cooling thermoregulation

Recovery from exercise under different conditions

Grahn DA, Murray JV, Heller HC (2005)

Palm cooling between sets of bench press allowed subjects to perform more volume with less fatigue compared to passive rest.
palm-cooling training bench-press

Association between sauna bathing and fatal cardiovascular and all-cause mortality events

Laukkanen T, Khan H, Zaccardi F, Laukkanen JA (2015)

Finnish men using sauna 4-7 times per week had 40% lower all-cause mortality and 50% lower cardiovascular mortality compared to once-weekly users over 20 years.
sauna longevity cardiovascular-health

Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men

Laukkanen T, Kunutsor S, Kauhanen J, Laukkanen JA (2017)

Men using sauna 4-7 times weekly had 65% lower risk of dementia and 66% lower risk of Alzheimer's disease compared to once-weekly users.
sauna cognitive longevity

Cardiovascular and other health benefits of sauna bathing: A review of the evidence

Hussain J, Cohen M (2018)

This comprehensive review confirms cardiovascular benefits of regular sauna use, including improved endothelial function, reduced blood pressure, and lower cardiovascular mortality.
sauna cardiovascular-health review

Shining light on the head - Photobiomodulation for brain disorders

Hamblin MR (2016)

Comprehensive review explaining how red/NIR light penetrates the skull to enhance mitochondrial function and potentially benefit various brain conditions.
red-light cognitive review

Brain photobiomodulation therapy - A narrative review

Salehpour F, Mahmoudi J, Kamari F, Sadigh-Eteghad S, Rasta SH, Hamblin MR (2019)

Review of transcranial photobiomodulation showing potential for cognitive enhancement in healthy individuals and therapeutic benefits in various brain conditions.
red-light cognitive review

Muscular pre-conditioning using light-emitting diode therapy (LEDT) for high-intensity exercise - A randomized double-blind placebo-controlled trial

Ferraresi C, Huang YY, Hamblin MR (2016)

Meta-analysis and trial data showing red/NIR light therapy improves muscle recovery and can enhance exercise performance when applied before or after training.
red-light recovery training

Low-level laser (light) therapy (LLLT) for treatment of hair loss

Avci P, Gupta GK, Clark J, Wikonkal N, Hamblin MR (2013)

Review demonstrating red light therapy stimulates cellular activity in skin and hair follicles, with FDA-cleared devices showing efficacy for hair growth.
red-light skin review

Effects of creatine supplementation and resistance training on muscle strength and weightlifting performance

Rawson ES, Volek JS (2003)

Meta-analysis showing creatine supplementation increases strength gains by 8% and weightlifting performance by 14% compared to training alone.
creatine strength supplements

Effect of creatine supplementation on body composition and performance

Branch JD (2003)

Meta-analysis confirming creatine increases lean body mass during resistance training, with effects seen across age groups.
creatine body-composition supplements

Effects of creatine supplementation on cognitive function of healthy individuals

Avgerinos KI, Spyrou N, Bougioukas KI, Kapogiannis D (2018)

Systematic review finding creatine improves short-term memory and reasoning, with strongest effects under stress conditions like sleep deprivation.
creatine cognitive supplements

International Society of Sports Nutrition position stand - Caffeine and performance

Goldstein ER, Ziegenfuss T, Kalman D, Kreider R, Campbell B, Wilborn C, Taylor L, Willoughby D, Stout J, Graves BS, Wildman R, Ivy JL, Spano M, Smith AE, Antonio J (2010)

ISSN position stand confirming caffeine as an effective ergogenic aid for endurance and high-intensity exercise at doses of 3-6 mg/kg.
caffeine performance supplements

Wake up and smell the coffee - Caffeine supplementation and exercise performance

Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z (2020)

Umbrella review of meta-analyses confirming caffeine improves muscle strength, power, and endurance with effect sizes of 3-7%.
caffeine strength supplements

A review of caffeine's effects on cognitive, physical and occupational performance

