The effect of a combined sprint training intervention on sprint force-velocity characteristics in junior Australian football players

BACKGROUND: Sprint performance in junior Australian football (AF) players has been shown to be a differentiating quality in ability level therefore developing sprint characteristics via sprint-specific training methods is an important aspect of their physical development. Assisted sprint training is one training method used to enhance sprint performance yet limited information exists on its effect on sprint force-velocity characteristics. Therefore, the main aim of this study was to determine the influence of a combined sprint training intervention using assisted and maximal sprint training methods on mechanical characteristics and sprint performance in junior Australian football players. METHODS: Upon completing familiarization and pre-testing, twenty-two male junior Australian football (AF) players (age 14.4 ± 0.3 years, body mass 58.5 ± 10.0 kg, and height 1.74 ± 0.08 m) were divided into a combined sprint training (CST) group (n = 14), and a maximal sprint training (MST) group (n = 8) based on initial sprint performance over 20-meters. Sprint performance was assessed during maximal 20-meter sprint efforts via a radar gun (36 Hz), with velocity-time data used to derive force-velocity characteristics and split times. All subjects then completed a 7-week in-season training intervention consisting of maximal sprinting (MST & CST groups) and assisted sprinting (CST only), along with their usual football specific exercises. RESULTS: Moderate to large pre-post within group effects (−0.65 ≤ ES ≥ 0.82. p ≤ 0.01) in the CST group for relative theoretical maximal force (F(0)) and power (P(max)) were reflected in improved sprint performance from 0–20 m, thereby creating a more force-oriented F-v profile. The MST group displayed statistically significant pre-post differences in sprint performance between 10–20 m only (ES = 0.18, p = 0.04). Moderate to high relative reliability was achieved across all sprint variables (ICC = 0.65–0.91), except for the force-velocity slope (S(FV)) and decrement in ratio of forces (D(RF)) which reported poor reliability (ICC = 0.41–0.44), while the CST group exceeded the pre-post minimal detectable change (MDC) in most sprint variables suggesting a ‘true change’ in performance across the intervention. CONCLUSION: It is concluded that implementing a short-term, combined sprint training intervention consisting of assisted and maximal sprint training methods may enhance sprint mechanical characteristics and sprint performance to 20-meters in junior AF players.