Effects of an 8-Week Combined Plyometric and Change-of-Direction Shuttle-Sprint Program on Physical Fitness and Blood Lactate Responses in Female High School Soccer Players

OBJECTIVES This study examined the effects of an 8-week combined plyometric and change-of-direction (COD) repeated-shuttle-sprint training program on physical fitness, intermittent running performance, and blood lactate responses in female high school soccer players.METHODS Seventeen female high school soccer players (age, 17.1 ± 0.8 years) completed the program twice weekly for 8 weeks (16 sessions) in addition to their regular soccer training. Each session included a progressive plyometric block and a COD repeated-shuttle-sprint block, with sets terminated when performance declined by more than 5% relative to the first repetition. Muscular power and lower-extremity muscular endurance (repeated jump, standing long jump, and vertical jump), agility and reaction ability (side-step, light and sound reaction time), linear sprint performance (20, 40, and 200 m), and 30-15 Intermittent Fitness Test (30-15 IFT) performance were assessed before and after training. Blood lactate concentration was measured at rest and immediately, 3 min, and 5 min after the 30-15 IFT. Paired-samples t-tests or Wilcoxon signed-rank tests were applied according to normality, and effect sizes were calculated (<i>p</i> < 0.05).RESULTS Repeated jump performance increased by 19.2% (<i>p</i> < 0.001, dᶻ = 1.51), standing long jump by 2.4% (<i>p</i> = 0.045, dᶻ = 0.53), and vertical jump by 3.7% (<i>p</i> = 0.023, r = 0.55). Side-step performance increased by 10.2% (<i>p</i> = 0.007, dᶻ = 0.75), while light reaction time decreased by 7.4% (<i>p</i> = 0.029, dᶻ = 0.58). Sound reaction time did not change significantly (<i>p</i> = 0.132, dᶻ = 0.38). In the 30-15 IFT, the number of repetitions increased by 10.6% (<i>p</i> = 0.001, r = 0.84), total distance by 14.2% (<i>p</i> = 0.001, r = 0.81), and final running velocity by 6.1% (<i>p</i> = 0.001, r = 0.83). Estimated VO₂max increased by 1.2% (<i>p</i> = 0.010, r = 0.62), whereas maximal heart rate did not change significantly (<i>p</i> = 0.389, dᶻ = 0.21). Blood lactate concentration decreased by 48.8% at rest (<i>p</i> < 0.001, dᶻ = 1.37), 42.3% immediately post-exercise (<i>p</i> < 0.001, r = 0.88), 43.4% at 3 min post-exercise (<i>p</i> < 0.001, dᶻ = 4.47), and 28.8% at 5 min post-exercise (<i>p</i> < 0.001, dᶻ = 1.48). No significant changes were observed in 20-, 40-, or 200-m sprint performance (<i>p</i> > 0.05).CONCLUSIONS The combined plyometric and COD repeated-shuttle-sprint program improved repeated lower-extremity power, change-of-direction ability, and intermittent running performance in female high school soccer players. The largest fitness-related effect was observed for repeated jump performance, suggesting that the program may be particularly effective for enhancing the ability to repeatedly produce and maintain lower-extremity power. Blood lactate concentrations were lower after training despite greater intermittent running performance; however, the physiological mechanisms underlying these changes were not directly assessed. Light reaction time improved, whereas sound reaction time did not; however, because visual-cue tasks were included only during the final two weeks and changes in ligh