Fatigue: Understanding and Overcoming the Top 5 Types
In our fast-paced and demanding world, fatigue has become a common experience, leaving many feeling drained and depleted. From brain fog and mental exhaustion to the weight of physical fatigue, understanding the various forms of fatigue is key to addressing its root causes and reclaiming our vitality.
This comprehensive article examines the science behind fatigue, exploring the five most prevalent types and offering practical strategies for combating each. Join us on this journey to enhance your energy, productivity, and overall well-being.
Understanding Fatigue:
Fatigue, characterised by feelings of tiredness, weakness, and diminished energy levels, is a multifaceted phenomenon with physical and psychological components. It can arise from a myriad of factors, including physical exertion, mental stress, inadequate sleep, underlying health conditions and poor gut health. By unravelling the intricate interplay of physiological and psychological factors contributing to fatigue, we gain insight into how to effectively address and mitigate its effects.
The 5 Types of Fatigue:
1 — Physical Fatigue
Physical fatigue is a common form of tiredness experienced by many individuals due to various factors such as strenuous physical activity, inadequate rest, or underlying health issues. It is characterised by feelings of exhaustion, weakness, and decreased energy levels, which can significantly impact daily functioning and overall well-being.
Causes of Physical Fatigue:
Strenuous Physical Activity:
Engaging in intense exercise or manual labour without proper conditioning or adequate rest can lead to physical fatigue. This type of fatigue often occurs when the body's energy reserves are depleted faster than they can be replenished, resulting in muscle fatigue and reduced stamina.
Inadequate Rest:
Insufficient sleep or poor sleep quality can contribute to physical fatigue by preventing the body from fully recovering and restoring energy levels. Chronic sleep deprivation disrupts the body's natural circadian rhythm and impairs hormonal regulation, leading to increased feelings of exhaustion and decreased physical performance.
Underlying Health Conditions:
Pain and certain medical conditions, such as anaemia, chronic fatigue syndrome, fibromyalgia, and autoimmune disorders, can cause or exacerbate physical fatigue. These conditions often affect energy metabolism, muscle function, or cardiovascular health, resulting in persistent feelings of tiredness and weakness.
Gut Health:
Poor gut health can contribute to feelings of fatigue through various interconnected pathways. The gut is often known as the "second brain" due to its extensive network of neurones and its role in regulating mood, cognition, and energy metabolism. When the gut microbiota, intestinal barrier, or digestive function becomes compromised, it can lead to systemic inflammation, nutrient malabsorption, and disruptions in neurotransmitter production, all of which can contribute to fatigue:
Inflammation: Imbalances in the gut microbiota, known as dysbiosis, can trigger an inflammatory response in the gut lining. This inflammation can disrupt the integrity of the intestinal barrier, allowing harmful substances like bacterial toxins, undigested food particles, and inflammatory cytokines to leak into the bloodstream. Systemic inflammation can then contribute to fatigue by activating immune cells and disrupting energy metabolism.
Nutrient Malabsorption: The gut plays a crucial role in absorbing essential nutrients from food, including vitamins, minerals, fatty acids and amino acids, which are necessary for energy production and cellular function. When the gut lining is damaged or inflamed, nutrient absorption may be impaired, leading to deficiencies in key nutrients like iron, vitamin B12, and magnesium. These deficiencies can negatively impact energy levels and contribute to feelings of fatigue.
Gut-Brain Axis: The gut communicates bidirectionally with the brain through the gut-brain axis, involving the vagus nerve, neurotransmitters, and the enteric nervous system. Disruptions in gut health can influence neurotransmitter production and signalling, affecting mood, cognition, and stress response. Dysregulation of the gut-brain axis has been implicated in various mental health conditions, such as depression and anxiety, which are often accompanied by poor sleep habits and fatigue.
Serotonin Production: The majority of serotonin, a neurotransmitter involved in mood regulation and sleep-wake cycles, is produced in the gut by enterochromaffin cells. Imbalances in the gut microbiota or disruptions in serotonin synthesis can affect serotonin levels in the brain, leading to mood disturbances and sleep disturbances, both of which can contribute to fatigue.
Mitochondrial Dysfunction: Mitochondria, often referred to as the powerhouse of the cell, are responsible for generating ATP, the primary source of cellular energy. Dysfunctional mitochondria can impair energy production, leading to decreased stamina and increased fatigue. Gut dysbiosis and inflammation can contribute to mitochondrial dysfunction through oxidative stress and metabolic disturbances.
