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https://www.readbyqxmd.com/read/28820857/kinematic-and-neuromuscular-measures-of-intensity-during-plyometric-jumps
#1
David Cristóbal Andrade, Oscar Manzo, Ana Rosa Beltrán, Cristian Álvarez, Rodrigo Del Rio, Camilo Toledo, Jason Moran, Rodrigo Ramirez-Campillo
The aim of this study was to assess jumping performance and neuromuscular activity in lower limb muscles after drop jumps (DJ) from different drop heights (intensity) and during continuous jumping (fatigue), using markers such as reactive strength, jump height, mechanical power and surface electromyography (sEMG). The eccentric (EC) and concentric (CON) sEMG from the medial gastrocnemius (MG), biceps femoris (BF) and rectus (R) muscles were assessed during all tests. In a cross-sectional, randomized study, eleven volleyball players (age 24...
August 15, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28768338/combined-effects-of-fatigue-and-surface-instability-on-jump-biomechanics-in-elite-athletes
#2
Olaf Prieske, Marie Demps, Melanie Lesinski, Urs Granacher
The present study aimed to examine the effects of fatigue and surface instability on kinetic and kinematic jump performance measures. Ten female and 10 male elite volleyball players (18±2 years) performed repetitive vertical double-leg box jumps until failure. Pre and post fatigue, jump height/performance index, ground reaction force and knee flexion/valgus angles were assessed during drop and countermovement jumps on stable and unstable surfaces. Fatigue, surface condition, and sex resulted in significantly lower drop jump performance and ground reaction force (p≤0...
August 2, 2017: International Journal of Sports Medicine
https://www.readbyqxmd.com/read/28767248/spreading-dynamics-of-molten-polymer-drops-on-glass-substrates
#3
Yichuan Zhang, Carlos A Fuentes, Robin Koekoekx, Christian Clasen, Aart Willem van Vuure, Joel De Coninck, David Seveno
Wetting dynamics drive numerous processes involving liquids in contact with solid substrates with a wide range of geometries. The spreading dynamics of organic liquids and liquid metals at, respectively, room temperature and above 1000 °C have been studied extensively, both experimentally and numerically. However, almost no attention has been paid to the wetting behavior of molten drops of thermoplastic polymers, despite its importance, for example, in the processing of fiber-reinforced polymer composites...
August 2, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28766333/monitoring-hydrogen-exchange-during-protein-folding-by-fast-pressure-jump-nmr-spectroscopy
#4
T Reid Alderson, Cyril Charlier, Dennis A Torchia, Philip Anfinrud, Ad Bax
A method is introduced that permits direct observation of the rates at which backbone amide hydrogens become protected from solvent exchange after rapidly dropping the hydrostatic pressure inside the NMR sample cell from denaturing (2.5 kbar) to native (1 bar) conditions. The method is demonstrated for a pressure-sensitized ubiquitin variant that contains two Val to Ala mutations. Increased protection against hydrogen exchange with solvent is monitored as a function of time during the folding process. Results for 53 backbone amides show narrow clustering with protection occurring with a time constant of ca...
August 16, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28745469/reliability-of-bounce-drop-jump-parameters-within-elite-male-rugby-players
#5
Lisa Costley, Eric Wallace, Michael Johnston, Rodney Kennedy
BACKGROUND: The aims of the study were to investigate the number of familiarisation sessions required to establish reliability of the bounce drop jump (BDJ) and subsequent reliability once familiarisation is achieved. METHOD: Seventeen trained male athletes completed 4 BDJs in 4 separate testing sessions. Force-time data from a 20 cm BDJ was obtained using two force plates (ensuring ground contact < 250 ms). Subjects were instructed to 'jump for maximal height and minimal contact time' while the best and average of four jumps were compared...
July 25, 2017: Journal of Sports Medicine and Physical Fitness
https://www.readbyqxmd.com/read/28730881/comparison-of-jump-landing-protocols-with-biodex-balance-system-as-measures-of-dynamic-postural-stability-in-athletes
#6
Zarko Krkeljas
The objective of the study was to determine whether a relationship exists between the two common methods for assessing postural stability in athletes: the time-to-stabilisation (TTS) via force-plate and the Biodex Balance System (BBS). The conditions under which these measurements assess dynamic postural control may not provide sufficient feedback to practitioners. Fourty-four amateur soccer players with no history of musculoskeletal disorders volunteered for the study. Pearson correlation was used to compare the anterior-posterior (AP), medio-lateral (ML), and the overall stability indexes measured by BBS, with the corresponding parameters of TTS assessed via force plate...
