[Effects of Complex Versus Block Strength Training on the Athletic Performance of Elite Youth Soccer Players].

Background: Muscle strength and speed are important determinants of soccer performance. It has previously been shown that complex training (CT, combination of strength and plyometric exercises within a single training session) is effective to enhance strength and speed performance in athletes. However, it is unresolved whether CT is more effective than conventional strength training that is delivered in one single block (BT) to increase proxies of athletic performance. Thus, the aim of the present study was to investigate the effects of CT versus BT on measures of muscle strength/power, speed, and agility in elite youth soccer players.

Methods: Eighteen male elite youth soccer players conducted six weeks (2 sessions/week, 30 min. each) of progressive CT (n = 10, age: 18.5 ± 2.2 years) or BT (n = 8, age: 18.1 ± 1.6 years) in addition to their regular soccer training (approx. 6 sessions/week, 60-90 min. each). Before and after training, tests were conducted for the assessment of strength (one-repetition maximum [1RM] squat), power (countermovement jump [CMJ]), speed (30-m linear sprint), and agility (T test). Non-parametric analyses were used to calculate differences within (Wilcoxon test) and between (Mann-Whitney-U test) groups.

Results: Both CT and BT proved to be safe (i.e. no training-related, but six match-related injuries reported) and feasible (i.e. attendance rate of ≥ 80% in both groups) training regimens when implemented in addition to regular soccer training. The statistical analysis revealed significant improvements from pre-training to post-training tests for the CT group in 1 RM squat (p = 0.043) and CMJ height (p = 0.046). For the BT-group, significantly enhanced sprint times were observed over 5 m (p = 0.039) and 10 m (p = 0.026). Furthermore, both groups significantly improved their t test time (CT: p = 0.046; BT: p = 0.027). However, group comparisons (CT vs. BT) over time (post-training minus pre-training test) did not show any significant differences.

Conclusion: Six weeks of CT and BT resulted in significant improvements in proxies of athletic performance. Yet CT did not produce any additional effects compared to BT. Future research is needed to examine whether the observed test-specific changes, i.e. improvements in strength/power for the CT-group and improvements in speed for the BT-group, are due to the applied configuration of strength, plyometric, and sprint exercises or if they rather indicate a general training response.