Symptoms of Physical Fatigue:
Persistent feelings of exhaustion, even after rest or sleep
Muscle weakness and reduced physical strength
Decreased stamina and endurance during physical activities
Difficulty performing routine tasks or activities of daily living
Slowed reaction times and impaired coordination
Increased susceptibility to injuries or accidents due to reduced alertness and concentration
Effects of Physical Fatigue:
Physical fatigue can have significant implications for both physical and mental well-being. In addition to impacting physical performance and productivity, it can also affect mood, cognitive function, and emotional resilience. Chronic physical fatigue may contribute to the development of other health problems, such as obesity, cardiovascular disease, and mental health disorders.
Management of Physical Fatigue:
Rest and Recovery:
Prioritising adequate rest and allowing sufficient time for recovery after physical exertion is essential for combating physical fatigue. Incorporating rest days into exercise routines and establishing a regular sleep schedule can help restore energy levels and promote overall well-being.
Nutrition and Hydration:
Consuming a balanced diet rich in nutrients, vitamins, and minerals is crucial for supporting energy metabolism and muscle function. Staying hydrated by drinking plenty of water throughout the day can also help prevent dehydration and alleviate feelings of fatigue.
Exercise and Physical Activity:
Engaging in regular exercise and physical activity can improve stamina, endurance, and overall physical fitness, reducing the risk of physical fatigue. However, it's important to listen to your body and avoid overexertion, as excessive exercise can contribute to fatigue and increase the risk of injury.
Stress Management:
Managing stress through relaxation techniques, mindfulness practices, and stress-reducing activities can help alleviate physical fatigue and promote relaxation and well-being. Finding healthy ways to cope with stressors and prioritising self-care activities can also improve resilience and combat feelings of exhaustion.
2 — Mental Fatigue
Mental fatigue, often referred to as cognitive fatigue, is a prevalent yet often overlooked form of exhaustion that affects cognitive function and mental well-being. It arises from prolonged cognitive activity, such as intense focus, problem-solving, or decision-making, which can deplete mental resources and impair cognitive performance.
Causes of Mental Fatigue:
Mental fatigue can stem from various factors, including:
Prolonged cognitive activity:
Engaging in tasks that require sustained attention, problem-solving, or decision-making for extended periods can deplete mental resources and lead to fatigue.
Stress:
Chronic stress can strain the body's stress response systems, including the hypothalamic-pituitary-adrenal (HPA) axis, leading to fatigue and cognitive impairment. It also taxes heavily on the adrenals.
Sleep deprivation:
Inadequate sleep disrupts cognitive function and impairs attention, memory, and decision-making abilities, contributing to mental fatigue.
Mental health disorders:
Conditions such as anxiety, depression, and burnout can exacerbate mental fatigue by affecting mood, motivation, and cognitive processing.
Environmental factors:
Noise, distractions, and information overload can overwhelm cognitive resources and lead to mental fatigue and cognitive overload.
Poor nutrition:
Nutrient deficiencies or imbalances can impair brain function and cognitive performance, increasing susceptibility to mental fatigue.
Lack of physical activity:
Sedentary behaviour and a lack of exercise can lead to reduced blood flow to the brain, affecting cognitive function and increasing the risk of mental fatigue.
Symptoms of mental fatigue:
Difficulty concentrating
Memory lapses
Reduced cognitive processing speed
Impaired decision-making
Emotional instability (Mental fatigue can exacerbate mood swings, irritability, and emotional volatility, making it harder to regulate emotions and cope with stress).
Effects of Mental Fatigue:
The effects of mental fatigue can be wide-ranging and impact various aspects of cognitive function, emotional well-being, and overall quality of life. Some common effects include:
Impaired cognitive performance:
Mental fatigue can lead to difficulties with concentration, attention, and memory. Individuals may experience slower reaction times, reduced processing speed, and decreased accuracy in tasks requiring cognitive effort.
Reduced productivity:
As mental fatigue sets in, individuals may find it challenging to maintain focus and complete tasks efficiently. Productivity levels may decline, and work performance may suffer as a result.
Emotional changes:
Mental fatigue can exacerbate feelings of irritability, frustration, and moodiness. Individuals may become more easily agitated or emotionally reactive, leading to conflicts in personal and professional relationships.
