Abstract

In soccer, the preseason is typically a short period where training loads are intensified to improve the physical abilities that determine athletic performance. The objective of this study was to analyze changes in physical performance and body composition after a seven-week preseason in young Chilean soccer players. Sixty young male soccer players (16.2±1.7 years) participated, assessed before and after a seven-week preseason. In anthropometry and body composition, height, weight, circumference, and skinfold thickness were measured. Body fat percentage and skeletal muscle mass were calculated, along with peak growth velocity acceleration (APVC). Physical performance was examined with, 10m, 20m and 30m sprints, 505 test, horizontal and countermovement jump (CMJ), and maximal oxygen consumption (VO2 max) with 30-15IFT intermittent endurance test. The results show that, in body composition, there are significant reductions (p<0.01) in ? 6 skinfolds (d=1.08; “large”) and body fat (d=1.25; “large”). Physical performance presents significant improvements (p<0.01) in 10m sprint (d=4.02; “very large”), 20m (d=3.53; “very large”), 30m (d=2.32; “very large”), VO2 max (d=1.02; “large”) and 505 test (p<0.05; d=0.34; “small”). In addition to the above improvements, U-19 soccer players showed significant improvements (p<0.01) in horizontal jump (d=1.19; "large"). We conclude that a seven-week preseason period induces significant improvements in indicators of adipose tissue, 10-30m sprint, VO2 max, and 505 test in young Chilean soccer players. © 2025, Campus EDUCA SPORTIS S.L.. All rights reserved.