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Maria K. Talarico, Robert C. Lynall, Timothy C. Mauntel, Erin B. Wasserman, Darin A. Padua and Jason P. Mihalik

Although single-leg squats are a common dynamic balance clinical assessment, little is known about the relationship between parameters that influence squat movement and postural control performance. The objective of this study was to determine the relationships between squat parameters (speed and depth) and postural control under single task and dual task. A total of 30 healthy college students performed single-leg squats under single task and dual task with Stroop. Random-intercepts generalized linear mixed models determined the effect of squat parameters on center of pressure (CoP) parameters. For each 1-cm·s−1 increase in squat speed, sway range (mediolateral: β = −0.03; anteroposterior: β = −0.05) and area (β = −0.25) decreased, whereas sway speed (mediolateral: β = 0.05; anteroposterior: β = 0.29; total: β = 0.29) increased. For each 1-cm increase in squat depth, sway range (mediolateral: β = 0.05; anteroposterior: β = 0.20) and area (β = 0.72) increased, whereas sway speed (anteroposterior: β = −0.14; total: β = −0.14) decreased. Compared with single task, the association between total and anteroposterior sway speed and squat speed was stronger under dual task. Clinicians and researchers should consider monitoring squat speed and depth when assessing dynamic balance during single-leg squats, as these parameters influence postural control, especially under dual task.

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Patrick Ippersiel, Richard Preuss and Shawn M. Robbins

Continuous relative phase (CRP) analysis using the Hilbert transform is prone to end effects. The purpose was to investigate the impact of padding techniques (reflection, spline extrapolation, extraneous data, and unpadded) on end effects following Hilbert-transformed CRP calculations, using sinusoidal, nonsinusoidal, and kinematic data from a repeated sit-to-stand-to-sit task in adults with low back pain (n = 16, mean age = 30 y). CRP angles were determined using a Hilbert transform of sinusoidal and nonsinusoidal signals with set phase shifts, and for the left thigh/sacrum segments. Root mean square difference and true error compared test signals with a gold standard, for the start, end, and full periods, for all data. Mean difference and 95% bootstrapped confidence intervals were calculated to compare padding techniques using kinematic data. The unpadded approach showed near-negligible error using sinusoidal data across all periods. No approach was clearly superior for nonsinusoidal data. Spline extrapolation showed significantly less root mean square difference (all periods) when compared with double reflection (full period: mean difference = 2.11; 95% confidence interval, 1.41 to 2.79) and unpadded approaches (full period: mean difference = −15.8; 95% confidence interval, −18.9 to −12.8). Padding sinusoidal data when performing CRP analyses are unnecessary. When extraneous data have not been collected, our findings recommend padding using a spline to minimize data distortion following Hilbert-transformed CRP analyses.

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Nili Steinberg, Roger Adams, Oren Tirosh, Janet Karin and Gordon Waddington

Context: Ankle sprains are common among adolescent ballet dancers and may be attributed to inadequate ankle proprioception. Thus, a short period of training utilizing proprioceptive activities requires evaluation. Objective: To assess training conducted for 3 or 6 weeks on a textured-surface balance board using ankle proprioception scores for ballet dancers with and without chronic ankle instability, and with and without previous ankle sprain (PAS). Design: Intervention study. Setting: The Australian Ballet School. Participants: Forty-two ballet dancers, aged 14–18 years. Interventions: Dancers randomized into 2 groups: group 1 undertook 1 minute of balance board training daily for 3 weeks; group 2 undertook the same training for 6 weeks. Main Outcome Measures: Preintervention, Cumberland Ankle Instability Tool questionnaire data were collected, and PAS during the last 2 years was reported. Active ankle inversion movement discrimination ability was tested immediately pre and post intervention and at 3 and 4 weeks. Results: Ankle discrimination acuity scores improved over time for both groups, with a performance decline associated with the early cessation of training for group 1 (P = .04). While dancers with PAS had significantly worse scores at the first test, before balance board training began (P < .01), no significant differences in scores at any test occasion were found between dancers with and without chronic ankle instability. A significantly faster rate of improvement in ankle discrimination ability score over the 4 test occasions was found for dancers with PAS (P = .002). Conclusions: Three weeks of textured balance board training improved the ankle discrimination ability of ballet dancers regardless of their reported level of chronic ankle instability and at a faster rate for dancers with PAS. Previous ankle sprain was associated with a lower level of ankle discrimination ability; however, following 3 weeks of balance board training, previously injured dancers had significantly improved their ankle discrimination acuity scores.