July 21, 2017: Sports Biomechanics
https://www.readbyqxmd.com/read/28723822/biomechanical-differences-in-female-basketball-and-soccer-players-during-multi-directional-jump-landings
#7
Jeffrey B Taylor, Kevin R Ford, Randy J Schmitz, Scott E Ross, Terry A Ackerman, Sandra J Shultz
Anterior cruciate ligament injury prevention programs are less successful in basketball than soccer and may be due to distinct movement strategies that these athletes develop from sport-specific training. The purpose of this study was to identify biomechanical differences between female basketball and soccer players during multi-directional jump landings. Lower extremity biomechanics of eighty-nine female athletes who played competitive basketball (n=40) or soccer (n=49) at the middle- or high-school level were analyzed with three-dimensional motion analysis during a drop vertical jump (DVJ), double- (SAG-DL) and single-leg forward jump (SAG-SL), and double- (FRONT-DL) and single-leg (FRONT-SL) lateral jump...
July 14, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28723816/importance-of-physical-qualities-for-speed-and-change-of-direction-ability-in-elite-female-soccer-players
#8
Stacey Emmonds, G Nicholson, C Beggs, B Jones, A Bissas
The purpose of this study was to determine the importance of physical qualities for speed and change of direction (CoD) ability in female soccer players. Data were collected on 10 female soccer players who were part of a professional English Women's Super League team. Player assessments included anthropometric (stature and body mass), body composition (dual-energy X-ray absorptiometry), speed (10m, 30m sprint), CoD ability (505 agility), aerobic (Yo-Yo Intermittent Recovery Test), lower-body strength (bilateral knee extensions) and power (countermovement jump [CMJ], squat jump [SJ], 30cm drop jump [DJ]) measures...
July 17, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28722467/the-influence-of-lower-extremity-lean-mass-on-landing-biomechanics-during-prolonged-exercise
#9
Melissa M Montgomery, Amanda J Tritsch, John R Cone, Randy J Schmitz, Robert A Henson, Sandra J Shultz
CONTEXT:   The extent to which lower extremity lean mass (LELM) relative to total body mass influences one's ability to maintain safe landing biomechanics during prolonged exercise when injury incidence increases is unknown. OBJECTIVES:   To examine the influence of LELM on (1) pre-exercise lower extremity biomechanics and (2) changes in biomechanics during an intermittent exercise protocol (IEP) and (3) determine whether these relationships differ by sex. We hypothesized that less LELM would predict higher-risk baseline biomechanics and greater changes toward higher-risk biomechanics during the IEP...
August 2017: Journal of Athletic Training
https://www.readbyqxmd.com/read/28719765/beetroot-juice-is-more-beneficial-than-sodium-nitrate-for-attenuating-muscle-pain-after-strenuous-eccentric-bias-exercise
#10
Tom Clifford, Glyn Howatson, Daniel J West, Emma J Stevenson
The aim of this study was to compare the effects of beetroot juice (BTJ) and a nitrate only drink (sodium nitrate; SN) on indices of exercise-induced muscle damage (EIMD). Thirty recreationally active males consumed either BTJ (n=10), a nitrate matched SN drink (n=10) or an isocaloric placebo (PLA; n=10) immediately, 24 and 48 h after performing 100 drop jumps. To assess muscle damage, maximal isometric voluntary contractions (MIVC), countermovement jumps (CMJ), pressure-pain threshold (PPT), creatine kinase (CK) and high sensitivity C-reactive protein (hs-CRP) were measured pre, immediately post, 24, 48 and 72 h following the drop jumps...
