Gh, Igf-i And Ifgbp-3 Responses To Maximal Rowing Exercise In Male Rowers

Introduction
Exercise is an important regulator of the GH-IGF system. There have been studies on responses of growth hormone
(GH), insulin-like growth factor-I (IGF-I) and IGF-bind protein-3 (IGFBP-3) to exercise in athletes such as swimmers,
skiers and wrestlers. However, few studies have described the responses in rowers. The aim of this study was to
investigate the effect of 2000m exhausting rowing ergometer exercise (lasting about 7 min) on serum GH, IGF-I and
IGFBP-3 in male rowers.

Methods
18 male regional and national level rowers (18.39±1.65years old, 84.41±6.97kg body weight and 191±5cm height) as
subjects participated in the study. After 15 min of warm-up, the subjects performed a 2000m "all-out" exercise test on a
rowing ergometer (Concept II, USA). Blood samples were taken from fingertips (for lactate determination) as well as
antecubital vein (for GH, IGF-I and IGFBP-3 determination, Radioimmunoassay kits: DSL Webster, Texas, USA)
before warm-up, at the end of exercise (0 min) and after exercise (5, 15, 30, 60 min). VO2max was measured using a
mixing chamber basis O2-CO2 analyzer (MAX-1,PHYSIO-DYNE, USA). All experiments were performed during
morning hours.
Statistical comparison between pre- and post-exercise values was performed by paired t-test. The level of Statistical
significance was set at p<0.05.

Results
VO2max was 54.79±4.47ml/min.kg, The mean power output was 356.2±22.7watt The exercise duration was
6.63±0.15min and post-exercise lactate level was 17.8±2.2mmol/L. The plasma level of GH, IGF-I and IGFBP-3 preand
post-exercise are shown in table 1.

Discussion/Conclusions
Serum GH, IGF-I and IGFBP-3 increased significantly after 2000m exhausting rowing exercise. Both values of GH and
IGF-I remained significantly higher more than an hour while IGF-I reached its peak before the GH peak. This result
was consistent with observation of Schwarz et al. [1]. We support the idea that acute IGF-I response to high-intensity
exercise may be independent of GH. IGF-I/IGFBP-3 ratio was not found significant change after the exercise. Differing
form several investigators[4], present study demonstrated neither GH nor IGF-I correlated with VO2max.

References
[1]. Schwarz et al. (1996). J Clin Endocrinol Metab, 81, 3492-3497.
[2]. Di Luigi et al. (2001). Int J Sports Wed, 22, 103-110.
[3]. Koziris et al. (1999). J Appl Physiol, 86, 1436-1442.
[4]. Poehlman et al. 1990). J Clin Endocrinol Metab, 71, 1468-1473.

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