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Kilohertz Frequency Alternating Current Induces Less Evoked Torque and Less Neuromuscular Efficiency Than Pulsed Current in Healthy People: A Randomized Crossover Trial

Isabel de Almeida Paz, Francesca Chaida Sonda, Matias Fröhlich, João Luiz Quagliotti Durigan, and Marco Aurélio Vaz

Context: Pulsed current and kilohertz frequency alternating current are 2 types of neuromuscular electrical stimulation (NMES) currents often used by clinicians during rehabilitation. However, the low methodological quality and the different NMES parameters and protocols used in several studies might explain their inconclusive results in terms of their effects in the evoked torque and the discomfort level. In addition, the neuromuscular efficiency (ie, the NMES current type that evokes the highest torque with the lowest current intensity) has not been established yet. Therefore, our objective was to compare the evoked torque, current intensity, neuromuscular efficiency (evoked torque/current intensity ratio), and discomfort between pulsed current and kilohertz frequency alternating current in healthy people. Design: A double-blind, randomized crossover trial. Methods: Thirty healthy men (23.2 [4.5] y) participated in the study. Each participant was randomized to 4 current settings: 2 kilohertz frequency alternating currents with 2.5 kHz of carrier frequency and similar pulse duration (0.4 ms) and burst frequency (100 Hz) but with different burst duty cycles (20% and 50%) and burst durations (2 and 5 ms); and 2 pulsed currents with similar pulse frequency (100 Hz) and different pulse duration (2 and 0.4 ms). The evoked torque, current intensity at the maximal tolerated intensity, neuromuscular efficiency, and discomfort level were evaluated. Results: Both pulsed currents generated higher evoked torque than the kilohertz frequency alternating currents, despite the similar between-currents discomfort levels. The 2 ms pulsed current showed lower current intensity and higher neuromuscular efficiency compared with both alternated currents and with the 0.4 ms pulsed current. Conclusions: The higher evoked torque, higher neuromuscular efficiency, and similar discomfort of the 2 ms pulsed current compared with 2.5-kHz frequency alternating current suggests this current as the best choice for clinicians to use in NMES-based protocols.

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Single-Leg Hop Stabilization Throughout Concussion Recovery: A Preliminary Biomechanical Assessment

Landon B. Lempke, Matthew C. Hoch, Jarrod A. Call, Julianne D. Schmidt, and Robert C. Lynall

Context: Aberrant movement patterns among individuals with concussion history have been reported during sport-related movement. However, the acute postconcussion kinematic and kinetic biomechanical movement patterns during a rapid acceleration–deceleration task have not been profiled and leaves their progressive trajectory unknown. Our study aimed to examine single-leg hop stabilization kinematics and kinetics between concussed and healthy-matched controls acutely (≤7 d) and when asymptomatic (≤72 h of symptom resolution). Design: Prospective, cohort laboratory study. Methods: Ten concussed (60% male; 19.2 [0.9] y; 178.7 [14.0] cm; 71.3 [18.0] kg) and 10 matched controls (60% male; 19.5 [1.2] y; 176.1 [12.6] cm; 71.0 [17.0] kg) completed the single-leg hop stabilization task under single and dual task (subtracting by 6’s or 7’s) at both time points. Participants stood on a 30-cm tall box set 50% of their height behind force plates while in an athletic stance. A synchronized light was illuminated randomly, queuing participants to initiate the movement as rapidly as possible. Participants then jumped forward, landed on their nondominant leg, and were instructed to reach and maintain stabilization as fast as possible upon ground contact. We used 2 (group) × 2 (time) mixed-model analyses of variance to compare single-leg hop stabilization outcomes separately during single and dual task. Results: We observed a significant main group effect for single-task ankle plantarflexion moment, with greater normalized torque (mean difference = 0.03 N·m/body weight; P = .048, g = 1.18) for concussed individuals across time points. A significant interaction effect for single-task reaction time indicated that concussed individuals had slower performance acutely relative to asymptomatic (mean difference = 0.09 s; P = .015, g = 0.64), while control group performance was stable. No other main or interaction effects for single-leg hop stabilization task metrics were present during single and dual task (P ≥ .051). Conclusions: Greater ankle plantarflexion torque coupled with slower reaction time may indicate stiff, conservative single-leg hop stabilization performance acutely following concussion. Our findings shed preliminary light on the recovery trajectories of biomechanical alterations following concussion and provide specific kinematic and kinetic focal points for future research.

