Effects of Stroboscopic Vision on Depth Jump Motor Control: A Biomechanical Analysis

Researchers commonly use the \u27free-fall\u27 paradigm to investigate motor control during landing impacts, particularly in drop landings and depth jumps (DJ). While recent studies have focused on the impact of vision on landing motor control, previous research fully removed continuous visual input, limiting ecological validity. The aim of this investigation was to evaluate the effects of stroboscopic vision on depth jump (DJ) motor control. Ground reaction forces (GRF) and lower-extremity surface electromyography (EMG) were collected for 20 young adults (11 male; 9 female) performing six depth jumps (0.51 m drop height) in each of two visual conditions (full vision vs. 3 Hz stroboscopic vision). Muscle activation magnitude was estimated from EMG signals using root-mean-square amplitudes (RMS) over specific time intervals (150 ms pre-impact; 30–60 ms, 60–85 ms, and 85–120 ms post-impact). The main effects of and interactions between vision and trial number were assessed using two-way within-subjects repeated measures analyses of variance. Peak GRF was 6.4% greater, on average, for DJs performed with stroboscopic vision compared to full vision (p = 0.042). Tibialis anterior RMS EMG during the 60–85 ms post-impact time interval was 14.1% lower for DJs performed with stroboscopic vision (p = 0.020). Vastus lateralis RMS EMG during the 85–120 ms post-impact time interval was 11.8% lower for DJs performed with stroboscopic vision (p = 0.017). Stroboscopic vision altered DJ landing mechanics and lower-extremity muscle activation. The observed increase in peak GRF and reduction in RMS EMG of the tibialis anterior and vastus lateralis post-landing may signify a higher magnitude of lower-extremity musculotendinous stiffness developed pre-landing. The results indicate measurable sensorimotor disruption for DJs performed with stroboscopic vision, warranting further research and supporting the potential use of stroboscopic vision as a sensorimotor training aid in exercise and rehabilitation. Stroboscopic vision could induce beneficial adaptations in multisensory integration, applicable to restoring sensorimotor function after injury and preventing injuries in populations experiencing landing impacts at night (e.g., military personnel)

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Cellularity of tendons.

<p>Both (A) cellularity scores and (B) DNA content demonstrated reduced cellularity in MSC-treated tendons. The values for normal horses are shown as mean (thick dashed line) with two standard deviations (thin dashed lines). (A) * p=0.007; ** p=0.001; (B) * p=0.037; ** p<0.001.</p

Morphological parameters of tendons.

<p>(A) Organisation and (B) crimp as assessed by blinded scores were taken from two separate histological sections for each tendon. Representative micrographs of haematoxylin and eosin stained histological SDFT sections from the treated and remote (less injured) sites in both MSC-treated and saline-treated groups are shown in the panels on the right. Normal tendon has a score of zero and the higher the score the more disrupted the tendon matrix and less crimp pattern, respectively. (A) * p = 0.003; ** p < 0.002; (B) * p = 0.046; ** p < 0.0001 (scale bars 50 µm).</p

Cross-sectional area of the superficial digital flexor tendon.

<p>(A) Cross-sectional areas were measured ultrasonographically at the time of implantation (Stem Cell 1, Saline 1 and Contra 1) and at 6 months (Stem Cell 6, Saline 6 and Contra 6). (B) Relative change in cross-sectional area between groups. The Wilcoxon Signed-Rank test showed that there was no difference in cross-sectional area between 1 and 6 months for either the stem cell treated group or the saline group, or between the contralateral limbs in each group. Contralateral limbs were therefore combined from both groups for statistical analysis. The values for normal horses are shown as mean (thick dashed line) with two standard deviations (thin dashed lines). * p = 0.006, ** p= 0.003, ***p<0.045.</p

Trilineage differentiation of putative bone marrow MSCs.

<p>Representative microscopic images of von Kossa and Oil-Red-O staining to confirm osteogenic and adipogenic differentiation of plastic adherent bone marrow derived cell populations (scale bars 100 µm). A higher magnification inset is shown in the adipogenesis image to demonstrate the presence of intracellular lipid droplets. Chondrogenic differentiation was confirmed by the formation of dense cell pellets (haematoxylin and eosin staining) that were positive for Safranin O (orange-red stain) (scale bars 1 mm). All respective controls (non-induced cultures) are shown in the upper row panels.</p