Physiologic and biochemical changes during a triathlon competition

Int J Sports Med. 1986 Feb;7(1):30-5. doi: 10.1055/s-2008-1025731.


The triathlon has come to be recognized as a distinct endurance event and although a substantial body of research information exists with regard to the individual components (canoeing, cycling, running, etc.), the physiologic demands imposed by combining the respective activities into one continuous event have not yet been assessed. Twenty-three male athletes (age = 33 +/- 5.2 yr; mass = 71.79 +/- 7.42 kg; height = 176.0 +/- 7.21 cm; means +/- SD) participated in the study on the basis of informed consent. Venous blood samples, taken immediately prior to and on completion of the Iron Man Triathlon held in Johannesburg during 1983, were assayed for parameters of energy metabolism, fluid and electrolyte balance, and stress (tissue enzymes in serum). On the basis of post-race blood glucose (6.17 mmol. l-1), free fatty acids (1943 mumol. l-1), and blood lactate (3.45 mmol. l-1) changes, it was concluded that the triathlon is primarily, in an overall sense, an aerobic event. With the exception of magnesium and iron, serum electrolyte changes agreed with literature findings. However, body mass reductions (average 3.23 kg, i.e., 4.5%) indicated that the extent of dehydration is more severe in the triathlon than in comparable endurance events. Post-race enzyme levels (LD, CK, and AST) were significantly elevated, and LD negatively correlated with total performance time (P less than 0.01). The general conclusion is that the physiologic demand of the triathlon exceeds that of other comparable endurance events.

MeSH terms

  • Adult
  • Aspartate Aminotransferases / blood
  • Bicycling
  • Blood Glucose / analysis
  • Body Weight
  • Creatine Kinase / blood
  • Electrolytes / blood
  • Energy Metabolism
  • Fatty Acids / blood
  • Humans
  • Iron / blood
  • L-Lactate Dehydrogenase / blood
  • Magnesium / blood
  • Male
  • Running
  • Sports*
  • Temperature
  • Time Factors
  • Water-Electrolyte Balance


  • Blood Glucose
  • Electrolytes
  • Fatty Acids
  • Iron
  • L-Lactate Dehydrogenase
  • Aspartate Aminotransferases
  • Creatine Kinase
  • Magnesium