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Objective: To examine the relationships between contexts of physical activity, grit, and GPA in a college population. Participants: 875 Undergraduate students from a large, southern university participated between October 2018 and March 2020. Methods: Participants completed an electronic survey evaluating physical activity and grit. The university provided official GPAs. Multiple linear regression models evaluated the correlations between grit, the different physical activity domains, and GPA. Results: Grit was positively associated with domestic physical activity, leisure time physical activity, and GPA. Consistency of interest had no associations with the domains of physical activity or GPA. Perseverance of effort was positively associated with walking, active transport physical activity, domestic physical activity, leisure physical activity, and GPA. Conclusion: Perseverance of effort is related to different domains of physical activity and GPA. Future studies should investigate if increasing leisure time physical activity causes increases in perseverance of effort.

Postural assessments of the lumbar spine lack valuable information about its properties. The purpose of this study was to assess neutral zone (NZ) characteristics via in vivo lumbar spine passive stiffness and relate NZ characteristics to standing lumbar lordosis. A comparison was made between those that develop low back pain during prolonged standing (pain developers) and those that do not (nonpain developers). Twenty-two participants with known pain status stood on level ground, and median lumbar lordosis angle was calculated. Participants were then placed in a near-frictionless jig to characterize their passive stiffness curve and location of their NZ. Overall, both pain developers and nonpain developers stood with a lumbar lordosis angle that was more extended than their NZ boundary. Pain developers stood slightly more extended (in comparison to nonpain developers) and had a lower moment corresponding to the location of their extension NZ boundary. Overall, in comparison to nonpain developers, pain developers displayed a lower moment corresponding to the location of their extension NZ boundary which could correspond to greater laxity in the lumbar spine. This may indicate why pain developers have a tendency to stand further beyond their NZ with greater muscle co-contraction. [ABSTRACT FROM AUTHOR]

A popular posture for using wireless technology is reclined sitting, with the trunk rotated posteriorly to the hips. This position decreases the head's gravitational moment; however, the head angle relative to the trunk is similar to that of upright sitting when using a tablet in the lap. This study compared cervical extensor musculotendon length changes from neutral among 3 common sitting postures and maximum neck flexion while using a tablet. Twenty-one participants had radiographs taken in neutral, full-flexion, and upright, semireclined, and reclined postures with a tablet in their lap. A biomechanical model was used to calculate subject-specific normalized musculotendon lengths for 27 cervical musculotendon segments. The lower cervical spine was more flexed during reclined sitting, but the skull was more flexed during upright sitting. Normalized musculotendon length increased in the reclined compared with an upright sitting position for the C4-C6/7 (deep) and C2-C6/7 (superficial) multifidi, semispinalis cervicis (C2-C7), and splenius capitis (Skull-C7). The suboccipital (R2 =.19–.71) and semispinalis capitis segment length changes were significantly correlated with the Skull-C1 angle (0.24–0.51). A semireclined reading position may be an ideal sitting posture to reduce the head's gravitational moment arm without overstretching the assessed muscles. [ABSTRACT FROM AUTHOR]

ObjectiveTo examine the relationships between contexts of physical activity, grit, and GPA in a college population. Participants: 875 Undergraduate students from a large, southern university participated between October 2018 and March 2020. Methods: Participants completed an electronic survey evaluating physical activity and grit. The university provided official GPAs. Multiple linear regression models evaluated the correlations between grit, the different physical activity domains, and GPA. Results: Grit was positively associated with domestic physical activity, leisure time physical activity, and GPA. Consistency of interest had no associations with the domains of physical activity or GPA. Perseverance of effort was positively associated with walking, active transport physical activity, domestic physical activity, leisure physical activity, and GPA. Conclusion: Perseverance of effort is related to different domains of physical activity and GPA. Future studies should investigate if increasing leisure time physical activity causes increases in perseverance of effort. [ABSTRACT FROM AUTHOR]

Objective: To determine how ultrawide (UW) and dual displays configurations can influence neck biomechanics and performance compared to a single display. Background: Studies have assessed neck kinematics and performance when using dual displays, but these studies have used screen sizes smaller than today's display size, have inconsistent participant placement, and few have assessed these two variables together. Methods: Seventeen participants completed five tasks on six display configurations. Neck kinematics and performance were tracked for each configuration. Results: Centered configurations produced significantly different median neck rotation angles compared to secondary configurations (p <.001) for three of the tasks. A 34" curved UW display with a longer viewing distance produced similar neck kinematics to a single 24" display with the potential to also reduce screen interactions. When compared to single, the benefit of secondary versus centered monitors was dependent on the type of task being performed. Users may prefer the UW, centered dual, and secondary dual configurations over the single display. Conclusion: The benefit of secondary versus centered displays is dependent on the type of task being performed. Dual displays are still beneficial but should be used with a monitor arm to switch between centered and secondary configurations as necessary. Future work should look at larger UW displays to see if these results hold compared to dual display configurations. Application: The results can be used to make evidence-based guidelines for displays based on size and task. Researchers can use this information to design future studies looking at specific configurations. [ABSTRACT FROM AUTHOR]

