11 research outputs found
Predictors of Performance during a 161 km Mountain Footrace
Training volume and cardiovascular dynamics influence endurance performance. However, there is limited information on the interplay between training volume, cardiovascular dynamics, and performance in ultra-marathon athletes. PURPOSE: We aimed to determine predictors of performance in finishers of the 2023 Western States Endurance Run (WSER). METHODS: Sixty participants who finished the race (49 males/11 females; mean age: 44.7 ± 9.6 y, range: 26–66 y; BMI: 22.7 ± 2.2 kg/m2) completed pre-race surveys including average training volume (AV) and peak training volume (PV), as well as resting cardiovascular measures including resting heart rate (RHR) and augmentation index (AIx), a measure of wave reflection characteristics. Based on WSER completion time, we calculated average running velocity (RV). We assessed associations among 22 variables using bivariate correlation analysis (Pearson’s Correlation for normally distributed data and Spearman’s Rank Correlation if normality was not met). Within our listed variables, normality was met in age and AV. Additionally, we completed multiple regression analyses for predictors. We present descriptive data as mean ± SD. RESULTS: Participants had an average RV of 6.33 ± 0.97 km/h (3.93 ± 0.6 mph), and reported an AV of 91.9 ± 24.5 km/wk (57.1 ± 15.2 miles/wk) and a PV of 141.0 ± 47.2 km/wk (87.6 ± 29.3 miles/wk). We observed significant associations between RV and age (r(58) = -0.57, p r(58) = 0.41, p r(58) = 0.34, p R2 = 0.37; F(3,56) = 12.4, pb1 = 0.013; t(56) = 2.57, p = 0.013), resulting in a 0.33 km/h increase in RV for every 25-km increase in AV. Last, significant relations existed between RV and AIx (r(58) = -0.30, p = 0.022); and RHR (r(58) = -0.26, p = 0.046). CONCLUSION: We found that (1) average weekly training volume is a significant predictor of performance in elite ultra-marathon athletes and (2) race performance was inversely associated with resting arterial wave reflection characteristics and heart rate
Nonlinear joint angle control for artificially stimulated muscle
Designs of both open- and closed-loop controllers of electrically stimulated muscle that explicitly depend on a nonlinear mathematical model of muscle input-output properties are presented and evaluated. The muscle model consists of three factors: a muscle activation dynamics factor, an angle-torque relationship factor, and an angular velocity torque relationship factor. These factors are multiplied to relate output torque to input simulation and joint angle. An experimental method for the determination of the parameters of this model was designed, implemented, and evaluated. An open-loop nonlinear compensator, based upon this model, was tested in an animal model. Its performance in the control of joint angle in the presence of a known load was compared with a PID (proportional-integral-derivative) controller, and with a combination of the PID controller and the nonlinear compensator. The results are presente
The evolution of a new publication type: Steps and challenges of producing overviews of reviews
360° Operative Videos: A Randomised Cross-Over Study Evaluating Attentiveness and Information Retention
Reduced Expression of CD45 Protein-tyrosine Phosphatase Provides Protection against Anthrax Pathogenesis*S⃞
The modulation of cellular processes by small molecule inhibitors, gene
inactivation, or targeted knockdown strategies combined with phenotypic
screens are powerful approaches to delineate complex cellular pathways and to
identify key players involved in disease pathogenesis. Using chemical genetic
screening, we tested a library of known phosphatase inhibitors and identified
several compounds that protected Bacillus anthracis infected
macrophages from cell death. The most potent compound was assayed against a
panel of sixteen different phosphatases of which CD45 was found to be most
sensitive to inhibition. Testing of a known CD45 inhibitor and antisense
phosphorodiamidate morpholino oligomers targeting CD45 also protected B.
anthracis-infected macrophages from cell death. However, reduced CD45
expression did not protect anthrax lethal toxin (LT) treated macrophages,
suggesting that the pathogen and independently added LT may signal through
distinct pathways. Subsequent, in vivo studies with both
gene-targeted knockdown of CD45 and genetically engineered mice expressing
reduced levels of CD45 resulted in protection of mice after infection with the
virulent Ames B. anthracis. Intermediate levels of CD45 expression
were critical for the protection, as mice expressing normal levels of CD45 or
disrupted CD45 phosphatase activity or no CD45 all succumbed to this pathogen.
Mechanism-based studies suggest that the protection provided by reduced CD45
levels results from regulated immune cell homeostasis that may diminish the
impact of apoptosis during the infection. To date, this is the first report
demonstrating that reduced levels of host phosphatase CD45 modulate anthrax
pathogenesis