Mean ± SD values of the exercise tolerance (s) obtained during the time exhaustion tests above (ET + 5%), below (ET – 5%), and at the same percentage of the maximal voluntary contraction (Similar %MVC) in relation to ET + 5% for PF

Mean ± SD values of the exercise tolerance (s) obtained during the time exhaustion tests above (ET + 5%), below (ET – 5%), and at the same percentage of the maximal voluntary contraction (Similar %MVC) in relation to ET + 5% for PF

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The objective of this study was to test the hypotheses that end-test torque (ET) (expressed as % maximal voluntary contraction; MVC) is higher for plantar flexors (PF) than knee extensors (KE) muscles, whereas impulse above ET (IET) is higher for KE than PF. Thus, we expected that exercise tolerance would be longer for KE than PF only during the ex...

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... The tolerance to high-intensity exercises is well-described by the critical power model, which suggests a hyperbolic relationship between the intensity of the exercise and the total duration that it can be sustained [3]. Two parameters can be derived from this relationship: the asymptote for the intensity measure (i.e., critical power, critical speed, or critical torque, CT) and the curvature constant (W prime, W ′ ), which together allow the estimation of the tolerance to exercises performed above critical power [4,5]. Physiologically, the critical power/CT represents the highest rate at which oxidative metabolism stabilizes and is considered the boundary between the heavy and severe-intensity domains as well as a threshold for neuromuscular fatigue [6,7]. ...
... Previous evidence demonstrates that the intensity associated with CT during handgrip exercise in untrained subjects is strongly influenced by oxygen availability, since when the oxygen supply is reduced, CT also decreases [9,10]. On the other hand, Bassan et al. (2019) [5] showed that when a short-term strength training program is performed, increases in both W ′ and tolerance to severe-intensity exercise occur without changes in CT. Hence, the first hypothesis of the present study is that GCS fighters would have a greater W ′ but a similar CT compared to the untrained individuals. ...
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Successful performance in grappling combat sports (GCS) can be influenced by the fighter's capacity to sustain high-intensity contractions of the handgrip muscles during combat. This study investigated the influence of GCS experience on the critical torque (CT), impulse above CT (W ′), tolerance, and neuromuscular fatigue development during severe-intensity handgrip exercise by comparing fighters and untrained individuals. Eleven GCS fighters and twelve untrained individuals participated in three experimental sessions for handgrip muscles: (1) familiarization with the experimental procedures and strength assessment; (2) an all-out test to determine CT and W ′ ; and (3) intermittent exercise performed in the severe-intensity domain (CT + 15%) until task failure. No significant differences were found in CT and neuromuscular fatigue between groups (p > 0.05). However, GCS fighters showed greater W ′ (GCS fighters 2238.8 ± 581.2 N·m·s vs. untrained 1670.4 ± 680.6 N·m·s, p < 0.05) and exercise tolerance (GCS fighters 8.38 ± 2.93 min vs. untrained 5.36 ± 1.42 min, p < 0.05) than untrained individuals. These results suggest that long-term GCS sports training can promote increased tolerance to severe-intensity handgrip exercise and improved W ′ without changes in CT or the magnitude of neuromuscular fatigue.
... The torquetime to task failure relationship, equivalent to the powertime to task failure relationship, for small muscle mass isometric exercise is hyperbolic and has important implications for human performance (Abdalla et al., 2018;Burnley, 2009). The asymptote of this hyperbola for intermittent isometric exercise is end-test torque (ET; analogous to critical power), which represents the highest attainable metabolic steady-state (Jones et al., 2008;Poole et al., 1988). ...
... Participants performed a 5-min all-out test consisting of a series of 60 MVC (3 s exercise, 2 s rest) (Abdalla et al., 2018;Burnley, 2009). Before the test, a warm-up was performed with a set of five submaximal isometric contractions (∼70-80% MVC) followed by a 5 min rest and three MVC of 3 s interspersed by 3 min of rest. ...
... After 30 min of rest, the target torque was displayed on a screen for the participants, and they were instructed to attain and maintain the target torque for 3 s. Task failure was determined by the first of three consecutive contractions where the participant was unable to achieve the target torque despite strong encouragement (Abdalla et al., 2018). Throughout each submaximal test, neuromuscular function was assessed every 12 contractions (i.e. 1 min) and immediately after task failure. ...