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A Systematic Review of Lower-Body Kinematic and Strength Factors Associated With Pitch Velocity in Adult Baseball Pitchers

Joseph E. Manzi, Jonathan S. Yu, Suleiman Y. Sudah, Mark Wishman, Theodore Quan, Alexander Koo, Kyle N. Kunze, Michelle Kew, James B. Carr II, Michael Fu, and Joshua S. Dines

Context: Ball velocity for baseball pitchers is influenced by a multitude of factors along the kinetic chain. While a vast amount of data currently exist exploring lower-extremity kinematic and strength factors in baseball pitchers, no previous study has systematically reviewed the available literature. Objective: The aim of this systematic review was to perform a comprehensive assessment of the available literature investigating the association between lower-extremity kinematic and strength parameters and pitch velocity in adult pitchers. Evidence Acquisition: Cross-sectional studies that investigated the association between lower-body kinematic and strength factors and ball velocity in adult pitchers were selected. A methodological index for nonrandomized studies checklist was used to evaluate the quality of all included studies. Evidence Synthesis: Seventeen studies met the inclusion criteria comprising a total of 909 pitchers (65%, professional, 33% college, and 3% recreational). The most studied elements were hip strength and stride length. The mean methodological index for nonrandomized studies score was 11.75 of 16 (range = 10–14). Pitch velocity was found to be influenced by several lower-body kinematic and strength factors including the following: (1) hip range of motion and strength of muscles around the hip and pelvis, (2) alterations in stride length, (3) alterations in lead knee flexion/extension, and (4) several pelvic and trunk spatial relationships throughout the throwing phase. Conclusions: Based on this review, we conclude that hip strength is a well-established predictor of increased pitch velocity in adult pitchers. Further studies in adult pitchers are needed to elucidate the effect of stride length on pitch velocity given mixed results across multiple studies. This study can provide a basis for trainers and coaches to consider the importance of lower-extremity muscle strengthening as a means by which adult pitchers can improve pitching performance.

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Computerized Cognitive Function Does Not Correlate With Choice Reaction Time During a Hopping Task

Ke’La H. Porter, Nathan Morelli, Nicholas R. Heebner, Jenna Wilson, Allison M. Parks, Dong Y. Han, and Matthew C. Hoch

Context: Cognitive performance has been shown to be associated with musculoskeletal injury risk. Cognitive assessments are often administered in controlled environments despite sport settings challenging cognition in uncontrolled, less predictable environments. Cognitive assessments should be representative of sport demands; thus, integrating motor with cognitive assessments may be more clinically relevant. Accordingly, the purpose of this research was to investigate the relationship between tablet-based cognitive tests and choice reaction time during a hopping task. Design: Cross-sectional. Methods: A total of 20 healthy participants volunteered to participate. Participants completed 3 tablet-based cognitive assessments. Average raw response time and fully corrected scores were used for analysis. In addition, participants completed a choice reaction hopping task to capture neuromuscular–cognitive reaction time. Participants completed a forward hop over a hurdle, landing on a single limb. Light sensors were utilized for the choice reaction component to capture reaction time in seconds, cue them when to hop, and indicate the landing limb. The relationship between the tablet-based cognitive assessments and reaction time during a hopping task was examined with Pearson correlations (α = .05). Results: The choice reaction time from the hop task had a negligible correlation (r = −.20−.07) to the fully corrected tablet-based cognitive tests. The choice reaction time from the hop task had a negligible correlation (r = .02) to the average response time of the Pattern Comparison Processing Speed Test and a low correlation (r = .34−.36) to the Dimensional Change Card Sort Test and Flanker Inhibitory Control and Attention Test. Conclusions: This study determined that tablet-based cognitive assessments had trivial relationships to choice reaction time during a hopping task. This research has implications as clinicians aim to evaluate and analyze cognitive performance. Although reaction time was a critical component of all the assessments in this study, an individual’s performance on a tablet-based assessment does not indicate performance during a functional reaction time assessment.

