Cyclic Strain Research Articles

The myosin and RhoGAP MYO9B influences osteocyte dendrite growth and responses to mechanical stimuli.

Introduction: Myosin IXB (MYO9B) is an unconventional myosin with RhoGAP activity and thus is a regulator of actin cytoskeletal organization. MYO9B was previously shown to be necessary for skeletal growth and health and to play a role in actin-based functions of both osteoblasts and osteoclasts. However, its role in responses to mechanical stimulation of bone cells has not yet been described. Therefore, experiments were undertaken to determine the role of MYO9B in bone cell responses to mechanical stress both in vitro and in vivo. Methods: MYO9B expression was knocked down in osteoblast and osteocyte cell lines using RNA interference and the resulting cells were subjected to mechanical stresses including cyclic tensile strain, fluid shear stress, and plating on different substrates (no substrate vs. monomeric or polymerized collagen type I). Osteocytic cells were also subjected to MYO9B regulation through Slit-Robo signaling. Further, wild-type or Myo9b -/- mice were subjected to a regimen of whole-body vibration (WBV) and changes in bone quality were assessed by micro-CT. Results: Unlike control cells, MYO9B-deficient osteoblastic cells subjected to uniaxial cyclic tensile strain were unable to orient their actin stress fibers perpendicular to the strain. Osteocytic cells in which MYO9B was knocked down exhibited elongated dendrites but were unable to respond normally to treatments that increase dendrite length such as fluid shear stress and Slit-Robo signaling. Osteocytic responses to mechanical stimuli were also found to be dependent on the polymerization state of collagen type I substrates. Wild-type mice responded to WBV with increased bone tissue mineral density values while Myo9b -/- mice responded with bone loss. Discussion: These results demonstrate that MYO9B plays a key role in mechanical stress-induced responses of bone cells in vitro and in vivo.

Female Soccer Periodization on Anaerobic Power/Capacity.

Purdom, TM, Levers, KS, Ryan, GA, Brown, L, Giles, J, and McPherson, C. Female soccer periodization on anaerobic power/capacity. J Strength Cond Res XX(X): 000-000, 2023-The purpose of this study was to observe changes in anaerobic power and capacity (resistance to fatigue) over an annual training cycle (ATC) in 14 Division I female soccer athletes (19.4 ± 1.0 years, 60.8 ± 5.4 kg, 164.9 ± 6.2 cm, 19.5 ± 3.2% body fat, and 48.9 ± 3.9 kg fat free mass). All subjects were evaluated across the ATC at 5 testing blocks (B1-B5) representing seasonal transitions: postcompetition I (B1), prespring (B2), postspring training (B3), precompetition (B4), and postcompetition II (B5) using 3 tests: countermovement vertical jump to measure peak vertical power (PVP), 40-yard sprint to measure peak horizontal power (PHP), and 35-m running anaerobic sprint test to measure anaerobic capacity via fatigue index (FI). Repeated measures analysis of variance was used with the Bonferroni post hoc test when relevant along with Cohen's d to evaluate effect size. Data are represented as mean ± SD; significance set to p < 0.05. Significant performance increases were observed from postseason I to spring season training (B1-B3) in PVP (6.61 ± 3.18 and 7.71 ± 3.20; p < 0.01, d = 1.12) while changes occurred from prespring season to postspring season (B2-B3) in PVP (6.84 ± 3.15 and 7.71 ± 3.20; p = 0.03, d = 0.93) and PHP (6.65 ± 0.97 and 7.55 ± 1.26; p < 0.01, d = 1.06) with no change in body composition. No other significant changes were observed across the ATC (p > 0.05). Increases in PHP and PVP occurred with directed training after B3 and then declined remaining so across the competitive season. Peak horizontal power and PVP may be more sensitive to coaching style and seasonal transition compared with FI and body composition changes.

