Cyclic Strain Research Articles

The Effect of Time-Equated Concurrent Training Programs in Resistance-Trained Men.

The purpose of this investigation was to compare the effects of three different concurrent training (CT) programs and a resistance training (RT) program. Twenty-three resistance trained men (age: 24 ± 3 years) were randomized into four groups: concurrent RT and high intensity interval cycling (CTH, n = 6), concurrent RT and moderate intensity continuous cycling (CTM, n = 5), RT and barbell circuit training (RTC, n = 6), or RT only (RT, n = 6). Back squat and bench press strength, quadriceps, and pectoralis muscle thickness, VO2peak, and maximum workload (Wmax, Watts) were assessed. Squat strength gains were meaningful in all groups and comparable among CTH (16.88 kg [95% CrI: 11.15, 22.63]), CTM (25.54 kg [95% CrI: 19.24, 31.96]), RTC (17.5 kg [95% CrI: 11.66, 23.39]), and RT (20.36 kg [95% CrI: 15.29, 25.33]) groups. Bench press strength gains were meaningful in all groups and comparable among CTH (11.86 kg [95% CrI: 8.28, 15.47]), CTM (10.3 kg [95% CrI: 6.49, 14.13]), RTC (4.84 kg [95% CrI: 1.31, 8.47]), and RT (10.16 kg [95% CrI: 7.02, 13.22]) groups. Quadriceps hypertrophy was meaningful in all groups and comparable among CTH (2.29 mm [95% CrI: 0.84, 3.76]), CTM (3.41 mm [95% CrI: 1.88, 4.91]), RTC (2.6 mm [95% CrI: 1.17, 4.05]), and RT (2.83 mm [95% CrI: 1.55, 4.12]) groups. Pectoralis hypertrophy was meaningful in CTH (2.29 mm [95% CrI: -0.52, 5.1]), CTM (5.14 mm [95% CrI: 2.1, 8.15]), and RTC (7.19 mm [95% CrI: 4.26, 10.02]) groups, but not in the RT group (1 mm [95% CrI: -1.59, 3.59]); further, between-group contrasts indicated less pectoralis growth in the RT compared to the RTC group. Regarding cardiovascular outcomes, only the RTH and RTM groups experienced meaningful improvements in either measure (VO2peak or Wmax). These data suggest that the interference effect on maximal strength and hypertrophy can be avoided when the aerobic training is moderate intensity cycling, high intensity cycling, or a novel barbell circuit for ~one hour per week and on non-RT days. However, the barbell circuit failed to elicit meaningful cardiovascular adaptations.

Physical modelling of cyclic loading-induced footing settlement with nearby pit excavation

A series of physical model tests and cyclic triaxial tests were conducted on a dry sand to investigate the effects of excavating an adjacent pit on the settlement behaviour of a footing under cyclic loading. The excavation was simulated by moving a retaining wall between loading cycles in the physical model tests. The excavation-induced stress disturbance on soil elements was modelled by reducing cell pressure between loading cycles in triaxial tests. The results indicate that nearby excavation leads to a reduction in lateral stress in ground, and therefore increases the settlement of footing in the subsequent loading cycles. However, there is no clear relationship between the settlement increment and the magnitude of wall movement, when the lateral movement of the wall is within the range of 0.1–0.37% of the wall height. The lateral excavation does not have a great impact on the influence zone of the footings under cyclic loading. An empirical model was proposed to estimate the cyclic loading-induced strain accumulation of sand with the consideration of lateral unloading effects between loading cycles. After being validated using cyclic triaxial test results, the proposed model was employed to predict cyclic loading-induced settlement of the footing before and after the excavation.