July 18, 2017: Applied Physiology, Nutrition, and Metabolism, Physiologie Appliquée, Nutrition et Métabolisme
https://www.readbyqxmd.com/read/28716970/prolonged-force-depression-after-mechanically-demanding-contractions-is-largely-independent-of-ca-2-and-reactive-oxygen-species
#11
Sigitas Kamandulis, Felipe de Souza Leite, Andres Hernández, Abram Katz, Marius Brazaitis, Joseph D Bruton, Tomas Venckunas, Nerijus Masiulis, Dalia Mickeviciene, Nerijus Eimantas, Andrejus Subocius, Dilson E Rassier, Albertas Skurvydas, Niklas Ivarsson, Håkan Westerblad
Increased production of reactive oxygen/nitrogen species (ROS) and impaired cellular Ca(2+) handling are implicated in the prolonged low-frequency force depression (PLFFD) observed in skeletal muscle after both metabolically and mechanically demanding exercise. Metabolically demanding high-intensity exercise can induce PLFFD accompanied by ROS-dependent fragmentation of the sarcoplasmic reticulum Ca(2+) release channels, the ryanodine receptor (RyR)-1. We tested whether similar changes occur after mechanically demanding eccentric contractions...
July 17, 2017: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
https://www.readbyqxmd.com/read/28712031/human-skeletal-muscle-type-1-fibre-distribution-and-response-of-stress-sensing-proteins-along-the-titin-molecule-after-submaximal-exhaustive-exercise
#12
Satu O A Koskinen, Heikki Kyröläinen, Riina Flink, Harri P Selänne, Sheila S Gagnon, Juha P Ahtiainen, Bradley C Nindl, Maarit Lehti
Early responses of stress-sensing proteins, muscle LIM protein (MLP), ankyrin repeat proteins (Ankrd1/CARP and Ankrd2/Arpp) and muscle-specific RING finger proteins (MuRF1 and MuRF2), along the titin molecule were investigated in the present experiment after submaximal exhaustive exercise. Ten healthy men performed continuous drop jumping unilaterally on a sledge apparatus with a submaximal height until complete exhaustion. Five stress-sensing proteins were analysed by mRNA measurements from biopsies obtained immediately and 3 h after the exercise from exercised vastus lateralis muscle while control biopsies were obtained from non-exercised legs before the exercise...
July 15, 2017: Histochemistry and Cell Biology
https://www.readbyqxmd.com/read/28712025/side-to-side-asymmetries-in-landing-mechanics-from-a-drop-vertical-jump-test-are-not-related-to-asymmetries-in-knee-joint-laxity-following-anterior-cruciate-ligament-reconstruction
#13
Christophe A G Meyer, Paul Gette, Caroline Mouton, Romain Seil, Daniel Theisen
PURPOSE: Asymmetries in knee joint biomechanics and increased knee joint laxity in patients following anterior cruciate ligament reconstruction (ACLR) are considered risk factors for re-tear or early onset of osteoarthritis. Nevertheless, the relationship between these factors has not been established. The aim of the study was to compare knee mechanics during landing from a bilateral drop vertical jump in patients following ACLR and control participants and to study the relationship between side-to-side asymmetries in landing mechanics and knee joint laxity...
July 15, 2017: Knee Surgery, Sports Traumatology, Arthroscopy: Official Journal of the ESSKA
https://www.readbyqxmd.com/read/28704344/effects-of-altering-trunk-position-during-landings-on-patellar-tendon-force-and-pain
#14
Rodrigo Scattone Silva, Craig R Purdam, Angela M Fearon, Wayne A Spratford, Claire Kenneally-Dabrowski, Peter Preston, Fábio V Serrão, James E Gaida
PURPOSE: To verify the immediate effects of altering sagittal plane trunk position during jump-landings on lower limb biomechanics, patellar tendon force and pain of athletes with and without patellar tendinopathy. METHODS: Twenty-one elite male athletes were categorized into 3 groups, athletes with patellar tendinopathy (TG, n=7), asymptomatic athletes with patellar tendon abnormalities (AG, n=7) and asymptomatic athletes without tendon abnormalities (CG, n=7)...
July 12, 2017: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/28704309/effect-of-three-different-muscle-action-training-protocols-on-knee-strength-ratios-and-performance
#15
Cassio V Ruas, Lee E Brown, Camila D Lima, Pablo B Costa, Ronei S Pinto
Hamstring to quadriceps (H:Q) ratios are often used to assess strength imbalances. The aims of this study were to compare three different muscle action training protocols on H:Q strength balance and functional performance. Forty untrained males (age: 22.87 ± 2.28 y, mass: 70.66 ± 11.049 kg, ht: 174.29 ± 6.90 cm) performed 6 weeks of training on an isokinetic dynamometer. They were randomly assigned to one of 4 groups; concentric quadriceps and concentric hamstring (CON/CON), eccentric quadriceps and eccentric hamstring (ECC/ECC), concentric quadriceps and eccentric hamstring (CON/ECC), or no training (CNTRL)...
