Central and peripheral fatigue development in the shoulder muscle with obesity during an isometric endurance task

To determine whether acute exposure to moderate hypoxia alters central and peripheral fatigue and to test whether carbohydrate ingestion impacts fatigue characteristics, 12 trained runners completed three running trials lasting 1 h each at 65% of normoxic maximum oxygen uptake. The first trial was performed in normoxia [inspired O2 fraction ([Formula: see text]) = 0.21], and the last two trials were completed in hypoxia ([Formula: see text] = 0.15). Participants ingested a placebo drink in normoxia (NORM-PLA), a placebo drink in hypoxia (HYP-PLA), or a carbohydrate solution in hypoxia (HYP-CHO). HYP conditions were randomized. Peripheral [change in potentiated quadriceps twitch force (ΔQtw,pot)] and central [change in voluntary activation (ΔVA)] fatigue were assessed via preexercise-to-postexercise changes in magnetically evoked quadriceps twitch. In HYP, blood was drawn to determine the ratio of free-tryptophan (f-TRP) to branched-chain amino acids (BCAA). After exercise, peripheral fatigue was reduced to a similar degree in normoxia and hypoxia (ΔQtw,pot = −4.5 ± 1.3% and −4.0 ± 1.5% in NORM-PLA and HYP-PLA, respectively; P = 0.61). Central fatigue was present after normoxic and hypoxic exercise but to a greater degree in HYP-PLA compared with NORM-PLA (ΔVA: −4.7 ± 0.9% vs. −1.9 ± 0.7%; P < 0.01). Carbohydrate ingestion did not influence central fatigue (ΔVA in HYP-CHO: −5.7 ± 1.2%; P = 0.51 vs. HYP-PLA). After exercise, no differences were observed in the ratio of f-TRP to BCAA between HYP-PLA and HYP-CHO ( P = 0.67). Central fatigue increased during prolonged running exercise in moderate hypoxia although the ratio of f-TRP to BCAA remained unchanged. Ingesting carbohydrates while running in hypoxia did not influence fatigue development. NEW & NOTEWORTHY Hypoxic exposure influences the origin of exercise-induced fatigue and the rate of fatigue development depending on the severity of hypoxia. Our data suggest that moderate hypoxia increases central, but not peripheral, fatigue in trained runners exercising at 65% of normoxic maximum oxygen uptake. The increase in central fatigue was unaffected by carbohydrate intake and occurred although the ratio of free tryptophan to branched-chain amino acids remained unchanged.

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Interaction between environmental temperature and hypoxia on central and peripheral fatigue during high-intensity dynamic knee extension

Journal of Applied Physiology ◽

10.1152/japplphysiol.00876.2015 ◽

2016 ◽

Vol 120 (6) ◽

pp. 567-579 ◽

Cited By ~ 20

Author(s):

Alex Lloyd ◽

Margherita Raccuglia ◽

Simon Hodder ◽

George Havenith

Keyword(s):

High Intensity ◽

Muscle Activation ◽

Knee Extension ◽

Climatic Conditions ◽

Peripheral Fatigue ◽

Time To Exhaustion ◽

Combined Exposure ◽

Fatigue Development ◽

C 50 ◽

The Impact

This study investigated causative factors behind the expression of different interaction types during exposure to multistressor environments. Neuromuscular fatigue rates and time to exhaustion (TTE) were investigated in active men ( n = 9) exposed to three climates [5°C, 50% relative humidity (rh); 23°C, 50% rh; and 42°C, 70% rh] at two inspired oxygen fractions (0.209 and 0.125 FiO2; equivalent attitude = 4,100 m). After a 40-min rest in the three climatic conditions, participants performed constant-workload (high intensity) knee extension exercise until exhaustion, with brief assessments of neuromuscular function every 110 s. Independent exposure to cold, heat, and hypoxia significantly ( P < 0.01) reduced TTE from thermoneutral normoxia (reductions of 190, 405, and 505 s from 915 s, respectively). The TTE decrease was consistent with a faster rate of peripheral fatigue development ( P < 0.01) compared with thermoneutral normoxia (increase of 1.6, 3.1, and 4.9%/min from 4.1%/min, respectively). Combined exposure to hypoxic-cold resulted in an even greater TTE reduction (−589 s), likely due to an increase in the rate of peripheral fatigue development (increased by 7.6%/min), but this was without significant interaction between stressors ( P > 0.198). In contrast, combined exposure to hypoxic heat reduced TTE by 609 s, showing a significant antagonistic interaction ( P = 0.003) similarly supported by an increased rate of peripheral fatigue development (which increased by 8.3%/min). A small decline (<0.4%/min) in voluntary muscle activation was observed only in thermoneutral normoxia. In conclusion, interaction type is influenced by the impact magnitude of the effect of the individual stressors' effect on exercise capacity, whereby the greater the effect of stressors, the greater the probability that one stressor will be abolished by the other. This indicates that humans respond to severe and simultaneous physiological strains on the basis of a worst-strain-takes-precedence principle.