Poor decision-making:
Fatigue can impair executive function, making it harder for individuals to make sound judgments and decisions. They may struggle with problem-solving and may be more prone to making errors or overlooking important details.
Increased risk of accidents:
Mental fatigue can compromise situational awareness and reaction times, increasing the risk of accidents and errors in tasks such as driving, operating machinery, or performing complex procedures.
Physical symptoms:
Mental fatigue can manifest as physical symptoms, including headaches, muscle tension, and general feelings of lethargy or malaise. These physical manifestations can further contribute to overall discomfort and decreased well-being.
Sleep disturbances:
Mental fatigue can disrupt sleep patterns, leading to difficulties falling asleep, staying asleep, or achieving restorative sleep. This can create a cycle of fatigue, where poor sleep exacerbates mental fatigue and vice versa.
Management of Mental Fatigue:
The underlying mechanisms of mental fatigue are complex and involve alterations in brain function, neurotransmitter activity, and cognitive processing. Prolonged engagement in cognitively demanding tasks can lead to changes in brain activation patterns, including decreased activity in the prefrontal cortex, which is responsible for executive functions such as attention, planning, and impulse control.
Chronic stress, sleep deprivation, and mental health disorders such as anxiety and depression can exacerbate mental fatigue by further taxing cognitive resources and disrupting neurochemical balance. Additionally, environmental factors such as noise, distractions, and information overload can contribute to mental fatigue and cognitive overload.
Managing mental fatigue requires a multifaceted approach that addresses both the underlying causes and the symptoms. Strategies for combating mental fatigue may include:
Taking regular breaks: Incorporating short breaks into tasks can help alleviate mental fatigue and prevent cognitive overload. Breaks allow the brain to rest and recharge, improving focus and concentration.
Practising mindfulness: Mindfulness techniques such as meditation, deep breathing, and progressive muscle relaxation can help reduce stress, improve cognitive function, and enhance mental resilience.
Prioritising sleep: Adequate sleep is essential for cognitive function and mental well-being. Establishing a consistent sleep schedule and creating a conducive sleep environment can promote restful sleep and combat mental fatigue.
Balancing workload: Managing workload and setting realistic goals can prevent burnout and reduce the risk of mental fatigue. Delegate tasks when possible and avoid over-committing to avoid overwhelming cognitive demands.
Seeking social support: Connecting with friends, family, or colleagues can provide emotional support and help alleviate feelings of isolation and stress. Social support networks can also offer practical assistance and valuable perspective on managing mental fatigue.
3 — Emotional Fatigue
Also known as emotional exhaustion, emotional fatigue is a prevalent condition resulting from prolonged exposure to emotional stressors. It can have profound effects on mental well-being, interpersonal relationships, and overall quality of life..
Causes of Emotional Fatigue:
Emotional fatigue can stem from a variety of sources, including:
Chronic Stress:
Continuous exposure to high levels of stress from work, relationships, or personal challenges can lead to emotional exhaustion.
Traumatic Events:
Experiencing or witnessing traumatic events can overwhelm the emotional coping mechanisms, resulting in fatigue.
Unresolved Emotional Issues:
Lingering unresolved emotions, such as grief, anger, or resentment, can contribute to emotional fatigue over time.
Caregiver Burnout:
Providing care for a loved one with a chronic illness or disability can be emotionally draining, leading to fatigue.
Work-related Pressures:
Demands of a high-pressure work environment, including long hours, tight deadlines, and interpersonal conflicts, can contribute to emotional fatigue.
Symptoms of Emotional Fatigue:
Feelings of Overwhelm (by daily tasks and responsibilities)
Reduced Emotional Resilience (e.g., Difficulty coping with minor stressors or setbacks that previously would not have been as challenging)
Emotional Numbness and feeling emotionally detached or disconnected from oneself or others.
Irritability (or short-temperedness in response to minor frustrations or inconveniences)
Decreased Motivation, including loss of interest in activities that were once enjoyable or fulfilling.
Effects of Emotional Fatigue:
The effects of emotional fatigue can permeate various aspects of life, leading to:
Impaired Relationships: Strained interpersonal relationships due to decreased emotional availability and responsiveness.
Reduced Productivity: Decreased performance and productivity at work or in daily tasks due to cognitive and emotional exhaustion.