Low-Cycle Fatigue Behaviour of Titanium-Aluminium-Based Intermetallic Alloys: A Short Review

Over the past decade, relentless efforts have brought lightweight high-temperature γ-TiAl-based intermetallic alloys into real commercialisation. The materials have found their place in General Electric’s (GE) high bypass turbofan aircraft engines for the Boeing 787 as well as in the PW1100GTF engines for low-pressure turbine (LPT) blades. In service, the alloys are required to withstand hostile environments dominated by cyclic stresses or strains. Therefore, to enhance the fatigue resistance of the alloys, a clear understanding of the alloys’ response to fatigue loading is pivotal. In the present review, a detailed discussion about the low-cycle fatigue (LCF) behaviour of γ-TiAl-based alloys in terms of crack initiation, propagation and fracture mechanisms, and the influence of temperature and environment on cyclic deformation mechanisms and the resulting fatigue life has been presented. Furthermore, a comprehensive discussion about modelling and prediction of the fatigue property of these alloys with regard to the initiation and propagation lives as well as the total fatigue life has been provided. Moreover, effective methods of optimising the microstructures of γ-TiAl-based alloys to ensure improved LCF behaviour have been elucidated.

Power production strategy during steady-state cycling is cadence dependent

Crank power is produced by extension and flexion of the hip and knee joints during steady-state pedaling below 120 rpm. Despite the pedaling cadence exceeding 120 rpm during track cycling, the power production strategy for lower-limb coordination above 120 rpm is unknown. This study aimed to assess the effects of various pedaling cadences on the power production strategy of lower-limb coordination during steady-state pedaling. Twenty trained collegiate cyclists performed a 30-s steady-state pedaling exercise at 50% of maximal anaerobic power under four different conditions with 90-, 120-, 150- and 180-rpm pedaling cadences. Pedal kinetics and limb kinematics were recorded using a pedal force measurement system and motion capture system, respectively. Positive mechanical work of hip extension significantly decreased with increasing pedaling cadence (P < 0.05). In contrast, the positive mechanical work of the knee joint flexion significantly increased with increasing pedaling cadence (P < 0.05). For contribution to the total mechanical work at 150 or above rpm, the knee joint showed > 70% of the total contribution, whereas the hip joint showed < 40%. Additionally, the positive mechanical work of the hip shifted to negative mechanical work under 180-rpm condition. These results indicate that power production strategy during steady-state pedaling at 180 rpm is different from the general pedaling cadence. Therefore, specific training needs to be conducted at an excessive-high pedaling cadence such as 180 rpm to achieve high performance in track cycling.

Cardiomyocyte external mechanical unloading activatesmodifications of α-actinin differently fromsarcomere-originated unloading.

Loss of myocardial mass in a neonatal rat cardiomyocyte culture is studied to determine whether there is a distinguishable cellular response based on the origin of mechano-signals. The approach herein compares the sarcomeric assembly and disassembly processes in heart cells by imposing mechano-signals at the interface with the extracellular matrix (extrinsic) and at the level of the myofilaments (intrinsic). Experiments compared the effects of imposed internal (inside/out) and external (outside/in) loading and unloading on modifications in neonatal rat cardiomyocytes. Unloading of the cellular substrate by myosin inhibition (1 μm mavacamten), or cessation of cyclic strain (1 Hz, 10% strain) after preconditioning, led to significant disassembly of sarcomeric α-actinin by 6 h. In myosin inhibition, this was accompanied by redistribution of intracellular poly-ubiquitin K48 to the cellular periphery relative to the poly-ubiquitin K48 reservoir at the I-band. Moreover, loading and unloading of the cellular substrate led to a three-fold increase in post-translational modifications (PTMs) when compared to the myosin-specific activation or inhibition. Specifically, phosphorylation increased with loading while ubiquitination increased with unloading, which may involve extracellular signal-regulated kinase 1/2 and focal adhesion kinase activation. The identified PTMs, including ubiquitination, acetylation, and phosphorylation, are proposed to modify internal domains in α-actinin to increase its propensity to bind F-actin. These results demonstrate a link between mechanical feedback and sarcomere protein homeostasis via PTMs of α-actinin that exemplify how cardiomyocytes exhibit differential responses to the origin of force. The implications of sarcomere regulation governed by PTMs of α-actinin are discussed with respect to cardiac atrophy and heart failure.