Acute Effects of Different Inter-Repetition Rest Intervals During ‘Composite’ Training on Fast Stretch-Shortening Cycle and Neuromuscular Performance in Hurling Players: A Pilot Study

One study to date has compared inter-repetition rest intervals when employing ‘composite’ training. Thus, the purpose of this study was to compare the acute effects of 2-, 3- and 4-mins ‘composite’ training inter-repetition rest intervals on fast stretch shortening cycle (SSC) and neuromuscular performance. A randomized crossover research design was employed. Drop jump (DJ), 20m sprint (with 5 and 10m splits), countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) tests were performed pre-session, post-session, and 7 days post-session to observe if supercompensation occurred. A 2-min rest interval showed enhancements in fast SSC DJ performance where supercompensation may have occurred in height, velocity, force and power (Cohen’s d = 0.22-0.55). A 3-minute rest interval elicited responses in 5 and 20m sprint performance (Cohen’s d = -0.29 to -0.30) and isometric RFD (Cohen’s d = 0.35-0.60) 7 days post-session. CMJ measures (Cohen’s d = 0.22-0.76) appeared to have experienced supercompensation when employing a 4-minute rest period. Significant (p < 0.05) decreases in performance pre- to post-session were found for certain sprint, CMJ and IMTP variables. The ‘composite’ training inter-repetition rest interval used, appears dependent on the primary goal of a training cycle. However, a 3-min rest interval may be used if there are multiple goals of a training cycle due to enhancements in sprint performance, isometric RFD and CMJ height. ‘Composite’ training is a time-efficient method of enhancing jump, sprint, and maximal strength, which is suitable for practitioners working in sports such as hurling where time is limited.

Acute physiological responses of blood flow restriction between high-intensity interval repetitions in trained cyclists.

Blood flow restriction (BFR) is increasingly being used to enhance aerobic performance in endurance athletes. This study examined physiological responses to BFR applied in recovery phases within a high-intensity interval training (HIIT) session in trained cyclists. Eleven competitive road cyclists (mean±SD, age: 28±7years, body mass: 69±6kg, peak oxygen uptake: 65±9mL ·kg-1· min-1) completed two randomised crossover conditions: HIIT with (BFR) and without (CON) BFR applied during recovery phases. HIIT consisted of six 30-s cycling bouts at an intensity equivalent to 85% of maximal 30-s power (523±93W), interspersed with 4.5-min recovery. BFR (200mmHg, 12cm cuff width) was applied for 2-min in the early recovery phase between each interval. Pulmonary gas exchange (V̇O2, V̇CO2, and V̇E), tissue oxygen saturation index (TSI), heart rate (HR), and serum vascular endothelial growth factor concentration (VEGF) were measured. Compared to CON, BFR increased V̇CO2 and V̇E during work bouts (both p<0.05, dz<0.5), but there was no effect on V̇O2, TSI, or HR (p>0.05). In early recovery, BFR decreased TSI, V̇O2, V̇CO2, and V̇E (all p<0.05, dz>0.8) versus CON, with no change in HR (p>0.05). In late recovery, when BFR was released, V̇O2, V̇CO2, V̇E, and HR increased, but TSI decreased versus CON (all p<0.05, dz>0.8). There was a greater increase in VEGF at 3-h post-exercise in BFR compared to CON (p<0.05, dz>0.8). Incorporating BFR into HIIT recovery phases altered physiological responses compared to exercise alone.

Formation of Professional Skills of Agricultural Engineers during Laboratory Practice when Studying Fundamental Science

The article deals with the problems of organizing and conducting professionally oriented laboratory classes in fundamental sciences, in particular physics in agricultural and technical universities. The research aim is to theoretically substantiate and develop the methodology for the formation of professionally oriented experimental skills of future agricultural engineers in the process of performing laboratory work in physics in the conditions of the integration of fundamental and professional training. To achieve the research aim, we used the following research methods: theoretical (comparative analysis of scientific, methodological and pedagogical literature) and empirical (observation, analysis, survey of respondents, generalization and modeling of research results, generalization of pedagogical learning experience). In order to select and understand the experiment results, we conducted a survey of teachers and students in order to reveal their understanding of the importance of studying physics for future professional activities. The analysis of the content of physics curricula and other subjects of the natural-mathematical and professional cycles of training made it possible to determine the topics that can be supplemented at laboratory classes in physics (these additions are aimed at the formation of practical skills, which are a necessary component of the professional competence of future specialists in the agricultural sector). The professional orientation in teaching natural sciences involves studying the science basics in an organic connection with the specifics of the future profession. The research experimentally proved that the practical focus of teaching physics changes the student’s attitude to theoretical training, helps him discover the deep internal interdependence of theory with future professional activity, his training as a specialist.

