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Relationship Between Muscle Activity and Force During Suspended Bridge Exercises

Andrew Skibski, Luk Devorski, Nolan Orfield, and L. Colby Mangum

Context: Isometric core stability exercises are commonly used to target muscles of the lumbopelvic–hip complex, including the rectus abdominis (RA) and erector spinae (ES). These exercises can be implemented in rehabilitation protocols to increase muscle strength and endurance. Difficulty can be progressed by modifying the base of support or adding an unstable element. Load cells can be affixed to suspension training devices to measure force exerted through the straps during exercise. The primary purpose of this study was to assess the relationship between activity of the RA and ES to force measured through a load cell fixed to suspension straps during bilateral and unilateral suspended bridge exercises. Design: Forty asymptomatic, active individuals completed a single laboratory visit. Methods: Participants completed 2 bilateral suspended bridges and 2 unilateral suspended bridges held to failure. Surface electromyography sensors were placed over the bilateral RA and ES to quantify muscle activity (% maximum voluntary isometric contraction). A load cell was affixed to the suspension straps to measure force exerted through the straps throughout the duration of the exercise. Pearson correlations were used to determine relationships between force and muscle activity of the RA and ES throughout exercise duration. Results: Force was negatively related to RA muscle activity in bilateral suspended bridges (r = −.735 to −.842, P < .001) and unilateral suspended bridges (r = −.300 to −.707, P = .002 to <.001). Force had a positive relationship with ES muscle activity in bilateral suspended bridges (r = .689 to .791, P < .001) and unilateral suspended bridges (r = .418 to .448, P < .001). Conclusions: Suspended bridge exercises can be a valuable tool to target posterior abdominal musculature such as the ES to contribute to core stability and endurance. Load cells can be applied during suspension training to quantify the interaction between individuals and the exercise equipment.

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Relationship Between Posterior Shoulder Tightness and Lower-Limb Flexibility in College Baseball Players

Tomonobu Ishigaki, Motoki Hirokawa, Yuya Ezawa, and Masanori Yamanaka

Context: Posterior shoulder tightness evaluated as limited glenohumeral internal rotation and horizontal adduction is a risk factor for throwing-related shoulder and elbow injuries. Given that the throwing motion uses the entire body kinematics, limited lower-limb flexibility might be associated with posterior shoulder tightness. Therefore, we aimed to investigate the relationships between posterior shoulder tightness and lower-limb flexibility in college baseball players. Design : Cross-sectional study. Setting: University laboratory. Participants: Twenty-two college baseball players (20 right-handed and 2 left-handed). Methods: To investigate the relationships between glenohumeral range of motion and lower-limb flexibility using simple linear regression analysis, we measured passive range of motion of glenohumeral internal rotation and horizontal adduction, hip internal/external rotation in the prone/sitting position, ankle dorsiflexion, and quadriceps and hamstrings flexibility from both shoulders and legs. Results: Our analysis indicated that decreases in the lead leg hip external rotation in the prone position were moderately associated with limitations in glenohumeral internal rotation (R 2 = .250, β [95% confidence interval, CI] = 0.500 [0.149 to 1.392], P = .018) and horizontal adduction (R 2 = .200, β [95% CI] = 0.447 [0.051 to 1.499], P = .019) on the throwing shoulder. Furthermore, there were significant moderate relationships between decreases in glenohumeral internal rotation and limited lead leg quadriceps flexibility (R 2 = .189, β [95% CI] = 0.435 [0.019 to 1.137], P = .022), and between decreases in glenohumeral horizontal adduction and limited stance leg ankle dorsiflexion (R 2 = .243, β [95% CI] = 0.493 [0.139 to 1.438], P = .010). Conclusion: College baseball players with limited lower-limb flexibilities including the lead leg hip external rotation in the prone position, the lead leg quadriceps flexibility, and the stance leg ankle dorsiflexion showed excessive posterior shoulder tightness. The current results support the hypothesis that lower-limb flexibility is associated with posterior shoulder tightness in college baseball players.