Article
We previously reported that creatine supplementation improved intermittent isometric exercise performance by augmenting the total impulse performed above end‐test torque (total IET′). However, our previous analyses did not enable mechanistic assessments. The objective of this study was to determine if creatine supplementation affected the IET′ speed of recovery. To achieve this objective, we retrospectively analyzed our data using the IET′ balance model to determine the time constant for the recovery of IET′ ( τ IET′). Sixteen men were randomly allocated into creatine ( N = 8) or placebo ( N = 8) groups. Prior to supplementation, participants performed quadriceps all‐out exercise to determine end‐test torque (ET) and IETʹ. Participants then performed quadriceps exercise at ET + 10% until task‐failure before supplementation (Baseline), until task‐failure after supplementation (Creatine or Placebo), and until the Baseline time after supplementation (Creatine‐ or Placebo‐Isotime). τ IET′ was faster than Baseline for Creatine (669 ± 98 vs 470 ± 66 s), but not Placebo (792 ± 166 vs 786 ± 161 s). The creatine‐induced change in τ IET′ was inversely correlated with the creatine‐induced changes in both the rate of peripheral fatigue development and time to task‐failure. τ IET′ was inversely correlated with total IET′ and ET in all conditions, but creatine supplementation shifted this relationship such that τ IET′ was faster for a given ET. Creatine supplementation, therefore, sped the recovery of IET′ during intermittent isometric exercise, which was inversely related to the improvement in exercise performance. These findings support that the improvement in exercise performance after creatine supplementation was, at least in part, specific to effects on the physiological mechanisms that determine the IET′ speed of recovery.
... The curvature of the power or load versus time to exhaustion hyperbola represents the work or load prime which is the total work that can be performed above critical power/load (Bergstrom et al. 2021). While the concepts of critical power/load and work/load prime have been extensively studied in both en-durance exercise and isometric contractions (Poole et al. 2016;Abdalla et al. 2018), their application to isotonic contractions, which are used in traditional RET, has been limited (Morton, Redstone and Laing 2014;Dinyer et al. 2019;Dinyer et al. 2020b). In other domains, such as endurance exercise, different training styles have divergent effects on critical power and work prime (Gaesser and Wilson 1988;Quigley 1992, 1993;Sawyer et al. 2014). ...
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The effect of resistance training with higher- and lower-loads on muscle mass and strength has been extensively studied, while changes in muscle endurance have received less attention. This trial aimed to assess the effect of training load on absolute muscle endurance (AME) and relative muscle endurance (RME). Sixteen untrained women (22.7 ± 3.3 yr: mean ± SD) had one arm and leg randomly assigned to train with higher loads (HL; 80–90% 1RM), and the contralateral limbs trained with lower loads (LL; 30–50% 1RM) thrice weekly to volitional fatigue for 10 weeks. Heavy and light load AME and RME, strength, and muscle mass were assessed pre- and post-training. Strength increased more in the HL compared to LL leg (P < 0.01), but similar increases in strength were observed between upper body conditions (P = 0.46). Lower body heavy and light load AME improved in both conditions, but HL training induced a larger improvement in heavy load AME (HL: 9.3 ± 4.3 vs. LL: 7.5 ± 7.1 repetitions, time × limb P < 0.01) and LL training induced a larger improvement in light load AME (LL: 24.7 ± 22.2 vs. HL: 15.2 ± 16.7 repetitions, time × limb P = 0.04). In the upper body, HL and LL training induced similar increases in both heavy (time × limb P = 0.99), and light load (time × limb P = 0.16) AME. Dual-energy X-ray absorptiometry showed no change in leg fat-and-bone-free mass (FBFM) for either condition, and an increase in only LL arm FBFM. AME improved in a manner specific to the training loads used. ClinicalTrials.gov (NCT04547972).