The strain demand of reinforced concrete bridge columns under seismic loading

The steel in reinforced concrete (RC) members that form plastic hinges must possess sufficient strain capacity to dissipate seismic deformation demands. Unfortunately, there is limited information on the seismic strain demands of bridge column plastic hinges. Instead, designers rely on a perception of cyclic strain capacity that is an approximate rule of thumb. A standard methodology needs to be established for quantifying the strain demand on these structural members as a function of the expected seismic hazard. To develop this methodology, 1944 columns were analyzed with nonlinear time-history analyses (NLTHAs) using ground motions from a range of earthquakes. This study evaluates the strain demand on RC bridge columns by defining the relationship between the strain demand and earthquake intensity. The results of the model are defined in terms of the peak tensile strain of the reinforcing bar, [Formula: see text]. The earthquake intensity with the highest correlation to the [Formula: see text] was determined to be the elastic spectral displacement at the optimal period ([Formula: see text]), which is defined as 75% of the effective period. The relationship between [Formula: see text] and [Formula: see text] can be used to predict the strain demand for an RC bridge column at a given geographic location. Results are presented as a probability density function (PDF), representing strain demand, compared to a PDF of the column capacity. The intersection of the capacity curve and demand curve represents the maximum acceptable strain given as a function of [Formula: see text]. This methodology can help understand the demand placed on a structural system given a region’s seismicity.

High‐Entropy Phase Stabilization Engineering Enables High‐Performance Layered Cathode for Sodium‐Ion Batteries

AbstractO3‐type layered oxides are considered as one of the most promising cathode materials for rechargeable sodium‐ion batteries (SIBs) due to their appealing energy density and feasible synthesis. Nevertheless, it undergoes complicated phase transitions and pronounced structural degradation during the cycling of charge/discharge process, rendering severe volumetric strain and poor cycling performance. Herein, a zero‐strain high‐entropy NaNi0.2Fe0.2Mn0.35Cu0.05Zn0.1Sn0.1O2 cathode for SIBs is presented by high‐entropy phase stabilization engineering. It is verified that this low‐nickel cobalt‐free high‐entropy cathode can deliver a highly reversible phase evolution, zero volumetric strain, and a significantly improved cycling performance in full cells (87% capacity retention after 500 cycles at 3.0 C). Combining X‐ray absorption spectra and first‐principles calculations, the varied elemental functions in the high‐entropy framework are clearly elucidated, namely, Ni/Fe/Cu acts as charge compensators, while Mn/Zn/Sn serve as interlayer slipping inhibitors through enhanced charge localization besides their stable valence states. By addressing the volumetric strain and cycling instability concerns for O3‐type cathode materials, this work presents a promising strategy for inhibiting irreversible phase transitions and structural degradation in intercalation electrodes, which significantly boosts the development of commercially feasible cathodes for high‐performance SIBs.

E-Learning challenges and trainee teacher engagement: Lessons from the COVID-19 pandemic

