title: Fatigue and rapid hamstring/quadriceps force capacity in professional soccer players.
abstract: The aim of this study was to investigate the effect of fatigue induced by an exhaustive laboratory-based soccer-specific exercise on different hamstrings/quadriceps (H:Q) ratios of soccer players. Twenty-two male professional soccer players (23·1 ± 3·4 year) performed maximal eccentric (ecc) and concentric (con) contractions for knee extensors (KE) and flexors (KF) at 60° s(-1) and 180° s(-1) to assess conventional (H(con) :Q(con)) and functional (H(ecc) :Q(con)) ratios. Additionally, they performed maximal voluntary isometric contraction for KE and KF, from which the maximal muscle strength, rate of force development (RFD) and RFD H:Q strength ratio (RFDH:Q) were extracted. Thereafter, subjects were performed an exhaustive laboratory-based soccer-specific exercise and a posttest similar to the pretest. There was significant reduction in H(con) :Q(con) (0·60 ± 0·06 versus 0·58 ± 0·06, P<0·05) and in H(ecc) :Q(con) (1·29 ± 0·2 versus 1·16 ± 0·2, P<0·01) after the soccer-specific exercise. However, no significant difference between Pre and Post exercise conditions was found for RFDH:Q at 0-50 (0·53 ± 0·23 versus 0·57 ± 0·24, P>0·05) and 0-100 ms (0·53 ± 0·17 versus 0·55 ± 0·17, P>0·05). In conclusion, H:Q strength ratios based on peak force values are more affected by fatigue than RFDH:Q obtained during early contraction phase. Thus, fatigue induced by soccer-specific intermittent protocol seems not reduce the potential for knee joint stabilization during the initial phase of voluntary muscle contraction.
authors.affiliation: Human Performance Laboratory, São Paulo State University, UNESP, Rio Claro, SP, Brazil.
authors.forename: Camila C
authors.initials: CC
authors.lastname: Greco
authors.forename: Wendell L
authors.initials: WL
authors.lastname: da Silva
authors.forename: Sérgio R A
authors.initials: SR
authors.lastname: Camarda
authors.forename: Benedito S
authors.initials: BS
authors.lastname: Denadai
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005080:Exercise Test; D006801:Humans; D007537:Isometric Contraction; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue; D053580:Muscle Strength; D010807:Physical Endurance; D052097:Quadriceps Muscle / Q000502:physiology*; D016059:Range of Motion, Articular; D012916:Soccer; D013997:Time Factors; D019415:Torque; D055815:Young Adult