Sprint cycling rate of torque development associates with strength measurement in trained cyclists

Purpose: A cyclist’s rate of force/torque development (RFD/RTD) and peak force/torque can be measured during single-joint or whole-body isometric tests, or during cycling. However, there is limited understanding of the relationship between these measures, and of the mechanisms that contribute to each measure. Therefore, we examined the: (i) relationship between quadriceps central and peripheral neuromuscular function with RFD/RTD in isometric knee extension, isometric mid-thigh pull (IMTP), and sprint cycling; and (ii) relationship among RFD/RTD and peak force/torque between protocols. Methods: Eighteen trained cyclists completed two familiarisation and two experimental sessions. Each session involved an isometric knee extension, IMTP, and sprint cycling protocol, where peak force/torque, average and peak RFD/RTD, and early (0 – 100 ms) and late (0–200 ms) RFD/RTD were measured. Additionally, measures of quadriceps central and peripheral neuromuscular function were assessed during the knee extension. Results: Strong relationships were observed between quadriceps early EMG activity (EMG50/M) and knee extension RTD (r or ρ = 0.51 – 0.65) and IMTP late RFD (r = 0.51), and between cycling early or late RTD and peak twitch torque (r or ρ = 0.70 – 0.75). Strong-to-very strong relationships were observed between knee extension, IMTP, and sprint cycling for peak force/torque, early and late RFD/RTD, and peak RFD/RTD (r or ρ = 0.59 – 0.80). Conclusion: In trained cyclists, knee extension RTD or IMTP late RFD are related to measures of quadriceps central neuromuscular function, while cycling RTD is related to measures of quadriceps peripheral neuromuscular function. Further, the strong associations among force/torque measures between tasks indicate a level of transferability across tasks

Ecological networks: Pursuing the shortest path, however narrow and crooked

International audienceRepresenting data as networks cuts across all sub-disciplines in ecology and evolutionary biology. Besides providing a compact representation of the interconnections between agents, network analysis allows the identification of especially important nodes, according to various metrics that often rely on the calculation of the shortest paths connecting any two nodes. While the interpretation of a shortest paths is straightforward in binary, unweighted networks, whenever weights are reported, the calculation could yield unexpected results. We analyzed 129 studies of ecological networks published in the last decade that use shortest paths, and discovered a methodological inaccuracy related to the edge weights used to calculate shortest paths (and related centrality measures), particularly in interaction networks. Specifically, 49% of the studies do not report sufficient information on the calculation to allow their replication, and 61% of the studies on weighted networks may contain errors in how shortest paths are calculated. Using toy models and empirical ecological data, we show how to transform the data prior to calculation and illustrate the pitfalls that need to be avoided. We conclude by proposing a five-point checklist to foster best-practices in the calculation and reporting of centrality measures in ecology and evolution studies. The last two decades have witnessed an exponential increase in the use of graph analysis in ecological and conservation studies (see refs. 1,2 for recent introductions to network theory in ecology and evolution). Networks (graphs) represent agents as nodes linked by edges representing pairwise relationships. For instance, a food web can be represented as a network of species (nodes) and their feeding relationships (edges) 3. Similarly, the spatial dynamics of a metapopulation can be analyzed by connecting the patches of suitable habitat (nodes) with edges measuring dispersal between patches 4. Data might either simply report the presence/absence of an edge (binary, unweighted networks), or provide a strength for each edge (weighted networks). In turn, these weights can represent a variety of ecologically-relevant quantities, depending on the system being described. For instance, edge weights can quantify interaction frequency (e.g., visitation networks 5), interaction strength (e.g., per-capita effect of one species on the growth rate of another 3), carbon-flow between trophic levels 6 , genetic similarity 7 , niche overlap (e.g., number of shared resources between two species 8), affinity 9 , dispersal probabilities (e.g., the rate at which individuals of a population move between patches 10), cost of dispersal between patches (e.g., resistance 11), etc. Despite such large variety of ecological network representations, a common task is the identification of nodes of high importance, such as keystone species in a food web, patches acting as stepping stones in a dispersal network , or genes with pleiotropic effects. The identification of important nodes is typically accomplished through centrality measures 5,12. Many centrality measures has been proposed, each probing complementary aspects of node-to-node relationships 13. For instance, Closeness centrality 14,15 highlights nodes that are "near" to all othe

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Effect of training surface on acute physiological responses after interval training

This study compared the effect of sand and grass training surfaces during a common preseason interval training session in well-trained team sport athletes (n = 10). The participants initially completed a preliminary testing session to gather baseline (BASE) performance data for vertical jump, repeated sprint ability, and a 3-km running time trial (RTT). Three days subsequent to BASE, all the athletes completed the first interval training session, which was followed by a repeat of the BASE performance tests the following day (24 hours postexercise). Seven days later, the same interval training session was completed on the opposing surface and was again followed 24 hours later by the BASE performance tests. During each session, blood lactate (BLa), ratings of perceived exertion, and heart rate (HR) were recorded. Additionally, venous blood was collected preexercise, postexercise, and 24 hours postexercise and analyzed for serum concentrations of myoglobin, creatine kinase, haptoglobin, and C-reactive protein. Results showed significantly higher BLa and HR responses experienced during the SAND session (p \u3c 0.05), with no differences observed between surfaces for the blood markers of muscle damage, inflammation, and hemolysis (p \u3e 0.05). Twenty-four hours later, the RTT was performed significantly faster after the SAND session compared with GRASS (p = 0.001). These results suggest that performing interval training on a sand (vs. grass) surface can result in a greater physiological response, without any additional detriment to next day endurance performance

Effect of surface-specific training on 20 m sprint performance on sand and grass surfaces