... Thus, the mechanical occlusion of perfusion in the contracting muscle occurs at a specific absolute force (Barnes, 1980). Consistent with this, the T lim during isometric muscle contractions is significantly greater for plantar flexor (PF) (301 s) than knee extensor (KE) (157 s) muscles, despite exercising at similar percentages of MVC (∼60%) (Abdalla et al., 2018). It has also been demonstrated that the hyperbolic torque-T lim relationships differ between the severe and extreme domains, with these relationships merging at ∼60% of maximal strength (Alexander et al., 2019). ...
... For the 5 min all-out tests, ET was determined as the mean of the final six contractions and IETʹ was determined as cumulative area under the torque versus time curve above ET (Abdalla et al., 2018;Burnley, 2009). The data were analysed using MatLab R2017a software (The MathWorks Inc., Natick, MA, USA). ...
... In the present study, a 5-min all-out intermittent test was utilized to predict IET′ and ET, requiring fewer laboratory visits. It is important to note that this test has been already used to successfully predict the critical power model parameters in previous studies conducted in whole body (Vanhatalo et al., 2007) and small muscle mass (Abdalla et al., 2018;Burnley, 2009) It is generally accepted that there is a close relationship between the muscular cross-sectional area (CSA) and its ability to generate force (Fukunaga et al., 1996;Ikai & Fukunaga, 1968;Maughan et al., 1983;Young et al., 1985). Muscle strength is related to its physiological CSA (PCSA), which can be estimated from muscle volume, muscle length and pennation angle. ...
Article
New findings: What is the central question of this study? Does muscle size, maximal force and exercise intensity influence the recovery time constant for the finite impulse above critical torque (τIET')? What is the main finding and its importance? This study showed that muscle size and maximal strength have different influences on the parameters of the hyperbolic torque - Tlim relationship. Greater muscle size and maximal strength, as well as exercise at an intensity of 60% MVC, prolong τIET' during intermittent isometric exercise. Abstract: Muscle perfusion and O2 delivery limitations through muscle force generation appear to play a major role in defining the hyperbolic torque - Tlim relationship. Therefore, we aimed to determine the influence of muscle size and maximal strength on the recovery time constant for the finite impulse above critical torque (τIET'). Ten men participated in the study and performed intermittent isometric tests until task-failure (Tlim ) for the knee-extensors (KE 35% and 60% MVC) and plantar flexors (PF 60% MVC). The τIET' was determined for each of these Tlim tests using the IET'BAL model. The IET' (9738 ± 3080 vs 2959 ± 1289 N · m · s) and ET (84.5 ± 7.1 vs 74.3 ± 12.7 N · m) were significantly lower for PF compared to KE (P < 0.05). Exercise tolerance (Tlim ) was significantly longer for PF (239 ± 81 s) than KE (150 ± 55 s) at 60% MVC, and significantly longer for KE at 35% MVC (641 ± 158 s) than 60% MVC. The τIET' was significantly faster at 35% MVC (641± 177 s) than 60% MVC (1840 ± 354 s) for KE, both of which were significantly slower than PF 60% MVC (317 ± 102 s). This study showed that τIET' during intermittent isometric exercise is slower with greater muscle size and maximal strength. This article is protected by copyright. All rights reserved.
... Theoretically, once this stable state is reached, it can be maintained indefinitely. The mean relative force asymptotes measured in the present study (FFs, 42.4% of MVC; PFs, 43.0% of MVC; not statistically different) are similar to those reported in previous studies for FFs (40.3% of MVC; Veni et al., 2018) and PFs (40.9% of MVC;Abdalla et al., 2018). Although these data are similar, it is important to note the high inter-individual variability (range, ∼20-70% of MVC for both muscle groups). ...