Mental Health Issues: Increased risk of developing anxiety, depression, or other mental health disorders as a result of chronic emotional strain.
Physical Symptoms: Manifestation of physical symptoms such as headaches, muscle tension, and gastrointestinal disturbances due to the interconnectedness of emotional and physical health.
Social Withdrawal: Withdrawal from social interactions and activities as a coping mechanism to conserve emotional energy and avoid further stressors.
Management of Emotional Fatigue:
Effectively managing emotional fatigue requires a holistic approach that addresses both the underlying causes and symptoms. Strategies for managing emotional fatigue include:
Self-care Practices:
Prioritising self-care activities such as mindfulness, relaxation techniques, and engaging in hobbies or activities that bring joy and fulfilment.
Seeking Support:
Reaching out to trusted friends, family members, or mental health professionals for emotional support and guidance.
Setting Boundaries:
Establishing clear boundaries in personal and professional relationships to protect emotional well-being and prevent overextension.
Stress Management:
Implementing stress-reduction techniques such as deep breathing exercises, meditation, or yoga to alleviate emotional tension and promote relaxation.
Time Management:
Organising and prioritising tasks to reduce feelings of overwhelm and create space for self-care and leisure activities.
Seeking Professional Help:
Consult a qualified therapist or counsellor to explore underlying emotional issues and develop coping strategies tailored to individual needs.
4 — Burnout
Burnout is a state of chronic physical and emotional exhaustion resulting from prolonged exposure to stressors, typically in the context of work or caregiving responsibilities. It can have profound implications for individual well-being, productivity, and overall quality of life.
Causes of Burnout:
Burnout often stems from prolonged exposure to high levels of stress, which can arise from various sources, including:
Work-related stressors such as excessive workload, lack of control, and interpersonal conflicts.
Chronic job dissatisfaction, feelings of unfulfillment, and a lack of recognition or reward.
Personal factors such as perfectionism, unrealistic expectations, and difficulty setting boundaries.
External pressures from societal expectations, financial concerns, and family obligations.
Symptoms of Burnout:
Persistent fatigue and exhaustion, both physical and emotional.
Feelings of cynicism, detachment, and depersonalisation towards work or personal responsibilities.
Reduced efficacy and productivity, accompanied by feelings of incompetence or ineffectiveness.
Physical symptoms such as headaches, muscle tension, and gastrointestinal disturbances.
Emotional symptoms including irritability, mood swings, and a sense of emptiness or hopelessness.
Cognitive impairments such as difficulty concentrating, memory lapses, and decision-making challenges.
Effects of Burnout:
The effects of burnout can permeate every aspect of an individual's life, impacting their physical health, mental well-being, and interpersonal relationships. Left unaddressed, burnout can lead to:
Increased risk of chronic health conditions such as cardiovascular disease, gastrointestinal disorders, and immune dysfunction
Mental health challenges including depression, anxiety disorders, and substance abuse
Impaired cognitive function and reduced performance in both professional and personal domains.
Strained interpersonal relationships due to irritability, withdrawal, and communication breakdowns.
Decreased job satisfaction, lower productivity, and higher rates of absenteeism and turnover in the workplace.
Management of Burnout:
Effectively managing burnout requires a multifaceted approach addressing its underlying causes and mitigating its effects. Key strategies include:
Setting realistic goals and expectations, both personally and professionally, and prioritising self-care activities.
Establishing healthy boundaries and learning to say no to excessive demands or commitments.
Engaging in stress-reduction techniques such as mindfulness meditation, deep breathing exercises, and progressive muscle relaxation.
Seeking social support from friends, family, or professional networks to share experiences and receive emotional validation.
Taking regular breaks, scheduling downtime, and incorporating leisure activities that promote relaxation and enjoyment.
Seeking professional help from a therapist, counsellor, or healthcare provider to address underlying mental health concerns and develop coping strategies tailored to individual needs.
Additional Note: Adrenal Fatigue and Associated Diseases:
In some cases, chronic stress and burnout can lead to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in a condition often referred to as adrenal fatigue, followed by adrenal exhaustion. This dysregulation can disrupt the body's natural stress response system, leading to imbalances in cortisol levels, energy production, and immune function. Over time, adrenal fatigue may contribute to the development of various diseases and health conditions, including:
Chronic fatigue syndrome (CFS)
Fibromyalgia
Autoimmune disorders
Thyroid dysfunction
Metabolic syndrome
Mood disorders such as depression and anxiety
Addison's disease, also known as adrenal insufficiency, is a condition associated with poorly functioning adrenal glands. It occurs when the adrenal glands fail to produce adequate amounts of cortisol and, in some cases, aldosterone. Addison's disease can result from relentless stress, chronic lack of sleep, and burnout, but also autoimmune disorders, infections, or other underlying conditions that damage the adrenal glands.