This study compared the effect of an 8-week pre-season conditioning program conducted on a sand (SAND) or grass (GRASS) surfaceon 20 m sprint performance.Twelve team sport athletes were required to attendthree 1 h training sessions perweek, including two surface-specific sessions (SAND, n=6 or GRASS, n=6), and one group session (conducted on grass). Throughout the training period, 20 m sprint timesof all athletes were recorded on both sand and grass surfaces at the end of week 1, 4and 8. Results showed a significant improvement in 20 m sand time in the SANDgroup only (p\u3c0.05), whereas 20 m grass time improved equally in both training sub-groups (p\u3c0.05). These results suggest that surface-specificity is essential for 20 mspeed improvements on sand, and also that there isno detriment to grass speed gains when incorporating sand surfaces into a pre-season program

Part 2: Effect of training surface on acute physiological responses after sport-specific training

This study compared the effect of sand and grass training surfaces during a sport-specific conditioning session in well-trained team sport athletes (n = 10). The participants initially completed a preliminary testing session to gather baseline (BASE) performance data for vertical jump, repeated sprint ability, and 3-km running time trial. Three days subsequent to BASE, all the athletes completed the first sport-specific conditioning session, which was followed by a repeat of the BASE performance tests the following day (24 hours postexercise). Seven days later, the same training session was completed on the opposing surface and was again followed 24 hours later by the BASE performance tests. During each session, blood lactate, ratings of perceived exertion (RPE), and heart rate (HR) were recorded, with player movement patterns also monitored via global positioning system units. Additionally, venous blood was collected preexercise, postexercise, and 24 hours postexercise, and analyzed for serum concentrations of Myoglobin, Haptoglobin, and C-Reactive Protein. Results showed significantly higher HR and RPE responses on SAND (p \u3e 0.05), despite significantly lower distance and velocity outputs for the training session (p \u3e 0.05). There were no differences in 24 hours postexercise performance (p \u3e 0.05), and blood markers of muscle damage, inflammation and hemolysis were also similar between the surfaces (p \u3e 0.05). These results suggest that performing a sport-specific conditioning session on a sand (vs. grass) surface can result in a greater physiological response, without any additional decrement to next-day performance

Evidence-based supplements for the enhancement of athletic performance

A strong foundation in physical conditioning and sport-specific experience, in addition to a bespoke and periodized training and nutrition program, are essential for athlete development. Once these underpinning factors are accounted for, and the athlete reaches a training maturity and competition level where marginal gains determine success, a role may exist for the use of evidence-based performance supplements. However, it is important that any decisions surrounding performance supplements are made in consideration of robust information that suggests the use of a product is safe, legal, and effective. The following review focuses on the current evidence-base for a number of common (and emerging) performance supplements used in sport. The supplements discussed here are separated into three categories based on the level of evidence supporting their use for enhancing sports performance: (1) established (caffeine, creatine, nitrate, beta-alanine, bicarbonate); (2) equivocal (citrate, phosphate, carnitine); and (3) developing. Within each section, the relevant performance type, the potential mechanisms of action, and the most common protocols used in the supplement dosing schedule are summarized

Examining the decay in serum ferritin following intravenous iron infusion : A retrospective cohort analysis of Olympic sport female athletes

The long-term decay rate of serum ferritin post-iron infusion in athletic populations is currently unknown. Here, we modelled the decay rate of serum ferritin in female athletes after an intravenous iron infusion (n = 22). The post-infusion serum ferritin response and the rate of decay was highly variable between athletes; however, we demonstrate that follow-up blood testing at 1 (154 μg/L; 77–300 μg/L) and 6 months (107 μg/L; 54–208 μg/L) post-infusion is appropriate to observe treatment efficacy and effectiveness

[In Press] Repeat application of ischemic preconditioning improves maximal 1,000-m kayak ergometer performance in a simulated competition format

Halley, SL, Peeling, P, Brown, H, Sim, M, Mallabone, J, Dawson, B, and Binnie, MJ. Repeat application of ischemic preconditioning improves maximal 1,000-m kayak ergometer performance in a simulated competition format. J Strength Cond Res XX(X): 000–000, 2020—This study examined the effects of ischemic preconditioning (IPC) on repeat 1,000-m kayak ergometer time-trial (TT) performance, completed in a simulated competition format. Eight well-trained male kayak athletes performed 3 experimental trials, each consisting of two 1,000-m TTs separated by 80 minutes (TT 1 and TT 2). Trials included; (a) IPC (4 3 5 minutes 220 mm Hg alternating bilateral leg occlusion) 40 minutes before TT 1 only (IPC1); (b) IPC 40 minutes before TT 1 and 20 minutes before TT 2 (IPC2); and (c) no IPC (CON). Time, power, stroke rate, and expired gas variables (V̇ O2 and accumulated oxygen deficit) were measured throughout each TT; blood gas variables (blood lactate, partial pressure of oxygen and blood pH) and rating of perceived exertion were measured before and after each effort. Physiological, perceptual, and physical measures were analyzed via a repeated measures analysis of variance with the level of significance set at p # 0.05. There were large improvements in completion time for TT 1 in IPC1 (d 5 1.24 6 0.68, p , 0.05) and IPC2 (d 5 1.53 6 0.99, p , 0.05) versus CON. There was also a large improvement in TT 2 completion time in IPC2 versus CON (d 5 1.26 6 1.13, p 5 0.03) whereas, IPC1 and CON were indifferent (d 5 0.3 6 0.54, p 5 0.23). This study showed that a repeat application of IPC in a simulated competition format may offer further benefit in comparison to a single pre-exercise application of IPC