Intra-and Intermuscular Coherence and Body Acceleration Control in Older Adults during Bipedal Stance

Our aim was to clarify the effect of aging on the coherence of electromyograms of plantar flexor pairs during bipedal stance and to clarify the relationship between coherence and center-of-mass acceleration (COMacc). The subjects were 16 adults and 18 older adults. Intra- and intermuscular coherence and phase analyses were used to analyze the muscle pairs of bilateral and unilateral plantar flexor muscle groups. The relationship between coherence value and anterior–posterior COMacc of the plantar flexor muscle pairs was also examined to determine whether the connectivity of the lower limb muscle pairs is functionally important. The older adults showed higher coherence in the frequency range of 0–4 Hz for muscle pairs than the younger adults. In phase analysis, the older adults showed a phase difference between bilateral heteronymous muscle pairs in the frequency range of 0–6 Hz, which was one of the characteristics not seen in the younger adults. Correlation analysis showed that all the muscle pairs were moderately correlated with COMacc in the older adults. Not only does aging affects the organization of the bilateral and unilateral postural muscle activity of the plantar flexors during bipedal stance, but such organization may also be related to the increased COMacc characteristics of older adults.

Development of a new militarily-relevant whole-body low-intensity blast model for mild and subconcussive traumatic brain injury: Examination of acute neurological and multi-organ pathological outcomes

This work describes a newly developed experimental mouse model reproducing features of blast-induced neurotrauma (BINT), induced in operationally relevant manner using a compressed air-driven shock tube. Mild BINT (smBINT) was induced by one exposure to a low-intensity blast (LIB), whereas subconcussive BINT (rscBINT) was caused by repeated exposures to LIB. To mimic an operational scenario when a soldier is standing when exposed to blast using a quadruped experimental animal (mouse), a whole-body holder was developed to position mice in a bipedal stance, face-on toward the pressure wave generated in a shock tube. This restraint avoids bobble head movement, thus prevents tertiary blast effects, and allows administration of fast-acting inhaled anesthetics via nose cone. Using this model, we established and validated paradigms for primary blast-induced mild and repetitive traumatic brain injuries Our results showed that a single exposure to 69 kPa (10 psi) was capable of inducing smBINT, whereas three-rounds of exposure to 41 kPa (6 psi) caused rscBINT. Mice recovered rapidly from both types of BINT without prolonged neurological dysfunction. Mild superficial pathology was found predominantly in the lungs 24h after injury, with equivalent pathology after smBINT or repetitive rscBINT. The Purkinje layer of the cerebellum exhibited neuronal damage persisting up to 7d. Similar to some other models as well as clinical findings, this model reproduces blast-induced cerebellar pathology. In conclusion, this model positioning mice in a bipedal stance and facing front-on toward the shockwave provides realistic representation of operational scenarios and reproduces militarily-relevant smBINT and rscBINT in the laboratory.

The presence of corticomuscular coherence during unipedal stance

Objective: To elucidate cortical involvement in postural control during unipedal stance by observing corticomuscular coherence (CMC) between the sensorimotor cortex and ankle joint muscles. Methods: Twenty-one participants performed three tasks: bipedal stance, unipedal stance, and isometric contraction. We measured the maximal peak of CMC (CMCmax) between electroencephalograms overlying the foot representation area and surface electromyograms from the tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (SOL), respectively, for each task. We measured the center of pressure (COP) during both stance tasks. Results: Although there was no significant CMC during bipedal stance, significant CMC was observed for all muscles during unipedal stance, with larger COP fluctuation. The results revealed significant differences in CMCmax between unipedal and bipedal stance tasks (TA, p = 0.002; MG, p = 0.016; LG, p = 0.003; SOL, p = 0.009). Additionally, CMCmax was obtained in higher frequency bands during the unipedal stance task than during the isometric contraction task. Conclusions: Significant CMC indicates direct involvement of the sensorimotor cortex in postural control during unipedal stance. Significance: Greater postural demands due to narrow base-of-support during unipedal stance requires voluntary control of muscle activity by the sensorimotor cortex.

Comparison of electromyographic activity of quadriceps muscle in persons with unilateral traumatic transtibial amputation using patellar tendon bearing supracondylar endoskeletal prosthesis with the unaffected limb in weight bearing positions.

Purpose: comparison of electromyographic activity of quadriceps muscle in persons with unilateral traumatic transtibial amputation using patellar tendon bearing supracondylar endoskeletal prosthesis with the unaffected limb in weight bearing positions. Method: 30 individuals aged 18-60 years were assessed using surface electromyography with functional level K3 according to K-level functional assessment scale to compare the activity of quadriceps of affected side using patellar tendon bearing supracondylar endoskeletal prosthesis with the unaffected side. The data was analysed using paired t-test. Result: There was a significant difference in the activity of VMO and VLO muscles of the quadriceps in high sitting positions. There was also a significant difference in the activity of VMO muscle in single limb stance and bipedal stance. However, there was no significant difference between the activity of VLO muscle in bipedal stance but there was reduced activity of VLO muscle in the prosthetic limb in single limb stance. Conclusion: The quadriceps activity was reduced in the affected limb in high sitting position, single limb stance and bipedal stance. However, no difference in the muscle activity was noted in VLO muscle in bipedal stance. Keywords: trans tibial amputation, patellar tendon bearing supracondylar prosthetis, surface electromyography.

