Causes of extreme fatigue in underperforming athletes - a synthesis of recent hypotheses and reviews

The underperformance syndrome (UPS), previously known as the overtraining syndrome (OTS), has been defined as a persistent decrement in athletic performance capacity despite 2 weeks of relative rest. Clinical research has suggested that cytokines play a key role in fatigue in disease and chronic fatigue syndrome. Furthermore, it has recently been demonstrated that exogenous administration of interleukin-6 (IL-6) increases the sensation of fatigue during exercise. In light of current cytokine and chronic fatigue syndrome research, this article reviews and updates the cytokine theories that attempt to explain the aetiology of the debilitating fatigue experienced in OTS/UPS. Initially, it was proposed that UPS may be caused by excessive cytokine release during and following exercise, causing a chronic inflammatory state and ‘cytokine sickness'. More recently, the hypothesis was extended and it was proposed that time-dependent sensitisation could provide a model through which the aetiology of UPS may be explained. According to this model, the principal abnormal factor in UPS is an intolerance/heightened sensitivity to IL-6 during exercise. South African Journal of Sports Medicine Vol. 18 (4) 2006: pp. 108-11

Causes of extreme fatigue in underperforming athletes - a synthesis of recent hypotheses and reviews

The underperformance syndrome (UPS), previously known as the overtraining syndrome (OTS), has been defined as a persistent decrement in athletic performance capacity despite 2 weeks of relative rest. Clinical research has suggested that cytokines play a key role in fatigue in disease and chronic fatigue syndrome. Furthermore, it has recently been demonstrated that exogenous administration of interleukin-6 (IL-6) increases the sensation of fatigue during exercise. In light of current cytokine and chronic fatigue syndrome research, this article reviews and updates the cytokine theories that attempt to explain the aetiology of the debilitating fatigue experienced in OTS/UPS. Initially, it was proposed that UPS may be caused by excessive cytokine release during and following exercise, causing a chronic inflammatory state and ‘cytokine sickness'. More recently, the hypothesis was extended and it was proposed that time-dependent sensitisation could provide a model through which the aetiology of UPS may be explained. According to this model, the principal abnormal factor in UPS is an intolerance/heightened sensitivity to IL-6 during exercise. South African Journal of Sports Medicine Vol. 18 (4) 2006: pp. 108-11

The impact of gastrointestinal symptoms and dermatological injuries on nutritional intake and hydration status during ultramarathon events

BACKGROUND: Debilitating gastrointestinal symptoms (GIS) and dermatological injuries (DI) are common during and after endurance events and have been linked to performance decrements, event withdrawal, and issues requiring medical attention. The study aimed to determine whether GIS and DI affect food and fluid intake, and nutritional and hydration status, of ultramarathon runners during multi-stage (MSUM) and 24-h continuous (24 h) ultramarathons. METHODS: Ad libitum food and fluid intakes of ultramarathon runners (MSUM n = 54; 24 h n = 22) were recorded throughout both events and analysed by dietary analysis software. Body mass and urinary ketones were determined, and blood samples were taken, before and immediately after running. A medical log was used to monitor symptoms and injuries throughout both events. RESULTS: GIS were reported by 85 and 73 % of ultramarathon runners throughout MSUM and 24 h, respectively. GIS during MSUM were associated with reduced total daily, during, and post-stage energy and macronutrient intakes (p < 0.05), whereas GIS during 24 h did not alter nutritional variables. Throughout the MSUM 89 % of ultramarathon runners reported DI. DI during MSUM were associated with reduced carbohydrate (p < 0.05) intake during running and protein intake post-stage (p < 0.05). DI during 24 h were low; thus, comparative analyses were not possible. Daily, during running, and post-stage energy, macronutrient and water intake variables were observed to be lower with severity of GIS and DI (p < 0.05) throughout the MSUM only. CONCLUSIONS: GIS during the MSUM, but not the 24 h, compromised nutritional intake. DI presence and severity also compromised nutrient intake during running and recovery in the MSUM

A narrative review on the similarities and dissimilarities between myalgic encephalomyelitis/chronic fatigue syndrome (me/cfs) and sickness behavior

It is of importance whether myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a variant of sickness behavior. The latter is induced by acute infections/injury being principally mediated through proinflammatory cytokines. Sickness is a beneficial behavioral response that serves to enhance recovery, conserves energy and plays a role in the resolution of inflammation. There are behavioral/symptomatic similarities (for example, fatigue, malaise, hyperalgesia) and dissimilarities (gastrointestinal symptoms, anorexia and weight loss) between sickness and ME/CFS. While sickness is an adaptive response induced by proinflammatory cytokines, ME/CFS is a chronic, disabling disorder, where the pathophysiology is related to activation of immunoinflammatory and oxidative pathways and autoimmune responses. While sickness behavior is a state of energy conservation, which plays a role in combating pathogens, ME/CFS is a chronic disease underpinned by a state of energy depletion. While sickness is an acute response to infection/injury, the trigger factors in ME/CFS are less well defined and encompass acute and chronic infections, as well as inflammatory or autoimmune diseases. It is concluded that sickness behavior and ME/CFS are two different conditions