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Nathaniel A. Bates, Nathan D. Schilaty, Ryo Ueno, and Timothy E. Hewett

Anterior cruciate ligament (ACL) injury videos estimate that rupture occurs within 50 milliseconds of initial contact, but are limited by imprecise timing and nondirect data acquisition. The objective of this study was to precisely quantify the timing associated with ligament strain during simulated landing and injury events. The hypotheses tested were that the timing of peak strain following initial contact would differ between ligaments and that peak strain timing would be independent of the injury-risk profile emulated during simulated landing. A mechanical impact simulator was used to perform landing simulations based on various injury-risk profiles that were applied to each specimen in a block-randomized order. The ACL and medial collateral ligament were instrumented with strain gauges that recorded continuously. The data from 35 lower-extremity specimens were included for analysis. Analysis of variance and Kruskal–Wallis tests were used to determine the differences between timing and profiles. The mean time to peak strain was 53 (24) milliseconds for the ACL and 58 (35) milliseconds for the medial collateral ligament. The time to peak ACL strain ranged from 48 to 61 milliseconds, but the timing differences were not significant between profiles. Strain timing was independent of injury-risk profile. Noncontact ACL injuries are expected to occur between 0 and 61 milliseconds after initial contact. Both ligaments reached peak strain within the same time frame.

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Vagner D.O. Tavares, Kell G. da Costa, Daniel A.R. Cabral, Maria L.M. Rego, Menna Price, and Eduardo B. Fontes

Impaired inhibitory control has been shown in individuals with substance use disorder (SUD). Cardiorespiratory fitness has been described as a potential factor to improve inhibitory control; however, the benefits in individuals with SUD are unclear. The aim of this study was to investigate the relationship between cardiorespiratory fitness with general and drug-specific inhibitory control in individuals with SUD. Sixty-two male participants under treatment for SUD performed a general and drug-specific inhibitory control test (go/no-go) and a cardiorespiratory fitness test. Cardiorespiratory fitness, age, and years of drug use were inversely associated with reaction time for both general and drug-specific inhibitory control. In addition, the regression models showed that cardiorespiratory fitness predicts general and drug-specific inhibitory control adjusted for age and time of drug use. However, cardiorespiratory fitness predicts equally both general and drug-specific inhibitory control. These findings suggest that increasing cardiorespiratory fitness could provide benefits in the inhibitory function of individuals with SUD.

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Clara Teixidor-Batlle, Carles Ventura Vall-llovera, Justine J. Reel, and Ana Andrés

The study purpose was to validate the psychometric properties of a Spanish-language version of the weight pressures in sport scale for male athletes. The weight pressures in sport scale for male athletes assesses risk factors associated with sport-specific weight pressures from coaches, peers, and team uniform. The scale was back translated and administered to 407 Spanish male college athletes. The sample was randomly split to perform the exploratory and confirmatory analysis. After item analysis, three items were removed. The exploratory analysis identified two latent constructs (referring to coaches and teammates pressures, and pressures due to uniform), and the confirmatory analysis produced a two-factor model (comparative fit indexSB = .946, Tucker–Lewis indexSB = .925, root mean square of approximationSB = .071, standardized root mean square residualSB = .068). The overall scale showed adequate internal consistency (α = .82) and demonstrated adequate convergent validity with the other questionnaires. The Spanish-language version of the weight pressures in sport scale for male athletes can be used to measure weight-related pressures among male athletes in sport psychology and clinical settings.

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Rebecca L. Krupenevich and Ross H. Miller

The causes of age-related differences in lower-extremity joint moments and powers are unknown. The purpose of this study was to determine the effects of highly physically active older adults walking with (1) a step length similar to young adults and (2) an upright trunk posture, on hip and ankle joint kinetics. The authors hypothesized that, compared with their self-selected walking mechanics, older adults would exhibit decreased hip kinetics and increased ankle kinetics when prescribed a young adult step length, and would exhibit decreased hip extension moments when maintaining an upright trunk posture during walking. A total of 12 active older adults (67 [5] y) and 13 active young adults (21 [3] y) walked at 1.3 m/s. The older adults also walked at 1.3 m/s with step lengths prescribed from height-matched young adults and, in a separate condition, walked with an upright trunk. The older adults did not display larger ankle kinetics or smaller hip kinetics in either condition compared to walking with a self-selected step length. These findings indicate that step length and trunk position do not primarily contribute to age-related differences in kinetics in highly active older adults and should serve as a starting point for investigating alternative explanations.