5 — Sleep Deprivation
Sleep deprivation is a prevalent condition characterised by insufficient or poor-quality sleep, resulting in a range of physical, cognitive, and emotional disturbances.
Causes of Sleep Deprivation:
Sleep deprivation can stem from various factors, including lifestyle choices, environmental factors, and underlying health conditions. Common causes include:
Poor Sleep Hygiene:
Irregular sleep schedules, excessive screen time before bed, and disruptive sleep environments can impair sleep quality and duration.
Stress and Anxiety:
Mental health issues such as anxiety and depression can lead to heightened arousal and difficulty falling or staying asleep.
Medical Conditions:
Certain medical conditions such as sleep apnoea, restless legs syndrome, and chronic pain can interfere with sleep architecture and contribute to sleep deprivation.
Medications:
Some medications, including certain antidepressants, stimulants, and corticosteroids, can disrupt sleep patterns and lead to sleep deprivation.
Lifestyle Factors:
Factors such as shift work, jet lag, and excessive caffeine or alcohol consumption can disrupt circadian rhythms and impair sleep quality.
Symptoms of Sleep Deprivation:
Daytime Fatigue (persistent feelings of tiredness, lethargy, and reduced energy levels during waking hours)
Cognitive Impairment (Difficulties with concentration, memory, attention, and decision-making)
Mood Disturbances (Increased irritability, mood swings, and emotional instability)
Physical Symptoms, including headaches, muscle aches, and gastrointestinal disturbances.
Impaired Performance (reduced productivity, creativity, and motor coordination)
Increased Risk of Accidents
Effects of Sleep Deprivation:
Sleep deprivation can have profound effects on both physical and mental health. Chronic sleep deprivation has been linked to an increased risk of various health problems, including:
Cardiovascular Disease: Sleep deprivation is associated with hypertension, heart disease, and stroke.
Metabolic Disorders: Poor sleep can disrupt hormonal regulation, leading to weight gain, insulin resistance, and type 2 diabetes.
Cognitive Decline: Chronic sleep deprivation has been linked to cognitive decline, memory loss, and an increased risk of neurodegenerative diseases such as Alzheimer's disease.
Mood Disorders: Sleep deprivation can exacerbate symptoms of depression and anxiety and increase the risk of mood disorders.
Immune Dysfunction: Inadequate sleep weakens the immune system, increasing susceptibility to infections and impairing the body's ability to fight off illness.
Management of Sleep Deprivation:
Managing sleep deprivation involves adopting healthy sleep habits and addressing underlying factors contributing to sleep disturbances. Here are some effective management strategies:
Establish a Consistent Sleep Schedule:
Go to bed and wake up at the same time every day, even on weekends, to regulate your body's internal clock. Avoid oversleeping to catch up on lost sleep.
Create a Relaxing Bedtime Routine:
Engage in calming activities such as reading, meditation, or gentle stretching before bed to signal to your body that it's time to wind down.
Optimise Your Sleep Environment:
Create a comfortable sleep environment that is dark, quiet, and cool, and invest in a supportive mattress and pillows.
Limit Stimulants and Electronics:
Avoid caffeine, nicotine, and electronic devices such as smartphones and tablets before bedtime, as they can interfere with sleep.
Manage Stress and Anxiety:
Practice relaxation techniques such as deep breathing, progressive muscle relaxation, or mindfulness meditation to reduce stress and promote relaxation.
Seek Treatment for Underlying Conditions:
If you suspect an underlying medical condition is contributing to your sleep deprivation, consult a healthcare professional for evaluation and treatment.
Consider Cognitive-Behavioural Therapy for Insomnia (CBT-I):
CBT-I is a highly effective treatment for insomnia that focuses on changing thoughts and behaviours that contribute to poor sleep.
Avoid Long Naps:
While short naps can be beneficial, avoid long naps during the day, as they can disrupt your sleep-wake cycle and make it harder to fall asleep at night.
