Caffeine Ingestion Attenuates Fatigue-induced Loss of Muscle Torque Complexity

Pethick, Jamie; Winter, Samantha L.

doi:10.1249/mss.0000000000001441

Cited by 42 publications

(87 citation statements)

References 37 publications

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“…Common synaptic input to muscles and motor unit synchronization have been proposed to be major determinants of force variability (Dideriksen, Negro, Enoka, & Farina, ; Farina & Negro, ) and have been demonstrated to increase with fatigue (Castronovo, Negro, Conforto, & Farina, ). We have, therefore, previously speculated a link between motor unit synchronization and torque complexity (Pethick et al., , ). However, direct measurement of individual motor units via high‐density surface EMG electrodes will be necessary to confirm a link between motor unit synchronization and torque complexity, rather than the analysis of motor unit action potential trains recorded using bipolar EMG, as was done in the present study.…”

Section: Discussionmentioning

confidence: 97%

“…Several computer simulation studies have suggested that increased motor unit synchronization substantially increases EMG amplitude (Yao, Fuglevand, & Enoka, ; Zhou & Rymer, ). Moreover, motor unit synchronization has previously been speculated to be a potential cause of the fatigue‐induced loss of torque (Pethick et al., , ) and EMG (Beretta‐Piccoli et al., ; Mesin, Cescon, Gazzoni, Merletti, & Rainoldi, ) complexity.…”

Section: Discussionmentioning

confidence: 99%

“…To estimate the temporal fractal scaling of torque, the detrended fluctuation analysis (DFA) exponent was used (Peng et al, 1994). The ApEn and DFA were calculated as in our previous studies (Pethick et al, 2015(Pethick et al, , 2016(Pethick et al, , 2018a, with these calculations briefly detailed below.…”

Section: Variability and Complexitymentioning

confidence: 99%

“…We have recently demonstrated that neuromuscular fatigue reduces the complexity of muscle torque output during both maximal and submaximal isometric contractions (Pethick, Winter, & Burnley, 2015). We subsequently demonstrated that this fatigue-induced loss of complexity is evident only during contractions performed above the critical torque (Pethick et al, 2016) and that such losses can be slowed by the ingestion of caffeine (Pethick, Winter, & Burnley, 2018a). These studies have demonstrated that the loss of torque complexity is tightly coupled to the fatigue process, with complexity declining in tandem with the loss of force-generating capacity.…”

Section: Introductionmentioning

confidence: 96%

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Prolonged depression of knee‐extensor torque complexity following eccentric exercise

Pethick

Whiteaway

Winter

2018

Experimental Physiology

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New Findings What is the central question of this study?Does eccentric exercise leading to prolonged knee‐extensor torque depression also result in a prolonged loss of knee‐extensor torque complexity? What is the main finding and its importance?The recovery of the loss of torque complexity after eccentric exercise took 24 h, whereas after acute muscle fatigue it took 10 min. The depression of torque complexity after eccentric exercise was prolonged. Abstract Neuromuscular fatigue reduces the temporal structure, or complexity, of muscle torque output. Exercise‐induced muscle damage reduces muscle torque output for considerably longer than high‐intensity fatiguing contractions. We hypothesized that muscle‐damaging eccentric exercise would lead to a persistent decrease in torque complexity, whereas fatiguing exercise would not. Ten healthy participants performed five isometric contractions (6 s contraction, 4 s rest) at 50% maximal voluntary contraction (MVC) before, immediately after and 10, 30 and 60 min and 24 h after eccentric (muscle‐damaging) and isometric (fatiguing) exercise. These contractions were also repeated 48 h and 1 week after eccentric exercise. Torque and surface EMG signals were sampled throughout each test. Complexity and fractal scaling were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis α exponent (DFA α). Global, central and peripheral perturbations were quantified using MVCs with femoral nerve stimulation. Complexity decreased after both eccentric [ApEn, mean (SD), from 0.39 (0.10) to 0.20 (0.12), P < 0.001] and isometric exercise [from 0.41 (0.13) to 0.09 (0.04); P < 0.001]. After eccentric exercise, ApEn and DFA α required 24 h to recover to baseline levels, but after isometric exercise they required only 10 min. The MVC torque remained reduced [from 233.6 (74.2) to 187.5 (64.7) N m] 48 h after eccentric exercise, with such changes evident only up to 60 min after isometric exercise [MVC torque, from 246.1 (77.2) to 217.9 (71.8) N m]. The prolonged depression in maximal muscle torque output is therefore accompanied by a prolonged reduction in torque complexity.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Variability and Complexitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