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Anderson Nascimento Guimarães, Herbert Ugrinowitsch, Juliana Bayeux Dascal, Alessandra Beggiato Porto, and Victor Hugo Alves Okazaki

According to Bernstein, the central nervous system solution to the human body’s enormous variation in movement choice and control when directing movement—the problem of degrees of freedom (DF)—is to freeze the number of possibilities at the beginning of motor learning. However, different strategies of freezing DF are observed in literature, and the means of selection of the control strategy during learning is not totally clear. This review investigated the possible effects of the class and objectives of the skill practiced on DF control strategies. The results of this review suggest that freezing or releasing the DF at the beginning of learning does not depend on the class (e.g., discrete skill class: football kick, dart throwing; continuous skill class: athletic march, handwriting) or objective of the skill (e.g., balance, velocity, and accuracy), in isolation. However, an interaction between these two skill elements seems to exist and influences the selection of the DF control strategy.

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Bill Stodart, Maria Cup, and Curtis Kindel

In current rehabilitation practice, exercise selection is commonly based on the amount of muscle recruitment demonstrated by electromyographic (EMG) analysis. A preponderance of evidence supports the concept that EMG of a muscle and torque output are positively correlated. This study was designed to investigate the relationship between surface EMG activity of the infraspinatus and torque production during exercises involving shoulder external rotation (ER). A total of 30 participants (average age = 24.6 y) performed maximum voluntary isometric contraction of ER at 5 points within the range of motion of 3 shoulder exercise positions with concomitant surface EMG recording. As a maximal internally rotated position was approached, maximum ER torque and minimum or near-minimum EMG recruitment were demonstrated. Conversely, at maximally externally rotated positions, EMG activity was greatest and torque values were lowest. An inverse relationship between joint torque output and EMG activity was established in each of the 3 exercises. The inverse relationship between EMG activity and torque output during Shoulder ER suggests that there may be additional factors warranting consideration during exercise selection. Further research may be needed to determine the relative value of electrical activity versus torque output to optimize the selection of rehabilitative exercises.

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Rasool Bagheri, Ismail Ebrahimi Takamjani, Mohammad R. Pourahmadi, Elham Jannati, Sayyed H. Fazeli, Rozita Hedayati, and Mahmood Akbari

The first purpose was to investigate the trunk muscle endurance, the second aim was to evaluate the trunk–pelvis kinematics during gait, and the third was to evaluate the relationship between trunk–pelvis kinematics and the trunk muscle endurance. Thirty participants (15 nonspecific chronic low back pain [NCLBP] and 15 healthy) were included. The authors first assessed trunk muscle endurance on endurance testing protocols. The authors next measured the trunk–pelvis kinematics during gait using a 3-dimensional motion capture system. Angular displacement, waveform pattern (CVp), and offset variability (CVo) were also examined. Statistical analysis revealed a significant difference in (1) the trunk muscle endurance and (2) sagittal, frontal, and transverse planes CVp between groups (P < .05). A significant moderate correlation was found between supine double straight-leg raise and frontal CVp (r = .521, P = .03) and transverse planes CVp (r = .442, P = .05). However, a significant moderate correlation was observed between prone double straight-leg raise and sagittal plane CVp (r = .528, P = .03) and transverse plane CVp (r = .678, P = .001). The relationship between (1) lower trunk extensor endurance with transverse and sagittal planes CVp and (2) lower abdominal muscle endurance with transverse and frontal planes CVp suggests that gait variability in these planes may result because of trunk muscle deconditioning accompanying NCLBP.