Gymnastics Experience Enhances the Development of Bipedal-Stance Multi-Segmental Coordination and Control During Proprioceptive Reweighting

Performance and control of upright bipedal posture requires a constant and dynamic integration of relative contributions of different sensory inputs (i. e., sensory reweighting) to enable effective adaptations as individuals face environmental changes and perturbations. Children with gymnastic experience showed balance performance closer to that of adults during and after proprioceptive alteration than children without gymnastic experience when their center of pressure (COP) was analyzed. However, a particular COP sway can be achieved through performing and coordinating different postural movements. The aim of this study was to assess how children and adults of different gymnastic experience perform and control postural movements while they have to adjust balance during and after bilateral tendon vibration. All participants were equipped with spherical markers attached to their skin and two vibrators strapped over the Achilles tendons. Bipedal stance was performed in three 45-s trials in two visual conditions (eyes open, EO, and eyes closed, EC) ordered randomly in which vibration lasted 10 s. Posture movements were analyzed by a principal component analysis (PCA) calculated on normalized and weighted markers coordinates. The relative standard deviation of each principal movement component (principal position, PP-rSTD) quantified its contribution to the whole postural movements, i.e., quantified the coordinative structure. The first (principal velocities, PV-rSTD) and second (principal accelerations, PA-rSTD) time-derivatives characterized the rate-dependent sensory information associated with and the neuromuscular control of the postural movements, respectively. Children without gymnastic experience showed a different postural coordinative structure and different sensory-motor control characteristics. They used less ankle movements in the anterior-posterior direction but increased ankle movements in medio-lateral direction, presented larger hip and trunk velocities, and exhibited more hip actions. Gymnastic experience during childhood seemed to benefit the development of proprioceptive reweighting processes in children, leading to a more mature form of coordinating and controlling posture similarly to adults.

The braincase, brain and palaeobiology of the basal sauropodomorph dinosaur Thecodontosaurus antiquus

Sauropodomorph dinosaurs underwent drastic changes in their anatomy and ecology throughout their evolution. The Late Triassic Thecodontosaurus antiquus occupies a basal position within Sauropodomorpha, being a key taxon for documenting how those morphofunctional transitions occurred. Here, we redescribe the braincase osteology and reconstruct the neuroanatomy of Thecodontosaurus, based on computed tomography data. The braincase of Thecodontosaurus shares the presence of medial basioccipital components of the basal tubera and a U-shaped basioccipital–parabasisphenoid suture with other basal sauropodomorphs and shows a distinct combination of characters: a straight outline of the braincase floor, an undivided metotic foramen, an unossified gap, large floccular fossae, basipterygoid processes perpendicular to the cultriform process in lateral view and a rhomboid foramen magnum. We reinterpret these braincase features in the light of new discoveries in dinosaur anatomy. Our endocranial reconstruction reveals important aspects of the palaeobiology of Thecodontosaurus, supporting a bipedal stance and cursorial habits, with adaptations to retain a steady head and gaze while moving. We also estimate its hearing frequency and range based on endosseous labyrinth morphology. Our study provides new information on the pattern of braincase and endocranial evolution in Sauropodomorpha.

Effect of Toe Type on Static Balance in Ballet Dancers

OBJECTIVES: Some forefoot shapes are ideal for pointe work in ballet. Egyptian-type, with the hallux being longest and the remaining toes decreasing in size, and Greek-type, with the second toe longer than the hallux, are considered less optimal for pointe work. Square-type, with the second toe the same length as the hallux, is considered optimal. This study compared postural stability in the bipedal stance, demi pointe, and en pointe between ballet dancers with the two toe types using a stabilometer. METHODS: This study included 25 Japanese ballet academy dancers who had received ballet lessons for at least 6 years. Toes were categorized into Egyptian-type (n=14) and square-type (n=11). Bipedal stance, demi pointe, and en pointe were tested. Center of pressure (COP) parameters were calculated from ground-reaction forces using two force plates: total trajectory length (LNG), velocities of anterior-posterior (VAP) and medial-lateral directions (VML), and maximum range displacement in the anterior-posterior (MAXAP) and medial-lateral directions (MAXML). Mann-Whitney U-tests were used to examine differences in COP parameters. RESULTS: There were no differences in parameters during bipedal stance or demi pointe. However, dancers with Egyptian-type toes had significantly greater LNG (p<0.01), VML (p=0.01), MAXML (p<0.01), and MAXAP (p=0.03) during en pointe. CONCLUSIONS: Ballet dancers with Egyptian-type toes demonstrated greater displacement in the medial-lateral and anterior-posterior directions during en pointe. Ballet dancers should be aware of toe types and sway character to optimize ballet training and balance.