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Alissa C. Rhode, Lauren M. Lavelle and David C. Berry

Clinical Scenario: ReBound is a portable shortwave diathermy unit used to heat tissues using the same principle as induction drum shortwave diathermy. It is unclear if ReBound can vigorously (4°C) heat intramuscular tissue as efficiently as other thermal agents. Clinical Question: In adults (P), is ReBound diathermy (I) compared with other thermal agents (C) effective at increasing intramuscular tissue temperature by 4°C (O)? Summary of Key Findings: (1) Three studies were included for review, all randomized crossover studies. (2) All studies agreed ReBound does not achieve vigorous (4°C) heating effects during a 30-minute treatment to the triceps surae muscle (depth = 1 and 3 cm). (3) Studies agreed that the heat generated by ReBound dissipates slower than (P < .001) or similar to pulsed shortwave diathermy at 3 cm and faster than moist hot packs (P < .001) at 1 cm. (4) One study found that intramuscular tissue temperatures increased more with ReBound (3.69°C [1.50°C]) than moist hot packs (2.82°C [0.90°C]) at superficial depths (1 cm, d = 0.70). (5) Two studies compared ReBound with MegaPulse II pulsed shortwave diathermy at a 3 cm depth. One found that the MegaPulse II increased intramuscular tissue temperature by 4.32°C (1.79°C) compared with the ReBound’s 2.31°C (0.87°C) increase (d = 1.43). The final study reported that the MegaPulse II increased triceps surae muscle temperature by 3.47°C (0.92°C) versus ReBound at 3.08°C (1.19°C) (d = 0.37). (6) The combined results are an increase of 3.81 (1.38°C) for the MegaPulse II and 2.77 (1.12°C) for ReBound (d = 0.83). Clinical Bottom Line: Results strongly indicate that the ReBound should not be used for vigorous (4°C) heating effects in the triceps surae muscle at 1 and 3 cm. Clinicians can use ReBound when traveling or instead of moist hot packs for moderate (2°C–3°C) heating effects at deep and superficial levels (1 and 3 cm) for large treatment areas with subcutaneous fat thickness <15 mm. Strength of Recommendation: Consistent level B findings indicate that ReBound does not achieve vigorous heating effects (4°C).

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Cindy N. Nguyen, Reuben N. Clements, Lucas A. Porter, Nicole E. Clements, Matthew D. Gray, Dustin J. Killian and Russell T. Baker

Context: The clinical reaction time (RTclin) test has been recommended as a valid test for assessing concussion and determining recovery of reaction time function following concussion. However, it is unknown whether repeat assessment, as is used in postconcussion testing, is affected by learning or practice phenomena. Objective: To determine if a practice or learning effect is present with serial administration of the RTclin test. Design: Randomized control trial. Setting: University athletic training clinics. Participants: A total of 112 healthy collegiate athletes (age = 19.46 [1.34] y). Interventions: The control group completed the RTclin test on days 1 and 60. The experimental group completed the RTclin test on days 1, 2, 3, 7, and 60. Main Outcome Measure: Reaction time as measured with the RTclin test. Results: The difference in RTclin test performance from day 1 to day 60 was not significant (mean change = −2.77 [14.46] ms, P = .42, 95% confidence intervals, −6.40 to 0.862) between groups. The experimental group experienced significant improvement (λ = 0.784, F4,49 = 3.365, P = .02, η2 = .216, power = 0.81) with acute repeat testing. However, post hoc analysis did not reveal a significant difference between scores during the 5 test periods. Conclusions: The results suggest serial administration of the RTclin test does not produce a practice or learning effect. Clinicians, however, should be cautious as the results do provide evidence patients may demonstrate improved scores when testing occurs on repetitive days after initial exposure to the test.

