Investigation of the Effects of 4-Week Core and Functional Training Programs on Physical Fitness Parameters in Soccer Players: An Inactive-Controlled Experimental Study

This study examined whether pre-to-post changes after four weeks differed among core training (CT), functional training (FT), and inactive control (CG) groups in male soccer players. Thirty participants (18-25 years; n=10/group) were allocated to CT, FT, or CG. CT and FT completed 45-60 min sessions three times weekly, whereas CG received no additional structured training. Body weight, body mass index (BMI), isometric back strength, vertical jump, Lewis-estimated anaerobic power, and unilateral/bilateral balance were assessed before and after the intervention. An omnibus MANOVA tested the multivariate Group × Time effect using pre-to-post change scores, followed by outcome-specific 3 × 2 mixed-design analyses. The omnibus effect was not significant (Wilks' Λ=.367, F(16,40)=1.629, p=.106). Nominal Group × Time interactions were non-significant for seven outcomes (p>.05). Right-foot balance showed a nominal interaction, F(2,27)=4.075, p=.028, ηp²=.232, but this did not remain significant after Holm correction across eight outcomes (adjusted p=.227). An exploratory Tukey comparison suggested greater improvement in FT than CG (p=.022). Thus, the data do not provide robust evidence that CT or FT was superior to control across the assessed outcomes. The isolated right-foot balance signal should be considered hypothesis-generating given the non-significant omnibus test and small sample.