title: Strength training effects on physical performance and serum hormones in young soccer players.
abstract: To determine the effects of simultaneous explosive strength and soccer training in young men, 8 experimental (S) and 11 control (C) players, aged 17.2 (0.6) years, were tested before and after an 11-week training period with respect to the load-vertical jumping curve [loads of 0-70 kg (counter-movement jump CMJ0-70)], 5- and 15-m sprint performances, submaximal running endurance and basal serum concentrations of testosterone, free testosterone and cortisol. In the S group, the 11-week training resulted in significant increases in the low-force portion of the load-vertical jumping curve (5-14% in CMJ0-30, P<0.01) and in resting serum total testosterone concentrations (7.5%, P<0.05), whereas no changes were observed in sprint running performance, blood lactate during submaximal running, resting serum cortisol and resting serum free testosterone concentrations. In the C group, no changes were observed during the experimental period. In the S group, the changes in CMJ0 correlated ( P<0.05-0.01) with the changes in the 5-m ( r=0.86) and 15-m ( r=0.92) sprints, whereas the changes in CMJ40 correlated negatively with the changes in the testosterone:cortisol ratio ( r=-0.84, -0.92, respectively, P<0.05). These data indicate that young trained soccer players with low initial strength levels can increase explosive strength by adding low-frequency, low-intensity explosive-type strength training. The inverse correlations observed between changes in CMJ40 and changes in the testosterone:cortisol ratio suggest that a transient drop in this ratio below 45% cannot always be interpreted as a sign of overstrain or neuroendocrine dysfunction.
authors.affiliation: Centro de Investigación y Medicina del Deporte de Navarra, Gobierno de Navarra, C/ Paulino Caballero 13, 31002 Pamplona, Spain. egorosta@cfnavarra.es
authors.forename: E M
authors.initials: EM
authors.lastname: Gorostiaga
authors.forename: M
authors.initials: M
authors.lastname: Izquierdo
authors.forename: M
authors.initials: M
authors.lastname: Ruesta
authors.forename: J
authors.initials: J
authors.lastname: Iribarren
authors.forename: J J
authors.initials: JJ
authors.lastname: González-Badillo
authors.forename: J
authors.initials: J
authors.lastname: Ibáñez
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000293:Adolescent; D000328:Adult; D001824:Body Constitution / Q000502:physiology; D005080:Exercise Test; D006728:Hormones / Q000097:blood*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D010806:Physical Education and Training / Q000379:methods*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D012420:Running / Q000502:physiology; D012916:Soccer / Q000502:physiology*; D013739:Testosterone / Q000097:blood
chemical_list: D006728:Hormones; D013739:Testosterone; D006854:Hydrocortisone