Minimal data exist on the neutral position for the lumbar spine, trunk, and thighs when adopting a hybrid posture. This study examined sex differences in the neutral zone lumbar stiffness and the lumbar and trunk-thigh angle boundaries of the neutral zone, and determined if the standing lumbar angle fell within the neutral zone. Passive lumbar flexion and extension moment-angle curves were generated for 31 participants (13 M, 18 F), pooled from two datasets, with trunk-thigh angles available for 10 participants. The neutral zone was defined as the low stiffness zone from both the flexion and extension curves. Males demonstrated significantly greater extensor stiffness. Neutral lumbar and trunk-thigh angles ranged on average −22.2 to 0.2° and 124.2 to 159.6° for males and −17.8 to −1.3° and 143.2 to 159.5° for females, respectively. Standing lumbar angles fell outside the neutral zone for 44% of participants. These neutral zone boundaries may inform kinematics for hybrid chair designs. Practitioner summary: Adoption of a neutral spinal posture may be achieved through hybrid chair design, yet minimal data exists on a physiologically defined neutral zone. Using measures of in vivo lumbar stiffness, the lumbar and trunk-thigh angular boundaries of the neutral zone were defined for both males and females. Abbreviations: EMG: electromyography; MVC: maximal voluntary contraction [ABSTRACT FROM AUTHOR]

While the individual tissues of the vertebral joint demonstrate viscoelastic properties, the global viscoelastic properties of the lumbar vertebral joint are not well established. This study investigated how changes in displacement rate influenced the mechanical response of the porcine cervical spine (a surrogate or model for the human lumbar spine) exposed to acute anterior shear failure loading. Thirty porcine cervical spine specimens (15 C3-C4 and 15 C5-C6) were placed under a 1600 N compressive load and subsequently loaded in anterior shear to failure at one of three randomly assigned displacement rates (1 mm/s, 4 mm/s, or 16 mm/s). Ultimate anterior shear force, ultimate displacement, average stiffness, and energy stored until failure were calculated. Load rate in the elastic region was also calculated to compare the load rates used in this study to those used in previous studies. Changes in displacement rate affected the C3-C4 and C5-C6 specimens differently. C5-C6 specimens tested at 16 mm/s had an ultimate force that was 28% and 23% higher than at 1 (p = 0.0215) and 4 mm/s (p = 0.0461), respectively. The average stiffness to failure of the C5-C6 specimens tested at 16 mm/s was 52% higher than at 4 mm/s (p = 0.0289). No such differences were found for the C3-C4 specimens. An increase in the anterior shear displacement rate did not necessarily demonstrate viscoelasticity of the vertebral joint. Specimen intervertebral levels were affected differently by changes in anterior shear displacement rate, which may have been a result of anatomical and postural differences between the two levels. Future studies should further investigate the effect of displacement rate on the spine and the inconsistencies between different specimen levels. [DOI: 10.1115/1.4001885]

Objective: To compare the impact of multiple computer monitor configurations on health and performance outcomes compared to the use of a single monitor.Background: Multiple monitor configurations are used in office settings to promote increased productivity by providing more screen space; however, it is unknown if there are health-related trade-offs to increased productivity.Method: A systematic review was conducted according to the PRISMA statement guidelines and adapted the best evidence synthesis.Results: Eighteen studies were included in our review. There was strong evidence that implementing dual monitors is in line with users' preference. There was also moderate evidence for controlled laboratory studies demonstrating that multiple monitors may increase task efficiency with decreased desktop interaction; however, implementing multiple monitors may also result in nonneutral neck postures for users.Conclusion: More research needs to be conducted on biomechanical exposures when using larger displays. Longitudinal field studies should be conducted to determine the influence of monitor interventions on health, productivity, and well-being. All studies must consider task complexity and user positioning and should measure health and productivity outcomes together. Researchers must also consider up-to-date purchasing trends when choosing the monitor configurations and sizes for their studies.Application: Regulatory bodies and practitioners can use the results to develop evidence-based monitor guidelines and inform decision-making in practice, respectively. Researchers can use this information to design future studies on monitor configurations that incorporate current purchasing trends. [ABSTRACT FROM AUTHOR]