Longitudinal Analysis Of Muscular Power And Strength Asymmetries In Elite Soccer Goalkeepers

The physical performance of a goalkeeper (GK) is greatly influenced by their muscular power (MP), which enables certain motor acts including jumping, diving, saving, kicking, punching, acceleration and deceleration. PURPOSE: The aim of this study was to monitor the long-term alterations in force impulses, strength asymmetries, and MP performance of professional soccer GKs over a five-year span. METHODS: Over the course of five years, ten male goalkeepers in the top division (ages 23-31) were monitored eight times (t1-t8), twice a year (January and June). MP performance was assessed during a countermovement jump (CMJ) with arm swing on two Kistler in-ground force plates. Repeated measures ANOVA with post hoc analysis (Bonferroni correction) and partial eta squared (ηp2) were used to examine jump height (JH), maximal vertical ground reaction force (VGRF) at take-off, differences in VGRF between legs (FD), and force impulse (FI) normalized to player body mass. RESULTS: The findings showed that time had a significant impact on JH during the testing period (F = 10.31, p < 0.05, ηp2 = 0.53). The difference between GKs' JH (t1 = 45.29 ± 4.46 cm and t8 = 51.94 ± 5.91 cm) was 12.8%. The JH was statistically higher in the t7 and t8 periods than in the t1 and t2 periods (p < 0.05). Between two or three successive measurements (e.g. t1 vs t3, or t6 vs. t8), no statistical differences were seen (p > 0.05). VGRF (F = 1.29, p > 0.05, ηp2 = 0.13), FD (F = 1.33, p > 0.05, ηp2 = 0.13), and FI (F = 0.40, p > 0.05, ηp2 = 0.04) did not differ significantly. CONCLUSIONS: Throughout the five soccer seasons, the data showed variations in high elite goalkeepers' MP performance. One year of consistent strength and conditioning should result in noticeable changes in JH. Over the course of the five years, strength asymmetries remained constant. Strength and conditioning instructors and sports scientists might find this information helpful.