Running into Fatigue: The Effects of Footwear on Kinematics, Kinetics, and Energetics.

Recent studies identified a redistribution of positive mechanical work from distal to proximal joints during prolonged runs, which might partly explain the reduced running economy observed with running-induced fatigue. Higher mechanical demand of plantar flexor muscle-tendon-units, e.g., through minimal footwear, can lead to an earlier onset of fatigue, which might affect the redistribution of lower extremity joint work during prolonged runs. Therefore, the purpose of this study was to examine the effects of a racing-flat and cushioned running shoe on the joint-specific contributions to lower extremity joint work during a prolonged fatiguing run. On different days, eighteen runners performed two 10-km runs with near-maximal effort in a racing-flat and a cushioned shoe on an instrumented treadmill synchronized with a motion-capture-system. Joint kinetics and kinematics were calculated at 13 pre-determined distances throughout the run. The effects of shoes, distance, and their interaction were analyzed using a two-factor repeated-measures ANOVA. For both shoes, we found a redistribution of positive joint work from ankle (-6%) to knee (+3%) and hip (+3%) throughout the entire run. Negative ankle joint work was higher (p<0.01) with the racing-flat compared to the cushioned shoe. Initial differences in foot-strike patterns between shoes disappeared after 2 km of running distance. Irrespective of the shoe design, alterations in the running mechanics occurred in the first 2 km of the run, which might be attributed to the existence of a habituation rather than fatigue effect. While we did not find a difference between shoes in the fatigue-related redistribution of joint work from distal to more proximal joints, more systematical studies are needed to explore the effects of specific footwear design features. [Abstract copyright: Copyright © 2020 American College of Sports Medicine.

The character map in deformation quantization

The third author recently proved that the Shoikhet-Dolgushev L-infinity-morphism from Hochschild chains of the algebra of smooth functions on manifold to differential forms extends to cyclic chains. Localization at a solution of the Maurer-Cartan equation gives an isomorphism, which we call character map, from the periodic cyclic homology of a formal associative deformation of the algebra of functions to de Rham cohomology. We prove that the character map is compatible with the Gauss-Manin connection, extending a result of Calaque and Rossi on the compatibility with the cap product. As a consequence, the image of the periodic cyclic cycle 1 is independent of the deformation parameter and we compute it to be the A-roof genus of the manifold. Our results also imply the Tamarkin-Tsygan index Theorem

Positive Work Contribution Shifts from Distal to Proximal Joints during a Prolonged Run

PURPOSE: To investigate the joint-specific contributions to the total lower extremity joint work during a prolonged fatiguing run. METHODS: Recreational long-distance runners (RR; n = 13) and competitive long-distance runners (CR; n = 12) performed a 10-km treadmill run with near-maximal effort. A three-dimensional motion capture system synchronized with a force-instrumented treadmill was used to calculate joint kinetics and kinematics of the lower extremity in the sagittal plane during the stance phase at 13 distance points over the 10-km run. RESULTS: A significant (P < 0.05) decrease of positive ankle joint work as well as an increase of positive knee and hip joint work was found. These findings were associated with a redistribution of the individual contributions to total lower extremity work away from the ankle towards the knee and hip joint which was more distinctive in the RR group than in the CR group. This redistribution was accomplished by significant (P < 0.05) reductions of the external ground-reaction force (GRF) lever arm and joint torque at the ankle and by the significant (P < 0.05) increase of the external GRF lever arm and joint torque at the knee and hip. CONCLUSION: The redistribution of joint work from the ankle to more proximal joints might be a biomechanical mechanism that could partly explain the decreased running economy in a prolonged fatiguing run. This might be because muscle-tendon units crossing proximal joints are less equipped for energy storage and return compared to ankle plantar flexors and require greater muscle volume activation for a given force. In order to improve running performance, long-distance runners may benefit from an exercise-induced enhancement of ankle plantar flexor muscle-tendon unit capacities

M. Kontsevich's graph complex and the Grothendieck-Teichmueller Lie algebra

We show that the zeroth cohomology of M. Kontsevich's graph complex is isomorphic to the Grothendieck-Teichmueller Lie algebra grt_1. The map is explicitly described. This result has applications to deformation quantization and Duflo theory. We also compute the homotopy derivations of the Gerstenhaber operad. They are parameterized by grt_1, up to one class (or two, depending on the definitions). More generally, the homotopy derivations of the (non-unital) E_n operads may be expressed through the cohomology of a suitable graph complex. Our methods also give a second proof of a result of H. Furusho, stating that the pentagon equation for grt_1-elements implies the hexagon equation

