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

Research output: Contribution to journalArticlepeer-review

32 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 1


  • 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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