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Julio Tous-Fajardo, Rafael A. Maldonado, José M. Quintana, Marco Pozzo and Per A. Tesch

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Bret Contreras, Andrew D. Vigotsky, Brad J. Schoenfeld, Chris Beardsley and John Cronin

The back squat and barbell hip thrust are both popular exercises used to target the lower body musculature; however, these exercises have yet to be compared. Therefore, the purpose of this study was to compare the surface electromyographic (EMG) activity of the upper and lower gluteus maximus, biceps femoris, and vastus lateralis between the back squat and barbell hip thrust. Thirteen trained women (n = 13; age = 28.9 years; height = 164 cm; mass = 58.2 kg) performed estimated 10-repetition maximums (RM) in the back squat and barbell hip thrust. The barbell hip thrust elicited significantly greater mean (69.5% vs 29.4%) and peak (172% vs 84.9%) upper gluteus maximus, mean (86.8% vs 45.4%) and peak (216% vs 130%) lower gluteus maximus, and mean (40.8% vs 14.9%) and peak (86.9% vs 37.5%) biceps femoris EMG activity than the back squat. There were no significant differences in mean (99.5% vs 110%) or peak (216% vs 244%) vastus lateralis EMG activity. The barbell hip thrust activates the gluteus maximus and biceps femoris to a greater degree than the back squat when using estimated 10RM loads. Longitudinal training studies are needed to determine if this enhanced activation correlates with increased strength, hypertrophy, and performance.

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Boyi Dai, Christopher J. Sorensen, Timothy R. Derrick and Jason C. Gillette

The effects of training on biomechanical risk factors for anterior cruciate ligament (ACL) injuries have been investigated, but the effects of detraining have received little attention. The purpose of this study was to evaluate the effects of a one-month postseason break on knee biomechanics and lower extremity electromyography (EMG) during a stop-jump task. A postseason break is the phase between two seasons when no regular training routines are performed. Twelve NCAA female volleyball players participated in two stop-jump tests before and after the postseason break. Knee kinematics, kinetics, quadriceps EMG, and hamstring EMG were assessed. After one month of postseason break, the players demonstrated significantly decreased jump height, decreased initial knee flexion angle, decreased knee flexion angle at peak anterior tibial resultant force, decreased prelanding vastus lateralis EMG, and decreased prelanding biceps femoris EMG as compared with prebreak. No significant differences were observed for frontal plane biomechanics and quadriceps and hamstring landing EMG between prebreak and postbreak. Although it is still unknown whether internal ACL loading changes after a postseason break, the more extended knee movement pattern may present an increased risk factor for ACL injuries.

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Conall F. Murtagh, Christopher Nulty, Jos Vanrenterghem, Andrew O’Boyle, Ryland Morgans, Barry Drust and Robert M. Erskine

(%iMVC) Peak biceps femoris EMG (%iMVC) Unilateral CMJ Jump phase Elite Nonelite Elite Nonelite Vertical Downward 106.5 (70.4) 105.2 (39.8) 47.6 (19.6) 60.5 (36.1) Upward 227.4 (134.5) 156.6 (78.3) 91.3 (46.2) 87.1 (45.6) Horizontal-forward Downward 139.1 (67.9) 103.6 (35.4) 118.0 (43.3) 124.3 (66

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Michael E. Hales and John D. Johnson II

.53 (5.96) Field B  VM 32.82 (8.25) 26.44 (7.57) 22.62 (5.61) 17.23 (2.93)  BF 33.11 (5.79) 26.49 (4.35) 21.74 (3.56) 16.82 (3.35)  MG 31.78 (6.14) 25.83 (3.62) 21.26 (3.91) 19.17 (3.43)  TA 27.65 (11.92) 23.27 (10.11) 20.32 (9.82) 19.78 (7.99) Abbreviations: BF, biceps femoris; EMG

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Neil Chapman, John Whitting, Suzanne Broadbent, Zachary Crowley-McHattan and Rudi Meir

stated >95 110° KE 20° 52 N Tilp et al 21 12 7 5 TA, GM >95 0° PF 15°/30° 10/45 Y Tilp et al 45 12 7 5 TA, GM >95 0° PF 15°/30° 10/45 Y Abbreviations: APB, adductor pollicis brevis; BF, biceps femoris; EMG, electromyography; G, gastrocnemius; GL, gastrocnemius lateralis; GM, gastrocnemius medialis; KE