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Le cancer et ses traitements entraînent un certain nombre d’effet secondaire qui impacte la qualité de vie des patients. Le principal effet secondaire est la fatigue liée au cancer (FLC), sa prévalence se situe entre 59 et 99% des patients, en fonction du type de cancer et de traitement. La FLC est définie comme une sensation persistante d’épuisement due au cancer et à ses traitements, qui n’est pas proportionnelle aux activités réalisées. Etant subjective, la FLC est évaluée par le biais de questionnaires. Cependant, cette modalité d’évaluation ne permet de prendre en compte les différents mécanismes sous-jacents de la FLC. Car en effet, il est communément admis que de multiples mécanismes appartenant aux dimensions physique, psychologique, sociale et comportementale peuvent être à l’origine de la FLC. Parmi les principales origines décrites dans la littérature, on retrouve les troubles du sommeil et les symptômes émotionnels d’anxiété et de dépression. Il semblerait également que la fatigabilité soit un mécanisme potentiel de la FLC, néanmoins les résultats des précédentes études sont équivoques. Par conséquent, l’objectif de ce travail de thèse est d’affirmer les liens entre la FLC et la fatigabilité et déterminer si la fatigabilité fait parti des mécanismes sous-jacents de la FLC. Pour répondre à ces objectifs, nous avons mis en place différentes expérimentations et proposé un protocole de recherche qui sera prochainement mis en place. Les principaux résultats de ces études sont que i) la fatigabilité semble être une caractéristique individuelle ; ii) l’amplitude de la fatigabilité est associée à la FLC ; et iii) la fatigabilité est un des mécanismes sous-jacents de la FLC.
... Burnley [2009] examined 5 min of maximum intermittent isometric contractions to determine critical torque of the knee extensors and showed that end-torque of these tests closely approximates CT. All-out tests have also been used for other exercises, e.g., for plantar flexion [Abdalla et al., 2018] or for handgrip exercise [Kellawan and Tschakovsky, 2014]. However, some authors have reported a possible overestimation of CP by the equivalent 3-min all-out test [Muniz-Pumares et al., 2018], which suggests that all-out tests might not be suitable for all subjects or might need to be adapted individually. ...
Thesis
In this thesis, we present a novel mathematical model-based approach to optimize loading schemes of isometric resistance training (RT) sessions for different training goals. To this end, we develop a nonlinear ordinary differential equation model of the time course of maximum voluntary isometric (MVIC) force under external isometric loading. To validate the model, we set up multi-experiment parameter estimation problems using a comprehensive dataset from the literature. We solve these problems numerically via direct multiple shooting and the generalized Gauss-Newton method. Moreover, we use the proposed model to examine hypotheses about fatigue and recovery of MVIC force. Then, we mathematically formulate key performance indicators and optimality criteria for loading schemes of isometric RT sessions identified in sports science and incorporate these into multi-stage optimal control problems. We solve these problems numerically via direct multiple shooting and structure-exploiting sequential quadratic programming. We discuss the results from a numerical and sports scientific point of view. Based on the proposed model, we additionally formulate the estimation of critical torque as a nonlinear program. This allows us to reduce the experimental effort compared to conventional testing when estimating these quantities. Furthermore, we formulate multi-stage optimum experimental design problems to reduce the statistical uncertainty of the parameter estimates when calibrating the model. We solve these problems numerically via direct single shooting and sequential quadratic programming. We discuss the solutions from a numerical and physiological point of view. For our approach, a small amount of data obtained in a single testing session is sufficient. Our approach can be extended to more elaborate physiological models and other forms of resistance training once suitable models become available.
... The '5 min all-out test' consisted of 60 intermittent isometric MVCs (3 s contraction, 2 s relaxation) (Abdalla, Denadai, Bassan, & Greco, 2018;Burnley, 2009 ...