July 12, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28698802/gait-analysis-in-children-with-cerebral-palsy
#16
Stéphane Armand, Geraldo Decoulon, Alice Bonnefoy-Mazure
Cerebral palsy (CP) children present complex and heterogeneous motor disorders that cause gait deviations.Clinical gait analysis (CGA) is needed to identify, understand and support the management of gait deviations in CP. CGA assesses a large amount of quantitative data concerning patients' gait characteristics, such as video, kinematics, kinetics, electromyography and plantar pressure data.Common gait deviations in CP can be grouped into the gait patterns of spastic hemiplegia (drop foot, equinus with different knee positions) and spastic diplegia (true equinus, jump, apparent equinus and crouch) to facilitate communication...
December 2016: EFORT open reviews
https://www.readbyqxmd.com/read/28697691/the-relationship-between-mechanical-stiffness-and-athletic-performance-markers-in-sub-elite-footballers
#17
Judd T Kalkhoven, Mark L Watsford
This study investigated the relationship between several measures of lower-body stiffness and physical performance variables in 22 sub-elite male football players (mean ± SD; 21.9 ± 1.5 yr; 1.79 ± 0.06 m; 72.2 ± 7.2 kg). The participants were assessed for individual muscle stiffness of the Rectus Femoris (RF), Biceps Femoris (BF) and Medial Gastrocnemius (MG) muscles and vertical stiffness (Kvert) was also assessed assessed running acceleration, maximal sprint speed, agility, vertical jumping and muscular strength...
July 12, 2017: Journal of Sports Sciences
https://www.readbyqxmd.com/read/28693535/alfredson-versus-silbernagel-exercise-therapy-in-chronic-midportion-achilles-tendinopathy-study-protocol-for-a-randomized-controlled-trial
#18
Bas Habets, Robert E H van Cingel, Frank J G Backx, Bionka M A Huisstede
BACKGROUND: Midportion Achilles tendinopathy (AT) is a common overuse injury, usually requiring several months of rehabilitation. Exercise therapy of the ankle plantar flexors (i.e. tendon loading) is considered crucial during conservative rehabilitation. Alfredson's isolated eccentric and Silbernagel's combined concentric-eccentric exercise programs have both shown beneficial results, but it is unknown whether any of these programs is superior for use in clinical practice. Therefore, the primary objective of this study is to compare the effectiveness of both programs on clinical symptoms...
July 11, 2017: BMC Musculoskeletal Disorders
https://www.readbyqxmd.com/read/28683233/development-of-a-clinician-rated-drop-vertical-jump-scale-for-patients-undergoing-rehabilitation-after-anterior-cruciate-ligament-reconstruction-a-delphi-approach
#19
Sheila S Gagnon, Trevor B Birmingham, Bert M Chesworth, Dianne Bryant, Melanie Werstine, J Robert Giffin
Study Design Delphi panel study. Background Biomechanical parameters measured during a drop vertical jump task are risk factors for anterior cruciate ligament (ACL) injury and are targeted during rehabilitation after ACL reconstruction. A clinically feasible tool that quantifies observed performance on the drop vertical jump would help inform treatment efforts. The content and scoring of such a tool should be deliberated on by a group of experts throughout its development. Objectives To establish consensus on the content and scoring of a clinician-rated drop vertical jump scale (DVJS) for use during rehabilitation after ACL reconstruction...
August 2017: Journal of Orthopaedic and Sports Physical Therapy
https://www.readbyqxmd.com/read/28674872/efficacy-of-wearing-compression-garments-during-post-exercise-period-after-two-repeated-bouts-of-strenuous-exercise-a-randomized-crossover-design-in-healthy-active-males
#20
Kazushige Goto, Sahiro Mizuno, Ayaka Mori
BACKGROUND: The efficacy of wearing [a] compression garment (CG) between repeated bouts of exercise within a same day has not been fully understood. The present study determined the effect of wearing a CG after strenuous exercise sessions (consisting of sprint exercise, resistance exercise, drop jump) twice a day on exercise performance, muscle damage, and inflammatory responses. METHODS: Eleven physically active males (age, 22.7 ± 0.9 years; height, 175...
December 2017: Sports Medicine—Open
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