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Todd L. Allinger and Robert W. Motl

This study used a vertical jump model to simulate the push-off phase for a skater using klap speed skates and evaluated die effects of pivot location and shoe base flexion on energy production. Boards of different lengths and one board with a hinge under the metatarsal heads were attached to the running shoes of volunteers. Six skaters performed 3 maximal effort vertical jumps across 5 different base conditions: running shoe, board that hinged under metatarsal heads, and rigid boards that pivoted with the ground al -25 mm (typical pivot location for klapskales), 0 mm, and +25 mm from the toes. There were no significant differences in total energy at take-off among the 3 rigid base conditions, but there were differences in potential and kinetic energy production. The total and kinetic energy produced at take-off was 9% greater in the hinged base condition than the corresponding rigid base condition. If differences in energy measures from the vertical jump reflect those for skating, a hinged boot base could increase skating speeds by about 3% over the current klap-skales, which have a rigid boot base.

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Yoann Blache, Maarten Bobbert, Sebastien Argaud, Benoit Pairot de Fontenay and Karine M. Monteil

In experiments investigating vertical squat jumping, the HAT segment is typically defined as a line drawn from the hip to some point proximally on the upper body (eg, the neck, the acromion), and the hip joint as the angle between this line and the upper legs (θUL-HAT). In reality, the hip joint is the angle between the pelvis and the upper legs (θUL-pelvis). This study aimed to estimate to what extent hip joint definition affects hip joint work in maximal squat jumping. Moreover, the initial pelvic tilt was manipulated to maximize the difference in hip joint work as a function of hip joint definition. Twenty-two male athletes performed maximum effort squat jumps in three different initial pelvic tilt conditions: backward (pelvisB), neutral (pelvisN), and forward (pelvisF). Hip joint work was calculated by integrating the hip net joint torque with respect to θUL-HAT (WUL-HAT) or with respect to θUL-pelvis (WUL-pelvis). θUL-HAT was greater than θUL-pelvis in all conditions. WUL-HAT overestimated WUL-pelvis by 33%, 39%, and 49% in conditions pelvisF, pelvisN, and pelvisB, respectively. It was concluded that θUL-pelvis should be measured when the mechanical output of hip extensor muscles is estimated.

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Deborah Jump

such as Anderson’s ( 2011 ) “inclusive masculinities” theory would have been welcomed. Indeed, an interrogation of work by Jump ( 2017 ) and Matthews and Channon ( 2017 ) into violence, sport, and praxis was also missing. To surmise, Groombridge suggests that: “sport is not a thing in itself that can

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Anne Delextrat, Sinead Mackessy, Luis Arceo-Rendon, Aaron Scanlan, Roger Ramsbottom and Julio Calleja-Gonzalez

− recently reported in the literature ( Gough et al., 2017 ; McNaughton et al., 2016 ; Sparks et al., 2017 ). Within this context, the aim of this study was to investigate the effects of 3-day serial NaHCO 3 ingestion on repeated sprint and jump ability and physiological parameters during a simulated

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Matthew Ellis, Mark Noon, Tony Myers and Neil Clarke

·kg −1 has been reported to increase jump height, 15-m sprint time, and repeated sprint ability in soccer players. 12 , 13 Approximately 2.6 mg·kg −1 of caffeinated gum has also demonstrated an increase in the distance covered during the Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1). 14 Thus

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Aymen Ben Othman, Mehdi Chaouachi, Issam Makhlouf, Jonathan P. Farthing, Urs Granacher, David G. Behm and Anis Chaouachi

) and lower (LP, knee extensors [KE] and flexors isometric strength, and countermovement jump [CMJ] [power]) limbs. The global training effects were extensive with significant strength improvements with the untrained muscles that were typically within 10% of the increases of the trained muscles from

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Matheus Barbalho, Ana Francisca Rozin Kleiner, Bianca Callegari, Ramon Costa de Lima, Givago da Silva Souza, Anselmo de Athayde Costa e Silva and Victor Silveira Coswig

force applied against a load. 2 With that said, jump performance has been widely applied for the evaluation of muscle strength, power, and interlimb asymmetries, 3 , 4 being well related to athletic performance, 5 , 6 injury risk, 7 and common motor gestures of several sports, 8 including soccer

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Nicola Giovanelli, Filippo Vaccari, Mirco Floreani, Enrico Rejc, Jasmine Copetti, Marco Garra, Lea Biasutti and Stefano Lazzer

conflicting results about the effects of these strategies on performance. 1 Indeed, static stretching, one of the most common strategies used, improves flexibility but can negatively affect the leg press 1 repetition maximum, muscle strength endurance, 20-m sprint performance, and vertical jump height. 2 – 5

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Hayley M. Ericksen, Caitlin Lefevre, Brittney A. Luc-Harkey, Abbey C. Thomas, Phillip A. Gribble and Brian Pietrosimone

previous levels of activity following reconstruction. 2 Aberrant lower-extremity movement biomechanics during dynamic movements have been implicated as a factor increasing the risk of ACL injury. 3 Specifically, the inability to attenuate high forces around the knee during dynamic movements, such as jump

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Mark D. Tillman, Rachel M. Criss, Denis Brunt and Chris J. Hass

The purposes of this study were to analyze double-limb, dominant-limb, and nondominant-limb landings, each with a two-footed takeoff, in order to detect potential differences in muscle activity and ground reaction forces and to examine the possible influence of leg dominance on these parameters. Each of the three jump landing combinations was analyzed in 11 healthy female volleyball players (age 21 ± 3 yrs; height 171 ± 5 cm, mass 61.6 ± 5.5 kg, max. vertical jump height 28 ± 4 cm). Ground reaction forces under each limb and bilateral muscle activity of the vastus medialis, hamstrings, and lateral gastrocnemius muscles were synchronized and collected at 1,000 Hz. Normalized EMG amplitude and force platform data were averaged over five trials for each participant and analyzed using repeated-measures ANOVA. During the takeoff phase in jumps with one-footed landings, the non-landing limb loaded more than the landing limb (p = 0.003). During the 100 ms prior to initial contact, single-footed landings generated higher EMG values than two-footed landings (p = 0.004). One-footed landings resulted in higher peak vertical loading, lateral loading, and rate of lateral loading than two-footed landings (p < 0.05). Trends were observed indicating that muscle activation during one-footed landings is greater than for two-footed landings (p = 0.053 vs. p = 0.077). The greater forces and rate of loading produced during single-limb landings implies a higher predisposition to injury. It appears that strategic planning and training of jumps in volleyball and other jumping sports is critical.