Self supervised learning and the poverty of the stimulus

Diathesis alternations are the possible expressions of the arguments of verbs in different, systematically related subcategorization frames. Semantically similar verbs such as spill and spray can behave differently with respect to the alternations they can participate in. For example one can “spill/spray water on the plant”, but while one can “spray the plant with water”, it is odd to say “spill the plant with water”. “Spray” is a verb which can alternate between syntactic frames while “spill” is not alternating. How human speakers learn the difference between such verbs is not clearly understood, because the primary linguistic data (PLD) they receive does not appear sufficient to infer the knowledge required for adult competence. More generally the poverty of the stimulus (POS) hypothesis states that the PLD is not sufficient for a learner to infer full adult competence of language. That is, learning relies on prior constraints introduced by the language faculty. We tested state-of-the-art machine learning models trained by self supervision, and found some evidence that they could in fact learn the correct pattern of acceptability judgement in the locative alternation. However, we argued that this was partially a result of fine-tuning which introduced negative evidence into the learning data, which facilitated shortcut learning. Large language models (LLMs) cannot learn some linguistic facts from normal language data, but they can compensate to some extent by learning spurious correlated features when negative feedback is introduced during the training cycle.

Comparing the reliability of muscle oxygen saturation with common performance and physiological markers across cycling exercise intensity.

Wearable near-infrared spectroscopy (NIRS) measurements of muscle oxygen saturation (SmO2) demonstrated good test-retest reliability at rest. We hypothesized SmO2 measured with the Moxy monitor at the vastus lateralis (VL) would demonstrate good reliability across intensities. For relative reliability, SmO2 will be lower than volume of oxygen consumption (V̇O2) and heart rate (HR), higher than concentration of blood lactate accumulation ([BLa]) and rating of perceived exertion (RPE). We aimed to estimate the reliability of SmO2 and common physiological measures across exercise intensities, as well as to quantify within-participant agreement between sessions. Twenty-one trained cyclists completed two trials of an incremental multi-stage cycling test with 5 min constant workload steps starting at 1.0 watt per kg bodyweight (W·kg-1) and increasing by 0.5 W kg-1 per step, separated by 1 min passive recovery intervals until maximal task tolerance. SmO2, HR, V̇O2, [BLa], and RPE were recorded for each stage. Continuous measures were averaged over the final 60 s of each stage. Relative reliability at the lowest, median, and highest work stages was quantified as intraclass correlation coefficient (ICC). Absolute reliability and within-subject agreement were quantified as standard error of the measurement (SEM) and minimum detectable change (MDC). Comparisons between trials showed no significant differences within each exercise intensity for all outcome variables. ICC for SmO2 was 0.81-0.90 across exercise intensity. ICC for HR, V̇O2, [BLa], and RPE were 0.87-0.92, 0.73-0.97, 0.44-0.74, 0.29-0.70, respectively. SEM (95% CI) for SmO2 was 5 (3-7), 6 (4-9), and 7 (5-10)%, and MDC was 12%, 16%, and 18%. Our results demonstrate good-to-excellent test-retest reliability for SmO2 across intensity during an incremental multi-stage cycling test. V̇O2 and HR had excellent reliability, higher than SmO2. [BLa] and RPE had lower reliability than SmO2. Muscle oxygen saturation measured by wearable NIRS was found to have similar reliability to V̇O2 and HR, and higher than [BLa] and RPE across exercise intensity, suggesting that it is appropriate for everyday use as a non-invasive method of monitoring internal load alongside other metrics.

