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"Drop jump" force

Takayuki Suzuki, Toshihiro Ikebukuro, Keitaro Kubo
BACKGROUND: The purpose of the present study was to compare changes in joint stiffness after repeated eccentric (ECC; leading to muscle fatigue) and isometric (ISO; leading to tendon fatigue) contractions and to elucidate the mechanisms responsible for decline in joint stiffness after repeated stretch-shortening cycle exercises reported previously. METHODS: Ankle joint stiffness (change in joint torque divided by change in joint angle during braking phase) and electromyographic activity (mEMG) of the plantar flexor muscles during drop jump using the ankle joint were measured before and after ECC, ISO, and control conditions...
December 13, 2018: Journal of Sports Medicine and Physical Fitness
Dana Guy-Cherry, Ahmad Alanazi, Lauren Miller, Darrin Staloch, Alexis Ortiz-Rodriguez
The aim was to determine which three landing styles - stiff (ST), self-selected (SS), or soft (SF) - exhibit safer landing mechanics and greater jumping performance. Thirty participants (age: 26.5±5.1 years; height: 171.0±8.8 cm; weight: 69.7±10.1 kg) performed five trials of three randomized drop jump (40 cm) landing styles including SF (~60° knee flexion), ST (knees as straight as possible), and SS. Knee flexion and valgus angles and kinetics were measured. An electromyography system measured muscle activity of the gluteus maximus, quadriceps, hamstrings, tibialis anterior, and gastrocnemius...
April 2018: Sports medicine international open
Duncan P Fransz, Arnold Huurnink, Idsart Kingma, Vosse A de Boode, Ide C Heyligers, Jaap H van Dieën
BACKGROUND: Soccer has a high injury rate, with lateral ankle sprains being a common injury. Therefore, an approach to prevent or at least reduce the occurrence is warranted. Injury prevention can be improved by identifying specific risk factors and individuals at risk. PURPOSE: To assess drop-jump landing performance as a potential predictor of lateral ankle sprain within 3-year follow-up. STUDY DESIGN: Case-control study; Level of evidence, 3...
December 2018: American Journal of Sports Medicine
Danguole Satkunskiene, Sigitas Kamandulis, Marius Brazaitis, Audrius Snieckus, Albertas Skurvydas
The study aims were to investigate the effects of muscle damage induced by high-volume stretch-shortening cycle exercise on countermovement jump (CMJ) performance and vertical leg stiffness during squat and landing phases. Changes in the peak torque of knee extensor muscles, soreness, plasma CK activity, vertical leg stiffness, and CMJ characteristics were measured in recreationally active men after 50, 100, 150 and 200 drop jumps (DJs) and again 24 h later. The isometric voluntary peak torque after 50 DJs decreased by 22 ± 12% (p < 0...
November 9, 2018: Sports Biomechanics
Brandon W Snyder, Shawn N Munford, Chris Connaboy, Hugh S Lamont, Shala E Davis, Gavin L Moir
The purpose of this study was to compare different methods for assessing plyometric ability during countermovement (CMJ) and drop jumps (DJ) in a group of adults and adolescents. Ten resistance-trained adult men (age: 22.6 ± 1.6 years) and ten adolescent male basketball players (age: 16.5 ± 0.7 years) performed a CMJ and a DJ from a height of 0.40 m. Jump height (JH), contact time, normalized work (WNORM ), and power output (PONORM ) during the absorption and propulsion phases were calculated from force platforms and 3-D motion analysis data...
October 27, 2018: Sports
Matthias König, Svenja Hemmers, Gaspar Epro, Christopher McCrum, Thijs Maria Anne Ackermans, Ulrich Hartmann, Kiros Karamanidis
Reductions in muscular power output and performance during multi-joint motor tasks with aging have often been associated with muscle weakness. This study aimed to examine if matching younger and middle-aged adults for triceps surae (TS) muscle strength and tendon stiffness eliminates age-related differences in muscular power production during drop jump. The maximal ankle plantar flexion moment and gastrocnemius medialis tendon stiffness of 29 middle-aged (40-67 years) and 26 younger (18-30 years) healthy physically active male adults were assessed during isometric voluntary ankle plantar flexion contractions using simultaneous dynamometry and ultrasonography...