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Hooman Minoonejad, Mohammad Karimizadeh Ardakani, Reza Rajabi, Erik A. Wikstrom and Ali Sharifnezhad

Context: Neuromuscular control deficit has been reported in people with chronic ankle instability (CAI) and hopping exercises have been recommended as a functional training tool to prevent lower limb injury, but its effects on lower-extremity neuromuscular control in those with CAI are unclear. Objective: To investigate the effect of hop stabilization training on neuromuscular control and self-reported function in college basketball players with CAI. Study Design: A randomized controlled trial. Setting: Research Laboratory. Patients (or Other Participants): A total of 28 college basketball players with CAI were randomly assigned to the experimental hop stabilization group (age = 22.78 [3.09] y, weight = 82.59 [9.51] kg, and height = 187.96 [7.93] cm) or the control group (age = 22.57 [2.76] y, weight = 78.35 [7.02] kg, and height = 185.69 [7.28] cm). Intervention: Participants in the experimental group performed supervised hop stabilization exercises 3 times per week for 6 weeks. The control group received no intervention. Main Outcome Measures: Preparatory and reactive muscle activation levels and muscle onset time were assessed from 8 lower-extremity muscles during a jump-landing task before and after the 6-week training program. Results: Significant improvements in preparatory muscle activation, reactive muscle activation, and muscle onset time were noted across the lower-extremity in the experimental group relative to the control group (P < .05). Self-reported function also improved in the experimental group relative to the control group (P < .05). Conclusions: These findings demonstrate that 6 weeks of hop stabilization training is effective in improving neuromuscular control and self-reported function in college basketball players with CAI. Hop stabilization exercises can be incorporated into the rehabilitation program for CAI.

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David R. Howell, Thomas A. Buckley, Brant Berkstresser, Francis Wang and William P. Meehan III

The purpose of this study was to identify the rate of abnormal single-task and dual-task gait performance following concussion compared to uninjured controls using previously established normative reference values. The authors examined athletes with a concussion (n = 54; mean age = 20.3 [1.1] y, 46% female, tested 2.9 [1.5] d postinjury), and healthy controls were tested during their preseason baseline examination (n = 60; mean age = 18.9 [0.7] y, 37% female). Participants completed an instrumented single-/dual-task gait evaluation. Outcome variables included average walking speed, cadence, and step length. A significantly greater number of those with concussion walked with abnormal dual-task gait speed compared with the control group (56% vs 30%, P = .01). After adjusting for potential confounding variables (age, concussion history, symptom severity, and sleep), concussion was associated with lower dual-task gait speed (β = −0.150; 95% confidence interval [CI] = −0.252 to −0.047), cadence (β = −8.179; 95% CI = −14.49 to −1.871), and stride length (β = −0.109; 95% CI = −0.204 to −0.014). Although group analyses indicated that those with a concussion performed worse on single-task and dual-task gait compared with controls, a higher rate of abnormal gait was detected for the concussion group compared with the control group for dual-task gait speed only. Dual-task gait speed, therefore, may be considered as a measure to compare against normative values to detect postconcussion impairments.

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Han-Kyu Park, Dong-Woo Kim and Tae-Ho Kim

