Critical power and fatigue

Shot peening is a process wherein the surface of a material is impacted by small, spherical metal shots at high velocity to create residual stresses. Nickel-based superalloy is a material with high strength and hardness along with excellent corrosion and fatigue resistance, and it is therefore used in nuclear power plants and aerospace applications. The application of shot peening to INCONEL, a nickel-based superalloy, has been actively researched, and the measurement of residual stresses has been studied as well...

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.

BACKGROUND AND PURPOSE: The symptom of fatigue impairs function in people with multiple sclerosis (MS). Choosing appropriate measures to assess fatigue is challenging. The purpose of this article is to report the findings of a systematic review of patient-reported fatigue measures for people with MS. METHODS: PubMed, CINAHL, and Embase databases were searched through January 2020 using terms related to fatigue and MS. Studies were included if the sample size was 30 or more or smaller samples if adequately powered, and if information about measurement characteristics (ie, test-retest reliability, content validity, responsiveness, interpretability, or generalizability) of the measure(s) could be extracted...

The aim of the present study was to determine whether fatigue affects internal and external load variables determining power profile in cyclists. Ten cyclists performed outdoor power profile tests (lasting 1-, 5 and 20-min) on two consecutive days, subject either to a fatigued condition or not. Fatigue was induced by undertaking an effort (10-min at 95% of average power output obtained in a 20-min effort followed by 1-min maximum effort) until the power output decreased by 20% compared to the 1-min power output...

OBJECTIVES: Early identification of mechanical complications of total knee arthroplasties is of great importance to minimize the complexity and iatrogenicity of revision surgeries. There is therefore a critical need to use smart knee implants during intra or postoperative phases. Nevertheless, these devices are absent from commercialized orthopaedic implants, mainly due to their manufacturing complexity. We report the design, simulations and tests of a force and moments sensor integrated inside the tibial tray of a knee implant...

AIM: This study investigated the development of power profiles and performance-related measures from the junior level (<19 years) via U23 (19-23 years) to senior level (>23 years) in 19 female and 100 male Norwegian national team cyclists. METHODS: A total of 285 tests were performed in a 3-day laboratory-standardized testing regime. The tests included power profiles with shorter duration (6-60 s) and longer durations (12-30 min) together with performance-related measures: Critical power (CP), work capacity above CP (W'), power output at 4 and 2 mmol·L-1 [BLa-] (L4 and L2), maximal aerobic power (Wmax), and maximal oxygen uptake (VO2max), gross efficiency (GE), and pedalling efficiency...

INTRODUCTION: Recent studies have questioned previous empirical evidence that mental fatigue negatively impacts physical performance. The purpose of this study is to investigate the critical role of individual differences in mental fatigue susceptibility by analyzing the neurophysiological and physical responses to an individualized mental fatigue task. METHODS: In a pre-registered (https://osf.io/xc8nr/), randomized, within-participant design experiment, twenty-two recreational athletes completed a time to failure test at 80% of their peak power output under mental fatigue (individual mental effort) or control (low mental effort)...

The insulated-gate bipolar transistor (IGBT) represents a crucial component within the domain of power semiconductor devices, which finds ubiquitous employment across a range of critical domains, including new energy vehicles, smart grid systems, rail transit, aerospace, etc. The main characteristics of its operating environment are high voltage, large current, and high power density, which can easily cause issues, such as thermal stress, thermal fatigue, and mechanical stress. Therefore, the reliability of IGBT module packaging has become a critical research topic...

We tested the hypothesis that a %SmO2 (muscle O2 saturation) slope can distinguish the heavy-severe exercise domain boundary and the highest steady-state metabolic rate. Thirteen participants (5 women) performed a graded exercise test (GXT) to determine peak oxygen consumption (V̇o2peak ) and lactate turn point (LTP). On a separate study day, a %SmO2 zero-slope prediction trial included completing 5-min cycling bouts in an estimated heavy domain, at an estimated critical power, and in an estimated severe domain...

As a widely used brain-computer interface (BCI) paradigm, steady-state visually evoked potential (SSVEP)-based BCIs have the advantages of high information transfer rates, high tolerance for artifacts, and robust performance across diverse users. However, the incidence of mental fatigue from prolonged, repetitive stimulation is a critical issue for SSVEP-based BCIs. Music is often used as a convenient, non-invasive means of relieving mental fatigue. This study investigates the compensatory effect of music on mental fatigue through the introduction of different modes of background music in long-duration, SSVEP-BCI tasks...

