Author(s): BALIS, N., BOGDANIS, G.C., PSARRAS, I., BABAULT, N., PAIZIS, C., Institution: UNIVERSITY OF BURGUNDY (UNIVERSITÉ DE BOURGOGNE), DIJON, FRANCE, Country: GREECE, Abstract-ID: 1703

INTRODUCTION:
Strategies aiming to acutely enhance neuromuscular performance before competition are of increasing interest in elite football. Recent studies suggest that low volume power or strength training may induce a delayed positive effect on neuromuscular performance 24 to 48 hours later. However, there is limited evidence of the effectiveness of such protocols in an elite football setting. The aim of this study was to investigate the effects of a French-Contrast training session combined with football training on lower limp strength and power measures 24 hours later, in elite academy football players
METHODS:
Fifteen elite academy players of an elite U-16 football team completed two conditions in a randomized crossover design with: (1) a French-contrast priming session, followed by MD-1 football training (PRIME), and (2) MD-1 football training only (CONTROL). The French-contrast series included two rounds the following four exercises: maximal isometric squat exercise for 3 s (knee angle: 150o), six Pogo-jumps with +20% body weight, eight unloaded Pogo-jumps, five assisted jumps, A 3 min rest separated the two rounds. Neuromuscular performance was assessed before and 24 h after each session. Countermovement jump (CMJ), reactive strength index (RSI), maximal voluntary isometric half-squat force (MVIC), and rate of force development (RFD) were assessed and analyzed using repeated-measures ANOVA. Effect sizes for pairwise comparisons were obtained as Cohen’s d.
RESULTS:
Significant main effects were found in RSI for both time and condition (p = 0.016 and p < 0.001) with no significant time x condition interaction (p = 0.269). At baseline, RSI was 1.59 ± 0.29 and 1.65 ± 0.27 m/s in PRIME and CONTROL. Twenty-four hours later, the respective RSI values were 1.74 ± 0.32 and 1.90 ± 0.30 (d=0.44 between conditions). CMJ at baseline was similar in PRIME and CONTROL (34.9 ± 3.8 and 34.9 ± 3.7 cm) and remained unchanged 24 h later (34.9 ± 4.0 and 36.1 ± 3.8 cm), with no main effects or interaction. Cohens’ d for changes in CMJ were 0.02 and 0.31 in PRIME and CONTROL. MVIC showed no significant main effects or interaction (p = 0.81, 0.124 and 0.42, respectively), Baseline MVIC in PRIME and CONTROL was 2614 ± 270 and 2564 ± 331 N, while values 24 hours later were 2697 ± 315 and 2720 ± 362 N, respectively (d=0.27 and 0.43, respectively). The effect sizes for changes in RFD were very low in CONTROL and moderate in PRIME (0.47 and 0.62 for RFD 0-250 and 0-300 ms).
CONCLUSION:
The combination of resistance-based priming with football training did not lead to statistically significant improvements the neuromuscular variables measured 24 h later, with the exception of RSI, where a main effect of condition was found. However, this preliminary study indicates that there may be small but meaningful improvements in explosive strength 24 hours after the combination of French-contrast and football training, as suggested by effect sizes.