Development of combined hardening model for spring-back simulation of DP600 in multi-stage sheet metal forming

High strength steel DP600 is widely used in automobile industry due to its excellent mechanical property compared to conventional steel, but spring-back issue is considered to be the major challenge of DP600 in forming process, as the spring-back is triggered by the release of complicated internal stress. In multi-stage sheet metal forming, the sheet may be subject to several cycles of loading and reverse loading, Bauschinger effect greatly influence the strain stress behaviour. A well designed material model can be used to accurately predict and compensate spring-back in forming process. A combined hardening model especially designed for multi-stage forming is proposed in this paper, and the iterated compensation method could be applied by using LS-DYNA to get an optimized result. An experimental testing facility was developed for calibration of this model with cyclic tension and compression strain stress curve. The compensation method is applied in the numerical simulation of a multi-stage manufacturing process of an A-pillar, the result demonstrates the feasibility of the combined hardening model.

Tramadol is a performance-enhancing drug in highly trained cyclists: a randomized controlled trial.

Tramadol is a potent narcotic analgesic reportedly used in multiple sports to reduce exertional pain and confer a performance advantage. This study sought to identify whether tramadol enhances performance in time trial cycling. Twenty-seven highly trained cyclists were screened for tramadol sensitivity and then attended the laboratory across three visits. Visit 1 identified maximal oxygen uptake, peak power output, and gas exchange threshold through a ramp incremental test. Participants returned to the laboratory on two further occasions to undertake cycling performance tests following the ingestion of either 100 mg of soluble tramadol or a taste-matched placebo control in a double-blind, randomized, and crossover design. In the performance tests, participants completed a 30 min non-exhaustive fixed intensity cycling task at a heavy exercise intensity (272 ± 42 W), immediately followed by a competitive self-paced 25-mile time trial (TT). Following removal of two outlier data sets, analysis was completed on n = 25. Participants completed the TT significantly faster (d = 0.54, P = 0.012) in the tramadol condition (3758 s ± 232 s) compared with the placebo condition (3808 s ± 248 s) and maintained a significantly higher mean power output (+9 W) throughout the TT (ηp2 = 0.262, P = 0.009). Tramadol reduced perception of effort during the fixed intensity trial (P = 0.026). The 1.3% faster time in the tramadol condition would be sufficient to change the outcomes of a race and is highly meaningful and pervasive in this cohort of highly trained cyclists. The data from this study suggests that tramadol is a performance-enhancing drug.NEW & NOTEWORTHY In the current study, when cycling with tramadol participants completed a time trial on average 50 s faster and at a 9 W higher power output than the placebo control. The study used both a fixed intensity and self-paced time trial exercise tasks to reflect the demands of a stage race. The outcomes from this study were used by the World Anti-Doping Agency to inform their addition of tramadol to the Prohibited List in 2024.

Study on the Microscopic Mechanism of Axle Steel EA4T during Uniaxial Cyclic Deformation Process

In order to reveal the dislocation evolution law of body-centered cubic axle steel EA4T during cyclic deformation and provide an experimental basis for the subsequent construction of cyclic constitutive models based on microscopic physical mechanisms, macroscopic deformation experiments were first conducted on axle steel EA4T, including monotonic tensile experiments under different deformation amounts, symmetric strain cycling experiments under a different number of cycles, and ratcheting deformation experiments under a different number of cycles. Then, systematic observations of different samples at different deformation stages were conducted using a Transmission Electron Microscope (TEM) to investigate the dislocation configuration and evolution during strain cycling and ratcheting deformation. The observed results show that the dislocation evolution law of axle steel EA4T during the uniaxial tensile experiment, symmetrical strain cycling, and ratcheting deformation is basically the same, and the dislocation density increases with the increase in plastic deformation and number of cycles. The dislocation configuration gradually develops from low-density dislocation configurations such as dislocation lines and dislocation pileups to high-density dislocation configurations such as severe dislocation tangles and dislocation walls. The microscopic mechanism of the uniaxial ratcheting evolution of axle steel EA4T can be qualitatively explained by the dislocation configuration and evolution.

