Study aim: To evaluate the effects of two strength training programmes on the explosive force of lower extremities and total testosterone levels in plasma of Brazilian football players.

Material and methods: A group of 24 male football players aged 16 - 19 years participated in a 12-week training: non-linear periodised (NLP) or non-periodised (NP), 12 subjects each. Before and after training period, all subjects performed countermovement vertical jump (CMJ), horizontal jump and Flegner's power test, and total testosterone concentrations were determined in plasma.

Results: Significant, training-induced changes in CMJ were found in both groups; by 7.4% (p<0.05) in the NLP group and by 8% (p<0.001) in NP group. Also in the long jump (SBJ) significant (p<0.05) changes were noted in both groups, by 0.9 and 4.4%, respectively. Serum testosterone concentrations significantly (p<0.05 - 0.01) increased post-training in both groups and the increase was significantly (p<0.01) greater in the NLP than in NP group.

Conclusion: A larger number of athletes in future studies, as well as other sport categories and levels and a longer training period would be advisable in order to strengthen the causal inferences between the variables studied.