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Shoulder muscle fatigue development in young and older female adults during a repetitive manual task

Ergonomics ◽

10.1080/00140139.2014.914576 ◽

2014 ◽

Vol 57 (8) ◽

pp. 1201-1212 ◽

Cited By ~ 16

Author(s):

Jin Qin ◽

Jia-Hua Lin ◽

Bryan Buchholz ◽

Xu Xu

Keyword(s):

Muscle Fatigue ◽

Manual Task ◽

Shoulder Muscle ◽

Fatigue Development

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Neuromuscular fatigue development during maximal concentric and isometric knee extensions

Journal of Applied Physiology ◽

10.1152/japplphysiol.00737.2005 ◽

2006 ◽

Vol 100 (3) ◽

pp. 780-785 ◽

Cited By ~ 80

Author(s):

Nicolas Babault ◽

Kevin Desbrosses ◽

Marie-Sophie Fabre ◽

Anne Michaut ◽

Michel Pousson

Keyword(s):

Root Mean Square ◽

Vastus Lateralis ◽

Neuromuscular Fatigue ◽

Peripheral Fatigue ◽

Vastus Lateralis Muscle ◽

Electromyographic Activity ◽

Median Frequency ◽

Mean Square ◽

Fatigue Development ◽

Frequency Changes

This study aimed to investigate mechanisms of neuromuscular fatigue during maximal concentric and isometric leg extensions inducing similar torque decrements. Nine physically active men performed two separate fatiguing sessions maintained until similar torque decreases were obtained. The first session, only conducted under isokinetic concentric conditions (CON), consisted of three series of 30 maximal voluntary concentric knee extensions (60°/s). The second session, exclusively isometric (ISO), mimicked the torque decreases registered during the CON session while performing three long-lasting ISO contractions. Maximal voluntary torque, activation level (twitch interpolation technique), electromyographic activity (root mean square and median frequency) of the vastus lateralis muscle, and electrically evoked doublet-twitch mechanical properties were measured before and at the end of each of the three series. After the three series, similar torque decrements were obtained for both fatiguing procedures. The total fatiguing contraction durations were not different among procedures. With equivalent voluntary torque decrements, the doublet-twitch amplitude reduction was significantly greater ( P < 0.01) during the two first series of the CON procedure compared with ISO. No difference was observed for the third series. Although no difference was recorded with fatigue for median frequency changes between CON and ISO, activation levels and root mean square values demonstrated greater reductions ( P < 0.05) for all three series during the ISO procedure compared with CON. Performing CON or ISO fatiguing exercises demonstrated different fatigue origins. With CON exercises, peripheral fatigue developed first, followed by central fatigue, whereas with ISO exercises the fatigue pattern was inverted.

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Distinct profiles of neuromuscular fatigue during muscle contractions below and above the critical torque in humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.00022.2012 ◽

2012 ◽

Vol 113 (2) ◽

pp. 215-223 ◽

Cited By ~ 99

Author(s):

Mark Burnley ◽

Anni Vanhatalo ◽

Andrew M. Jones

Keyword(s):

