Changes in tactical behavior during small-sided and conditioned games performed within a training session PraçaGibson Moreira BarbosaGustavo Fernandes MoreiraPedro Emilio Drumond SousaRaphael Brito e BredtSarah Glória Teles ChagasMauro Heleno MoralesJuan Carlos Pérez GrecoPablo Juan MemmertDaniel 2020 <div><p>Abstract This study aimed to verify the acute effects of 3vs.3 soccer small-sided and conditioned games (SSCG) on the tactical behavior of youth soccer athletes within one training session. Twenty-four soccer athletes (U-13 and U-14 categories) from a professional club participated in the study. They played four 4-minute 3vs.3 SSCG with 4 minutes of passive recovery in-between. All SSCG were recorded and players’ tactical behavior was analyzed using the System of Tactical Assessment in Soccer. We compared the frequencies and percentages of successful tactical principles over the four 3vs.3 SSCG bouts performed within the training session. Results showed an increased number of defensive unity actions (p= 0.005; large effect size) and a higher percentage of successful defensive principles (p<0.001; moderate effect size) in the fourth bout. We can conclude that players’ tactical behaviors change over the SSCG bouts performed within one training session. This suggests that players adapt their tactical behavior according to the tactical problems presented in the SSCG performed within the training session. We can suggest that the long-term improvement in the tactical skills of soccer athletes may be based on these small acute changes in tactical behavior observed in each training session.</p></div>