Limit Alcohol and Heavy Meals Before Bed:
Avoid consuming alcohol and large meals close to bedtime, as they can disrupt sleep patterns and cause discomfort.
Restoring Healthy Sleep Patterns:
Restoring healthy sleep patterns requires a multifaceted approach addressing both behavioural and environmental factors. By adopting healthy sleep habits, managing stress, and seeking treatment for underlying conditions, individuals can improve their sleep quality and duration, leading to enhanced overall well-being and vitality. If you continue to experience persistent sleep disturbances despite implementing these strategies, book a consultation with us.
The Top 5 Types of Fatigue: Key Points
1. Physical Fatigue:
Characterised by a sense of physical exhaustion and decreased energy levels.
Results from strenuous physical activity, inadequate rest, or underlying health issues.
Strategies for combatting physical fatigue include optimising nutrition, hydration, and sleep, as well as incorporating regular exercise into daily routines.
2. Mental Fatigue:
Associated with prolonged cognitive activity and high levels of mental stress.
Symptoms include difficulty concentrating, memory lapses, and reduced productivity.
Combatting mental fatigue involves cognitive rest breaks, mindfulness practices, and relaxation techniques to restore cognitive resources and enhance mental resilience.
3. Emotional Fatigue:
Arises from prolonged emotional stress and can lead to feelings of overwhelm and emotional exhaustion.
Strategies for managing emotional fatigue include self-care practices, seeking social support, and engaging in stress-reducing activities to promote emotional well-being and resilience.
4. Burnout:
Characterised by chronic physical and emotional exhaustion resulting from prolonged exposure to stressors.
Burnout can have significant implications for both individual well-being and organisational productivity.
Mitigating burnout requires multifaceted interventions, including stress management programmes, fostering a supportive work environment, and developing coping strategies to enhance resilience.
5. Sleep Deprivation:
Occurs when individuals consistently fail to obtain adequate sleep, leading to daytime fatigue and impaired cognitive function.
Chronic sleep deprivation disrupts circadian rhythm and increases the risk of various health problems.
Combatting sleep deprivation involves adopting healthy sleep hygiene practices, addressing underlying sleep disorders, and prioritising sleep as a vital component of overall well-being.
Who is Most Affected by Fatigue?
While fatigue can affect individuals across various demographics, certain groups are more susceptible than others. Women, older adults, and individuals with chronic health conditions or high levels of stress are particularly vulnerable to experiencing fatigue.
By understanding the demographic factors associated with fatigue, targeted interventions can be implemented to address these disparities and improve overall well-being.
Combatting Fatigue: 3 Key Tips
Prioritise Sleep:
Maintain a consistent sleep schedule and create a conducive sleep environment.
Practice relaxation techniques before bedtime to promote restful sleep.
Address underlying sleep disorders through medical intervention or behavioural therapy.
Incorporate Physical Activity:
Engage in regular aerobic exercises such as walking or cycling to boost energy levels and improve mood.
Incorporate resistance training to enhance muscle strength and endurance, combating physical fatigue.
Maintain a Balanced Diet:
Consume a variety of nutrient-rich foods to provide essential vitamins, minerals, and antioxidants necessary for energy production.
Stay hydrated by drinking an adequate amount of water throughout the day to support cognitive function and combat fatigue.
In conclusion, combatting fatigue requires a comprehensive approach addressing both its physical and psychological components.
By understanding the different types of fatigue and implementing targeted strategies, you can reclaim your vitality and improve your overall quality of life.
References
Aaron, LA. et al. (2000). Overlapping conditions among patients with chronic fatigue syndrome, fibromyalgia, and temporomandibular disorder. Archives of Internal Medicine. 160(2), pp. 221-227.
Bakker, AB. Demerouti, E. (2017). Job demands-resources theory: Taking stock and looking forward. Journal of Occupational Health Psychology. 22(3), pp. 273–285.
Boksem, MA. Tops, M. (2008). Mental fatigue: Costs and benefits. Brain Research Reviews. 59(1), pp. 125-139.
Fernstrom, JD. Fernstrom, MH. (2006). Tyrosine, phenylalanine, and catecholamine synthesis and function in the brain. Journal of Nutrition. 137(6), 1539S–1547S.