See 2 more Smart Citations

Prolonged depression of knee‐extensor torque complexity following eccentric exercise

Pethick

Whiteaway

Winter

2018

Experimental Physiology

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“…We have recently observed that caffeine ingestion attenuates the development of central fatigue (assessed using the twitch interpolation technique) and the fatigue‐induced loss of torque complexity, independently of the development of peripheral fatigue (Pethick, Winter, & Burnley, ). This suggests that the central processes make a small, but significant, contribution to the fatigue‐induced loss of torque.…”

Section: Introductionmentioning

confidence: 99%

Effects of ipsilateral and contralateral fatigue and muscle blood flow occlusion on the complexity of knee‐extensor torque output in humans

Pethick

Winter

2018

Experimental Physiology

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Neuromuscular fatigue reduces the temporal structure, or complexity, of torque output during muscular contractions. To determine whether the fatigue-induced loss of torque complexity could be accounted for by central or peripheral factors, nine healthy participants performed four experimental trials involving intermittent isometric contractions of the knee extensors at 50% of the maximal voluntary contraction torque. These trials involved: (i) two bouts of contractions to failure using the right leg separated by 3 min recovery (IPS); (ii) the same protocol but with cuff occlusion during the 3 min recovery (IPS-OCC); (iii) contractions of the left leg to failure, followed 1 min later by contractions of the right leg to failure (CONT); and (iv) the same protocol but with cuff occlusion applied to the left leg throughout both the recovery period and right leg contractions (CONT-OCC). Supramaximal electrical stimulation during maximal voluntary contractions was used to determine the degree of central and peripheral fatigue, whilst complexity was determined using approximate entropy (ApEn) and detrended fluctuation analysis α exponent (DFA α). Neuromuscular fatigue was consistently associated with a loss of torque complexity in all conditions [e.g. IPS bout 1, ApEn from (mean ± SD) 0.46 ± 0.14 to 0.12 ± 0.06 (P < 0.001)]. In IPS-OCC, occlusion abolished the recovery from fatigue, and torque complexity remained at the values observed at task failure in the preceding bout (IPS-OCC bout 2, first minute 0.14 ± 0.03, P < 0.001). Prior contralateral contractions, with or without blood flow occlusion, had no effect on torque complexity.

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Sleep deprivation increases the regularity of isometric torque fluctuations

Oliveira,

Santos,

Pezarat-Correia

et al. 2024

Exp Brain Res

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The regularity of the fluctuations present in torque signals represent the adaptability of the motor control. While previous research showed how it is affected by neuromuscular fatigue and ageing, the underlying mechanisms remain unclear. It is currently under debate whether these changes are explained by central or peripheral neuromuscular mechanisms. Here, we experimentally manipulated the sleep of thirteen young adults through a supervised 24 h-sleep deprivation protocol. This study aimed to investigate the effect of sleep deprivation on the regularity of torque fluctuations, and other standard torque-related outcomes (Peak Torque – PT – and Rate of Torque Development – RTD). The participants were asked to perform knee extension maximal voluntary contractions (MVC) and submaximal knee extensions at 40% of MVC for 30 s. PT and RTD were calculated from the MVC and the regularity of the torque fluctuations was determined on the submaximal task through Sample Entropy (SampEn). In addition, rate of perceived effort (RPE) was collected. We found no significant changes in PT and RTD. The regularity of torque fluctuations significantly increased (i.e., a decrease in SampEn) after 24 h-sleep deprivation (PRE = 1.76 ± 0.268, POS24 = 1.71 ± 0.306; p = 0.044). Importantly, we found a negative correlation between RPE and SampEn relative changes after sleep deprivation. This study brings new insights towards the understanding of the underlying mechanisms that explain changes in torque fluctuations, demonstrating that these changes are not limited to neuromuscular processes but are also likely to be affected by other domains, such as psychological profile, which can indirectly affect the neural drive to the muscles.

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Caffeine Ingestion Attenuates Fatigue-induced Loss of Muscle Torque Complexity

Abstract: Caffeine ingestion slowed the fatigue-induced loss of torque complexity and increased the time to task failure during intermittent isometric contractions, most likely through central mechanisms.

Cited by 42 publications

References 37 publications

Prolonged depression of knee‐extensor torque complexity following eccentric exercise

Prolonged depression of knee‐extensor torque complexity following eccentric exercise

Effects of ipsilateral and contralateral fatigue and muscle blood flow occlusion on the complexity of knee‐extensor torque output in humans

Sleep deprivation increases the regularity of isometric torque fluctuations

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