Context: Several factors, such as balance and respiration training programs, have been identified as contributing to a shooting performance. However, little is known about the benefits of these programs on the shooting records of adolescent air rifle athletes. Objective: The purpose of this study was to investigate whether balance and respiration training can contribute to the shooting performance required for adolescent air rifle shooting athletes. Design: Case-control study. Setting: Shooting range. Participants: A total of 21 adolescent air rifle athletes were recruited from the local school community and assigned to an experimental (n = 11; EG) or control (n = 10; CG) group. Intervention: The EG performed respiration and balance training for 30 minutes 3 times a week for 6 weeks, and the CG performed balance training only. Main Outcome Measures: Data were collected on the respiratory function, muscle activity, and shooting record before and after the 6-week intervention. Results: The forced vital capacity (FVC), forced expired volume in 1 second (FEV1), FEV1 as a percentage of FVC, peak expiratory flow, and maximum voluntary ventilation were significantly increased in the EG, and FEV1 as a percentage of FVC was significantly increased in the CG (P < .05). The FVC and peak expiratory flow postintervention were significantly different between the groups (P < .05). The activity of the right internal oblique (IO) and left IO muscles of the FVC were significantly different in the EG (P < .05). Within-group changes in right external oblique, right IO, and left IO of the maximum voluntary ventilation were significantly increased in the EG (P < .05). The right IO and left IO activity improved more significantly in the EG than CG (P < .05). There was no difference between the groups with respect to the shooting records. Conclusions: The clinical significance of this study is the balance and respiration training affected the respiration function capacity and muscle activity, but did not affect the shooting record. Nevertheless, these training are a potential approach method to improve athletes’ shooting record.

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Patricia M. Kelshaw, Trenton E. Gould, Mark Jesunathadas, Nelson Cortes, Amanda Caswell, Elizabeth D. Edwards and Shane V. Caswell

Girls’ lacrosse participation and head injury rates have increased within the past decade. In response, optional headgear was implemented following the recently developed ASTM International lacrosse headgear performance standards. It remains unknown how lacrosse headgear responds to blunt impacts after use. Our purpose was to compare the peak linear acceleration between girls’ lacrosse headgear conditions (pristine and used) during blunt impacts. Pristine headgear (n = 10) were tested in their original condition and used headgear (n = 10) were worn for an entire competitive season. A Cadex Monorail Impactor impacted all headgear following ASTM standards (F1446-15b, F2220-15, and F3137-15) in the required testing locations. A 2 × 7 repeated-measures analysis of variance compared peak linear acceleration among headgear conditions and impact locations with a simple effects analysis planned comparison. There was no difference between headgear conditions for peak linear acceleration (pristine: 47.12 [13.92] g; used: 46.62 [14.84] g; F = 2.11, P > .05). A main effect for impact location (F = 983.52, P < .01), and an interaction effect of condition and impact location (F = 12.79, P < .01) were observed. All headgear, regardless of condition, met the ASTM performance standard. This suggests that headgear performance may not degrade subsequent to a single season of high school girls’ lacrosse.

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Jeffrey D. Simpson, Ethan M. Stewart, Anastasia M. Mosby, David M. Macias, Harish Chander and Adam C. Knight

Context: Lateral ankle sprains are a common injury in which the mechanics of injury have been extensively studied. However, the anticipatory mechanisms to ankle inversion perturbations are not well understood. Objective: To examine lower-extremity kinematics, including spatial and temporal variables of maximum inversion displacement and maximum inversion velocity, during landings on a tilted surface using a new experimental protocol to replicate a lateral ankle sprain. Setting: Three-dimensional motion analysis laboratory. Participants: A total of 23 healthy adults. Interventions: Participants completed unexpected (UE) and expected (EXP) unilateral landings onto a tilted surface rotated 25° in the frontal plane from a height of 30 cm. Main Outcome Measures: Ankle, knee, and hip kinematics at each discrete time point from 150 ms pre-initial contact (IC) to 150 ms post-IC, in addition to maximum ankle inversion and maximum inversion velocity, were compared between UE and EXP landings. Results: The UE landing produced significantly greater maximum inversion displacement (P < .01) and maximum inversion velocity (P = .02) than the EXP landing. Significantly less ankle inversion and internal rotation were found during pre-IC, whereas during post-IC, significantly greater ankle inversion, ankle internal rotation, knee flexion, and knee abduction were observed for the UE landing (P < .05). In addition, significantly less hip flexion and hip adduction were observed for the UE landing during pre-IC and post-IC (P < .05). Conclusions: Differences in the UE and EXP landings indicate the experimental protocol presented a UE inversion perturbation that approximates the mechanism of a lateral ankle sprain. Furthermore, knowledge of the inversion perturbation elicited a hip-dominant strategy, which may be utilized to assist with ankle joint stabilization during landing to further protect the lateral ankle from injury.