2018: Frontiers in Physiology
Gavin L Moir, Brandon W Snyder, Chris Connaboy, Hugh S Lamont, Shala E Davis
The purpose of this study was to investigate the eccentric and concentric force-velocity (Fv) characteristics recorded during drop jumps (DJ) from different heights and loaded jump squats (JS) and to determine the number of jumps required to accurately model the eccentric and concentric Fv relationships. Fourteen resistance-trained men (age: 21.9 ± 1.8 years) performed a countermovement jump (CMJ) and DJ from heights of 0.40, 0.60, and 0.80 m. JS with loads equivalent to 0%, 27%, 56%, and 85% 1-repetition maximum were performed in a separate session...
October 24, 2018: Sports
Nicole M Mueske, Akash R Patel, J Lee Pace, Tracy L Zaslow, Curtis D VandenBerg, Mia J Katzel, Bianca R Edison, Tishya A L Wren
Motion analysis offers objective insight into biomechanics, rehabilitation progress and return to sport readiness. This study examined changes in three-dimensional movement patterns during drop jump landing between early and late stages of rehabilitation in adolescent athletes following anterior cruciate ligament reconstruction (ACLR). Twenty-four athletes (58% female; mean age 15.4 years, SD 1.2) with unilateral ACLR underwent motion analysis testing 3-6 months and again 6-10 months post-operatively. Kinematics and kinetics were compared between visits and between limbs using repeated measures ANOVA...
October 2, 2018: Sports Biomechanics
Jeheon Moon, Hyeyoung Kim, Jusung Lee, Siddhartha Bikram Panday
BACKGROUND: Knee braces are considered to be extremely useful tools in reducing the shear force of knee joints for non-contact anterior cruciate ligament (ACL) injury prevention. However, the effectiveness of sports knee braces and sleeves remains to be identified. Therefore, the purpose of this study was to evaluate the effectiveness of wearing commercialized sports knee braces and sleeves on knee kinematics, kinetics, and ACL force during drop jumps using musculoskeletal modeling analysis...
August 15, 2018: Knee
Robin Healy, Carol Smyth, Ian C Kenny, Andrew J Harrison
Healy, R, Smyth, C, Kenny, IC, and Harrison, AJ. Influence of reactive and maximum strength indicators on sprint performance. J Strength Cond Res XX(X): 000-000, 2018-The primary aim of this study was to assess the relationship between reactive and maximal strength measures with 40 m sprint performance and mechanical properties. Fourteen male and 14 female sprinters participated in this study. On the first day, subjects performed 40 m sprints with 10-m split times recorded in addition to maximal theoretical velocity, maximal theoretical force and peak horizontal power, which were calculated from force-velocity relationships...
June 22, 2018: Journal of Strength and Conditioning Research
Christopher Thomas, Irene Kyriakidou, Thomas Dos'Santos, Paul A Jones
The countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) are commonly used to compare one's force capacity during dynamic and isometric assessments, respectively. However, little research has investigated the influence of maximum isometric strength on drop-jump (DJ) performance. Therefore, the purpose of this study was to explore differences in CMJ and DJ force-time characteristics between stronger and weaker adolescent male basketball players. Sixteen adolescent male basketball players performed the IMTP to assess measures of peak force (IMTP PF), whereas CMJ and DJ calculated a range of kinetic and kinematic variables...
August 24, 2017: Sports
Eric D Magrum, John P Wagle, Brad H DeWeese, Kimitake Sato, Michael H Stone
The purpose of this study was to compare ground contact time between an optical measurement system and a force platform. Participants in this study included six collegiate level athletes who performed drop jumps and sprint strike steps for a total of 15 repetitions each. Ground contact data was simultaneously collected from an optical measurement system and a force platform, at a sampling frequency of 1000 Hz. Data was then analyzed with Pearson's correlation and paired sample t -tests. The measures from the optical measurement system were found to be significantly higher ( p < 0...
February 17, 2018: Sports
Anne A G Aune, Chris Bishop, Anthony N Turner, Kostas Papadopoulos, Sarah Budd, Mark Richardson, Sean J Maloney
Foam rolling and eccentric exercise interventions have been demonstrated to improve range of motion (ROM). However, these two modalities have not been directly compared. Twenty-three academy soccer players (age: 18 ± 1; height: 1.74 ± 0.08 m; body mass: 69.3 ± 7.5 kg) were randomly allocated to either a foam rolling (FR) or eccentric exercise intervention designed to improve dorsiflexion ROM. Participants performed the intervention daily for a duration of four weeks. Measurements of dorsiflexion ROM, isometric plantar flexion torque and drop jump reactive strength index were taken at baseline (pre-intervention) and at three subsequent time-points (30-min post, 24-hours post and 4-weeks post)...
