marathon runners

Marathon runners: Metabolic markers of peak performance

Differences in the metabolic response to exercise between sedentary and trained subjects are well-rehearsed. And much is now known about the differences between moderately- and highly-trained athletes. But what separates the high-level performers from those at the very top of the game?

That is what a French research team set out to investigate with a small-scale study comparing blood chemical parameters in 14 top-class male marathon runners from French and Portugese Olympic teams a few weeks before they were due to compete in international marathon events.

The subjects were asked to give the velocity they thought they would reach during their next event, and a 10km run at this velocity was used for testing purposes. The mean extrapolated performance time for the marathon was 133.7 (2:13:42) minutes, with a range from 126.9 to 142 minutes.

After a 15-minute warm-up, subjects were equipped with heart and gas exchange monitoring apparatus. Fingertip blood samples were taken at rest (before warm-up) and immediately after the 10km test. They were then analysed by a technique known as ‘Fourier-transform infrared spectrometry’, which is acknowledged to be the best method of analysing the global metabolic response to exercise.

In the event, several biochemical parameters of the metabolic response to a 10km run at individual marathon velocity were found to be strongly linked with the best performance. These were:

  1. a slightly, but significantly, higher increase in blood glucose concentration;
  2. improved fatty acid selectivity, with longer and/or less unsaturated fatty acids predominantly metabolised;
  3. higher fatty acid uptake by skeletal muscle, as indicated by a more pronounced decrease in blood triglycerides and a proportional glycerol concentration increase;
  4. higher amino acid production and blood release, correlated with an apparent breakdown of several proteins for amino acid supply to skeletal muscles.

‘These metabolic adaptations to intense endurance training probably explained in part the difference between high and top-class marathon performances,’ conclude the researchers. ‘… the best runners have enhanced both carbohydrate, lipid and amino acid metabolisms to improve energetic supply to skeletal muscle during exercise.’

Japanese Journal of Physiology, 52, 181-190, 2002

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