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The Effects of Light Pressure Instrument-Assisted Soft Tissue Mobilization at Different Rates on Grip Strength and Muscle Stiffness in Healthy Individuals

Scott W. Cheatham, Nickolai Martonick, Lukas Krumpl, and Russell T. Baker

Context: Instrument-assisted soft tissue mobilization (IASTM) is a popular myofascial treatment utilized by health care professionals. Currently, there is a lack of research on the effects of a light pressure IASTM treatment on the forearm region. The purpose of this study was to explore the effects of a light pressure IASTM technique at different application rates on grip strength and muscle stiffness. This study was considered exploratory with the goal of establishing methodology for future controlled studies. Design: Observational pretest and posttest clinical study. Methods: Twenty-six healthy adults underwent one light pressure IASTM treatment to their dominant forearm muscles. Participants were allocated to 2 groups of 13 based upon treatment rate: 60 beats per minute and 120 beats per minute. Participants were tested pretreatment and posttreatment for grip strength and tissue stiffness via diagnostic ultrasound. One-way analyses of covariance were used to assess group differences posttreatment for grip strength and tissue stiffness. Results: Statistically significant posttreatment changes for grip strength and tissue stiffness were not found. Despite the nonstatistical significance, there were small decreases in grip strength and tissue stiffness. Faster (120 beats/min) IASTM application may have produced clinically meaningful decreases in grip strength along with a small decrease in tissue stiffness. Conclusions: This report helps to establish methodology for future controlled studies on this topic. Sports medicine professionals should consider these results as exploratory and interpret them with caution. Future research is needed to confirm these findings and begin to postulate possible neurophysiological mechanisms.

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Intrinsic Foot Muscle Exercises With and Without Electric Stimulation

Katherine R. Newsham

Context: Exercising intrinsic foot muscles (IFMs) can improve dynamic balance and foot posture. The exercises are not intuitive and electrotherapy (neuromuscular electrical stimulation [NMES]) has been suggested to help individuals execute the exercises. The aim of this study was to evaluate the effects of training IFM program on dynamic balance and foot posture and compare traditional training methods (TRAIN) with traditional training plus NMES on the perceived workload of the exercises, balance, and foot posture. Design: Randomized controlled trial. Methods: Thirty-nine participants were randomized to control, TRAIN, or NMES. TRAIN and NMES performed IFM exercises daily for 4 weeks; NMES received electrotherapy during the first 2 weeks of training. The Y-Balance test and arch height index were measured in all participants at baseline. The training groups were measured again at 2 weeks; all participants were measured at 4 weeks and 8 weeks, after 4 weeks of no training. Perceived workload (National Aeronautics and Space Administration Task Load Index) of exercises was assessed throughout the first 2 weeks and at 4 weeks. Results: A 4-week IFM training program demonstrated increases in Y-Balance (P = .01) for TRAIN and in arch height index (seated P = .03; standing P = .02) for NMES, relative to baseline. NMES demonstrated improvement in Y-Balance (P = .02) and arch height index standing (P = .01) at 2 weeks. There were no significant differences between the training groups. Groups were similar in the number responding to exercises in excess of minimal detectable change on all clinical measures. Perceived workload of the exercises decreased during the first 2 weeks of training (P = .02), and more notably at 4 weeks (P < .001). The groups did not differ in how they perceived the workload. Conclusions: A 4-week IFM training program improved dynamic balance and foot posture. Adding NMES in early phases of training provided early improvement in dynamic balance and foot posture, but did not affect perceived workload.

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Volume 32 (2023): Issue 4 (May 2023)

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Differences in Neurocognitive Functions Between Healthy Controls and Anterior Cruciate Ligament-Reconstructed Male Athletes Who Passed or Failed Return to Sport Criteria: A Preliminary Study