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The Effect of Real-Time Tibial Acceleration Feedback on Running Biomechanics During Gait Retraining: A Systematic Review and Meta-Analysis

Xiaohan Li, Junwu Yu, Jianjuan Bai, Huiming Huang, Shanshan Ying, Aiwen Wang, and Ping Wang

Objectives: To explore the immediate and retention effect of real-time tibial acceleration feedback on running biomechanics during gait retraining. Methods: Five electronic databases were searched to identify relevant studies published before May 2022. The included studies were evaluated for methodological quality and bias risk, and data were extracted. A meta-analysis was conducted on the primary outcomes, including peak tibial acceleration (PTA) and vertical ground reaction force. Subgroup analysis was performed by gender, feedback criterion, mode, dosage, fading, retention period, and running environment to evaluate the source of heterogeneity. Qualitative analysis was performed to describe other variables. Results: Fourteen studies (174 participants) were eligible. Meta-analysis showed that real-time tibial acceleration feedback reduced PTA (P < .01, P < .01), vertical impact peak (P = .004, P < .01), vertical average loading rate (P < .01, P < .01), and vertical instantaneous loading rate (P < .01, P < .01) after feedback and during retention period (5 min–12 mo). Subgroup analysis showed that the immediate effect of vertical impact peak was more noticeable with mixed gender (P = .005) and fading feedback (P = .005) conditions, and the retention effect of PTA was more noticeable with high feedback dosage (P < .01) and fading feedback (P < .01) conditions. Conclusions: Real-time tibial acceleration feedback can reduce PTA and vertical ground reaction force during gait retraining, and for periods of 5 minutes to 12 months when the feedback is removed.

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Rasch Calibration of the International Knee Documentation Committee Subjective Knee Form

Seungho Ryu, Ryan Richardson, Adam C. Cady, Ashley Reeves, Madeline P. Casanova, and Russell T. Baker

Context: Among numerous knee-related patient-reported outcome measures, the International Knee Documentation Committee Subjective Knee Form (IKDC-SKF) has been used across a wide variety of knee pathologies. However, traditional validation procedures (classical test theory) and existing studies (estimating item parameters) have limitations in establishing the measurement properties of the IKDC-SKF. Rasch analysis reveals a strong validation approach to improve IKDC-SKF clinical interpretation with larger samples. Objective: To assess psychometric properties, including differential item functioning, of the IKDC-SKF as a patient-reported measure of knee function. Design: Cross-sectional study. Setting: Secondary data. Data were extracted from the cloud-based orthopedic and sports medicine global registry Surgical Outcome System (Arthrex). Patients: A total of 1725 individuals who underwent an arthroscopic knee procedure and completed all items on the IKDC-SKF. Main Outcome Measure(s): Rasch analysis including model-data fit, rating scale’s function, item-person map (distribution of item difficulty and person ability), and differential item functioning (sex and age groups) was used to evaluate the psychometric properties of the IKDC-SKF. Results: Ten misfit items were found and removed. The 5-point Likert scale of the 9-item IKDC-SKF worked well. Item difficulty ranged from 0.58 to 0.81 logits, and person’s knee function had ranged from –5.56 to 4.86 logits, with a wide distribution. The IKDC-SKF was found to function similarly for sex (male vs female) and age. Conclusions: Rasch analysis identified a unidimensional structure retaining 9 of the original IKDC-SKF items; however, a more comprehensive inventory is necessary to assess a wider range of knee function and improve measurement validity.

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Activation of Anterolateral Abdominal Muscles During Sling Bridge Exercises: Comparison of Different Pelvic Positions

Seungmin Kim, Jhosedyn Carolaym Salazar Fajardo, and BumChul Yoon

Context: Inappropriate activation of the anterolateral abdominal muscles affects the stability of the lumbopelvic zone and increases the appearance of pain and lesion in the area. Therefore, ways to improve its effective contraction are crucial in rehabilitation. The aim of this study was to compare the activation of the transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles in 3 different pelvic positions (down pelvis [DP], horizontal pelvis [HP], and up pelvis [UP]) during sling bridge exercise (SBE) to determinate which position is more effective to promote a correct contraction of the anterolateral abdominal muscles. Design: Cross-sectional study. Methods: Fifteen participants performed 3 variations (DP, HP, and UP) of a one-legged exercise called “supine pelvic lift” on a sling device. The thicknesses of the TrA, IO, and EO were recorded at rest and at the 3 positions using ultrasound imaging. Thickness, change ratio, lateral slide of TrA, and preferential and contraction activation ratio of TrA, IO, and EO were analyzed. Results: TrA and IO showed greater activation (P = .01) in the UP position than the other pelvic positions. In addition, UP position decreased the activation of the EO (P = .01). Conclusion: Based on the results of this study, SBE in the UP position has the potential to improve normal contraction patterns of the musculature and can be used in future intervention of the lumbopelvic zone.