Vastus Lateralis ◽

Central Fatigue ◽

Neuromuscular Fatigue ◽

Voluntary Activation ◽

Peripheral Fatigue ◽

Critical Threshold ◽

Task Failure ◽

Fatigue Development ◽

The Right ◽

Experimental Trials

Whether the transition in fatigue processes between “low-intensity” and “high-intensity” contractions occurs gradually, as the torque requirements are increased, or whether this transition occurs more suddenly at some identifiable “threshold”, is not known. We hypothesized that the critical torque (CT; the asymptote of the torque-duration relationship) would demarcate distinct profiles of central and peripheral fatigue during intermittent isometric quadriceps contractions (3-s contraction, 2-s rest). Nine healthy men performed seven experimental trials to task failure or for up to 60 min, with maximal voluntary contractions (MVCs) performed at the end of each minute. The first five trials were performed to determine CT [∼35–55% MVC, denoted severe 1 (S1) to severe 5 (S5) in ascending order], while the remaining two trials were performed 10 and 20% below the CT (denoted CT-10% and CT-20%). Dynamometer torque and the electromyogram of the right vastus lateralis were sampled continuously. Peripheral and central fatigue was determined from the fall in potentiated doublet torque and voluntary activation, respectively. Above CT, contractions progressed to task failure in ∼3–18 min, at which point the MVC did not differ from the target torque (S1 target, 88.7 ± 4.3 N·m vs. MVC, 89.3 ± 8.8 N·m, P = 0.94). The potentiated doublet fell significantly in all trials, and voluntary activation was reduced in trials S1–S3, but not trials S4 and S5. Below CT, contractions could be sustained for 60 min on 17 of 18 occasions. Both central and peripheral fatigue developed, but there was a substantial reserve in MVC torque at the end of the task. The rate of global and peripheral fatigue development was four to five times greater during S1 than during CT-10% (change in MVC/change in time S1 vs. CT-10%: −7.2 ± 1.4 vs. −1.5 ± 0.4 N·m·min−1). These results demonstrate that CT represents a critical threshold for neuromuscular fatigue development.

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Convective oxygen transport and fatigue

Journal of Applied Physiology ◽

10.1152/japplphysiol.01008.2007 ◽

2008 ◽

Vol 104 (3) ◽

pp. 861-870 ◽

Cited By ~ 163

Author(s):

Markus Amann ◽

Jose A. L. Calbet

Keyword(s):

Central Fatigue ◽

Peripheral Fatigue ◽

Healthy Human ◽

Reduction In Force ◽

Fatigue Development ◽

Inhibitory Feedback ◽

Generating Capacity ◽

Exercise Fatigue ◽

Acute And Chronic Exposure ◽

Rate Of Accumulation

During exercise, fatigue is defined as a reversible reduction in force- or power-generating capacity and can be elicited by “central” and/or “peripheral” mechanisms. During skeletal muscle contractions, both aspects of fatigue may develop independent of alterations in convective O2delivery; however, reductions in O2supply exacerbate and increases attenuate the rate of accumulation. In this regard, peripheral fatigue development is mediated via the O2-dependent rate of accumulation of metabolic by-products (e.g., inorganic phosphate) and their interference with excitation-contraction coupling within the myocyte. In contrast, the development of O2-dependent central fatigue is elicited 1) by interference with the development of central command and/or 2) via inhibitory feedback on central motor drive secondary to the peripheral effects of low convective O2transport. Changes in convective O2delivery in the healthy human can result from modifications in arterial O2content, blood flow, or a combination of both, and they can be induced via heavy exercise even at sea level; these changes are exacerbated during acute and chronic exposure to altitude. This review focuses on the effects of changes in convective O2delivery on the development of central and peripheral fatigue.

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Peripheral fatigue is not critically regulated during maximal, intermittent, dynamic leg extensions

Journal of Applied Physiology ◽

10.1152/japplphysiol.00988.2013 ◽

2014 ◽

Vol 117 (9) ◽

pp. 1063-1073 ◽

Cited By ~ 16

Author(s):

Ryan J. Christian ◽

David J. Bishop ◽

François Billaut ◽

Olivier Girard

Keyword(s):