Fredrickson, BL. (2004). The broaden-and-build theory of positive emotions. Philosophical Transactions of the Royal Society B: Biological Sciences. 359(1449), p. 1367
Grandner, MA. (2019). Sleep, health, and society. Sleep Medicine Clinics. 14(3), pp. 231–236.
Grandner, MA. (2017). Sleep, Health, and Society. Sleep Medicine Clinics. 12(1), pp. 1–22.
Hamer, M. Chida, Y. (2009). Active commuting and cardiovascular risk: A meta-analytic review. Preventive Medicine. 46(1), pp. 9-13.
Hjollund, NH. et al. (2007). Job strain and the risk of depression: Is reporting biased? American Journal of Epidemiology. 165(10), pp. 1285-1294.
Hockey, GR. (1997). Compensatory control in the regulation of human performance under stress and high workload; a cognitive-energetical framework. Biological Psychology. 45(1-3), pp. 73-93.
Hölzel, BK. et al. (2011). Mindfulness practice leads to increases in regional brain grey matter density. Psychiatry Research: Neuroimaging. 191(1), pp. 36-43.
Institute of Medicine (US) Committee on Sleep Medicine and Research. (2006). Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Colten HR, Altevogt BM, editors. Washington (DC): National Academies Press (US). PMID: 20669438.
Ivy, J.L. (2004). Regulation of muscle glycogen repletion, muscle protein synthesis and repair following exercise. Journal of Sports Science and Medicine. 3(3), pp. 131-138.
Kent-Braun, J.A. (1999). Central and peripheral contributions to muscle fatigue in humans during sustained maximal effort. European Journal of Applied Physiology and Occupational Physiology. 80(1), pp. 57-63.
Lim, J. Dinges, DF. (2010). A meta-analysis of the impact of short-term sleep deprivation on cognitive variables. Psychological Bulletin. 136(3), pp. 375-389.
Lorist, MM. et al. (2009). The influence of mental fatigue and motivation on neural network dynamics; an EEG coherence study. Brain Research. 1270, pp. 95-106.
Maslach, C. Leiter, MP. (2016). Understanding the burnout experience: Recent research and its implications for psychiatry. World Psychiatry. 15(2), 103–111.
McEwen, BS. (2017). Neurobiological and systemic effects of chronic stress. Chronic Stress. doi:10.1177/2470547017692328
Medic, G. et al. (2017). Short- and long-term health consequences of sleep disruption. Nature and Science of Sleep. 9, pp. 151–161.
Meeusen, R. et al. (2006). Exercise, fatigue, neurotransmission and the influence of the neuroendocrine axis. Sports Medicine. 36(10), pp. 839-862.
Meeusen, R. et al. (2005). Fatigue: A complex interplay of central and peripheral factors. Sports Medicine. 35(10), pp. 929-945.
Nijrolder, I. et al. (2009). Determinants of fatigue in general practice. Family Practice. 26(6), pp. 419-424.
Panagioti, M. et al. (2018). Association between physician burnout and patient safety, professionalism, and patient satisfaction: A systematic review and meta-analysis. JAMA Internal Medicine. 178(10), pp. 1317–1331.
Popkin, BM. et al. (2010). Water, hydration and health. Nutrition Reviews. 68(8), pp. 439–458.
Puetz, T. W. et al. (2006). Effects of chronic exercise on feelings of energy and fatigue: A quantitative synthesis. Psychological Bulletin. 132(6), pp. 866–876.
Strasser, B. et al. (2013). Resistance training in the treatment of the metabolic syndrome: A systematic review and meta-analysis of the effect of resistance training on metabolic clusters, and factors associated with the metabolic syndrome. Sports Medicine. 43(3), pp. 273–288.
Thayer, JF. Lane, RD. (2000). A model of neurovisceral integration in emotion regulation and dysregulation. Journal of Affective Disorders. 61(3), pp. 201-216.
Walker, MP. (2017). Why we sleep: Unlocking the power of sleep and dreams. Scribner. New York. ISBN13: 9781501144325.
Warburton, DER. et al. (2006). Health benefits of physical activity: the evidence. Canadian Medical Association Journal. 174(6), pp. 801–809.
Watson, NF. et al. (2015). Recommended amount of sleep for a healthy adult: A joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 38(6), pp. 843–844.
West, CP. Dyrbye, LN. Shanafelt, TD. (2018). Physician burnout: Contributors, consequences and solutions. Journal of Internal Medicine. 283(6), pp. 516–529.