AIM: To systematically review the effectiveness of wheeled mobility interventions in children and young people with cerebral palsy (CP). METHOD: A systematic literature search was performed in MEDLINE, Embase, Cochrane Central Register of Controlled Trials, EBSCO, PEDro, and Web of Science using database-specific concepts such as 'child' and 'wheelchair'. Studies focusing on wheeled mobility skill interventions with participants aged 6 to 21 years with CP were included...

BACKGROUND: Rotary nickel-titanium files have become the most commonly used engine-powered endodontic instruments due to their improvement in fatigue resistance and flexibility. The autoclaving is the most commonly used method for sterilization. However, the risk of instrument fracture, mainly due to cyclic fatigue during rotation within a curved canal, is still a matter of critical concern. AIMS: This study aimed to measure and compares the cyclic fatigue resistance of EdgeFile X7, 2Shape, and F-One files in a single curved simulated canal before and after autoclave sterilization...

This study aimed to determine work-rest schedules for visual tasks of different lengths by evaluating visual fatigue and visually induced motion sickness (VIMS) using an optical head-mounted display (OHMD). Thirty participants were recruited to perform 15 and 30 min visual tasks using an OHMD. After completing each visual task, participants executed six levels of rest time. Critical flicker fusion frequency (CFF) values, relative electroencephalography indices, and Simulator Sickness Questionnaire (SSQ) scores were collected and analyzed...

OBJECTIVE: A passive brain-computer interface (pBCI) is a system that enhances a human-machine interaction by monitoring the mental state of the user and, based on this implicit information, making appropriate modifications to the interaction. Key to the development of such a system is the ability to reliably detect the mental state of interest via neural signals. Many different mental states have been investigated, including fatigue, attention and various emotions, however one of the most commonly studied states is mental workload, i...

BACKGROUND: The effects of pre-sleep protein supplementation on endurance athletes remain unclear, particularly whether its potential benefits are due to the timing of protein intake or solely to an increased total protein intake. We assessed the effects of pre-sleep protein supplementation in professional cyclists during a training camp accounting for the influence of protein timing. METHODS: Twenty-four professional U23 cyclists (19 ± 1 years, peak oxygen uptake: 79...

The physiological determinants of high-intensity exercise tolerance are important for both elite human performance and morbidity, mortality and disease in clinical settings. The asymptote of the hyperbolic relation between external power and time to task failure, critical power, represents the threshold intensity above which systemic and intramuscular metabolic homeostasis can no longer be maintained. After ~ 60 years of research into the phenomenon of critical power, a clear understanding of its physiological determinants has emerged...

OBJECTIVES: This study assesses how female footballers perceive how their menstrual cycle impacts their physical and psychological performance, informing future research and intervention. METHODS: Semi-structured interviews, developed using piloting and peer review took place with fifteen elite female footballers from two English WSL clubs (age: 25.2 [18-33]). Data was audio recorded, transcribed verbatim, and analysed thematically using NVivo. RESULTS: All players (100%) perceive their menstrual cycle to negatively impact performance...

Relative sensitivities of the maximal oxygen uptake (V̇O2max ), critical power (CP) and transition time of the primary phase II of the V̇O2 on-kinetics (t0.63 ) to selected factors in skeletal muscle are simulated using a computer model of the skeletal muscle bioenergetic system. In normoxia, V̇O2max is significantly positively sensitive to peak Pi (Pipeak , Pi at which exercise is terminated because of fatigue), OXPHOS (oxidative phosphorylation) activity (kOX ) and ESA (each-step-activation) intensity (AOXmax ), and negatively sensitive to the accessible phosphate (and total creatine) pool (Pacc )...

The activity and quantity of mitochondrial proteins and the mitochondrial volume density (MitoVD ) are higher in trained muscles; however, the underlying mechanisms remain unclear. Our goal was to determine if 20 weeks' endurance training simultaneously increases running performance, the amount and activity of mitochondrial proteins, and MitoVD in the gastrocnemius muscle in humans. Eight healthy, untrained young men completed a 20-week moderate-intensity running training program. The training increased the mean speed of a 1500 m run by 14...

PURPOSE: With few cycling races on the calendar in 2020 due to COVID-19, Everesting became a popular challenge: you select one hill and cycle up and down it until you reach the accumulated elevation of Mt. Everest (8,848 m or 29,029ft). With an almost infinite number of different hills across the world, the question arises what the optimal hill for Everesting would be. Here, we address the biomechanics and energetics of up- and downhill cycling to determine the characteristics of this optimal hill...