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Denys Batista Campos, Isabella Christina Ferreira, Matheus Almeida Souza, Macquiden Amorim Jr, Leonardo Intelangelo, Gabriela Silveira-Nunes and Alexandre Carvalho Barbosa

Objective: To examine the selective influences of distinct acceleration profiles on the neuromuscular efficiency, force, and power during concentric and eccentric phases of isoinertial squatting exercise. Design: Cross-sectional study. Setting: Biomechanics laboratory of the university. Participants: A total of 38 active adults were divided according to their acceleration profiles: higher (n = 17; >2.5 m/s2) and lower acceleration group (n = 21; <2.5 m/s2). Intervention: All subjects performed squats until failure attached to an isoinertial conic pulley device monitored by surface electromyography of rectus femoris, vastus medialis, vastus lateralis, biceps femoris, and semitendinosus. Main Outcome Measures: An incremental optical encoder was used to assess maximal and mean power and force during concentric and eccentric phases. The neuromuscular efficiency was calculated using the mean force and the electromyographic linear envelope. Results: Between-group differences were observed for the maximal and mean force (P range = .001–.005), power (P = .001), and neuromuscular efficiency (P range = .001–.03) with higher significant values for the higher acceleration group in both concentric and eccentric phases. Conclusion: Distinct acceleration profiles affect the neuromuscular efficiency, force, and power during concentric and eccentric phases of isoinertial squatting exercise. To ensure immediate higher levels of power and force output without depriving the neuromuscular system, acceleration profiles higher than 2.5 m/s2 are preferable. The acceleration profiles could be an alternative to evolve the isoinertial exercise.

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Kyung-eun Lee, Seung-min Baik, Chung-hwi Yi, Oh-yun Kwon and Heon-seock Cynn

Context: Side bridge exercises strengthen the hip, trunk, and abdominal muscles and challenge the trunk muscles without the high lumbar compression associated with trunk extension or curls. Previous research using electromyography (EMG) reports that performance of the side bridge exercise highly activates the gluteus medius (Gmed). However, to the best of our knowledge, no previous research has investigated EMG amplitude in the hip and trunk muscles during side bridge exercise in subjects with Gmed weakness. Objective: The purpose of this study was to examine the EMG activity of the hip and trunk muscles during 3 variations of the side bridge exercise (side bridge, side bridge with knee flexion, and side bridge with knee flexion and hip abduction of the top leg) in subjects with Gmed weakness. Design: Repeated-measures experimental design. Setting: Research laboratory. Patients: Thirty subjects (15 females and 15 males) with Gmed weakness participated in this study. Intervention: Each subject performed 3 variations of the side bridge exercise in random order. Main Outcome Measures: Surface EMG was used to measure the muscle activities of the rectus abdominis, external oblique, longissimus thoracis, multifidus, Gmed, gluteus maximus, and tensor fasciae latae (TFL), and Gmed/TFL muscle activity ratio during 3 variations of the side bridge exercise. Results: There were significant differences in Gmed (F 2,56 = 110.054, P < .001), gluteus maximus (F 2,56 = 36.416, P < .001), and TFL (F 2,56 = 108.342, P < .001) muscles among the 3 side bridge exercises. There were significant differences in the Gmed/TFL muscle ratio (F 2,56 = 20.738, P < .001). Conclusion: Among 3 side bridge exercises, the side bridge with knee flexion may be effective for the individuals with Gmed weakness among 3 side bridge exercises to strengthen the gluteal muscles, considering the difficulty of the exercise and relative contribution of Gmed and TFL.

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Bruno Augusto Lima Coelho, Helena Larissa das Neves Rodrigues, Gabriel Peixoto Leão Almeida and Sílvia Maria Amado João

