Changes in circulating IGF-I and their correlation with self-assessment and fitness among elite athletes

The evaluation of training load and effectiveness in elite athletes is difficult. We determined the effect of a four-week training camp on changes in self-assessment physical conditioning scores, fitness and circulating IGF-I in elite Israeli handball players during their preparation for the 1999 World junior Handball Championship. Training consisted of two weeks of intense training followed by two weeks of relative tapering. Fitness was assessed by field test measurements of 1000-m run, 4 x 10-m shuttle run and vertical jump. Serum IGF-I levels were measured by immunoradiometric assay. Measurements were performed before, after two weeks, and at the end of training. Training resulted in a significant (p < 0.05) improvement in the results of the 4 x 10-m run, 1000-m run and vertical jump. Changes in the self-assessment physical conditioning score showed a bi-directional pattern. After two weeks of training the players reported decreased physical conditioning scores, with return to basal levels after four weeks. Similarly, circulating IGF-I decreased significantly after two weeks, and returned to basal levels after four weeks of training. We found a significant correlation between changes in circulating IGF-I, and self-assessments of physical conditioning scores (r = 0.71, p < 0.001). Intensive training resulted in a decrease, while tapering was associated with an increase in IGF-I levels. These changes were accompanied by parallel changes in subjective physical conditioning self-assessments.