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Michaela Gstöttner, Andreas Neher, Arne Scholtz, Martin Millonig, Sandra Lembert and Christian Raschner

The aim of this study was to evaluate balance abilities and electromyographic (EMG) latency times of the preferred and nonpreferred leg in soccer players. Whereas side differences between the two legs in force, kicking speed, and joint laxity have been demonstrated in athletes in previous studies, no data are so far available on balance differences. Low balance ability is generally associated with an increased risk of ligament injuries, and the detection of a possible asymmetry in balance is important because a bilateral difference may be a contributing factor to injury. Twenty-one amateur soccer players were tested. Two different balance test instruments were used: the Biodex Stability System and the Tetrax System. For the evaluation of muscle latency times, EMGs were recorded by means of the EquiTest system. None of the tests performed in this study revealed statistically significant differences in balance ability between the preferred and the nonpreferred leg. The investigations of balance function and muscle response in amateur soccer players did not reveal significant differences between the preferred and nonpreferred leg in the current study. However, a certain tendency to better balance in the nonpreferred leg was observed.

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Ashley Stern, Chris Kuenze, Daniel Herman, Lindsay D. Sauer and Joseph M. Hart

Context:

Central and peripheral muscle fatigue during exercise may exacerbate neuromuscular factors that increase risk for noncontact anterior cruciate ligament injury.

Objective:

To compare lower extremity motor-evoked potentials (MEPs), muscle strength, and electromyography (EMG) activation after an exercise protocol.

Design:

Pretest, posttest group comparison.

Setting:

University laboratory.

Participants:

34 healthy volunteers (17 female, age = 21.9 ± 2.3 years, weight = 77.8 ± 3.0 kg, height = 171.1 ± 6.6 cm, and 17 male, age = 23.4 ± 6.5 years, weight = 81.6 ± 3.3 kg, height = 179.6 ± 7.3 cm).

Intervention:

A standardized 30-min exercise protocol that involved 5 repeated cycles of uphill walking, body-weight squatting, and step-ups.

Main Outcome Measures:

Quadriceps and hamstring MEP amplitude (mV) and transmission velocity normalized to subject height (m/s) were elicited via transcranial magnetic stimulation and measured via surface EMG. Quadriceps and hamstring peak EMG activation (% MVIC) and peak torque (Nm/kg) were measured during MVICs. Separate ANCOVAs were used to compare groups after exercise while controlling for baseline measurement.

Results:

At baseline, males exhibited significantly greater knee-extension torques (males = 2.47 ± 0.68 Nm/kg, females = 1.95 ± 0.53 Nm/kg; P = .036) and significantly higher hamstring MEP amplitudes (males = 223.5 ± 134.0 mV, females = 89.3 ± 77.6 mV; P = .007). Males exhibited greater quadriceps MEP amplitude after exercise than females (males = 127.2 ± 112.7 mV, females = 32.3 ± 34.9 mV; P = .016).

Conclusions:

Males experienced greater peripheral neuromuscular changes manifested as more pronounced reductions in quadriceps torque after exercise. Females experienced greater central neuromuscular changes manifested as more pronounced reduction in quadriceps MEP amplitude. Reduced central neural drive of the quadriceps coupled with knee-extension torque preservation after exercise may increase risk of knee injury in females.

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Cody B. Bremner, William R. Holcomb, Christopher D. Brown and Melanie E. Perreault

Clinical Scenario:

Orthopedic knee conditions are regularly treated in sports-medicine clinics. Rehabilitation protocols for these conditions are often designed to address the associated quadriceps strength deficits. Despite these efforts, patients with orthopedic knee conditions often fail to completely regain their quadriceps strength. Disinhibitory modalities have recently been suggested as a clinical tool that can be used to counteract the negative effects of arthrogenic muscle inhibition, which is believed to limit the effectiveness of therapeutic exercise. Neuromuscular electrical stimulation (NMES) is commonly accepted as a strengthening modality, but its ability to simultaneously serve as a disinhibitory treatment is not as well established.

Clinical Question:

Does NMES effectively enhance quadriceps voluntary activation in patients with orthopedic knee conditions?

Summary of Key Findings:

Four randomized controlled trials (RCTs) met the inclusion criteria and were included. Of those, 1 reported statistically significant improvements in quadriceps voluntary activation in the intervention group relative to a comparison group, but the statistical significance was not true for another study consisting of the same sample of participants with a different follow-up period. One study reported a trend in the NMES group, but the between-groups differences were not statistically significant in 3 of the 4 RCTs.

Clinical Bottom Line:

Current evidence does not support the use of NMES for the purpose of enhancing quadriceps voluntary activation in patients with orthopedic knee conditions.