Context: Restriction in ankle dorsiflexion range of motion (ROM) has been previously associated with excessive dynamic knee valgus. This, in turn, has been correlated with knee pain in women with patellofemoral pain. Objectives: To investigate the immediate effect of 3 ankle mobilization techniques on dorsiflexion ROM, dynamic knee valgus, knee pain, and patient perceptions of improvement in women with patellofemoral pain and ankle dorsiflexion restriction. Design: Randomized controlled trial with 3 arms. Setting: Biomechanics laboratory. Participants: A total of 117 women with patellofemoral pain who display ankle dorsiflexion restriction were divided into 3 groups: ankle mobilization with anterior tibia glide (n = 39), ankle mobilization with posterior tibia glide (n = 39), and ankle mobilization with anterior and posterior tibia glide (n = 39). Intervention(s): The participants received a single session of ankle mobilization with movement technique. Main Outcome Measures: Dorsiflexion ROM (weight-bearing lunge test), dynamic knee valgus (frontal plane projection angle), knee pain (numeric pain rating scale), and patient perceptions of improvement (global perceived effect scale). The outcome measures were collected at the baseline, immediate postintervention (immediate reassessment), and 48 hours postintervention (48 h reassessment). Results: There were no significant differences between the 3 treatment groups regarding dorsiflexion ROM and patient perceptions of improvement. Compared with mobilization with anterior and posterior tibia glide, mobilization with anterior tibia glide promoted greater increase in dynamic knee valgus (P = .02) and greater knee pain reduction (P = .02) at immediate reassessment. Also compared with mobilization with anterior and posterior tibia glide, mobilization with posterior tibia glide promoted greater knee pain reduction (P < .01) at immediate reassessment. Conclusion: In our sample, the direction of the tibia glide in ankle mobilization accounted for significant changes only in dynamic knee valgus and knee pain in the immediate reassessment.

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Arthur Alves Dos Santos, James Sorce, Alexandra Schonning and Grant Bevill

This study evaluated the performance of 6 commercially available hard hat designs—differentiated by shell design, number of suspension points, and suspension tightening system—in regard to their ability to attenuate accelerations during vertical impacts to the head. Tests were conducted with impactor materials of steel, wood, and lead shot (resembling commonly seen materials in a construction site), weighing 1.8 and 3.6 kg and dropped from 1.83 m onto a Hybrid III head/neck assembly. All hard hats appreciably reduced head acceleration to the unprotected condition. However, neither the addition of extra suspension points nor variations in suspension tightening mechanism appreciably influenced performance. Therefore, these results indicate that additional features available in current hard hat designs do not improve protective capacity as related to head acceleration metrics.

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Stephan G. Bodkin, Jay Hertel and Joseph M. Hart

Context: Individuals following anterior cruciate ligament reconstruction (ACLR) demonstrate altered postural stability and functional movement patterns. It is hypothesized that individuals following ACLR may compensate with sensory adaptations with greater reliance on visual mechanisms during activities. It is unknown if visual compensatory strategies are implemented to maintain postural stability during functional tasks. Objective: To examine visual gaze accuracy during a single-leg balance task in individuals following ACLR compared with healthy, active controls. Design: Case control. Setting: Controlled laboratory. Participants: A total of 20 individuals (10 ACLR and 10 healthy controls) participated in the study. Data Collection and Analysis: Visual gaze patterns were obtained during 20-second single-leg balance trials while participants were instructed to look at presented targets. During the Stationary Target Task, the visual target was presented in a central location for the duration of the trial. The Moving Target Task included a visual target that randomly moved to 1 of 9 target locations for a period of 2 seconds. Targets were stratified into superior, middle, and inferior levels for the Moving Target Task. Results: The Stationary Target Task demonstrated no differences in visual error between groups (P = .89). The Moving Target Task demonstrated a significant interaction between group and target level (F 2,36 = 3.76, P = .033). Individuals following ACLR demonstrated greater visual error for the superior targets (ACLR = .70 [.44] m, healthy = .41 [.21] m, Cohen d = 0.83 [0.06 to 1.60]) and inferior targets (ACLR = .68 [.25] m, healthy = .33 [.16] m, Cohen d = 1.67 [0.81 to 2.52]). Conclusion: Individuals following ACLR demonstrate greater visual error during settings of high or low visual stimuli compared with healthy individuals to maintain single-limb postural stability. This population may rely on visual input to compensate for the somatosensory changes following injury.

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Uri Gottlieb and Shmuel Springer