An Ultrastretchable Gradient Ionogel Induced by a Self-Floating Strategy for Strain Sensing.

The fabrication of gradient ionogels for flexible strain sensors remains challenging because of the complex preparation procedures, and it is still difficult to prepare highly stretchable ionogels (strain > 10000%). In this study, a strategy is proposed to successfully fabricate gradient ionogels and apply them to flexible strain sensors by utilizing the self-floating character of the polysiloxane cross-linker. A gradient ionogel with ultrahigh stretchability (>14000%) is prepared via a one-step in situ photopolymerization process of the precursor with long-chain poly(dimethylsiloxane) bis(2-methyl acrylate) (PDMSMA). PDMSMA, which has a self-floating ability and excellent flexibility, induces a gradient composition distribution in the ionogel, thereby endowing the ionogel with superior stretchability and gradient changes in conductivity and adhesivity from the top to the bottom layer. Because of multiple molecular interactions, the bottom surface of the ionogel possesses good resilience and self-adhesion, whereas the top surface, which has a high PDMSMA content, shows a nonsticky performance. As a result, a singular gradient ionogel having both a sticky bottom surface and a nonsticky top surface is achieved. Furthermore, the flexible strain sensor that is created based on these gradient ionogels exhibits high sensitivity (its gauge factor reaching 5.08), a wide detection range (1-1500%), fast response times, and good linearity. Notably, the detection signal remains repeatable over 1000 uninterrupted strain cycles. The fabricated strain sensor was further utilized to monitor joint movements and physiological signals. This work provides a facile strategy for fabricating gradient ionogels and shows their application potential in the field of flexible electronics.

Sodium Bicarbonate Ingestion in a Fasted State Improves 16.1-km Cycling Time-Trial Performance.

The use of sodium bicarbonate (SB) as a preexercise ergogenic aid has been extensively studied in short-duration high-intensity exercise. Very few studies have considered the effects of SB ingestion before prolonged high-intensity exercise. The aim of the present study was to determine the effects of a 0.3 g·kg -1 body mass dose of SB ingested before the start of a 16.1-km cycling time trial in cyclists. Ten trained male cyclists (age, 31.1 ± 9 yr; height, 1.84 ± 0.05 m; body mass, 82.8 ± 8.5 kg; and V̇O 2peak , 60.4 ± 3.1 mL·kg -1 ·min -1 ) completed this study. Participants ingested 0.3 g·kg -1 in gelatine (SB-G) and enteric capsules (SB-E) 1 wk apart to determine individualized time-to-peak alkalosis for each ingestion form. Using a randomized crossover design, participants then performed simulated 16.1-km time trials after ingestion of SB-G, SB-E, or a placebo. There were significant differences in performance between the SB and placebo ingestion strategies ( f = 5.50, P = 0.014, p η2 = 0.38). Performance time was significantly improved by SB ingestion (mean improvement: 34.4 ± 42.6 s ( P = 0.031) and 40.4 ± 45.5 s ( P = 0.020) for SB-G and SB-E, respectively) compared with the placebo. Gastrointestinal symptoms were lower after SB-E compared with SB-G (36.3 ± 4.5 vs 5.6 ± 3.1 AU, P < 0.001, g = 7.09). This study demonstrates that increased buffering capacity after acute preexercise SB ingestion can improve endurance cycling time-trial performances. The use of SB could be considered for use in 16.1-km cycling time trials, but further work is required to establish these effects after a preexercise meal.