Sprint start kinetics of amputee and non-amputee sprinters

The purpose of this study was to explore the relationship between the forces applied to the starting blocks and the start performances (SPs) of amputee sprinters (ASs) and non-amputee sprinters (NASs). SPs of 154 male and female NASs (100-m personal records [PRs], 9.58–14.00 s) and 7 male ASs (3 unilateral above knee, 3 unilateral below knee, 1 bilateral below knee; 100 m PRs, 11.70–12.70 s) with running specific prostheses (RSPs) were analysed during full-effort sprint starts using instrumented starting blocks that measured the applied forces in 3D. Using the NAS dataset and a combination of factor analysis and multiple regression techniques, we explored the relationship between force characteristics and SP (quantified by normalized average horizontal block power). Start kinetics were subsequently compared between ASs and NASs who were matched based on their absolute 100 m PR and their 100 m PR relative to the world record in their starting class. In NASs, 86% of the variance in SP was shared with five latent factors on which measured parameters related to force application to the rear and front blocks and the respective push-off directions in the sagittal plane of motion were loaded. Mediolateral force application had little influence on SP. The SP of ASs was significantly reduced compared to that of NASs matched on the basis of relative 100-m PR (−33.8%; d = 2.11, p < 0.001), while a non-significant performance reduction was observed when absolute 100-m PRs were used (−17.7%; d = 0.79, p = 0.09). These results are at least partially explained by the fact that force application to the rear block was clearly impaired in the affected legs of ASs

Lower limb joint kinetics during the first stance phase in athletics sprinting: three elite athlete case-studies

This study analysed the first stance phase joint kinetics of three elite sprinters to improve the understanding of technique and investigate how individual differences in technique could influence the resulting levels of performance. Force (1000 Hz) and video (200 Hz) data were collected and resultant moments, power and work at the stance leg metatarsal-phalangeal (MTP), ankle, knee and hip joints were calculated. The MTP and ankle joints both exhibited resultant plantarflexor moments throughout stance. Whilst the ankle joint generated up to four times more energy than it absorbed, the MTP joint was primarily an energy absorber. Knee extensor resultant moments and power were produced throughout the majority of stance, and the best-performing sprinter generated double and four times the amount of knee joint energy compared to the other two sprinters. The hip joint extended throughout stance. Positive hip extensor energy was generated during early stance before energy was absorbed at the hip as the resultant moment became flexor-dominant towards toe-off. The generation of energy at the ankle appears to be of greater importance than in later phases of a sprint, whilst knee joint energy generation may be vital for early acceleration and is potentially facilitated by favourable kinematics at touchdown

Synthesis, Molecular Editing, and Biological Assessment of the Potent Cytotoxin Leiodermatolide

It was by way of total synthesis that the issues concerning the stereostructure of leiodermatolide (1) have recently been solved; with the target now being unambiguously defined, the mission of synthesis changes as to secure a meaningful supply of this exceedingly scarce natural product derived from a deep-sea sponge. To this end, a scalable route of 19 steps (longest linear sequence) has been developed, which features a catalytic asymmetric propargylation of a highly enolizable β-keto-lactone, a ring closing alkyne metathesis and a modified Stille coupling as the key transformations. Deliberate digression from this robust blueprint brought a first set of analogues into reach, which allowed the lead qualities of 1 to be assessed. The acquired biodata show that 1 is a potent cytotoxin in human tumor cell proliferation assays, distinguished by GI50 values in the ≤3 nM range even for cell lines expressing the Pgp efflux transporter. Studies with human U2OS cells revealed that 1 causes mitotic arrest, micronucleus induction, centrosome amplification and tubulin disruption, even though no evidence for direct tubulin binding has been found in cell-free assays; moreover, the compound does not seem to act through kinase inhibition. Indirect evidence points at centrosome declustering as a possible mechanism of action, which provides a potentially rewarding outlook in that centrosome declustering agents hold promise of being inherently selective for malignant over healthy human tissue

Drastic Reductions in Mental Well-Being Observed Globally During the COVID-19 Pandemic: Results From the ASAP Survey