Introduction The sudden emergence of the COVID-19 pandemic resulted in a compulsory shift to distance learning due to school closures. Consequently, all educational courses were delivered virtually. To facilitate this transition for students and educators, the Ministry of Education implemented digital learning platforms, such as Taalim.ma and TelmidTice. Furthermore, the Broadcasting and Television National Company reorganized its television channels to maintain continuity throughout the academic year. As a result, trainee teachers have effectively shifted to distance learning, using resources such as e-Takwine, MOOC classes, and digital classrooms.Objectives This study examines the factors that cause discomfort among trainee teachers and evaluates their influence on satisfaction with distance learning during the COVID-19 pandemic.Methods We conducted a descriptive study with 370 Moroccan trainee teachers, with a mean age of 28.30 ± 5.99 years. We collected data using a self-administered questionnaire that was divided into three sections. The initial section examined sociodemographic and professional factors, including gender, age, marital status, academic level, and training cycle. The subsequent section focuses on discomfort-inducing factors, including living arrangements during lockdown, digital skills, material availability, network connectivity, and training schedules. Finally, the concluding section analyzes the trainees’ satisfaction and perceptions within their learning community.ResultsThe study indicated that 75% of trainee teachers lived in homes with four to seven residents, leading to confined living arrangements. Furthermore, 55% of the participants did not have a designated workspace for studying, focusing, or engaging with instructors. Participants identified various obstacles to online learning, including 80% lacking digital skills, 60% having insufficient equipment, 73.33% experiencing connection and network issues, 78.33% being unfamiliar with online learning, and 68.33% facing an unsuitable training schedule. The study indicates a positive correlation between trainee satisfaction and engagement (r = 0.422, p&lt; 0.001).Conclusions The COVID-19 pandemic has necessitated online education as a crucial resource for ensuring the continuity of education. This study highlights the paramount significance of developing effective e-training policies to direct novice teachers toward successful online learning by alleviating their discomfort factors.Disclosure of InterestNone Declared

Physical Training Profile and Training Patterns of Paragliding Athletes

This study aims to determine the ideal physical training program and optimal training patterns for paragliding athletes. The research method used is qualitative with a case study approach to describe and analyze the perceptions of athletes and coaches. In this case, the participants in this study were 1 female athlete aged 22 years and 1 male coach aged 61 years in the paragliding sport of DKI Jakarta. Questionnaires, interviews, and documentation were used to collect data. The results of the athlete's questionnaire with the following indicators: 1) talent/seed guidance 83%, 2) coaching 67%, 3) physical, technical, tactical and psychological training program 75%, 4) nutrition intake 100%, 5) training cycle 50%, 6) facilities and infrastructure 100%, 7) Achievement 100%. Likewise, the results of the coach's questionnaire with the following indicators: 1) talent/seed guidance 100%, 2) coaching program 100%, 3) training cycle 75%, 4) management structure 80%, 5) facilities and infrastructure 50%, 6) Achievement 100%. This study shows that the ideal physical training pattern for paragliding athletes is one that is systematic, progressive, and tailored to the needs of the athlete, the optimal training pattern to improve the performance of paragliding athletes is to follow a structured and consistent training pattern.

Adaptive changes in young football players working in a modified tactical periodization model based on the example of endurance

Introduction: Adequate endurance is a critical element of success in football, both at professional and amateur levels. Therefore, this study aimed to assess the effectiveness of training based on a modified wave (repeating) periodization model on the endurance of players aged 12–16 at the RKS Raków Academy in 2018–2022. Material and Method: The analysis involved football players aged 12 to 16 with 4–8 years of training experience, involved in a program called "wave periodization". Two tests were performed each year, one in June (Test A) and the other one in December (Test B). Maximal Aerobic Speed (MAS) and Velocity Intermittent Fitness Test (VIFT) indicators were measured using the Intermittent Fitness Test 30–15 by M. Buchheit. Results: Tests conducted after a 6-month training cycle in subsequent years statistically significantly increased the MAS (Z = 14.45; p &lt; 0.001) and VIFT (Z = 13.11; p &lt; 0.001) values. The importance of MAS (F = 206.31; p &lt; 0.001) and VIFT (F = 209.11; p &lt; 0.001) increased in both tests in subsequent years of training. The player’s position on the pitch does not correlate with the results of endurance tests. However, there is a relationship between players’ age and endurance. Conclusions: The training based on the wave periodization model significantly increased the endurance of the RKS Raków Częstochowa Academy players. The research shows that in each year between 2018 and 2022, the training intervention increased the tested players’ MAS and VIFT values. The tested players’ position on the pitch does not correlate with the results of endurance tests. The recorded positive correlation between age and endurance confirms the current knowledge.