Experimental investigation on transverse tension-tension fatigue behavior of pultruded glass-fiber reinforced polymer (GFRP) unidirectional lamina

Inadequate transverse or shear strength is the key factor contributing to the failure of pultruded GFRP structures. In this paper, the static and fatigue performance of 90° pultruded unidirectional GFRP lamina were tested. A series of macroscopic phenomenological models were established to describe the performance variations during cyclic loading, including fatigue life, energy dissipation capacity and cyclic creep strain. The fracture surfaces of specimens were observed by a field-emission scanning electron microscopy (SEM). Experimental results indicated that the transverse fatigue life of GFRP unidirectional lamina can be fitted by S-N-R regression equation. The transverse stiffness degradation can be even ignored during fatigue loading. The results also show that the proposed equations can reasonably reflect the growth trend of dissipated energy per unit volume (UDE) and successfully predict cyclic creep strain increment of pultruded GFRP during cyclic loading.

Tremella polysaccharide-based conductive hydrogel with anti-freezing and self-healing ability for motion monitoring and intelligent interaction

The application of conductive hydrogels in flexible wearable devices has garnered significant attention. In this study, a self-healing, anti-freezing, and fire-resistant hydrogel strain sensor is successfully synthesized by incorporating sustainable natural biological materials, viz. Tremella polysaccharide and silk fiber, into a polyvinyl alcohol matrix with borax cross-linking. The resulting hydrogel exhibits excellent transparency, thermoplasticity, and remarkable mechanical properties, including a notable elongation (1107.3 %) and high self-healing rate (91.11 %) within 5 min, attributed to the dynamic cross-linking effect of hydrogen bonds and borax. A strain sensor based on the prepared hydrogel sensor can be used to accurately monitor diverse human movements, while maintaining exceptional sensing stability and durability under repeated strain cycles. Additionally, a hydrogel touch component is designed that can successfully interact with intelligent electronic devices, encompassing functions like clicking, writing, and drawing. These inherent advantages make the prepared hydrogel a promising candidate for applications in human health monitoring and intelligent electronic device interaction.

A dynamic model of the bi-exponential reconstitution and expenditure of W′ in trained cyclists

ABSTRACT The aim of this study was to investigate the effects of different recovery power outputs on the reconstitution of W′ and to develop a dynamic bi-exponential model of W′ during depletion and reconstitution. Ten trained cyclists (mass 71.7 ± 8.4 kg; V̇O2max 60.0 ± 6.3 ml·kg−1·min−1) completed three incremental ramps (20 W·min−1) to the limit of tolerance on each of six occasions with recovery durations of 30 and 240 s. Recovery power outputs varied between 50 W (LOW); 60% of critical power (CP) (MOD) and 85% of CP (HVY). W′ reconstitution was measured following each recovery and fitted to a bi-exponential model. Amplitude and time constant (τ) parameters were then determined via regression analysis accounting for relative intensity and duration to produce a dynamic model of W′. W′ reconstitution slowed disproportionately as recovery power output increased (p < 0.001) and increased with recovery duration (p < 0.001). The amplitudes of each recovery component were strongly correlated to W′ reconstitution after 240 s at HVY (r = 0.95), whilst τ parameters were found to be related to the fractional difference between recovery power and CP. The predictive capacity of the resultant model was assessed against experimental data with no differences found between predicted and experimental values of W′ reconstitution (p > 0.05). The dynamic bi-exponential model of W′ accounting for varying recovery intensities closely described W′ kinetics in trained cyclists facilitating real-time decisions about pacing and tactics during competition. The model can be customised for individuals from known CP and W′ and a single additional test session. Highlights A dynamic bi-exponential model of W′ accounting for both varying power output and duration. Individual customisation of the model can be achieved with a single specific test session. W′ reconstitution slows disproportionally with increasing intensity after repeated bouts.

The Predictive Validity of Individualised Load-Velocity Relationships for Predicting 1RM: A Systematic Review and Individual Participant Data Meta-analysis.