June 12, 2018: Journal of Sports Sciences
Mohamed Abdelsattar, Andreas Konrad, Markus Tilp
The purpose of this study was to investigate the relationship between Achilles tendon stiffness and ground contact time (GCT) during drop jumps. The property of "springiness" and a short GCT during the movement is required in several types of sports. Therefore, a stiff tendon might be advantageous due to the quick force transmission from the muscle to the bone. Hence, a secondary aim was to relate Achilles tendon stiffness with squat jump (SJ) and counter movement jump (CMJ) performance, respectively...
June 2018: Journal of Sports Science & Medicine
Mark C Richardson, Sinead Murphy, Tom Macpherson, Bryan English, Iain Spears, Paul Chesterton
Richardson, MC, Murphy, S, Macpherson, T, English, B, Spears, I, and Chesterton, P. Effect of sand on knee load during a single-leg jump task: implications for injury prevention and rehabilitation programs. J Strength Cond Res XX(X): 000-000, 2018-The purpose of the study was to determine potential differences in landing strategies and subsequent joint loads at the knee (knee abduction moment [KAM], anterior-posterior [AP] tibial translation, and total knee shear force) when jumping onto sand and firm ground from both a level surface and a 30-cm height...
May 7, 2018: Journal of Strength and Conditioning Research
Matthew G King, Adam I Semciw, Harvi F Hart, Anthony G Schache, Kane J Middleton, Josh J Heerey, Rintje Agricola, Kay M Crossley
Background Hip-related groin pain is common in sub-elite football players and may be associated with altered hip biomechanics. Objectives To compare the hip biomechanics, bony hip morphology associated with femoroacetabular impingement (FAI) syndrome, and hip strength and range of motion (ROM) between the symptomatic and asymptomatic limbs of sub-elite football players with unilateral hip-related groin pain and a positive flexion, adduction, and internal rotation (FADIR) test. Methods Fifteen sub-elite football (soccer) players with unilateral hip-related groin pain and a positive FADIR test were recruited for this observational cross-sectional study...
July 2018: Journal of Orthopaedic and Sports Physical Therapy
Tom Haynes, Chris Bishop, Mark Antrobus, Jon Brazier
BACKGROUND: This is the first study to independently assess the concurrent validity and reliability of the My Jump 2 app for measuring drop jump performance. It is also the first to evaluate the app's ability to measure the reactive strength index (RSI). METHODS: Fourteen male sport science students (age: 29.5 ± 9.9 years) performed three drop jumps from 20 cm and 40 cm (totalling 84 jumps), assessed via a force platform and the My Jump 2 app. Reported metrics included reactive strength index, jump height, ground contact time, and mean power...
March 27, 2018: Journal of Sports Medicine and Physical Fitness
Helene Moser, Monika Leitner, Patric Eichelberger, Annette Kuhn, Jean-Pierre Baeyens, Lorenz Radlinger
PURPOSE: Stress urinary incontinence (SUI) symptoms can be provoked during impact loads such as vertical jumps. To investigate and compare pelvic floor muscle (PFM) activity in women with SUI and continent women (CON) during drop jumps (DJ) and counter movement jumps (CMJ) could clarify the activity of the PFMs during impact loads. METHODS: A tripolar vaginal probe was used to record surface electromyographic (EMG) activity of the PFMs during DJ and CMJ. Time intervals of 30 ms were used to parameterize data from 30 ms before (pre-activity) to 150 ms after (reflex activity) ground contact on a force plate during the landing and take-off phase...
June 2018: Archives of Gynecology and Obstetrics
Christian Maurer, Sebastian Heller, Jil-Julia Sure, Daniel Fuchs, Christoph Mickel, Eileen M Wanke, David A Groneberg, Daniela Ohlendorf
OBJECTIVE: The influence of the jaw position on postural control, body posture, walking and running pattern has been reported in the literature. All these movements have in common that a relatively small, but well controlled muscle activation is required. The induced effects on motor output through changed jaw positions have been small. Therefore, it has been questioned if it could still be observed in maximal muscle activation. METHOD: Twenty-three healthy, mid age recreational runners (mean age = 34...
2018: PloS One
John J McMahon, Timothy J Suchomel, Jason P Lake, Paul Comfort
Two reactive strength index (RSI) variants exist, the RSI and RSI modified (RSImod) which are typically calculated during the drop jump (DJ) and countermovement jump (CMJ), respectively. Both RSI variants have been used to monitor athletes' ability to complete stretch-shortening cycle actions quickly, but they have never been compared. The purpose of this study was to determine if they yield relatable information about reactive strength characteristics. Male professional rugby league players (n = 21, age = 20...
February 1, 2018: Journal of Strength and Conditioning Research
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