The Effect of Menthol Mouth Rinsing and Fluid Temperature on Male Cycling Performance in Thermoneutral Conditions.

The purpose of this study was to determine the effect of a menthol (MEN) mouth rinse (MR) on cycling time trial (TT) performance in thermoneutral conditions and to explore the impact of fluid temperature (cold water [CW] or thermoneutral water [TNW]) on MEN's effect on performance. Twelve trained male cyclists (VO2 peak, 61.4 ± 12.1 mL/kg/min) completed a cycling TT in thermoneutral conditions (21 ± 0.2 °C, 40 ± 0.6% relative humidity) with four different mouth rinses: (1) MEN + CW; (2) MEN + TNW; (3) CW; and (4) TNW. The time to complete the TT and the power output (W) were recorded. The ratings of perceived exertion (RPE, Borg 6-20), thermal sensation (TS), and thermal comfort (TC) were recorded prior to and throughout the TT. The core body temperature (Tc) and heart rate (HR) were recorded throughout. The TT duration was not significantly different between trials (MEN + TNW: 38:11 ± 12:48, MEN + CW: 37:21 ± 13:00, CW: 38:12 ± 13:54, TNW: 36:06 ± 14:12 mins:secs, p < 0.05). The mean trial power output did not significantly differ between conditions (>0.05). The Tc, HR, RPE, TS, and TC were not significantly different between trials (p > 0.05). The results suggest that a MEN MR with either CW or TNW does not significantly improve cycling TT performance in trained male cyclists compared to a CW or TNW MR in thermoneutral conditions.

Prediction of the fatigue life in a textured AZ31 Mg alloy as a function of orientation using fatigue indicator parameters

Computational homogenization was used to simulate the mechanical response of a textured AZ31Mg alloy subjected to fully-reversed cyclic deformation. The behavior of each grain in the polycrystal followed a phenomenological crystal plasticity model that considered different deformation mechanisms, namely pyramidal, basal, and prismatic slip, as well as twinning and detwinning. It also accounted for both kinematic and isotropic hardening effects. The crystal plasticity model's parameters were adjusted to replicate the cyclic stress-strain curves along three different orientations (rolling direction, normal direction and at 45° between the rolling and normal directions) at different cyclic strain semi-amplitudes. Three different fatigue indicator parameters were calculated from the simulations, based on the accumulated plastic shear strain in one stabilized fatigue cycle from basal slip and pyramidal slip, and from the shear strain accommodated by twinning/de-twinning during one fatigue cycle. The predictions of the fatigue life based on the fatigue indicator parameters were compared with the experimental results for the three orientations. It was found that the most accurate prediction was obtained by using the fatigue indicator parameter associated with twinning/de-twinning. Thus, it is concluded that fatigue cracks nucleated at twin boundaries control the fatigue life of textured Mg alloys.

A hyperelastic hydrogel with an ultralarge reversible biaxial strain.

Hyperelastic materials exhibit a nonlinear elastic response to large strains, whereas hydrogels typically possess a low elastic range due to the nonuniform cross-linking and limited chain segments among cross-links. We developed a hyperelastic hydrogel that possesses a broader elastic range by introducing a reversible pearl-necklace structure, in which beads are connected by strings. The subnanometric beads can efficiently unfold and refold under cyclic mechanical strains; thus, the hydrogel can rapidly recover after being stretched to an areal strain of more than 10,000%. Additionally, the hydrogel can quickly heal from minor mechanical damages such as needle punctures and cuts. These advancements make our ionic hydrogels ideal for multifunctional pneumatic gripper materials; they simultaneously offer an ultralarge gripping range, self-sensing capabilities, and fast healing abilities.

