Effects of heavy resistance training on maximal and explosive force production, endurance and serum hormones in adolescent handball players

To determine the effects of 6-weeks of heavy-resistance training on physica l fitness and serum hormone status in adolescents (range 14-16 years old) 1 9 male handball players were divided into two different groups: a handball training group (NST, n = 10), and a handball and heavy-resistance strength training group (ST, n = 9). A third group of 4 handball goalkeepers of simi lar age served as a control group (C, n = 4). After the 6-week training per iod, the ST group showed an improvement in maximal dynamic strength of the leg extensors (12.2%; P < 0.01) and the upper extremity muscles (23%; P < 0 .01), while no changes were observed in the NST and C groups. Similar diffe rences were observed in the maximal isometric unilateral leg extension forc es. The height of the vertical jump increased in the NST group from 29.5 (S D 4)cm to 31.4 (SD 5) cm (P < 0.05) while no changes were observed in the S T and C groups. A significant increase was observed in the ST group in the velocity of the throwing test [from 71.7 (SD 7) km . h(-1) to 74.0 (SD 7) k m . h(-1) P < 0.001] during the 6-week period while no changes were observe d in the NST and C groups. During a submaximal endurance test running at 11 km . h(-1), a significant decrease in blood lactate concentration occurred in the NST group [from 3.3 (SD 0.9) mmol . l(-1) to 2.4 (SD 0.8) mmol . l( -1) P < 0.01] during the experiment, while no change was observed in the ST or C groups. Finally, a significant increase (P < 0.01) was noted in the t estosterone:cortisol ratio in the C group, while the increase in the NST gr oup approached statistical significance (P < 0.08) and no changes in this r atio occurred in the ST group. The present findings suggested that the addi tion of 6-weeks of heavy resistance training to the handball training resul ted in gains in maximal strength and throwing velocity but it compromised g ains in leg explosive force production and endurance running. The tendency for a compromised testosterone:cortisol ratio observed in the ST group coul d have been associated with a state of overreaching or overtraining.