title: EMG amplitude of the biceps femoris during jumping compared to landing movements.
abstract: Hamstrings injury is a common occurrence in athletic performance. These injuries tend to occur during a deceleration or landing task suggesting the negative work may be a key component in hamstrings injury. The purpose of this study was to investigate the muscular activity (EMG) of the biceps femoris (BF) in different phases (concentric vs. eccentric) of a Counter Movement Jump (CMJ), Squat Jump (SJ) and the Braking Phase (BP) of a landing task. Twelve female volleyball players performed 5 CMJs, SJs and BPs while surface EMG was recorded using a MuscleLab (BoscoSystem(TM), Norway). EMG values were normalized to an maximal voluntary contraction. A repeated measures analysis of variance (ANOVA) was used to compare mean normalized EMG values of the concentric and eccentric portions of the CMJ with the BP and SJ. The ANOVA revealed significantly lower BF activation in the concentric and eccentric portions of the CMJ compared to the BP (64%, p < 0.001) and SJ (7%, p = 0.02), respectively. These findings suggest that the CMJ relies on a greater contribution of elastic tissues during the concentric and eccentric portions of the movement and thus requires less muscle activation of the BF.
authors.affiliation: Faculty of Medicine & Surgery, University of "Tor Vergata", Rome, Italy ; Tunisian Research Laboratory "Sports Performance Optimization", National Center of Medicine & Science in Sport, Tunis, Tunisia ; CONI - Italian Regional Olympic Committee, Sardinia, Italy.
authors.forename: Johnny
authors.initials: J
authors.lastname: Padulo
authors.forename: Alessandra
authors.initials: A
authors.lastname: Tiloca
authors.forename: Douglas
authors.initials: D
authors.lastname: Powell
authors.forename: Giampietro
authors.initials: G
authors.lastname: Granatelli
authors.forename: Antonino
authors.initials: A
authors.lastname: Bianco
authors.forename: Antonio
authors.initials: A
authors.lastname: Paoli
keywords: Braking phase; Counter movement jump; Electromyography; Hamstring injuries; Squat jump; Stretch-shortening cycle