Strength of Recommendation:

There is level B evidence that the use of NMES alone or in conjunction with therapeutic exercise does not enhance quadriceps voluntary activation in patients with orthopedic knee conditions (eg, anterior cruciate ligament injuries, osteoarthritis, total knee arthroplasty).

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Derek N. Pamukoff, Sarah E. Bell, Eric D. Ryan and J. Troy Blackburn

Context:

Hamstring musculotendinous stiffness (MTS) is associated with lower-extremity injury risk (ie, hamstring strain, anterior cruciate ligament injury) and is commonly assessed using the damped oscillatory technique. However, despite a preponderance of studies that measure MTS reliably in laboratory settings, there are no valid clinical measurement tools. A valid clinical measurement technique is needed to assess MTS and permit identification of individuals at heightened risk of injury and track rehabilitation progress.

Objective:

To determine the validity and reliability of the Myotonometer for measuring active hamstring MTS.

Design:

Descriptive laboratory study.

Setting:

Laboratory

Participants:

33 healthy participants (15 men, age 21.33 ± 2.94 y, height 172.03 ± 16.36 cm, mass 74.21 ± 16.36 kg).

Main Outcome Measures:

Hamstring MTS was assessed using the damped oscillatory technique and the Myotonometer. Intraclass correlations were used to determine the intrasession, intersession, and interrater reliability of the Myotonometer. Criterion validity was assessed via Pearson product–moment correlation between MTS measures obtained from the Myotonometer and from the damped oscillatory technique.

Results:

The Myotonometer demonstrated good intrasession (ICC3,1 = .807) and interrater reliability (ICC2,k = .830) and moderate intersession reliability (ICC2,k = .693). However, it did not provide a valid measurement of MTS compared with the damped oscillatory technique (r = .346, P = .061).

Conclusions:

The Myotonometer does not provide a valid measure of active hamstring MTS. Although the Myotonometer does not measure active MTS, it possesses good reliability and portability and could be used clinically to measure tissue compliance, muscle tone, or spasticity associated with multiple musculoskeletal disorders. Future research should focus on portable and clinically applicable tools to measure active hamstring MTS in efforts to prevent and monitor injuries.

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Kathryn Mills, Aula Idris, Thu-An Pham, John Porte, Mark Wiggins and Manolya Kavakli

healthy individuals (61% female, age: 23.46 [2.29] y; height: 172.7 [9.9] cm; and weight: 66.87 [12.8] kg) was recruited. Participants were excluded if they had a history of knee ligament injury, patellofemoral pain, or known motion sickness when experiencing VR. Ethics approval for the study was granted

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Nathan Millikan, Dustin R. Grooms, Brett Hoffman and Janet E. Simon

cognitive variables interact, 19 , 38 as video analysis indicates many noncontact anterior cruciate ligament injuries occur almost immediately after initial contact during landing, cutting, and movement with the knee in full extension, 19 , 39 , 40 and typically with many players or visual distractors in

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Jonathan Sinclair and Paul J. Taylor

Sports Med . 2014 ; 48 : 871 – 877 . PubMed ID: 24100287 doi:10.1136/bjsports-2013-092538 24100287 10.1136/bjsports-2013-092538 3. Boden BP , Torg JS , Knowles SB , Hewett TE . Video analysis of anterior cruciate ligament injury abnormalities in hip and ankle kinematics . Am J Sports Med

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Scott Bonnette, Christopher A. DiCesare, Adam W. Kiefer, Michael A. Riley, Kim D. Barber Foss, Staci Thomas, Katie Kitchen, Jed A. Diekfuss and Gregory D. Myer

(1 ACL injury and 1 medial collateral ligament injury); however, the dates of occurrence were not within 5 years of their participation and performance was not unusual when compared with other participants. The study was approved by Cincinnati Children’s Hospital and Medical Center’s Institutional

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Azahara Fort-Vanmeerhaeghe, Ariadna Benet, Sergi Mirada, Alicia M. Montalvo and Gregory D. Myer

adolescent and adult populations, 9 , 25 , 35 – 37 which is thought to place them at increased risk of noncontact ACL injuries. In addition to ACL injuries, dynamic knee valgus is also associated with patellofemoral pain and medial collateral knee ligament injuries. 8 , 38 , 39 However, research regarding

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Jonathon R. Staples, Kevin A. Schafer, Matthew V. Smith, John Motley, Mark Halstead, Andrew Blackman, Amanda Haas, Karen Steger-May, Matthew J. Matava, Rick W. Wright and Robert H. Brophy

correlated with episodes of instability or giving way. In addition, alterations in core dynamic stability have demonstrated clinic significance as a risk factor for knee injury. Zazulak et al 15 demonstrated that increased lateral displacement of the trunk most strongly predicted ligament injury in the knee