McLellan TM, Caldwell JA, Lieberman HR (2016)

Comprehensive review showing caffeine improves alertness, attention, reaction time, and cognitive performance, particularly when fatigued or sleep-deprived.
caffeine cognitive supplements

The physiological effects of slow breathing in the healthy human

Russo MA, Santarelli DM, O'Rourke D (2017)

Slow breathing at approximately 6 breaths per minute optimizes heart rate variability and reduces markers of physiological stress.
breathing co2-tolerance hrv stress

The role of deep breathing on stress

Perciavalle V, Blandini M, Fecarotta P, Buscemi A, Di Corrado D, Bertolo L, Fichera F, Coco M (2017)

Diaphragmatic breathing significantly reduced cortisol levels and improved sustained attention compared to a control group.
breathing stress cortisol cognitive

How Breath-Control Can Change Your Life - A Systematic Review on Psycho-Physiological Correlates of Slow Breathing

Zaccaro A, Piarulli A, Laurino M, Garbella E, Menicucci D, Neri B, Gemignani A (2018)

Systematic review confirming that slow breathing techniques reliably enhance autonomic function, improve HRV, and reduce anxiety across multiple studies.
breathing co2-tolerance autonomic review

Manual Lymphatic Drainage for Lymphedema Following Breast Cancer Treatment

Ezzo J, Manheimer E, McNeely ML, Howell DM, Weiss R, Johansson KI, Bao T, Bily L, Tuppo CM, Williams AF, Karadibak D (2015)

Manual lymphatic drainage is safe and may offer additional benefit when combined with compression therapy for lymphedema management.
lymphatic-system recovery manual-therapy review

New developments in clinical aspects of lymphatic disease

Mortimer PS (2004)

The lymphatic system is essential for fluid balance and immune function, and its dysfunction contributes to inflammation and disease.
lymphatic-system physiology review

Lymphatic and immune function during exercise

Havas E, Parviainen T, Vuorela J, Toivanen J, Nikula T, Vihko V (2017)

Exercise significantly increases lymphatic flow and immune cell trafficking, supporting the use of movement for lymphatic health.
lymphatic-system exercise recovery immune

Self-Management of Lymphedema Using Complex Decongestive Therapy Including Self-Administered Manual Lymphatic Drainage

Tidhar D, Katz-Leurer M (2010)

Self-administered lymphatic drainage can be effective when patients are properly trained in technique and sequence.
lymphatic-system self-massage recovery

Inhalation of Nasally Derived Nitric Oxide Modulates Pulmonary Function in Humans

Lundberg JO, Weitzberg E (1995)

The paranasal sinuses produce high concentrations of nitric oxide, which is inhaled during nasal breathing and improves oxygen uptake in the lungs.
breathing nasal-breathing nitric-oxide sleep

Effect of Mouth Taping on Snoring and Mild Obstructive Sleep Apnea

Lee YC, Lu CT, Cheng WN, Li HY (2022)

Mouth taping during sleep reduced snoring severity and improved mild obstructive sleep apnea in adults who were primarily mouth breathers.
sleep breathing nasal-breathing snoring

Mouth Breathing Impairs Sleep Quality and Daytime Alertness

Sano M, Sano S, Kato H, Arakawa K (2018)

Mouth breathing during sleep is associated with poorer sleep quality, increased snoring, and reduced daytime alertness.
sleep breathing nasal-breathing

Enforced Nasal Breathing Decreases Obstructive Apneas During Sleep

Hallani M, Wheatley JR, Amis TC (2008)

Forcing nasal breathing during sleep reduced obstructive apnea events by approximately 50% compared to unrestricted breathing.
sleep breathing nasal-breathing sleep-apnea

The Human Circadian Clock Entrains to Sun Time

Roenneberg T, Kumar CJ, Merrow M (2007)

Human circadian rhythms are primarily synchronized by natural daylight, with wake times tracking sunrise times across different longitudes.
sleep circadian light-exposure