Article
New findings: What is the central question of this study? Does creatine supplementation augment the total torque impulse accumulated above end-test torque (IET) during severe-intensity knee-extensor exercise by attenuating the rate of decrease in peak potentiated twitch torque (PT)? What is the main finding and its importance? Creatine augmented the IET and attenuated the rate of decrease in both voluntary activation and PT during severe-intensity exercise. The IET was related to the rate of decrease in PT. These findings reveal an important role for the rates of neuromuscular fatigue development as key determinants of exercise tolerance within the severe domain. Abstract: This study investigated the effect of creatine supplementation on exercise tolerance, total torque impulse accumulated above end-test torque (total IET) and neuromuscular fatigue development of the knee extensors during severe-intensity intermittent isometric exercise. Sixteen men were randomly allocated into Creatine (n = 8, 20 g day-1 for 5 days) or Placebo (n = 8) groups and performed knee-extensor maximal voluntary contraction (MVC) testing, all-out testing to determine end-test torque (ET) and the finite torque impulse accumulated above end-test torque (IET'), and three submaximal tests at ET + 10%: (i) time to task failure without supplementation (Baseline); (ii) time to task failure after creatine or placebo supplementation; and (iii) time matched to Baseline after creatine (Creatine-Isotime) or placebo (Placebo-Isotime) supplementation. Creatine supplementation significantly increased the time to task failure (Baseline = 572 ± 144 s versus Creatine = 833 ± 221 s) and total IET (Baseline = 5761 ± 1710 N m s versus Creatine = 7878 ± 1903 N m s), but there were no significant differences within the Placebo group. The percentage change pre- to postexercise in MVC, voluntary activation, peak potentiated twitch torque and integrated EMG during MVC were not significantly different between Baseline and Creatine but were all significantly attenuated in Creatine-Isotime compared with Baseline. There were no significant differences in these variables within the placebo group. The total IET was significantly correlated with the rates of change in potentiated twitch torque peak (r = 0.83-0.87) and rate of torque development (r = -0.83 to -0.87) for the submaximal tests to task failure. These findings reveal an important role for the rates of neuromuscular fatigue development as key determinants of exercise tolerance during severe-intensity intermittent isometric exercise.
... There is no relationship between initial maximal force produced, rate of force decrease and force plateau reached after a prolonged supramaximal task (Poole et al., 2016). To counteract these limitations, it is possible to perform repeated maximal voluntary contractions until the force plateau is reached, as initially proposed by Burnley (2009) on knee extensors and further validated for finger flexors (Kellawan & Tschakovsky, 2014) and plantar flexors (Abdalla et al., 2018). ...
... The force asymptote represents maximal force decrease for a given exercise condition, and thus (Abdalla et al., 2018). While these data are similar, it is important to note the high inter-individual variability (range: ~20 to 70% of MVC for both muscle groups). ...
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New findings: What is the central question of this study? Is neuromuscular fatigability interrelated between different muscle groups from the same individual during isometric all-out exercise? What is the main finding and its importance? Although the average decrease can vary between muscles, an individual demonstrates interrelated fatigability etiology regardless of the muscle group tested. The inter-individual variability provides evidence of different profiles common between muscles which can be regarded as an individual characteristic. Abstract: Purpose Neuromuscular fatigability is commonly divided into central and peripheral origins. However, there is strong evidence of interactions between these two mechanisms. According to the idea that peripheral fatigability may be centrally regulated, one can hypothesize that neuromuscular fatigability would be correlated between different muscle groups at the individual level. Methods Thirty-two healthy participants (16 women and 16 men) completed two, 5 min fatiguing exercises (60 isometric maximal voluntary contractions (MVC)) with finger flexors (FF) and ankle plantar flexors (PF) in two randomized sessions. Neuromuscular testing was conducted before, during (every 6 MVCs) and directly after the fatigue procedure. Force asymptote (FA ) was calculated as the asymptote of the force-time relationship. Pre to post-changes in exercise evoked force (ΔDb100 ), voluntary activation (ΔVA) and central activation ratio (∆CAR) were also investigated. Results Significant correlations were found between FF and PF for FA , ΔDb100 and ΔVA (r = 0.65; r = 0.63 and r = 0.50 respectively). A significant negative correlation between ∆CAR and ∆Db100 was evidenced for both PF (r = - 0.82) and FF (r = - 0.57). Conclusion Neuromuscular fatigability is correlated between different muscle groups at the individual level. Results of the current study support the idea that a restrained motor drive prevents large peripheral perturbations and that individuals exhibit correlated fatigability etiology regardless of the muscle group tested. Widely different central/peripheral profiles can be found amongst individuals and a part of the fatigability etiology can be regarded as an individual characteristic. This article is protected by copyright. All rights reserved.
... Cross-sectional and longitudinal experimental designs produced evidence that maximal strength can influence W ′ estimated during whole-body and small muscle mass exercises. Abdalla, Denadai, Bassan, and Greco (2018) showed that both maximal voluntary isometric contraction (MVC) and IET (analogous to W ′ ) (Kellawan & Tschakovsky, 2014) were significantly higher for knee extensors than for plantar flexors. Moreover, inter-individual variability of IET, independent of muscle group, was moderate, which could be explained by MVC (r > 0.62, P < 0.05). ...
