Isokinetic Strength Of Knee Extensors And Flexors Are Important Determinants Of The Maximal Running Speed In Elite Soccer Players.

PURPOSE: To analyze determinants of maximal running speed (MRS) and determine if differences in strength and power exist between faster (G1: MS > 35 km/h) and slower players (G2: MS < 35 km/h). METHODS: 24 males from the highest professional Czech soccer division were divided into 2 groups based on their maximal running speed taken from GPS measurement during the first half of the season (G1: n = 9, G2: n = 15). Subjects were assessed on NorBord device (Hecc), isokinetic strength of knee extensors (KE), flexors (KF), height of countermovement jump (CMJ) and peak vertical ground reaction force (VGRF) in take-off phase. Means comparison for independent samples, correlation coefficient (r) and linear regression equation were used to calculate maximal running speed from strength and power variables. RESULTS: Faster players (G1) generated significantly higher strength in KE and KF compared to slower players (KE: G1 = 3.38 ± .28 N.m/kg vs. G2 = 2.89 ± .29 N.m/kg, t22 = 4.06, p < .01, KF: G1 = 2.00 ± .37 N.m/kg vs. G2 = 1.78 ± .26 N.m/kg, t22 = 1.76, p < .05). There were no other significant differences between groups (p > .05). Significant correlations were (r = .63, p < .01, R2 = .40) between MS and KE for whole group of players and, KE vs. KF (r = .60, p < .01, R2 = .36). Eccentric strength (Hecc), CMJ and VGRF did not hold any significant relationships to any other variable (p > .05). Results also highlighted an interesting regression equation; MRS = 30.43 + 1.41*KE. In total, 39.6 % of the variation was explained through linear regression model. CONCLUSIONS: Players with higher MRS showed significantly higher muscle strength production in both KE and KF in concentric muscle contraction compared to players with lower MRS. KE strength was significantly related to MRS in professional players. The results also indicated independence and specificity for some parameters. Thus, the assessment of speed, power, and strength should be considered with a multifaceted approach with aim of developing physical performance and reducing injury risk in professional players. Research has been supported by Cooperatio FTVS UK, B&R Medicine