Effects of unloaded vs. Ankle-loaded plyometric training on the physical fitness of U-17 male soccer players

Mehrez Hammami*, Nawel Gaamouri, Katsuhiko Suzuki, Ridha Aouadi, Roy J. Shephard, Mohamed Souhaiel Chelly

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


The aim of this study was to compare the impact of two differing plyometric training programs (loaded plyometrics (with 2.5% of body mass placed above the ankle joint) vs. unloaded plyometrics), performed biweekly for 10 weeks, on the physical fitness of elite junior male soccer players. Participants aged 16.0 ± 0.5 years were randomly assigned between unloaded plyometrics (UP; n = 12), loaded plyometrics (LP; n = 14) and control (C; n = 12) groups. Two-way analyses of performance (group x time) were assessed by 40-m sprint times; 9–3–6–3–9 m sprints with 180 turns (S180); 9–3–6–3–9 m sprints with backward and forward running (SBF); and 4 × 5 m sprints (S4 × 5 m); four jump tests; measures of static and dynamic balance; repeated change of direction tests and the Yo-Yo intermittent recovery test. Both LP and UP enhanced sprinting performance relative to C (p < 0.05) but performance increased more in LP relative to UP (p < 0.05) in all sprints except 40 m. Change of direction times were also significantly shortened by LP relative to UP (p < 0.05) and C (p < 0.01) in all tests, with no significant differences between UP and C. Jumps heights increased similarly in both LP and UP relative to C (p < 0.05), with no significance between LP and UP. LP and UP also enhanced repeated change of direction scores relative to C (p < 0.01) with greater changes in LP than in UP (p < 0.01). Finally, LP enhanced some balance scores relative to UP (p < 0.05) and C (p < 0.05). We conclude that the introduction of 10 weeks of in-season loaded plyometrics into the regimen of U17 male soccer players yields gains in several physical performance scores relative to either unloaded plyometrics or the control training regimen.

Original languageEnglish
Article number7877
Pages (from-to)1-18
Number of pages18
JournalInternational journal of environmental research and public health
Issue number21
Publication statusPublished - 2020 Nov 1


  • Ability-to-change-direction
  • Additional weight
  • Balance
  • Repeated change of direction
  • Speed
  • Stretch-shortening cycle

ASJC Scopus subject areas

  • Pollution
  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis


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