... and to estimate both ET and IET involving different muscle groups (e.g. knee extensors and forearm flexors)(Abdalla et al., 2018;Burnley, 2009;Kellawan & Tschakovsky, 2014). Moreover, a 5 min all-out intermittent isometric exercise could estimate ET(Burnley, 2009) and predict exercise tolerance during an exercise at a constant intensity above ET(Abdalla et al., 2018;Kellawan & Tschakovsky, 2014). ...
... knee extensors and forearm flexors)(Abdalla et al., 2018;Burnley, 2009;Kellawan & Tschakovsky, 2014). Moreover, a 5 min all-out intermittent isometric exercise could estimate ET(Burnley, 2009) and predict exercise tolerance during an exercise at a constant intensity above ET(Abdalla et al., 2018;Kellawan & Tschakovsky, 2014). Our study revealed, for the first time, that isometric resistance training improves IET during small muscle mass exercise, whereas ET remains unchanged. ...
Article
New findings: What is the central question of this study? What role do neuromuscular fatigue mechanisms play in resistance training-induced adaptations of the impulse above end-test torque (IET) after the training period? What is the main finding and its importance? IET and global and peripheral fatigue were increased after a short period of resistance training. Thus, resistance training-induced adaptations in neuromuscular fatigue seem to contribute to enhanced IET after the training period. Abstract: Short-term resistance training has a positive influence on the curvature constant of the power-duration relationship (W'). The physiological mechanism of W' enhancement after resistance training is unclear. This study aimed to determine whether one-leg maximal isometric resistance training influences (1) impulse above end-test torque (IET; an analogue of W') during a 5 min all-out isometric test; and (2) exercise tolerance (limit of tolerance, Tlim) and neuromuscular fatigue during severe exercise (i.e. above end-test torque; ET). Sixteen healthy active males participated in a 3-week unilateral knee extensor resistance-training programme, and 10 matched subjects participated as controls. The subjects were instructed to ramp up to 100% of maximal voluntary contraction (MVC) over 1 s, hold it for 3 s, and relax. Each repetition had a 2 s interval (10) and each set, a 2 min interval (3). MVC (18.6%) and muscle thickness (12.8%) were significantly improved after training. Significantly greater global (i.e. reduced MVC, 43.2 ± 13.5% vs. 58.9 ± 6.9%) and peripheral (51.7 ± 13.6% vs. 57.3 ± 15.3%) fatigue, IET (26%) and Tlim (92%) were obtained after resistance training. Moreover, both global (r = 0.57, P < 0.05) and peripheral fatigue (r = 0.55, P < 0.05) accrued during severe exercise were associated with IET. However, echo intensity, which reflects muscle quality, ET and central fatigue remained unchanged throughout the training period. No significant changes in the control group for any variable were observed. Resistance training-induced adaptations in muscle size and neuromuscular fatigue seem to contribute to enhanced IET and Tlim after the training period.
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The objective of this study was to test the hypothesis that neuromuscular fatigue influences the rate of torque development (RTD) in a similar manner to isometric torque. Nine men participated in this study and performed 5-min all-out isometric tests for knee extensors (KE) and plantar flexors (PF) muscles, to determine the end-test torque (ET) and the critical rate of torque development (critical RTD). Additionally, participants performed submaximal constant-torque tests to task failure for KE and PF muscles. Both maximal voluntary contraction and RTD exhibited hyperbolic behavior and reached an asymptote at the end of the 5-min all out isometric test with similar relative values (KE 29.5 ± 5.6% MVC and PF 50.9 ± 2.9% MVC and KE 25.1 ± 3.6 to 28.5 ± 4.4% RTD and PF 48.4 ± 6.5 to 52.4 ± 5.8% RTD). However, both % MVC and % RTD were statistically different between muscle groups (P < 0.05), even when normalized by muscle volume (P < 0.05). Torque and RTD after the constant-torque test were similar to the values of ET and critical RTD (P > 0.05), respectively. In this study, it was observed that neuromuscular fatigue affects RTD and torque similarly, with the magnitude of this effect varying according to the muscle size.