Exercise-associated collapse in cyclists is unrelated to endotoxemia

Area of Science:

• Exercise physiology
• Immunology
• Gastroenterology

Background:

• Endotoxemia, caused by bacterial lipopolysaccharide translocation, triggers inflammatory cytokines leading to severe symptoms like shock.
• Previous studies noted higher endotoxin levels in athletes requiring medical attention, prompting speculation about its role in heat stroke.
• The relationship between endotoxemia and mild post-exertional illness in athletes remained unclear.

Purpose of the Study:

• To investigate the association between endotoxemia and mild post-exertional illness in cyclists after a 100-mile ride.
• To determine if endotoxin levels correlate with symptoms such as orthostatic hypotension, rigors, nausea, vomiting, diarrhea, or syncope.
• To compare physiological markers between ill cyclists and healthy controls.

Main Methods:

• Recruited 39 cyclists after a 100-mile ride, categorizing them into ill (n=13) and case-control (n=26) groups based on symptoms.
• Measured endotoxin and tumor necrosis factor alpha (TNF-alpha) titers using chromogenic assay and ELISA, respectively.
• Collected data on vital signs, hemoglobin, serum sodium, creatine kinase, creatinine, and uric acid.

Main Results:

• One ill cyclist exhibited a high endotoxin level (330 pg/mL); one control had 150 pg/mL; all others had ≤64 pg/mL.
• Ill cyclists showed lower serum sodium levels compared to controls (138 vs. 142 mEq/L).
• No significant differences were found in creatine kinase, creatinine, or uric acid levels between ill cyclists and controls.

Conclusions:

• Endotoxemia may be a complicating factor in mild post-exertional illness among cyclists.
• The study suggests endotoxemia does not appear to be the primary cause of mild post-exertional illness.
• Further research is needed to fully elucidate the role of endotoxemia in exercise-induced conditions.