Time Course ◽

Intermittent Exercise ◽

Rectus Femoris ◽

Peak Torque ◽

Peripheral Fatigue ◽

Knee Extensors ◽

Motor Drive ◽

Peripheral Muscle ◽

Fatigue Development ◽

And Performance

Central motor drive to active muscles is believed to be reduced during numerous exercise tasks to prevent excessive peripheral fatigue development. The purpose of the present study was to use hypoxia to exacerbate physiological perturbations during a novel, intermittent exercise task and to explore the time-course and interplay between central and peripheral neuromuscular adjustments. On separate days, 14 healthy men performed four sets of 6 × 5 maximal-intensity, isokinetic leg extensions (1 repetition lasting ∼7 s) at 300°/s (15 and 100 s of passive rest between repetitions and sets, respectively) under normoxia (NM, fraction of inspired O2 0.21), moderate (MH, 0.14), and severe normobaric hypoxia (SH, 0.10). Neuromuscular assessments of the knee extensors were conducted before and immediately after each set. There was an interaction between time and condition on the mean peak torque produced during each set ( P < 0.05). RMS/M-wave activity of the rectus femoris decreased across the four sets of exercise, but there was no difference between conditions (8.3 ± 5.1% all conditions compounded, P > 0.05). Potentiated twitch torque decreased post set 1 in all conditions (all P < 0.05) with greater reductions following each set in SH compared with NM but not MH (end-exercise reductions 41.3 ± 3.0% vs. 28.0 ± 3.2%, P < 0.05 and 32.1 ± 3.3%, P > 0.05). In conclusion, severe hypoxia exacerbates both peripheral fatigue development and performance decrements during maximal, intermittent, dynamic leg extensions. In contrast to observations with other exercise modes, during exercise involving a single muscle group the attenuation of central motor drive does not appear to independently regulate the development of peripheral muscle fatigue.

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Supplemental Material for The Meaning and Measurement of Work Fatigue: Development and Evaluation of the Three-Dimensional Work Fatigue Inventory (3D-WFI)

Journal of Occupational Health Psychology ◽

10.1037/a0038700.supp ◽

2015 ◽

Keyword(s):

Three Dimensional ◽

Fatigue Development

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Peripheral Modulators of the Central Fatigue Development and Their Relationship with Athletic Performance in Jumper Horses

Animals ◽

10.3390/ani11030743 ◽

2021 ◽

Vol 11 (3) ◽

pp. 743

Author(s):

Francesca Arfuso ◽

Claudia Giannetto ◽

Elisabetta Giudice ◽

Francesco Fazio ◽

Michele Panzera ◽

...

Keyword(s):

Blood Lactate ◽

Athletic Performance ◽

Lactate Concentration ◽

Indirect Evidence ◽

Blood Lactate Concentration ◽

Central Fatigue ◽

Serotoninergic System ◽

Stressful Situation ◽

Passive Behavior ◽

Fatigue Development

The current study aimed to investigate whether peripheral modulators of serotoninergic function and neurohumoral factors’ changes in athletic horses during an official jumping competition, and to evaluate their relationship with the physical performance of competing horses. From 7 Italian Saddle mares (6–9 years; mean body weight 440 ± 15 kg), performing the same standardized warm-up and jumping course during an official class, heart rate (HR) was monitored throughout the competition. Rectal temperature (RT) measurement, blood lactate and glucose concentration, serum tryptophan, leucine, valine, the tryptophan/branched-chain amino-acids ratio (Try/BCAAs), dopamine, prolactin, and non-esterified fatty acids (NEFAs) were assessed before the exercise event (T0), at the end of the competition stage (5 min ± 10 s following the cessation of the exercise, TPOST5), and 30 min after the end of competition (TPOST30). Highest HR values were recorded during the course and at the outbound (p < 0.0001); blood lactate concentration and RT increased after exercise with respect to the rest condition (p < 0.0001). Lower leucine and valine levels (p < 0.01), and higher tryptophan, Try/BCAAs ratio, and NEFAs values were found at TPOST5 and TPOST30 with respect to T0 (p < 0.0001). A higher prolactin concentration was found at TPOST5 and TPOST30 compared to T0 (p < 0.0001), whereas dopamine showed decreased values after exercise compared to rest (p < 0.0001). Statistically significant correlations among the peripheral indices of serotoninergic function, neurohumoral factors, and athletic performance parameters were found throughout the monitoring period. The findings provide indirect evidence that the serotoninergic system may be involved in fatigue during jumper exercise under a stressful situation, such as competition, in which, in addition to physical effort, athletic horses exhibit more passive behavior.

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