Journal: Journal of the Royal Society Interface

Article Title: Passive cervical spine ligaments provide stability during head impacts

doi: 10.1098/rsif.2019.0086

Figure Lengend Snippet: Angular impulse contributions during simulated mild head impacts. Impacts were divided into an acceleration and deceleration phase based on the planar angular acceleration time history (positive acceleration is the sagittal extension of lateral flexion towards the non-dominant side). We included a short 30 ms of zero force pre-load to allow the model to reach a balanced steady state (pre-motion). In some conditions, head stabilization was achieved before the end of the 300 ms impact simulation, resulting in a post-motion period with low angular accelerations (|α| < 10 rad s−2). Impulse contributions during acceleration and deceleration phases were computed for external load, gravity, all muscles (active component), all muscles (passive component) and all ligaments for each condition and aggregated over all subjects. Angular impulse contributions were also normalized by total angular impulse produced by the external force. When neck muscles were relaxed, ligaments and passive muscles had the largest angular impulse contribution in deceleration for (a) sagittal extension and (c) coronal lateral flexion, respectively. When neck muscles were cocontracted, the active muscle had the largest angular impulse contribution in deceleration for both (b) sagittal extension and (d) coronal lateral flexion. In all cases, external load provided the angular impulse that accelerated the head, with active muscles providing over 30% resistive angular impulse during cocontracted muscle cases. (Online version in colour.)

Article Snippet: Relaxed OpenSim neck muscle activations were found by minimizing the sum of all muscle activations while maintaining head and neck balance under gravity and with the constraint that SCM activation was 20%.

Techniques: Muscles, Produced

Journal: Journal of the Royal Society Interface

Article Title: Passive cervical spine ligaments provide stability during head impacts

doi: 10.1098/rsif.2019.0086

Figure Lengend Snippet: Moments produced by model forces demonstrate important structures for stabilization. Moments over the impact period from force elements in the simulation are presented (positive moments are moments in sagittal extension or lateral flexion to the non-dominant side). We show samples from a sagittal extension and coronal lateral flexion simulation with relaxed neck muscle activations. (a) Moments from external load, gravity, aggregated active muscle, passive muscle and ligaments are shown first to demonstrate how moments from each group change with time. Moments from (b) active muscle component and (c) passive muscle component show that the SCM produces large negative moments resisting impact motion in both directions. Moments from (d) ligaments show that AF fibres and capsular ligaments dominate in sagittal extension and coronal lateral flexion, respectively. (Online version in colour.)

Article Snippet: Relaxed OpenSim neck muscle activations were found by minimizing the sum of all muscle activations while maintaining head and neck balance under gravity and with the constraint that SCM activation was 20%.

Techniques: Produced

Journal: Journal of the Royal Society Interface

Article Title: Passive cervical spine ligaments provide stability during head impacts

doi: 10.1098/rsif.2019.0086

Figure Lengend Snippet: Extrapolated American football median impact shows a change in stabilization contributions. (a) We applied a simulated American football impact force in sagittal extension and coronal lateral flexion to our strongest subject with cocontracted neck muscle activations. (b) Simulation kinematics were within 20% of the median American football impact kinematics. Angular impulse contributions in (c) sagittal extension and (d) coronal lateral flexion show that the active muscle has less relative contribution than in the experimental trials. In sagittal extension, the ligaments provide the most angular impulse in deceleration. (Online version in colour.)

Article Snippet: Relaxed OpenSim neck muscle activations were found by minimizing the sum of all muscle activations while maintaining head and neck balance under gravity and with the constraint that SCM activation was 20%.

Techniques:

Journal: Journal of the Royal Society Interface

Article Title: Passive cervical spine ligaments provide stability during head impacts

doi: 10.1098/rsif.2019.0086

Figure Lengend Snippet: OpenSim head and neck impact model. The OpenSim musculoskeletal model is a 20 degree-of-freedom model that was based on the Mortensen 2018 model. (a) We added 80 individual cervical spine ligament sections representing 11 ligament groups to represent soft tissue stabilization force elements. The constitutive material model for the ligaments was represented with a (b) force–length and (c) force–velocity curve, which were identified previously in the literature. The force–length relationship of ligaments has a characteristic shape corresponding to the straightening (toe region), stretching (linear region) and breaking (yield region) of collagen fibres. Our constitutive model does not include a yield region, similar to how passive tendon is modelled. (d) The model also contains 84 muscle subvolumes over 15 muscle groups, which were defined in the original Mortensen 2018 model. Muscles were represented using the Hill-type muscle model, with a (e) force–length curve modelling myosin cross bridges in sarcomere functional units and a (f) force–velocity curve scaling force output depending on muscle fibre velocities. Ligament and muscle peak lengthening velocities are marked in (c,e) during experimental mild external loads and extrapolated median American football impacts. While the (e) muscle force–velocity scaling is similar in both load regimes, the (c) ligament force–velocity scaling is substantially larger during median American football impacts, resulting in greater moments produced by ligaments in the high-severity regime. (Online version in colour.)

Article Snippet: Relaxed OpenSim neck muscle activations were found by minimizing the sum of all muscle activations while maintaining head and neck balance under gravity and with the constraint that SCM activation was 20%.

Techniques: Muscles, Functional Assay, Produced

Journal: Journal of Exercise Rehabilitation

Article Title: Functional assessment of respiratory muscles and lung capacity of CrossFit athletes

doi: 10.12965/jer.2244594.297

Figure Lengend Snippet: Differences in mean±standard error of normalized electromyographic activity of respiratory muscles between groups

Article Snippet: These data are consistent with the findings of this study, which demonstrated greater electromyographic activities for the respiratory muscles in the CrossFit athlete group during forced inspiration and expiration, compared to the sedentary group without comorbidities, since the level of vascularization and redistribution of blood flow of practitioners must be well structured in adapting to training periods ( ).

Techniques: Activity Assay, Muscles