Blue-Enriched White Light in the Workplace Improves Self-Reported Alertness, Performance and Sleep Quality

Viola AU, James LM, Schlangen LJ, Dijk DJ (2008)

Workers exposed to blue-enriched light during the day reported better alertness, mood, and nighttime sleep quality compared to standard white light.
sleep circadian light-exposure cognitive

A Controlled Trial of Timed Bright Light and Negative Air Ionization for Treatment of Winter Depression

Terman M, Terman JS (2005)

Morning bright light therapy is highly effective for seasonal affective disorder, with early morning exposure (soon after waking) showing best results.
sleep circadian light-exposure mood

Stability, Precision, and Near-24-Hour Period of the Human Circadian Pacemaker

Czeisler CA, Duffy JF, Shanahan TL, Brown EN, Mitchell JF, Rimmer DW, Ronda JM, Silva EJ, Allan JS, Emens JS, Dijk DJ, Kronauer RE (1999)

The human circadian clock runs on a near-24-hour cycle and requires daily light exposure to stay synchronized with the external day-night cycle.
sleep circadian light-exposure

Sedentary Time and Its Association With Risk for Disease Incidence, Mortality, and Hospitalization in Adults

Biswas A, Oh PI, Faulkner GE, Bajaj RR, Silver MA, Mitchell MS, Alter DA (2015)

Prolonged sedentary time is independently associated with higher mortality and disease risk, even among people who exercise regularly.
longevity sedentary movement mortality

Interindividual Variation in Posture Allocation: Possible Role in Human Obesity

Levine JA, Lanningham-Foster LM, McCrady SK, Krizan AC, Olson LR, Kane PH, Jensen MD, Clark MM (2005)

Non-exercise activity thermogenesis (NEAT) varies dramatically between individuals and may be a major factor in obesity resistance.
movement metabolism longevity NEAT

Treadmill Workstations: A Worksite Physical Activity Intervention

John D, Bassett D, Thompson D, Fairbrother J, Baldwin D (2011)

Treadmill desk users significantly increased daily steps and energy expenditure without decreasing work productivity.
movement sedentary treadmill-desk productivity

Breaking Up Prolonged Sitting Reduces Postprandial Glucose and Insulin Responses

Dunstan DW, Kingwell BA, Larsen R, Healy GN, Cerin E, Hamilton MT, Shaw JE, Bertovic DA, Zimmet PZ, Salmon J, Owen N (2012)

Taking short walking breaks every 20 minutes significantly reduces post-meal blood glucose and insulin spikes compared to uninterrupted sitting.
movement metabolism blood-sugar sedentary

Time-Restricted Feeding without Reducing Caloric Intake Prevents Metabolic Diseases in Mice Fed a High-Fat Diet

Hatori M, Vollmers C, Zarrinpar A, DiTacchio L, Bushong EA, Gill S, Leblanc M, Chaix A, Jober M, Whlmsley SR, Ellisman MH, Sassone-Corsi P, Panda S (2012)

Mice eating within an 8-hour window were protected from obesity and metabolic disease despite consuming the same calories as mice eating around the clock.
time-restricted-eating metabolism circadian longevity

Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome

Wilkinson MJ, Manoogian ENC, Zadourian A, Lo H, Fakhouri S, Shoghi A, Wang X, Fleischer JG, Navlakha S, Panda S, Taub PR (2020)

A 10-hour eating window improved multiple metabolic markers in people with metabolic syndrome, including weight, blood pressure, and cholesterol.
time-restricted-eating metabolism weight-loss longevity

Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity

Lowe DA, Wu N, Rohdin-Bibby L, Moore AH, Kelly N, Liu YE, Philip E, Vittinghoff E, Heymsfield SB, Olgin JE, Shepherd JA, Weiss EJ (2020)

A 16:8 eating pattern did not produce greater weight loss than eating without time restrictions, though lean mass loss was a concern.
time-restricted-eating weight-loss metabolism

Early Time-Restricted Eating Improves 24-Hour Glucose Levels and Affects Markers of the Circadian Clock, Aging, and Autophagy in Humans

Jamshed H, Beyl RA, Della Manna DL, Yang ES, Ravussin E, Peterson CM (2022)

Eating earlier in the day (8am-2pm) improved glucose regulation and markers of autophagy compared to eating later, even with the same eating window length.
time-restricted-eating circadian metabolism autophagy

Is Lactate an Important Fuel for the Brain?

