The effects of physical exercise on the concentrations of ferritin and transferrin receptor in plasma of male judoists.

The aim of the study was to assess the within-subject (day-to-day) variability for iron status variables: ferritin (ferr) and soluble transferrin receptor (sTfR) concentrations in plasma and the sTfR/log ferr index in athletes subjected daily to high physical loads. Blood was sampled in the morning from 8 healthy male elite judoists, aged 20 - 31 years, for 10 consecutive days while at training camp. Mean concentrations of ferritin and sTfR in plasma for the 10 day period were 32.0. 1.771(+/-1) and 2.41. 1.324(+/-1) mg/l, respectively. The average within-subject, day-to-day variability for ferritin was 27.4 % (range: 16 - 44 %), and was much lower for sTfR (6.7 %; range: 4 - 15 %). Ferritin concentrations were significantly, albeit weakly, correlated with training loads on the preceding day (r = 0.256; p < 0.05) and with creatine kinase (CK) activities on the same day (r = 0.397; p < 0.001), while sTfR did not correlate with either training loads or CK activities. Mean day-to-day variability for the sTfR/log ferr index was 11.8 % (range: 5 - 21 %), i.e. markedly lower than for ferritin. Although the physical load-induced changes in iron metabolism indices in male subjects were similarly oriented as in the earlier reported female ones representing the same sport, the magnitude of those changes was less pronounced than in the females. This was evidenced by a markedly lower within-subject day-to-day variability in ferritin, still significant but weak correlation between load magnitude and ferritin levels, and a significant, negative correlation between ferritin and sTfR concentrations, not found previously in the female athletes. However, despite lower variability in ferritin than in women, the exercise-induced ferritin increases in male athletes might make a reliable assessment of iron stores in them difficult. The present results confirm our earlier reports that sTfR levels are stable under high physical loads, thus making them a useful indicator of iron status. Also sTfR/log ferr index is of a much higher diagnostic value than ferritin, despite high variability of the latter. That index is particularly valuable in detecting iron-deficient erythropoiesis.