Chronic Fatigue Syndrome: Shephard RJ

Shephard RJ. · Faculty of Physical Education and Health and , Department of Public Health Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada. · J Sports Med Phys Fitness. · Pubmed #16230991 No free full text.

Abstract: The chronic fatigue syndrome (CFS) is debilitating for both athletes and the general population. A review of etiology and mechanisms underlying functional disturbances is undertaken to provide a valid basis for therapeutic options. The review focuses on CFS as characterized by standard diagnostic criteria, building on previous reviews through use of articles identified by Medline search. Overtraining, a negative energy balance, excessive physical or environmental stress, disorders of personality and affect, dysfunction of the hypophyseal-pituitary adrenal axis, hormonal imbalance, nutritional deficits, immune suppression or activation and chronic infection have all been proposed as factors precipitating CFS, but none of these precipitants are observed consistently. Impairments of peak aerobic power and muscle strength, together with many functional disturbances, seem related to patient- or physician-imposed inactivity. Once CFS is established, treatment should aim at breaking the vicious cycle of effort avoidance, deterioration in physical condition and increasing fatigue through a combination of psychotherapy, general encouragement and a progressive exercise regimen.

Shephard RJ. · Faculty of Physical Education and Health, Department of Public Health Sciences, Faculty of Medicine, University of Toronto, Toronto, Canada. · Crit Rev Immunol. · Pubmed #12498381 No free full text.

Abstract: The present review examines the cytokine response to acute exercise stress, with particular emphasis on the balance between proinflammatory and anti-inflammatory mechanisms, and the release of IL-6. Prolonged endurance exercise induces a sequenced release of pro- and anti-inflammatory cytokines, and IL-6 plays a dominant role. The magnitude of this response bears a general relationship to the intensity of effort, but the duration of activity and many environmental factors also modulate cytokine release. Although many types of cells are capable of producing cytokines, the main source of the exercise-induced IL-6 production appears to be the exercising muscle. The primary function of the additional IL-6 may be to regulate the supply of carbohydrate as muscle reserves of glycogen become depleted. There is also a delayed release of cytokines following eccentric exercise that is related to the repair of muscle injury. Since the production of cytokines is greater with endurance than with resistance exercise, it seems unlikely that they play an important role in the hypertrophy of muscle and bone. More research is needed on a number of important clinical issues where the exercise-induced release of cytokines may have relevance. Exercise-induced cytokine secretion has the potential to provide a simple model of sepsis. Preliminary observations suggest it may also modulate the risk of type 2 diabetes mellitus. Cytokine concentrations are increased in chronic fatigue syndrome, although it is less dear that the cytokine secretion is responsible for fatigue in humans. Exercise-induced modulations in cytokine secretion may contribute to allergies, bronchospasm, and upper respiratory infections in the endurance athlete. Further, the cytokine cascade is involved in the process of atherogenesis, and exercise-induced changes in cytokine production may expose latent HIV to chemotherapeutic agents.

Shephard RJ. · Defence & Civil Institute of Environmental Medicine, and Faculty of Physical Education & Health, University of Toronto, Ontario, Canada. · Sports Med. · Pubmed #11286355 No free full text.

Abstract: The chronic fatigue syndrome is characterised by a fatigue that is disproportionate to the intensity of effort that is undertaken, has persisted for 6 months or longer, and has no obvious cause. Unless there has been a long period of patient- or physician-imposed inactivity, objective data may show little reduction in muscle strength or peak aerobic power, but the affected individual avoids heavy activity. The study of aetiology and treatment has been hampered by the low disease prevalence (probably <0.1% of the general population), and (until recently) by a lack of clear and standardised diagnostic criteria. It is unclear how far the aetiology is similar for athletes and nonathletes. It appears that in top competitors, overtraining and/or a negative energy balance can be precipitating factors. A wide variety of other possible causes and/or precipitating factors have been cited in the general population, including psychological stress, disorders of personality and affect, dysfunction of the hypothalamic-pituitary-adrenal axis, hormonal imbalance, nutritional deficits, immune suppression or activation and chronic infection. However, none of these factors have been observed consistently. The prognosis is poor; often disability and impairment of athletic performance are prolonged. Prevention of overtraining by careful monitoring seems the most effective approach in athletes. In those where the condition is established, treatment should aim at breaking the vicious cycle of effort avoidance, deterioration in physical condition and an increase in fatigue through a combination of encouragement and a progressive exercise programme.

Shephard RJ. · No affiliation provided · Med Sci Sports Exerc. · Pubmed #12673157 No free full text.

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