Most countries affected by the COVID-19 pandemic have repeatedly restricted public life to control the contagion. However, the health impact of confinement measures is hitherto unclear. We performed a multinational survey investigating changes in mental and physical well-being (MWB/PWB) during the first wave of the pandemic. A total of 14,975 individuals from 14 countries provided valid responses. Compared to pre-restrictions, MWB, as measured by the WHO-5 questionnaire, decreased considerably during restrictions (68.1 +/- 16.9 to 51.9 +/- 21.0 points). Whereas 14.2% of the participants met the cutoff for depression screening pre-restrictions, this share tripled to 45.2% during restrictions. Factors associated with clinically relevant decreases in MWB were female sex (odds ratio/OR = 1.20, 95% CI: 1.11-1.29), high physical activity levels pre-restrictions (OR = 1.29, 95% CI 1.16-1.42), decreased vigorous physical activity during restrictions (OR = 1.14, 95% CI: 1.05-1.23), and working (partially) outside the home vs. working remotely (OR = 1.29, 95% CI: 1.16-1.44/OR = 1.35, 95% CI: 1.23-1.47). Reductions, although smaller, were also seen for PWB. Scores in the SF-36 bodily pain subscale decreased from 85.8 +/- 18.7% pre-restrictions to 81.3 +/- 21.9% during restrictions. Clinically relevant decrements of PWB were associated with female sex (OR = 1.62, 95% CI: 1.50-1.75), high levels of public life restrictions (OR = 1.26, 95% CI: 1.18-1.36), and young age (OR = 1.10, 95% CI: 1.03-1.19). Study findings suggest lockdowns instituted during the COVID-19 pandemic may have had substantial adverse public health effects. The development of interventions mitigating losses in MWB and PWB is, thus, paramount when preparing for forthcoming waves of COVID-19 or future public life restrictions.DJ-P is supported by a grant from the Spanish Ministry of Science and Innovation-MINECO (RYC-2014-16938). The research fellowship of KH was funded by the German Research Foundation (Grant no. HO 6214/2-1)

A Pandemic within the Pandemic? Physical Activity Levels Substantially Decreased in Countries Affected by COVID-19

Governments have restricted public life during the COVID-19 pandemic, inter alia closing sports facilities and gyms. As regular exercise is essential for health, this study examined the effect of pandemic-related confinements on physical activity (PA) levels. A multinational survey was performed in 14 countries. Times spent in moderate-to-vigorous physical activity (MVPA) as well as in vigorous physical activity only (VPA) were assessed using the Nordic Physical Activity Questionnaire (short form). Data were obtained for leisure and occupational PA pre- and during restrictions. Compliance with PA guidelines was calculated based on the recommendations of the World Health Organization (WHO). In total, n = 13,503 respondents (39 +/- 15 years, 59% females) were surveyed. Compared to pre-restrictions, overall self-reported PA declined by 41% (MVPA) and 42.2% (VPA). Reductions were higher for occupational vs. leisure time, young and old vs. middle-aged persons, previously more active vs. less active individuals, but similar between men and women. Compared to pre-pandemic, compliance with WHO guidelines decreased from 80.9% (95% CI: 80.3-81.7) to 62.5% (95% CI: 61.6-63.3). Results suggest PA levels have substantially decreased globally during the COVID-19 pandemic. Key stakeholders should consider strategies to mitigate loss in PA in order to preserve health during the pandemic

Restrictercise! Preferences Regarding Digital Home Training Programs during Confinements Associated with the COVID-19 Pandemic

Confinement measures during the COVID-19 pandemic have caused substantial reductions in global physical activity (PA) levels. In view of the manifold health benefits of PA, the development of interventions counteracting this trend is paramount. Our survey with 15,261 participants (38 +/- 15 years, 58.5% females) examined preferences towards digital home exercise programs in 14 countries affected by COVID-19. More than two-thirds of the sample (68.4%, n = 10,433) indicated being interested in home exercise, and most participants were willing to work out at least three times per week (89.3%, n = 9328). Binary logistic regression revealed that female sex, working part-time, younger age, and being registered in a gym were associated with willingness to exercise. Flexibility (71.1%, n = 7377), resistance (68.6%, n = 7116), and endurance training (62.4%, n = 6478) were the most preferred types of exercise. Our results may guide health providers in developing individually tailored PA interventions during the current and future pandemic