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Body Composition Asymmetry in University Rugby Players: Influence of Sex, Position, and Injury

Tamara R. Cohen, Brent Rosenstein, Amanda Rizk, Stephane Frenette, and Maryse Fortin

Context: Measures of side-to-side asymmetry in body composition may help identify players who are predisposed to lower limb injuries (LLI) or lower back pain (LBP). This study aimed to examine (1) side-to-side asymmetry in college rugby players according to sex and position and (2) whether side-to-side asymmetry is associated with LBP or LLI. Design: Cross-sectional study. Methods: Thirty-six rugby players (61% female) underwent a dual-energy X-ray absorptiometry assessment for total and regional (appendicular, truncal) outcomes of fat mass, lean mass, and bone mass. A subsample (n = 23) of players had a second dual-energy X-ray absorptiometry assessment 2 months postbaseline. Two-way analysis of variance was used to assess the effect of position (forward and backs) and sex on body composition asymmetry. Student paired t tests were used to assess side-to-side difference in body composition and compare baseline and follow-up measures. Logistic regression was used to assess possible associations between LLI, LBP, and the degree of side-to-side asymmetry in body composition. Results: Male players had greater asymmetry in arm bone mass compared with female players (P = .026), and trunk fat mass asymmetry was greater in forwards as compared with backs (P = .017). Forwards had significantly greater fat mass (P = .004) and percentage of fat (P = .048) on the right leg compared with the left. Backs had significantly greater bone mass in the right arm compared with the left (P = .015). From baseline to postseason, forwards had a significant increase in side-to-side asymmetry in arm lean mass (P = .006) and a significant decrease in side-to-side asymmetry in leg fat mass (P = .032). In backs, side-to-side asymmetry at baseline compared with postseason was significantly different (P = .011) for trunk fat mass. There were no significant associations between body composition asymmetry, LLI, or LBP by sex or position. Conclusion: Our results revealed the presence of side-to-side asymmetries in body composition in university rugby players between sex and position. The amount of asymmetry, however, was not associated with LBP and LLI.

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Volume 32 (2023): Issue 2 (Feb 2023): Special Section: Ankle Outcomes and Large Datasets

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Mental Fatigue Uniquely Influences Drop Landing Biomechanics for Individuals With a Concussion History

Eric J. Shumski, Tricia M. Kasamatsu, Kathleen S. Wilson, and Derek N. Pamukoff

Context: Induced mental fatigue negatively impacts sport performance and neurocognition. However, it is unclear how induced mental fatigue influences landing biomechanics. The purpose of this study was to examine the influence of mental fatigue on drop landing biomechanics in individuals with and without a concussion history. Design: Crossover design. Methods: Forty-eight (24 per group) recreationally active individuals were matched on age (±3 y), sex, and body mass index (±1 kg/m2). All participants completed an experimental (30-min Stroop task) and control (30-min reading magazines) intervention on separate days separated by a minimum of 24 hours. Drop landings were performed before and after both interventions. Outcomes included peak vertical ground reaction force (vGRF), vertical loading rate (VLR), knee flexion angle, knee abduction angle, external knee flexion moment, external knee abduction moment, and initial ground contact knee flexion and knee abduction angles. Separate 2 (group) × 2 (intervention) between-within analyses of covariance compared drop landing outcomes. Each group’s average pre-Stroop and premagazine outcomes were covariates. Results: There was a significant interaction for vGRF (P = .033, η p 2 = .097 ) and VLR (P = .0497, η p 2 = .083 ). The vGRF simple effects were not statistically significantly (P range = .052–.325). However, individuals with a concussion history displayed a medium effect size for greater vGRF post-Stroop compared with their own postmagazine vGRF (mean difference (95% confidence interval [95% CI] = 0.163 (–0.002 to 0.327) bodyweight (BW), p =.052, η p 2 = .081 . In contrast, the control group displayed a small effect size (mean difference [95% CI] = 0.095 [–0.069 to 0.259] BW, p =.251, η p 2 = .029 ). Individuals with a concussion history displayed greater VLR post-Stroop compared with controls (mean difference [95% CI], 26.29 [6.19 to 46.40] BW/s, P = .012, η p 2 = .134 ) and their own postmagazine values (mean difference [95% CI] = 32.61 [7.80 to 57.42] BW/s, p =.011, η p 2 = .135 ). Conclusion: Mental fatigue leads to greater VLR for individuals with a concussion history. Athletic competition and activities of daily living can increase mental fatigue. Training programs may seek to teach mental fatigue reducing strategies to athletes with a concussion history.