The effects of increased endurance training load on biomarkers of heat intolerance during intense exercise in the heat

Chin Leong Lim*, David Pyne, Peggy Horn, Amelia Kalz, Philo Saunders, Jonathan Peake, Katsuhiko Suzuki, Gary Wilson, Laurel T. Mackinnon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


The effects of increased training (IT) load on plasma concentrations of lipopolysaccharides (LPS), proinflammatory cytokines, and anti-LPS antibodies during exercise in the heat were investigated in 18 male runners, who performed 14 days of normal training (NT) or 14 days of 20% IT load in 2 equal groups. Before (trial 1) and after (trial 2) the training intervention, all subjects ran at 70% maximum oxygen uptake on a treadmill under hot (35 °C) and humid (*40%) conditions, until core temperature reached 39.5 °C or volitional exhaustion. Venous blood samples were drawn before, after, and 1.5 h after exercise. Plasma LPS concentration after exercise increased by 71% (trial 1, p < 0.05) and 21% (trial 2) in the NT group and by 92% (trial 1, p < 0.01) and 199% (trial 2, p < 0.01) in the IT group. Postintervention plasma LPS concentration was 35% lower before exercise (p < 0.05) and 47% lower during recovery (p < 0.01) in the IT than in the NT group. Anti-LPS IgM concentration during recovery was 35% lower in the IT than in the NT group (p < 0.05). Plasma interleukin (IL)-6 and tumor necrosis factor (TNF)-α concentrations after exercise (IL-6, 3-7 times, p < 0.01, and TNF-α, 33%, p < 0.01) and during recovery (IL-6, 2-4 times, p < 0.05, and TNF-α, 30%, p < 0.01) were higher than at rest within each group. These data suggest that a short-term tolerable increase in training load may protect against developing endotoxemia during exercise in the heat.

Original languageEnglish
Pages (from-to)616-624
Number of pages9
JournalApplied Physiology, Nutrition and Metabolism
Issue number4
Publication statusPublished - 2009 Aug


  • Anti-LPS antibodies
  • Cytokines
  • Endotoxemia
  • Heat tolerance
  • Lipopolysaccharides

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Nutrition and Dietetics
  • Physiology (medical)


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