![]() ![]() Previous research comparing bíceps femoris activity between exercises is conflicting. The unique exercise in this experiment showing selective activation of biceps femoris was fitball flexion, a common track and field sports–specific open kinetic chain exercise, which showed peak EMG activity during the MTU shortening phase. 22, 23 Given these characteristics, semitendinosus may be more sensitive to exercise involving a large change in MTU length, such as when hip flexion actions are required. 18, 21 These findings may be partially explained by the fact that the semitendinosus is a fusiform muscle with parallel fibers and long fiber lengths, whereas biceps femoris and semimembranosus have a unipennate and bipennate arrangement. Previous authors have also found greater activation of semitendinosus vs biceps femoris for the single leg Roman dead-lift T-drop with 12 repetition maximum load and kettle bell swings. However, the intensity level of these exercises can be categorized as low. The main finding of our study was that commonly prescribed hamstring exercises can be divided into semitendinosus-dominant and biceps femoris longus-dominant, and can be classified into high, medium, or low according to their activation intensity.ĭuring execution of the lunge, kettle swing, and single leg Roman dead-lift T-drop, the semitendinosus muscle is preferentially targeted. Peak EMG was shown during the MTU lengthening and shortening phases with no preferential hamstring activity. The slide leg is an open kinetic chain exercise with the highest intensity of all exercises. It was the only exercise causing greater activation of biceps femoris than semitendinosus. Fitball flexion exercise is a track and field sports–specific open kinetic chain exercise and showed peak EMG activity during the MTU shortening phase. The fitball flexion and slide leg exercises were found to be high intensity. After a root-mean-square (μV) adjustment, the trial with the highest averaged EMG signal was chosen and 80% of the value of the last 3 seconds was used as a reference for normalization of the EMG scores for each exercise. Standardized verbal encouragement and visual feedback from the monitor was given to each participant. ![]() The EMG signal (μV) from the two recorded channels was averaged. During the test, they performed three MVICs with an isokinetic dynamometer. The subjects performed two to three submaximal (50% of maximum) isometric contractions to warm up and feel comfortable with the test that followed. A detailed presentation of the procedure for the MVICs and for familiarization with the isokinetic dynamometer (CSMI, Lumex, Ronkonkoma, NY, USA) was given, with participants lying prone and stabilized with knee flexion to 45°. The participants completed a warm-up that consisted of 10 minutes of submaximal cycling and 10 minutes of static stretching of the thigh muscles (quadriceps/hamstrings and adduction/abduction). Results of this study could be used to guide rehabilitation from injury to different hamstring muscles. 15– 18 The aim of this study was to evaluate individual hamstring muscle activation patterns during various hamstring exercises. 10– 12 Despite published data showing that hamstring strains affect different segments of the hamstrings, 9, 13, 14 little is known about hamstring activation during common prerehabilitation and rehabilitation hamstring exercises. ![]() 5, 6, 8, 9 Therefore, increasing hamstring strength may partly explain the success of recently proposed prevention programs. 5– 8 In addition, kinetic and electromyogram (EMG) studies reveal that the hamstrings are most active and develop the greatest torque at the hip and knee during the late swing phase through to the mid stance phase of running. 6 The most commonly reported mechanism of hamstring injury in track and field athletes involves high load eccentric contraction during the late swing phase (open kinetic chain). 1– 3ĭuring late swing phase of sprinting, the hamstring muscles act as decelerators of hip flexion and knee extension, 5 and this is followed quickly by hip extension, constituting a stretch shorten cycle in the hamstring muscle. 1– 4 Recent published evidence suggests that these injuries often cause prolonged symptoms and carry a high risk of reinjury, with devastating consequences for both performance and earning ability in elite athletes. Hamstring strain injuries are the most prevalent muscle injuries in track and field. ![]()
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