Load-velocity relationships are commonly used to estimate one-repetition maximums (1RMs). Proponents suggest these estimates can be obtained at high frequencies and assist with manipulating loads according to session-by-session fluctuations. Given their increasing popularity and development of associated technologies, a range of load-velocity approaches have been investigated. This systematic review and individual participant data (IPD) meta-analysis sought to quantify the predictive validity of individualised load-velocity relationships for the purposes of 1RM prediction. In September 2022, a search of MEDLINE, SPORTDiscus, Web of Science and Scopus was conducted for published research, with Google Scholar, CORE and British Ethos also searched for unpublished research. Studies were eligible if they were written in English, and directly compared a measured and predicted 1RM using load-velocity relationships in the squat, bench press, deadlift, clean or snatch. IPD were obtained through requests to primary authors and through digitisation of in-text plots (e.g. Bland-Altman plots). Risk of bias was assessed using the Prediction model Risk Of Bias ASsessment Tool (PROBAST) and the review conducted in accordance with PRISMA-IPD guidelines and an a priori protocol. Absolute and scaled standard error of the estimates (SEE/SEE%) were calculated for two-stage aggregate analyses, with bootstrapping performed for sampling variances. Estimates were pooled using three-level hierarchical models with robust 95% confidence intervals (CIs). One-stage analyses were conducted with random intercepts to account for systematic differences across studies and prediction residuals calculated in the absolute scale (kg) and as a percentage of the measured 1RM. Moderator analyses were conducted by including a priori defined categorical variables as fixed effects. One hundred and thirty-seven models from 26 studies were included with each identified as having low, unclear or high risk of bias. Twenty studies comprising 434 participants provided sufficient data for meta-analyses, with raw data obtained for 8 (32%) studies. Two-stage analyses identified moderate predictive validity [SEE% 9.8, 95% CI 7.4% to 12.2%, with moderator analyses demonstrating limited differences based on the number of loads (β2Loads:>2Loads = 0.006, 95% CI - 1.6 to 1.6%) or the use of individual or group data to determine 1RM velocity thresholds (βGroup:Individualised = - 0.4, 95% CI - 1.9 to 1.0%)]. One-stage analyses identified that predictions tended to be overestimations (4.5, 95% CI 1.5to 7.4kg), which expressed as a percentage of measured 1RM was equal to 3.7 (95% CI 0.5 to 6.9% 1RM). Moderator analyses were consistent with those conducted for two-stage analyses. Load-velocity relationships tend to overestimate 1RMs irrespective of the modelling approach selected. On the basis of the findings from this review, practitioners should incorporate direct assessment of 1RM wherever possible. However, load-velocity relationships may still prove useful for general monitoring purposes (e.g. assessing trends across a training cycle), by providing high-frequency estimates of 1RM when direct assessment may not be logistically feasible. Given limited differences in predictions across popular load-velocity approaches, it is recommended that practitioners opting to incorporate this practice select the modelling approach that best suits their practical requirements. https://osf.io/agpfm/ .

Finite Element Analysis Using the Crack Strain Separation Model for Reinforced Concrete Membrane

This paper presents a finite element analysis of the bi-directional orthogonal model, which incorporates individual crack strain separation and tracking. The objective of this research is to expand the current shear friction model to manage bi-directional cracking at any angle, allowing for a more universal model that can be applied to intricate structures and non-proportional loading cases. The proposed model was initially developed as a total strain-based model, with the assumption that crack strains are equivalent to total strains, but it was subsequently recalculated to improve accuracy by separating crack strains from total strains. Furthermore, a separate crack strain formulation was created to account for strains in the concrete’s uncracked portions and locked-in crack strains. The article then discusses the testing of various convergence methods and loading programs to achieve high convergence. Comparative analyses of the generalized shear friction model with other models for crack orientation, and loading cases similar to those of a reinforced concrete membrane, are also presented. The MATLAB program successfully applied the bi-directional cracking model for one finite element under a uniform cyclical strain state, using a secant stiffness formulation.