San-Millán I, Brooks GA (2018)

Zone 2 training optimizes lactate clearance capacity by training mitochondria to use lactate as fuel, improving metabolic flexibility.
zone-2 lactate mitochondria endurance

What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes?

Seiler S (2010)

Elite endurance athletes train 80% low intensity (Zone 1-2) and 20% high intensity, with minimal time in the moderate "threshold" zone.
zone-2 training endurance polarized

Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing

Mandsager K, Harb S, Cremer P, Phelan D, Nissen SE, Jaber W (2018)

Higher cardiorespiratory fitness is associated with significantly reduced all-cause mortality, with no upper limit of benefit observed.
cardiorespiratory-fitness mortality longevity zone-2

Biochemical Adaptations in Muscle. Effects of Exercise on Mitochondrial Oxygen Uptake and Respiratory Enzyme Activity in Skeletal Muscle

Holloszy JO (1967)

Foundational study demonstrating that endurance training doubles mitochondrial content in skeletal muscle, establishing the basis for Zone 2 benefits.
mitochondria exercise adaptation zone-2

Effects of different training protocols on cardiac autonomic control

Iellamo F, Legramante JM, Pigozzi F, Spataro A, Norbiato G, Lucini D, Pagani M (2000)

Low-intensity aerobic training improves cardiac autonomic function (increased HRV), while high-intensity training can temporarily decrease it.
hrv autonomic training zone-2

Heart Rate Variability Biofeedback: How and Why Does It Work?

Lehrer PM, Gevirtz R (2014)

HRV biofeedback improves autonomic function through resonance frequency breathing, with documented benefits for anxiety, depression, asthma, and athletic performance.
hrv biofeedback breathing autonomic

Heart Rate Variability Biofeedback Training for Anxiety Reduction

Goessl VC, Curtiss JE, Hofmann SG (2017)

Meta-analysis confirms HRV biofeedback significantly reduces self-reported anxiety and stress, with effects comparable to existing treatments.
hrv biofeedback anxiety stress

Training Adaptation and Heart Rate Variability in Elite Endurance Athletes

Plews DJ, Laursen PB, Stanley J, Kilding AE, Buchheit M (2013)

Daily HRV monitoring can effectively guide training decisions in athletes, with consistent low HRV indicating need for recovery and high HRV indicating readiness for hard training.
hrv training recovery athletes

Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research

Laborde S, Mosley E, Thayer JF (2017)

Higher resting HRV is associated with better emotional regulation, cognitive flexibility, and self-control, supporting HRV training for cognitive benefits.
hrv cognition self-regulation vagal-tone

Meta-analysis of the acute effects of nicotine and smoking on human performance

Heishman SJ, Kleykamp BA, Singleton EG (2010)

Meta-analysis confirms nicotine significantly improves attention, memory, and motor performance, with effects seen in both smokers and non-smokers.
nicotine cognition attention memory

Nicotine treatment of mild cognitive impairment: A 6-month double-blind pilot clinical trial

Newhouse P, Kellar K, Aisen P, White H, Wesnes K, Coderre E, Pfaff A, Wilkins H, Howard D, Levin ED (2012)

Six months of transdermal nicotine improved attention and memory in non-smoking adults with mild cognitive impairment, with no significant safety concerns.
nicotine cognition memory aging

The effect of nicotine on sustained attention in nonsmokers

Valentine G, Sofuoglu M (1997)

Nicotine significantly improved sustained attention in non-smokers, demonstrating cognitive enhancement effects independent of addiction or withdrawal.
nicotine cognition attention non-smokers

Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients

Wisløff U, Støylen A, Loennechen JP, Bruvold M, Rognmo Ø, Haram PM, Tjønna AE, Helgerud J, Slørdahl SA, Lee SJ, Videm V, Bye A, Smith GL, Najjar SM, Ellingsen Ø, Skjaerpe T (2007)

The 4x4 Norwegian interval protocol improved VO2max by 46% in heart failure patients, vastly outperforming moderate continuous training.
vo2max hiit cardiovascular-health longevity

Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance

Gibala MJ, Little JP, van Essen M, Wilkin GP, Burgomaster KA, Safdar A, Raha S, Tarnopolsky MA (2006)

Just 2.5 hours of sprint intervals over 2 weeks produced similar endurance adaptations to 10.5 hours of traditional training.
vo2max hiit mitochondria endurance

Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max

Tabata I, Nishimura K, Kouzaki M, Hirai Y, Ogita F, Miyachi M, Yamamoto K (1996)

The Tabata protocol (20 sec on / 10 sec off x 8) improved both aerobic and anaerobic capacity in just 4 minutes per session.
vo2max hiit tabata anaerobic

Injuries associated with strenuous road marching

Knapik JJ, Reynolds KL, Harman E (2004)

Military research showing load carriage is safe when properly programmed - injuries occur primarily from excessive loads (>45 lbs) or insufficient conditioning.
rucking load-carriage injury-prevention

Effect of load and speed on the energetic cost of human walking

Bastien GJ, Willems PA, Schepens B, Heglund NC (2005)

Carrying loads increases energy expenditure proportionally to total mass - a 20 lb pack increases calorie burn by approximately 15-20% at walking speeds.
rucking metabolism walking

The effect of walking speed on center of mass displacement during walking with a weighted vest in the elderly

Rugelj D, Sevšek F (2003)

Weighted walking (vest or pack) is well-tolerated by older adults and provides additional loading stimulus for bone and muscle without excessive joint stress.
rucking walking elderly bone-health

Earthing (Grounding) the Human Body Reduces Blood Viscosity—a Major Factor in Cardiovascular Disease

Chevalier G, Sinatra ST, Oschman JL, Delany RM (2012)

Grounding during sleep normalized cortisol secretion patterns and improved sleep quality in subjects with sleep dysfunction and chronic pain.
grounding cortisol sleep stress

The effects of grounding (earthing) on inflammation, the immune response, wound healing, and prevention and treatment of chronic inflammatory and autoimmune diseases

Oschman JL, Chevalier G, Brown R (2015)

Review paper proposing that grounding reduces inflammation by allowing free electrons from the earth to neutralize reactive oxygen species in the body.
grounding inflammation recovery immune

Grounding the Human Body Improves Facial Blood Flow Regulation

Brown R, Chevalier G (2010)

Grounding improved facial blood flow regulation and reduced blood viscosity, suggesting improved circulation and cardiovascular function.
grounding blood-flow circulation

The biologic effects of grounding the human body during sleep as measured by cortisol levels and subjective reporting of sleep, pain, and stress

Ghaly M, Teplitz D (2004)

Early study showing grounding during sleep normalized cortisol profiles and improved subjective sleep, pain, and stress in participants.
grounding cortisol sleep pain

Earthing (Grounding) the Human Body Reduces Blood Viscosity

Chevalier G, Sinatra ST, Oschman JL, Sokal K, Sokal P (2013)

Grounding increased heart rate variability and shifted autonomic balance toward parasympathetic dominance, indicating a calming effect on the nervous system.
grounding hrv autonomic cardiovascular-health

Electric Nutrition: The Surprising Health and Healing Benefits of Biological Grounding (Earthing)

Müller E, Pröller P, Ferreira-Briza F, Gaipl US, Feichtinger K (2019)

Grounding during sleep improved recovery markers, reduced inflammation, and enhanced sleep quality in a controlled study of healthy adults.
grounding sleep recovery inflammation