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Jeffrey C. Cowley, Steven T. McCaw, Kelly R. Laurson and Michael R. Torry

to explain the motor patterns and characteristics underlying movement difficulties faced by children who are overweight ( 8 , 38 ). The vertical jump is a common measure of gross motor skill ( 22 ) with a documented performance deficiency among children who are overweight ( 26 ). Beyond the obvious

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Gabriel Andrade Paz, Marianna de Freitas Maia, Haroldo Gualter Santana, Humberto Miranda, Vicente Lima and John D. Willson

Volleyball is the widely played sport in the world and requires several physiological attributes, such as aerobic profile, strength, vertical jump ability, agility, and speed, 1 which are frequently developed in strength and conditioning programs. 2 , 3 However, previous studies have shown a

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Pedro Jiménez-Reyes, Pierre Samozino, Fernando Pareja-Blanco, Filipe Conceição, Víctor Cuadrado-Peñafiel, Juan José González-Badillo and Jean-Benoît Morin

Purpose:

To analyze the reliability and validity of a simple computation method to evaluate force (F), velocity (v), and power (P) output during a countermovement jump (CMJ) suitable for use in field conditions and to verify the validity of this computation method to compute the CMJ force–velocity (Fv) profile (including unloaded and loaded jumps) in trained athletes.

Methods:

Sixteen high-level male sprinters and jumpers performed maximal CMJs under 6 different load conditions (0–87 kg). A force plate sampling at 1000 Hz was used to record vertical ground-reaction force and derive vertical-displacement data during CMJ trials. For each condition, mean F, v, and P of the push-off phase were determined from both force-plate data (reference method) and simple computation measures based on body mass, jump height (from flight time), and push-off distance and used to establish the linear Fv relationship for each individual.

Results:

Mean absolute bias values were 0.9% (± 1.6%), 4.7% (± 6.2%), 3.7% (± 4.8%), and 5% (± 6.8%) for F, v, P, and slope of the Fv relationship (SFv), respectively. Both methods showed high correlations for Fv-profile-related variables (r = .985–.991). Finally, all variables computed from the simple method showed high reliability, with ICC >.980 and CV <1.0%.

Conclusions:

These results suggest that the simple method presented here is valid and reliable for computing CMJ force, velocity, power, and Fv profiles in athletes and could be used in practice under field conditions when body mass, push-off distance, and jump height are known.

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Neil E. Fowler and Adrian Lees

The aim of this study was to compare the kinetic and kinematic characteristics of plyometric drop-jump and pendulum exercises. Exercises were filmed (100 Hz) from the sagittal view and manually digitized; the data were smoothed and differentiated using cross-validated quintic splines. Ground reaction force data were sampled using a Kistler force platform sampling at 500 Hz. Differences between movement amplitudes and coordination strategies were assessed using t tests and conjugate cross-correlations. Pendulum exercises involved a greater range of motion at the ankle and knee but less motion at the hip joint than drop-jumps. Although different in absolute terms, the exercises used a similar coordination strategy. Drop-jumps resulted in greater peak vertical ground reaction forces than the pendulum exercises although the latter involved a greater net impulse. The similarity between the movement patterns for the two modes of exercise led to the conclusion that pendulum exercises offer a training stimulus similar to that of drop-jumps.

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Timothy J. Suchomel, Christopher B. Taber and Glenn A. Wright

The purpose of this study was to examine the effect that load has on the mechanics of the jump shrug. Fifteen track and field and club/intramural athletes (age 21.7 ± 1.3 y, height 180.9 ± 6.6 cm, body mass 84.7 ± 13.2 kg, 1-repetition-maximum (1RM) hang power clean 109.1 ± 17.2 kg) performed repetitions of the jump shrug at 30%, 45%, 65%, and 80% of their 1RM hang power clean. Jump height, peak landing force, and potential energy of the system at jump-shrug apex were compared between loads using a series of 1-way repeated-measures ANOVAs. Statistical differences in jump height (P < .001), peak landing force (P = .012), and potential energy of the system (P < .001) existed; however, there were no statistically significant pairwise comparisons in peak landing force between loads (P > .05). The greatest magnitudes of jump height, peak landing force, and potential energy of the system at the apex of the jump shrug occurred at 30% 1RM hang power clean and decreased as the external load increased from 45% to 80% 1RM hang power clean. Relationships between peak landing force and potential energy of the system at jump-shrug apex indicate that the landing forces produced during the jump shrug may be due to the landing strategy used by the athletes, especially at lighter loads. Practitioners may prescribe heavier loads during the jump-shrug exercise without viewing landing force as a potential limitation.

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Walter L. Jenkins, D.S. Williams, Brandon Bevil, Sara Stanley, Michael Blemker, Drue Taylor and Kevin O’Brien

Excessive hip motion has been linked to lower extremity pathology. Foot orthoses are commonly used to control motion within lower extremity joints when lower extremity pathology and dysfunction are present. Few studies have investigated the effect of foot orthoses on hip angular kinematics during functional activities. Eighteen females and 18 males performed a vertical jump with and without a prefabricated foot orthoses to determine the biomechanical effect of foot orthoses on hip kinematics when landing from a jump. Data collection included three-dimensional motion analysis of the lower extremity. Paired t tests were performed to determine if differences existed within genders with and without foot orthoses. At the hip joint, there was significantly less hip adduction motion in the foot orthoses condition as compared with the no foot orthoses condition in females (p < .05). There were no differences between foot orthoses conditions in males. Females appear to have a different proximal response to foot orthoses when landing from a forward jump than males.

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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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James Hackney, Jade McFarland, David Smith and Clinton Wallis

a study in order to investigate two questions. First, are 20 repetitions of drop landing adequate to promote consistency in (a) maximum ground reaction force, (b) linear lower body stiffness, (c) maximum depth of the landing, and (d) maximum jump height? The second objective more directly involves

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João Ribeiro, Luís Teixeira, Rui Lemos, Anderson S. Teixeira, Vitor Moreira, Pedro Silva and Fábio Y. Nakamura

Soccer is the most widely practiced sport in the world. It is considered an intermittent activity in which an increased demand in high-intensity explosive actions (such as jumping, sprinting, or multidirectional movements) has been observed during official matches. 1 Consequently, this has led to

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Kevin A. Becker, Ayana F. Georges and Christopher A. Aiken

referring to the feeling of shooting a basketball) leading to better performance for skilled performers under pressure than part-process goals (e.g., “straightening of knees” when shooting a basketball) in basketball shooting, long jumping, and golf putting ( Mullen & Hardy, 2010 ). Similar results were