Relationships between blood viscosity and insulin‐like growth factor I status in athletes

Article type: Research Article

Authors: Monnier, J.F. | Aïssa Benhaddad, A. | Micallef, J.P. | Mercier, J. | Brun, J.F.

Affiliations: Service Central de Physiologie Clinique, Centre d'Exploration et de Réadaptation des Anomalies du Métabolisme Musculaire (CERAMM), CHU Lapeyronie 34295 Montpellier‐cédex 5, France, and CHRU de Montpellier F‐34295, Montpellier, France

Note: [] Corresponding author: Dr J.F. Brun, MD, PhD, Service Central de Physiologic Clinique, Centre d'Exploration et de Réadaptation des Anomalies du Métabolisme Musculaire (CERAMM), CHU Lapeyronie 34295 Montpellier‐cédex 5, France. Tel.: +33 4 67 33 82 84; Fax: +33 4 67 33 89 66; Telex: CHR MONTP 480 766 F; E‐mail: [email protected].

Abstract: Exercise training is known (1) to enhance the function of the GH–IGF‐I system, which has profound effects on body fluid status; (2) to increase blood fluidity. Thus, we investigated during an exercise‐test in 39 male elite sportsmen (age 23.7±0.72 years; body mass index 23.7±0.28 kg/m2) the possible relationships between GH and IGF‐I status and the rheological properties of blood. Two correlations indicate a relationship between body hydration and fitness: isometric handgrip strength is correlated with the percentage of extracellular water in total body water (r=0.432, p=0.02) and the aerobic working capacity W170 is negatively correlated with hematocrit (r=−0.341, p=0.039). Water loss during exercise appears to be inversely related to fitness as evaluated by W170 (r=−0.529, p=0.05), and is positively correlated with the score of signs of overtraining (r=0.725, p=0.003) and with the red boood cell aggregation index (r=0.584, p=0.036). Finally, while the GH peak value is correlated with the extracellular water volume (r=0.393, p=0.02), IGF‐I is correlated with blood viscosity (r=0.546, p=0.0003), suggesting that when IGF‐I values are within the upper quintile (>340 ng/ml) IGF‐I may unfavourably affect blood rheology. Among factors of blood viscosity, IGF‐I exhibits a borderline correlation (p=0.05) with “Tk” and the ratio IGF1/IGFBP3 which reflects free circulating IGF‐I is correlated with red cell aggregability measured with the Myrenne “M” (r=0.485, p=0.014) and S60 (r=0.396, p=0.494). These findings confirm the importance of hydration and dehydration as determinants of both blood rheology and exercise performance. Moreover, they suggest that values of IGF‐I within the upper quintile are associated with an impairment of blood fluidity, possibly due to a direct effect of IGF‐I on red cell deformability and aggregability.

Keywords: Blood viscosity, hemorheology, erythrocyte deformability, erythrocyte aggregability, human, male, exercise training, overtraining, insulin‐like growth factor binding protein 1, insulin‐like growth factor binding protein 3, insulin‐like growth factor I, growth hormone, body fluids, sweating

Journal: Clinical Hemorheology and Microcirculation, vol. 22, no. 4, pp. 277-286, 2000