Artificial neural networks-based J-integral prediction for cracked bodies under elasto-plastic deformation state –cyclic loading

The study builds upon a prior modeling framework designed for monotonic loading to compute the cyclic J-integral encompassing a crack tip experiencing elastic–plastic deformation due to cyclic loads. The proposed modeling approach extends the authors' earlier time-efficient method for computing the J-integral by combining artificial neural networks (ANNs) with finite element (FE) analyses. The ANN-FE integration allows efficient and accurate prediction of elastic–plastic stresses, strains and displacement fields for a crack body under cyclic loadings from the linear elastic FE solution. In the context of cyclic loading, stress, strain, and displacement fields near the crack tip of stainless steel (SS304) are determined by FE analyses under both elastic and elasto-plastic states for various crack sizes and R-ratios. ANNs models are developed to establish the nonlinear relationship between these two states. Consequently, the proposed approach enables the prediction of the elasto-plastic cyclic J-integral through the equivalent domain integral method, based on the elastic FE solution bypassing the need of a complicated elasto-plastic FE solution under cyclic loadings. The results show that this approach can effectively predict elasto-plastic cyclic J-integral while avoiding the complex computation of elastic–plastic deformation fields around the crack tip during cyclic loadings.

Open-Set Facial Expression Recognition

Facial expression recognition (FER) models are typically trained on datasets with a fixed number of seven basic classes. However, recent research works (Cowen et al. 2021; Bryant et al. 2022; Kollias 2023) point out that there are far more expressions than the basic ones. Thus, when these models are deployed in the real world, they may encounter unknown classes, such as compound expressions that cannot be classified into existing basic classes. To address this issue, we propose the open-set FER task for the first time. Though there are many existing open-set recognition methods, we argue that they do not work well for open-set FER because FER data are all human faces with very small inter-class distances, which makes the open-set samples very similar to close-set samples. In this paper, we are the first to transform the disadvantage of small inter-class distance into an advantage by proposing a new way for open-set FER. Specifically, we find that small inter-class distance allows for sparsely distributed pseudo labels of open-set samples, which can be viewed as symmetric noisy labels. Based on this novel observation, we convert the open-set FER to a noisy label detection problem. We further propose a novel method that incorporates attention map consistency and cycle training to detect the open-set samples. Extensive experiments on various FER datasets demonstrate that our method clearly outperforms state-of-the-art open-set recognition methods by large margins. Code is available at https://github.com/zyh-uaiaaaa.

General physical training in Ukrainian national martial arts

The article deals with the issues of improving general physical training in Ukrainian martial arts. An analysis of modern approaches to the general physical training of martial artists was made. The content, methods and means of physical training in the Ukrainian national sports of Horting and Cossack fight are shown. The peculiarities of building the training process of athletes in the annual training cycle are revealed. The relationship between the indicators of the development of physical qualities and the stability of competitive results in Ukrainian national martial arts is analyzed. The choice of test exercises for determining the development of the main physical qualities of athletes in Ukrainian martial arts is substantiated. Differences in the level of development of the physical qualities of athletes are determined, depending on the competitive division in which they specialize. The prospects for the further development of Ukrainian national martial arts in Europe and the world are shown. Ukrainian martial arts compete with Eastern martial arts. Horting and Cossack fight use modern methods of general and special physical training in the training process. Sports science conducts fundamental research of Ukrainian national sports martial arts.

The {332} Twinning Behavior of a Ti-15Mo Medical Alloy during Cyclic Deformation and Its Effect on Microstructure and Performance.

In this study, the microstructural evolution of a Ti-15Mo medical alloy was investigated, when the in situ cyclic tensile strain had 2% amplitude and the tension-compression cyclic deformation had 1%, 2%, and 3% amplitude. The Vickers hardness and wear resistance of the alloy were also optimized due to the grain-refining effect after cyclic deformation and annealing. The twinning-induced plasticity (TWIP) was considered the main deformation mechanism of the Ti-15Mo alloy during the tensile-compressive cycle deformation with suitable strain amplitude. The {332}<113> twins and boundaries were the main contributors to the grain refinement. The optimal microstructure, hardness, and wear resistance were obtained in the alloy deformed by tension-compression cyclic strain with a 3% strain amplitude. The wear resistance of the annealed alloy in Hank's solution was excellent in contrast to the original Ti-15Mo alloy due to its reasonable microstructure and hardness. It is clear that abundant twins were formed and retained in the coarse grains of the original alloy after cyclic deformation and annealing, which provided the expected refined grains and performance.