Context: Arthroscopic surgical repair of the shoulder is recommended when conservative treatment for shoulder instability (SI) fails. However, many patients undergoing this procedure do not return to same level of activity. Psychological factors and muscle strength have been shown to be associated with postoperative outcomes in other musculoskeletal conditions. Objective: To investigate the association between fear avoidance, muscle strength, and short-term function in patients after surgical SI repair. Methods: Twenty-five male patients who underwent shoulder surgery following at least one event of SI were included in this study. Evaluations of fear avoidance related to physical activity and disability were performed at baseline (during the first encounter with the physical therapist) and 7 to 8 weeks postsurgery. Fear avoidance beliefs were assessed using the Fear Avoidance Beliefs Questionnaire. Disability was assessed using the Disabilities of Arm, Shoulder, and Hand questionnaire and the Western Ontario SI index. The follow-up evaluation (weeks 7–8) included measurement of maximal isometric strength of the internal and external rotators. Nonparametric Kendall tau was used to determine the correlations between baseline fear avoidance, muscle strength, and disability at follow-up. Results: Disabilities of Arm, Shoulder, and Hand questionnaire at follow-up was significantly correlated with baseline Disabilities of Arm, Shoulder, and Hand questionnaire (τ = .520, P < .001), baseline fear avoidance (τ = .399, P = .008), and both internal rotator (τ = −.400, P = .005) and external rotator strength (τ = −.353, P = .014). Western Ontario SI index at follow-up was moderately correlated with baseline Western Ontario SI index (τ = .387, P = .007), internal rotator (τ = −.427, P = .003), and external rotator (τ = −.307, P = .032), but not with baseline Fear Avoidance Beliefs Questionnaire (τ = .22, P = .145). Conclusions: The results indicate a possible association between fear avoidance beliefs and short-term disability. Further studies are warranted to better explore and understand these relationships.

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Andy Mitchell, Craig Holding and Matt Greig

Context: Professional soccer players who have sustained a lower limb injury are up to 3× more likely to suffer a reinjury, often of increased severity. Previous injury has been shown to induce compensatory strategies during neuromuscular screening tests, which might mask deficits and lead to misinterpretation of readiness to play based on task outcome measures. Objective: To investigate the influence of previous injury in professional soccer players on countermovement jump (CMJ) performance and movement strategy. Design: Cross-sectional. Setting: Professional soccer club competing in the English Championship (tier 2). Patients (or Other Participants): Outfield players with a minimum of 6 years as a professional. Intervention(s): Players were categorized as previously injured (n = 10) or not injured (n = 10). All players completed double- and single-leg CMJ trials. Main Outcome Measures: CMJ performance was quantified as jump height and flight time:contraction time ratio. CMJ movement strategy was quantified as force–time history, differentiating eccentric and concentric phases and CMJ depth. Results: Double-leg CMJ was not sensitive to previous injury in performance or movement strategy. In contrast, single-leg CMJ performance was impaired in players with previous injury, who generated significantly lower eccentric and concentric peak force and rate of force development, and a deeper countermovement. Impaired single-leg CMJ performance was also evident in the nonaffected limb of previously injured players, suggesting cross-contamination. Hierarchical ordering revealed that the eccentric phase of the CMJ contributed little to performance in previously injured players. In noninjured players, the eccentric rate of force development and concentric peak force were able to account for up to 89% of the variation in CMJ performance. Conclusions: Single-leg CMJ is advocated for player profiling, being more sensitive to previous injury, and negating the opportunity for interlimb compensation strategies. Movement strategy deficits in previously injured players suggest rehabilitation foci specific to eccentric force development.

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Zachary Y. Kerr, Julianna Prim, J.D. DeFreese, Leah C. Thomas, Janet E. Simon, Kevin A. Carneiro, Stephen W. Marshall and Kevin M. Guskiewicz

Context: Little research has examined health-related quality of life in former National Football League (NFL) players. Objective: Examine the association of musculoskeletal injury history and current self-reported physical and mental health in former NFL players. Setting: Cross-sectional questionnaire. Patients or Other Participants: Historical cohort of 2,103 former NFL players that played at least one season between 1940 and 2001. Intervention: Players were grouped by self-reported professional career musculoskeletal injury history and whether injuries affected current health: (1) no musculoskeletal injury history; (2) musculoskeletal injury history, currently affected by injuries; and (3) musculoskeletal injury history, not currently affected by injuries. Main Outcome Measure: The Short Form 36 Measurement Model for Functional Assessment of Health and Well-Being (SF-36) yielded physical and mental health composite scores (PCS and MCS, respectively); higher scores indicated better health. Multivariable linear regression computed mean differences (MD) among injury groups. Covariates included demographics, playing history characteristics, surgical intervention for musculoskeletal injuries, and whether injury resulted in premature end to career. MD with 95% CI excluding 0.00 were deemed significant. Results: Overall, 90.3% reported at least one musculoskeletal injury during their professional football careers, of which 74.8% reported being affected by their injuries at time of survey completion. Adjusting for covariates, mean PCS in the “injury and affected” group was lower than the “no injury” (MD = −3.2; 95% CI: −4.8, −1.7) and “injury and not affected” groups (MD = −4.3; 95% CI: −5.4, −3.3); mean MCS did not differ. Conclusion: Many players reported musculoskeletal injuries, highlighting the need for developing and evaluating injury management interventions.