Maryam Kiani Haft Lang, Razieh Mofateh, Neda Orakifar, and Shahin Goharpey

Background: Only 55% of anterior cruciate ligament-reconstructed (ACLR) athletes return to competitive sports. This brings into question the usefulness of current return to sport (RTS) criteria. High cognitive demand of sport environment clarifies the value of incorporating neurocognitive tests when making decisions regarding the time of RTS. This preliminary study aimed to compare the neurocognitive functions between healthy controls and ACLR male athletes who passed or failed RTS criteria. Methods: A total of 45 male football players, including 15 ACLR who passed RTS criteria, 15 ACLR who did not pass, and 15 healthy controls participated in this cross-sectional study. The Cambridge Neuropsychological Test Automated Battery was used to measure a battery of neurocognitive tasks, including speed of response, sustained attention, working memory, cognitive flexibility, and response inhibition. Results: The results revealed that compared with both the ACLR-passed and healthy groups, the ACLR-failed group showed greater values of 5-choice movement time (P = .02, P = .01, respectively) but lower values of stop signal reaction time (P = .03, P = .001, respectively) and proportion of successful stops variables (P = .02). In addition, compared with the healthy group, both the ACLR-failed and ACLR-passed groups indicated greater values in between errors (P < .001, P = .008, respectively) and reaction latency variables (P = .002, P = .01, respectively) but lower values of A′ (P < .001, P = .007, respectively), probability of hit (P < .001, P = .03, respectively), and percent correct trials variables (P = .006, P = .02, respectively). Conclusions: Our findings indicated deficits in neurocognitive functions in ACLR male athletes. In addition, poor performance in sustained attention, working memory, and cognitive flexibility measures observed in the ACLR-passed group highlighted the necessity for using a multimodal approach via implementation of neurocognitive measures in conjunction with the functional and muscular assessments when making RTS decisions.

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Effects of Gluteus Maximus Muscle Activity and Pelvic Width on Dynamic Frontal Plane Hip Joint Stiffness During Gait in Healthy Young Women

Shogo Takano, Yoshitaka Iwamoto, Norifumi Fujii, Rei Konishi, Junya Ozawa, and Nobuhiro Kito

Context: Excessive hip adduction and internal rotation are abnormal movements that may lead to the onset and progression of patellofemoral pain. Previous studies have reported that lower dynamic frontal plane hip joint stiffness in the gait of women is associated with the magnitude of hip adduction and internal rotation angles. However, the factors contributing to the lack of dynamic frontal plane hip joint stiffness in the gait of young women are unclear. This study aims to investigate the factors affecting dynamic frontal plane hip joint stiffness during the weight-acceptance phase of the gait of healthy young women. Design: Cross-sectional study. Methods: This study included 30 healthy women between the ages of 18 and 30 years. The pelvic width/femur length ratio was calculated by dividing the pelvic width by the femur length. Data on hip kinematics and kinetics and activation of the gluteus maximus and medius, tensor fasciae latae, and adductor longus muscles during gait were collected using a motion capture system, force plates, and surface electromyography. Stepwise multiple regression analysis was conducted to determine the extent to which each independent factor affected dynamic frontal plane hip joint stiffness. Results: In healthy young women, decreased dynamic frontal plane hip joint stiffness was associated with decreased muscle activity of the gluteus maximus during the gait, as well as greater pelvic width/femur length ratio. Conclusions: Women with a relatively great pelvic width relative to femur length may have more difficulty in producing dynamic frontal plane hip joint stiffness. However, increasing the muscle activity of the gluteus maximus may contribute to increased dynamic frontal plane hip joint stiffness.

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Impact Magnitude and Symmetry in Females During Return to Sport Tasks Measured With Inertial Sensors