Quantifying the Human Perception: Development and Characterization of Textile-Based Capacitive Strain and Pressure Sensors

In the research field of smart textiles, one main goal concerns quantifying environmental forces acting on the wearer's body since textiles, acting as the boundary between the two, are an excellent way of integrating sensors. Integrating strain and pressure sensors into wearables promises a simple way of monitoring a person's posture and forces acting on their body. Sensors relying on a capacitive measuring principle are highly suitable for this, as they are less sensitive to changes in temperature than resistive or inductive types. In this paper, textile-based capacitive sensors are produced by braiding conductive yarns with and without an electrically insulating TPU sheath. The produced sensors are analyzed in cyclic strain and compression tests. Moreover, their behavior under changing temperatures is tested to prove their resilience against environmental changes. To extend their capabilities from an integral measurement to a localized assessment of the strain, time-domain-reflectometry (TDR) is employed. Finally, the sensors are integrated into a flexible actuated bending beam, and their adoption for soft robotics is discussed. Strain is tested cyclically, showing good long-term stability. Pressure sensitivity is measured in a static compression test under increasing force. TDR is used to localize strain in two discreet sections of the sensor. Although strain could not be quantified through TDR, characteristic points in the measured response signal indicating the position of the strain were identified. Textile-based capacitive sensors are suitable for strain up to 10 % and pressure up to 8 N. The determined gauge factors are satisfactory, with strain sensors inherently having a higher gauge factor than pressure sensors. Furthermore, they display good long-term stability and no adverse reaction to changes in temperature. TDR is proven to provide localization of strain in flexible sensors.

Bone-inspired stress-gaining elastomer enabled by dynamic molecular locking.

The limited capacity of typical materials to resist stress loading, which affects their mechanical performance, is one of the most formidable challenges in materials science. Here, we propose a bone-inspired stress-gaining concept of converting typically destructive stress into a favorable factor to substantially enhance the mechanical properties of elastomers. The concept was realized by a molecular design of dynamic poly(oxime-urethanes) network with mesophase domains. During external loading, the mesophase domains in the condensed state were aligned into more ordered domains, and the dynamic oxime-urethane bonds served as the dynamic molecular locks disassociating and reorganizing to facilitate and fix the mesophase domains. Consequently, the tensile modulus and strength were enhanced by 1744 and 49.3 times after four cycles of mechanical training, respectively. This study creates a molecular concept with stress-gaining properties induced by repeated mechanical stress loading and will inspire a series of innovative materials for diverse applications.

Validity of the 8-minute time trial in determining variables for mountain bike cycling training

The 8-minute time trial (TT) is a methodological alternative to the 60-minute TT for evaluating the Functional Threshold Power (FTP) of cyclists, however, studies that tested its validity were not found in the researched literature. Therefore, research aims to assess the validity of the 8-minute TT. The study included 9 trained male cyclists, aged between 25.46 ± 7.49 years, who were assessed on three different days. On the first day, we measured personal data, anthropometrics, ventilatory thresholds and peak oxygen consumption. On the other days, we submitted the volunteers to the 8- and 60-minute TT. We analyzed the agreement between the procedures using the intraclass correlation coefficient (ICC) and its validity by Bland-Altman. We adopted a significance level of 5%, and we performed all analyses using the SPSS. The results suggest great agreement, especially between the second 8-minute stimulus and the reference test, for FTP (ICC: 0.792, p= 0.016), Wats per kilogram (ICC: 0.952, p&lt; 0.001), Wats per kilogram of lean mass (ICC: 0.912, p= 0.001) and peak oxygen consumption (ICC: 0.882, p= 0.001). In addition, in all these variables, the volunteers were within the mean ± two standard deviations, as verified by the Bland-Altman plots. These results demonstrate the validity of the 8-minute TT, with more robust data being observed by the second stimulus of this protocol.