Cyclic behavior of hot-rolled titanium-clad bimetallic steel under large plastic strain reversals

Titanium-clad (TC) bimetallic steel is a versatile and high-performance material that offers a unique combination of different service properties, making it ideal for various engineering applications where both durability and strength are critical. Existing studies are exploring the application possibility of TC bimetallic steel in seismic zones. The severe seismic action tends to induce large-strain cyclic reversals in structural members. Thus, it is necessary to clarify the cyclic behavior of TC bimetallic steel under large-magnitude cyclic strains, whose strain range exceeds the strain level of conventional low-cycle fatigue tests. This paper has performed 7 large-strain cyclic coupon experiments on hot-rolled TA2 + Q355B TC bimetallic steel. The influences of different loading protocol on cyclic behaviors are clarified. All hysteretic stress-strain relations of TC bimetallic steel exhibit favorable plumpness under large-strain reversals. The increase in maximum strain and accumulation of plastic strain both induce apparent deterioration on elastic modulus. Based upon the experimental stress-strain relations, the Chaboche combined isotropic/kinematic hardening model parameters are calibrated and validated. The flow stresses of most tests exhibit little change over the full-range plasticity, illustrating that the isotropic hardening behavior is negligible. The cyclic behavior of TC bimetallic steel under large-strain reversals can be precisely simulated by a pure kinematic hardening constitutive model rather than a combined isotropic/kinematic hardening model. The Chaboche parameters calibrated from small-strain and mediate-strain cyclic loading tests tend to overestimate the hysteretic energy dissipation ability under large-strain reversals. In addition, the stress-strain relations of TC bimetallic steel are compared with those of low yield point steels, mild steels and high strength steels. The hysteretic energy dissipation ability of TA2 + Q355B TC bimetallic steel is greater than that of low yield point steels, but less than those of mild steels and high strength steels.

Wearable Strain Sensor With a Graphene Localized Warping Structure for Ultra-Wide Range Strain Detection and Bending Direction Recognition

The practical need for the accurate detection of human activities requires wearable flexible strain sensors that can detect subtle and large strains and recognize the bending direction of joints. However, it remains challenging to integrate these detection capabilities into a single strain sensor. Herein, we prepared flexible strain sensors with firmly attached locally warped graphene on the surface of anhydride-grafted styrene-butadiene-styrene triblock copolymer films using a swelling-self-assembly method. The unique localized warpage structure of graphene sheets gives the sensor excellent strain response performance and the ability to recognize the bending direction. The detection limit of the sensor to strain is independent of the sensitivity to strain, which allows it to detect ultralow (0.01%) and large strains (500%). Moreover, the sensor has a large linear response range (0~94%) and good test stability (3000 cycles of strain). The sensor can be used to recognize the bending direction by generating opposite response signals to different bending directions. The excellent response behavior allows the sensor to accurately monitor the joint bending angle, direction of the human body, and subtle tremors of the human skin, which makes it a potential application for wearable devices and smart prosthetics.

Design and development of networked real-life cycling training system based on mixed reality technology

The intelligent riding platform cooperates with the PC-side riding training system to simulate the effect of outdoor riding with a certain sense of reality. With the rapid development of information technology, users have also put forward higher requirements for cycling training systems. The 3D virtual scene riding mode provided by the existing intelligent riding training system does not meet the user's preference for real riding, and the domestic riding platform cannot simulate the real road feeling, lacking realism and fun. Therefore, developing a richer and more interesting new cycling training mode and creating a more realistic and accurate real cycling experience based on mixed reality are the new demands of users for the cycling training system. At the same time, the calculation and development of rider power based on the platform is the core of it. In the original single-person riding training mode, the server framework and client-side functional modules are constructed by using the principle of network communication and related technologies such as the production of online game rooms to realize the multi-player competitive function.