Courtney R. Chaaban, Camille King, and Darin A. Padua

Context: Impact magnitude, such as peak tibial acceleration, may be associated with lower extremity injury risk and can be measured with an inertial sensor. An understanding of impact magnitude across functional tasks could guide clinicians in exercise prescription during rehabilitation of lower extremity injuries. Objectives: To determine (1) differences in impact magnitude based on task and (2) which tasks have asymmetrical impact magnitude based on limb dominance. Design: Observational cohort design. Thirty-three healthy, recreationally active adult females participated in 1 testing session on a basketball court. Methods: Participants wore inertial sensors with embedded accelerometers on bilateral distal shanks. Participants completed 9 plyometric, speed, and agility tasks commonly utilized during the return to sport phase of lower extremity rehabilitation. Main Outcome Measures: Average impact magnitude (peak tibial acceleration in multiples of gravity, g) for each limb for each task. Analyses: We used a repeated-measures analysis of variance (factor: task) to determine the differences in impact magnitude based on task. We categorized tasks by magnitude of impact into low, medium, high, and very high impact. We utilized paired t tests for each task to compare limbs (dominant vs nondominant). Results: Impact magnitude differed based on task (P < .001). We classified tasks as low impact (≤10g; single-leg [SL] lateral jump, double-leg [DL] lateral jump); medium impact (11–20g; SL vertical jump, box drill); high impact (21–30g; modified T test, DL forward jump, SL forward jump); and very high impact (≥31g; sprint, DL tuck jump). Impact magnitude differed by limb in 3 tasks (DL forward jump, DL lateral jump, and box drill), with a higher impact on the dominant limb in each task. Conclusions: Impact magnitude differed based on task. While most tasks had symmetric impact magnitude between limbs, 3 tasks had a higher impact magnitude on the dominant limb.

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Instructions Promoting an External Focus Are More Effective for Altering Impact Forces in Female Runners

Jacy Zajac, Kelsey Redman, Emily Watkins, and Thomas Gus Almonroeder

Context: Previous studies have found that instructions promoting an external focus (EF) tend to be more effective for movement pattern retraining compared to instructions promoting an internal focus (IF), for a variety of movement tasks. However, few studies have examined how different types of instructions affect running mechanics associated with running-related injury risk. Therefore, the purpose of this study was to compare the effects of instructions promoting different attentional foci on impact forces during running. Design: Cross-sectional study. Methods: Twenty uninjured female recreational runners ran at a self-selected speed with their typical pattern (no instructions condition) on an instrumented treadmill that measured ground reaction forces. Next, they were given 2 sets of instructions intended to alter their running pattern; one promoted an IF and the other promoted an EF. Repeated-measures analysis of variance was used to compare impact peaks and loading rates across the conditions (no instructions, IF, and EF), with post hoc tests conducted in the case of a significant omnibus test. Results: There were differences among the conditions in the impact peaks (P < .001) and loading rates (P < .001). Impact peaks were lower for the IF (P = .002) and EF (P < .001) conditions compared to the no instructions condition. Loading rates were lower for the EF condition compared to the no instructions (P < .001) and IF (P < .001) conditions; there was no difference between the IF and no instructions conditions (P = .24). Conclusions: Our findings indicate that instructions promoting an EF may be more effective at reducing loading rates during running compared to instructions promoting an IF. Clinicians should consider these findings when attempting to retrain a runner’s running pattern.

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The Relationship Between Eating Disorders, Disordered Eating, and Injury in Athletes: A Critically Appraised Topic

Karrie L. Hamstra-Wright, Kellie C. Huxel Bliven, John E. Coumbe-Lilley, Eddin Djelovic, and Jahnvi Patel

Clinical Scenario: Eating disorders (EDs) and disordered eating (DE) result in numerous physical and psychological complications for female and male athletes. Besides bone-related injury, little research exists investigating what injuries EDs and/or DE contribute to. Clinical Question: Are EDs and/or DE a risk factor for injury incidence in athletes? Summary of Key Findings: We searched for prospective studies assessing EDs or DE as a risk factor for injury in female or male athletes high school age and older. Our search returned 5 studies. One study found Eds, or DE were not a risk for any type of injury in female cross-country and track-and-field athletes. Two studies found a possible relationship between EDs or DE, as one contributing factor of others, in the incidence of bone stress injuries (BSIs) in female athletes who compete in various sports. One study found female, but not male, cross-country and track-and-field athletes with a history of EDs were more at risk for stress fractures than those without a history. One study found Eds, or DE were not a risk for BSI in female runners and triathletes. Clinical Bottom Line: Large and important gaps in the literature exist investigating injuries related to EDs or DE outside of BSIs. There is low–moderate evidence that EDs and/or DE are either a sole, or contributing, risk factor for BSIs in female athletes. Strength of Recommendation: Grade B evidence exists to support the idea that EDs and/or DE are a risk factor for a specific type of injury (BSI) in female athletes only.