Delayed effects of heavy resistance or ballistic priming on sprint and agility in elite U19 football.

Background: In elite football, optimization of physical performance increases athlete performance. Sprint and change of directional performance can be improved by previously conducting a priming protocol. However, it is unknown if this priming-induced performance enhancement is long-lasting.

Methods: Eighteen under 19 years old elite football players (mean ± standard deviation [SD] age: 17.8±0.8 years, height: 181±8 cm, body mass: 72±8 kg) with 34±6 months of strength training experience were tested in 30 m sprint and 505 agility without previous exercise (baseline) or 20 hours following a priming protocol consisting of heavy resistance (heavy) or ballistic (ballistic) training. Baseline testing was performed between 3 and 5pm and the effects of priming were tested between 10 and 11 am the day after training. Heavy consisted of 3*2 repetitions of 85% of 1RM in the back squat, and ballistic consisted of 3*5 repetitions of 40% of 1RM in the specialized jump squat.

Results: Compared to baseline, sprint was improved after 10 m with heavy and ballistic by 0.01 and 0.03 s, respectively (P<0.05), whereas only ballistic improved sprint after 5 m (0.03 s, P<0.05). There were no differences after 30 m sprint or in the agility test.

Conclusions: Acceleration (i.e., 5 m sprint) is improved 20 hours after performing heavy resistance or ballistic priming exercise. Since these priming exercises can be performed on the previous day, coaches should consider incorporating these in their regular training and match plans.