Short-term detraining in semi-professional male football players: impact of a 5-day mid-season break on performance - an observational study

Abstract

Background: Detraining is a partial reduction or total stoppage of training workloads, resulting in physical and physiological modifications. Prior studies have shown significant reductions in strength and power typically after long-term interruptions (i.e., > 4 weeks), whereas evidence for short-term detraining (i.e., < 4 weeks) remains inconclusive. This observational study describes acute changes in the physical abilities of football players associated with a 5-day in-season break under real-world conditions. Methods: In this uncontrolled observational study, repeated sprinting ability (primary outcome), body composition, vertical jump performance, and maximum thigh adduction and abduction strength were assessed in 17–21 semi-professional male football players (n = 17 for the primary outcome; other tests ranged from 17 to 21) before and after a 5-day in-season break (age: 21.5 ± 1.37 years; height: 178.96 ± 6.59 cm). Descriptive statistics and paired t-tests were used for comparisons. Intra-individual differences were also calculated. Results: After the 5-day break, repeated sprinting ability was significantly worse. Total time to complete the RAST was approximately 1.0 s higher (before: 29.89 ± 1.14 s; after: 30.77 ± 1.62 s, p = 0.009, d = 0.634). Peak power and maximal velocity showed mean reductions of 55 watts (before: 892.34 ± 125.46 W; after: 837.54 ± 108.92 W, p = 0.049, d = -0.427) and 0.65 km.hˉ¹ (before: 26.86 ± 1.03 km.hˉ¹; after: 26.21 ± 1.35 km.hˉ¹, p = 0.030, d = -0.489), respectively, indicating small-to-moderate effect sizes. Vertical jump performance showed slight, non-significant improvements. No significant changes were found for maximum thigh strength or body composition. Conclusion: A brief 5-day in-season break under uncontrolled, real-world conditions was associated with small-to-moderate impairments in repeated sprinting ability, while body composition, maximal strength, and vertical jump performance were largely maintained. These findings underscore the need for practitioners to prioritise targeted interventions for repeated sprinting ability following short in-season breaks, alongside strategies to restore performance without compromising technical-tactical demands.