Lower Cognitive Set Shifting Ability Is Associated With Stiffer Balance Recovery Behavior and Larger Perturbation-Evoked Cortical Responses in Older Adults

The mechanisms underlying associations between cognitive set shifting impairments and balance dysfunction are unclear. Cognitive set shifting refers to the ability to flexibly adjust behavior to changes in task rules or contexts, which could be involved in flexibly adjusting balance recovery behavior to different contexts, such as the direction the body is falling. Prior studies found associations between cognitive set shifting impairments and severe balance dysfunction in populations experiencing frequent falls. The objective of this study was to test whether cognitive set shifting ability is expressed in successful balance recovery behavior in older adults with high clinical balance ability (N = 19, 71 ± 7 years, 6 female). We measured cognitive set shifting ability using the Trail Making Test and clinical balance ability using the miniBESTest. For most participants, cognitive set shifting performance (Trail Making Test B-A = 37 ± 20 s) was faster than normative averages (46 s for comparable age and education levels), and balance ability scores (miniBESTest = 25 ± 2/28) were above the threshold for fall risk (23 for people between 70 and 80 years). Reactive balance recovery in response to support-surface translations in anterior and posterior directions was assessed in terms of body motion, muscle activity, and brain activity. Across participants, lower cognitive set shifting ability was associated with smaller peak center of mass displacement during balance recovery, lower directional specificity of late phase balance-correcting muscle activity (i.e., greater antagonist muscle activity 200–300 ms after perturbation onset), and larger cortical N1 responses (100–200 ms). None of these measures were associated with clinical balance ability. Our results suggest that cognitive set shifting ability is expressed in balance recovery behavior even in the absence of profound clinical balance disability. Specifically, our results suggest that lower flexibility in cognitive task performance is associated with lower ability to incorporate the directional context into the cortically mediated later phase of the motor response. The resulting antagonist activity and stiffer balance behavior may help explain associations between cognitive set shifting impairments and frequent falls.

Recovery behavior after matches for returning to training in volleyball athletes

The aim of this research was to evaluate the behavior of vertical jumps performance in professional volleyball athletes during matches and training and their relationships with fatigue and recovery through heart rate variability (HRV), ratings of perceived exertion (RPE) and perceived recovery status (PRS). Nine male professional volleyball athletes participated in the study, with mean age: 25.66 ± 5.7 years, mean body mass: 97.81 ± 8.65 Kg and mean height: 200.94 ± 5.19 cm, with experience in national and international competitions. HRV and PRS were evaluated in the morning of matches and in the presentation for the first day of training after matches. RPE was collected immediately after matches and at the end of training days. Jumps performance was monitored during the matches and during the first days of training. The data was grouped by matches and training sessions. Significance level adopted was α ≤ 0.05. There were no alterations in HRV and PRS evaluated after matches and before training sessions, as well as in RPE after training. Jumps height was greater during the matches (p< 0.013) and there were no differences in the number of jumps. There was a positive correlation between the number of jumps during matches and PRS before matches (r= 0.336, p= 0.015) and a negative correlation between the number of jumps during training and pre-training PRS (r= -0.318, p= 0.002). We conclude that the recovery period proposed by the team proved to be sufficient for the athletes to maintain the same condition for returning to training. This information can assist physical trainers to prescribe training loads for the return to training.

Rheological and Printability Assessments on Biomaterial Inks of Nanocellulose/Photo-Crosslinkable Biopolymer in Light-Aided 3D Printing

Biomaterial inks based on cellulose nanofibers (CNFs) and photo-crosslinkable biopolymers have great potential as a high-performance ink system in light-aided, hydrogel extrusion-based 3D bioprinting. However, the colloidal stability of surface charged nanofibrils is susceptible to mono-cations in physiological buffers, which complexes the application scenarios of these systems in formulating cell-laden bioinks. In this study, biomaterial inks formulated by neutral and negatively surface charged CNFs (GrowInk-N and GrowInk-T) and photo-crosslinkable biopolymers (gelatin methacryloyl (GelMA) and methacrylated galactoglucomannan (GGMMA)) were prepared with Milli-Q water or PBS buffer. Quantitative rheological measurements were performed on the ink formulations to characterize their shear flow recovery behavior and to understand the intermolecular interactions between the CNFs of different kinds with GGMMA or GelMA. Meanwhile, printability assessments, including filament extrudability and shape fidelity of the printed scaffold under varying printing conditions, were carried out to optimize the printing process. Our study provides extensive supporting information for further developing these nanocellulose-based systems into photo-crosslinkable bioinks in the service of cell-laden 3D bioprinting.