Fatigue: Biomedicine, Health & Behavior - Volume 1, Issue 3, 2013

Volume 1, Issue 3, 2013

 * Editorial, by Fred Friedberg. Full Text
 * Occupational fatigue, underlying sleep and circadian mechanisms, and approaches to fatigue risk management "Abstract - In most occupational settings, a primary reason for fatigue is incompatible timing of duty schedules relative to circadian (i.e., 24-hour) rhythm and the need for sleep. This review describes the sleep-related neurobiology of fatigue; factors in the operational environment that contribute to fatigue; and the effects of fatigue on cognitive performance that lead to errors, incidents, and accidents. A range of fatigue countermeasures are reviewed, broadly categorized as preventive countermeasures and operational countermeasures. Fatigue-related optimization of duty schedules and fatigue risk management systems are discussed as comprehensive ways to reduce fatigue and increase safety while maintaining productivity and operational integrity. Occupational fatigue is of significant concern at the individual, organizational, and societal levels, and strategies have been developed to help successfully manage and mitigate fatigue at each level."
 * Chronic fatigue syndrome/fibromyalgia: a “stress-adaptation” model "Abstract - Background: A symptom cluster consisting of ‘medically-unexplained’ chronic fatigue, effort intolerance and widespread pain is a complex and still poorly understood condition. Purpose: To demonstrate the theoretical and clinical value of a biopsychosocially-oriented ‘stress-adaptation’ model for this multi-symptom illness. Methods: Clinical observation and review of the relevant literature. Results: Symptoms and functional limitations of these patients may reflect a loss of normal physical, mental and emotional adaptability, primarily based on stress system dysregulation. Conclusions: The proposed stress-adaptation model may facilitate diagnosis, defy dualistic causal thinking, and offer tailor-made treatment options to help patients find a better balance in their lives."
 * Holistic approaches to understanding mechanisms of fatigue in high-intensity sport "Abstract - Purpose: The purpose of this article is to provide a holistic understanding of likely mechanisms of fatigue during high-intensity sports lasting 1–10 min. Methods: The contributions from skeletal muscle, central nervous system (motor drive), and fatigue sensations to lower performance during intense cycling, running, rowing, repeated sprints, or knee extensions were evaluated. Results: At the end of exercise, reductions of external power, force, or velocity and peak isometric forces are moderate (10–30%), motor drive falls by <8%, and fatigue sensations are extreme, e.g., Borg's rating of perceived exertion >18. Multiple putative fatigue factors can change simultaneously to interactively lower performance and/or provide protection. Major detrimental factors include raised intramuscular inorganic phosphate, severe extra- and intracellular acidosis, cerebral hypoxemia, large reduction of trans-sarcolemmal K+-gradient (also Na+- and Cl−-gradients), and reduced muscle glycogen levels. Factors resisting fatigue include elevated adrenaline, extracellular lactate, interstitial [H+] and [K+], and a normal trans-sarcolemmal Cl−-gradient. Conclusions: Raised inorganic phosphate interacting with intracellular H+, and a large rundown of trans-sarcolemmal ion gradients are likely to cause peripheral fatigue. Severe arterial hypoxemia (due to plasma acidosis, raised core temperature, lowered PaO2), and factors released from glycogen lowered muscles, e.g., interleukin-6, may cause central fatigue and strong fatigue sensations."
 * Contrasting chronic fatigue syndrome versus myalgic encephalomyelitis/chronic fatigue syndrome"Abstract - Background: Much debate is transpiring regarding whether chronic fatigue syndrome (CFS) and myalgic encephalomyelitis (ME) are different illnesses. Several prior studies that compared the Fukuda et al. CFS criteria to the Canadian ME/CFS criteria found that the Canadian criteria identified patients with more functional impairments and greater physical, mental, and cognitive problems than those who met Fukuda et al. criteria. These samples were located in the Chicago metropolitan area, so the results could not be generalized to other locations. In addition, past studies used a symptom questionnaire that was not specifically developed to tap the Canadian criteria. Purpose: The present comparative study of CFS and ME/CFS criteria was intended to correct the limitations of prior studies. Methods: This article used data from three distinct samples to compare patients who met criteria for the ME/CFS Canadian clinical case definition to those who met the Fukuda et al. CFS case definition. Results: Findings indicated that fewer individuals met the Canadian criteria than the Fukuda et al. criteria. Those who met the Canadian criteria evidenced more severe symptoms and physical functioning impairment. Conclusions: Future research should continue to compare existing case definitions and determine which criteria best select for this illness."